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author | Denis Bitouzé <dbitouze@wanadoo.fr> | 2021-02-25 18:23:07 +0000 |
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committer | Denis Bitouzé <dbitouze@wanadoo.fr> | 2021-02-25 18:23:07 +0000 |
commit | c6101f91d071883b48b1b4b51e5eba0f36d9a78d (patch) | |
tree | 1bf7f5a881d7a4f5c5bf59d0b2821943dd822372 /Build/source/texk/web2c/tex.web | |
parent | 07ee7222e389b0777456b427a55c22d0e6ffd267 (diff) |
French translation for tlmgr updated
git-svn-id: svn://tug.org/texlive/trunk@57912 c570f23f-e606-0410-a88d-b1316a301751
Diffstat (limited to 'Build/source/texk/web2c/tex.web')
-rw-r--r-- | Build/source/texk/web2c/tex.web | 25010 |
1 files changed, 0 insertions, 25010 deletions
diff --git a/Build/source/texk/web2c/tex.web b/Build/source/texk/web2c/tex.web deleted file mode 100644 index 62374028b2c..00000000000 --- a/Build/source/texk/web2c/tex.web +++ /dev/null @@ -1,25010 +0,0 @@ -% This program is copyright (C) 1982 by D. E. Knuth; all rights are reserved. -% Unlimited copying and redistribution of this file are permitted as long -% as this file is not modified. Modifications are permitted, but only if -% the resulting file is not named tex.web. (The WEB system provides -% for alterations via an auxiliary file; the master file should stay intact.) -% See Appendix H of the WEB manual for hints on how to install this program. -% And see Appendix A of the TRIP manual for details about how to validate it. - -% TeX is a trademark of the American Mathematical Society. -% METAFONT is a trademark of Addison-Wesley Publishing Company. - -% Version 0 was released in September 1982 after it passed a variety of tests. -% Version 1 was released in November 1983 after thorough testing. -% Version 1.1 fixed ``disappearing font identifiers'' et alia (July 1984). -% Version 1.2 allowed `0' in response to an error, et alia (October 1984). -% Version 1.3 made memory allocation more flexible and local (November 1984). -% Version 1.4 fixed accents right after line breaks, et alia (April 1985). -% Version 1.5 fixed \the\toks after other expansion in \edefs (August 1985). -% Version 2.0 (almost identical to 1.5) corresponds to "Volume B" (April 1986). -% Version 2.1 corrected anomalies in discretionary breaks (January 1987). -% Version 2.2 corrected "(Please type...)" with null \endlinechar (April 1987). -% Version 2.3 avoided incomplete page in premature termination (August 1987). -% Version 2.4 fixed \noaligned rules in indented displays (August 1987). -% Version 2.5 saved cur_order when expanding tokens (September 1987). -% Version 2.6 added 10sp slop when shipping leaders (November 1987). -% Version 2.7 improved rounding of negative-width characters (November 1987). -% Version 2.8 fixed weird bug if no \patterns are used (December 1987). -% Version 2.9 made \csname\endcsname's "relax" local (December 1987). -% Version 2.91 fixed \outer\def\a0{}\a\a bug (April 1988). -% Version 2.92 fixed \patterns, also file names with complex macros (May 1988). -% Version 2.93 fixed negative halving in allocator when mem_min<0 (June 1988). -% Version 2.94 kept open_log_file from calling fatal_error (November 1988). -% Version 2.95 solved that problem a better way (December 1988). -% Version 2.96 corrected bug in "Infinite shrinkage" recovery (January 1989). -% Version 2.97 corrected blunder in creating 2.95 (February 1989). -% Version 2.98 omitted save_for_after at outer level (March 1989). -% Version 2.99 caught $$\begingroup\halign..$$ (June 1989). -% Version 2.991 caught .5\ifdim.6... (June 1989). -% Version 2.992 introduced major changes for 8-bit extensions (September 1989). -% Version 2.993 fixed a save_stack synchronization bug et alia (December 1989). -% Version 3.0 fixed unusual displays; was more \output robust (March 1990). -% Version 3.1 fixed nullfont, disabled \write{\the\prevgraf} (September 1990). -% Version 3.14 fixed unprintable font names and corrected typos (March 1991). -% Version 3.141 more of same; reconstituted ligatures better (March 1992). -% Version 3.1415 preserved nonexplicit kerns, tidied up (February 1993). -% Version 3.14159 allowed fontmemsize to change; bulletproofing (March 1995). -% Version 3.141592 fixed \xleaders, glueset, weird alignments (December 2002). -% Version 3.1415926 was a general cleanup with minor fixes (February 2008). -% Version 3.14159265 was similar (January 2014). -% Version 3.141592653 was similar but more extensive (January 2021). - -% A reward of $327.68 will be paid to the first finder of any remaining bug. - -% Although considerable effort has been expended to make the TeX program -% correct and reliable, no warranty is implied; the author disclaims any -% obligation or liability for damages, including but not limited to -% special, indirect, or consequential damages arising out of or in -% connection with the use or performance of this software. This work has -% been a ``labor of love'' and the author hopes that users enjoy it. - -% Here is TeX material that gets inserted after \input webmac -\def\hang{\hangindent 3em\noindent\ignorespaces} -\def\hangg#1 {\hang\hbox{#1 }} -\def\textindent#1{\hangindent2.5em\noindent\hbox to2.5em{\hss#1 }\ignorespaces} -\font\ninerm=cmr9 -\let\mc=\ninerm % medium caps for names like SAIL -\def\PASCAL{Pascal} -\def\ph{\hbox{Pascal-H}} -\def\pct!{{\char`\%}} % percent sign in ordinary text -\font\logo=logo10 % font used for the METAFONT logo -\def\MF{{\logo META}\-{\logo FONT}} -\def\<#1>{$\langle#1\rangle$} -\def\section{\mathhexbox278} - -\def\(#1){} % this is used to make section names sort themselves better -\def\9#1{} % this is used for sort keys in the index via @@:sort key}{entry@@> - -\outer\def\N#1. \[#2]#3.{\MN#1.\vfil\eject % begin starred section - \def\rhead{PART #2:\uppercase{#3}} % define running headline - \message{*\modno} % progress report - \edef\next{\write\cont{\Z{\?#2]#3}{\modno}{\the\pageno}}}\next - \ifon\startsection{\bf\ignorespaces#3.\quad}\ignorespaces} -\let\?=\relax % we want to be able to \write a \? - -\def\title{\TeX82} -\def\topofcontents{\hsize 5.5in - \vglue 0pt plus 1fil minus 1.5in - \def\?##1]{\hbox to 1in{\hfil##1.\ }} - } -\def\botofcontents{\vskip 0pt plus 1fil minus 1.5in} -\pageno=3 -\def\glob{13} % this should be the section number of "<Global...>" -\def\gglob{20, 26} % this should be the next two sections of "<Global...>" - -@* \[1] Introduction. -This is \TeX, a document compiler intended to produce typesetting of high -quality. -The \PASCAL\ program that follows is the definition of \TeX82, a standard -@:PASCAL}{\PASCAL@> -@!@:TeX82}{\TeX82@> -version of \TeX\ that is designed to be highly portable so that identical output -will be obtainable on a great variety of computers. - -The main purpose of the following program is to explain the algorithms of \TeX\ -as clearly as possible. As a result, the program will not necessarily be very -efficient when a particular \PASCAL\ compiler has translated it into a -particular machine language. However, the program has been written so that it -can be tuned to run efficiently in a wide variety of operating environments -by making comparatively few changes. Such flexibility is possible because -the documentation that follows is written in the \.{WEB} language, which is -at a higher level than \PASCAL; the preprocessing step that converts \.{WEB} -to \PASCAL\ is able to introduce most of the necessary refinements. -Semi-automatic translation to other languages is also feasible, because the -program below does not make extensive use of features that are peculiar to -\PASCAL. - -A large piece of software like \TeX\ has inherent complexity that cannot -be reduced below a certain level of difficulty, although each individual -part is fairly simple by itself. The \.{WEB} language is intended to make -the algorithms as readable as possible, by reflecting the way the -individual program pieces fit together and by providing the -cross-references that connect different parts. Detailed comments about -what is going on, and about why things were done in certain ways, have -been liberally sprinkled throughout the program. These comments explain -features of the implementation, but they rarely attempt to explain the -\TeX\ language itself, since the reader is supposed to be familiar with -{\sl The \TeX book}. -@.WEB@> -@:TeXbook}{\sl The \TeX book@> - -@ The present implementation has a long ancestry, beginning in the summer -of~1977, when Michael~F. Plass and Frank~M. Liang designed and coded -a prototype -@^Plass, Michael Frederick@> -@^Liang, Franklin Mark@> -@^Knuth, Donald Ervin@> -based on some specifications that the author had made in May of that year. -This original proto\TeX\ included macro definitions and elementary -manipulations on boxes and glue, but it did not have line-breaking, -page-breaking, mathematical formulas, alignment routines, error recovery, -or the present semantic nest; furthermore, -it used character lists instead of token lists, so that a control sequence -like \.{\\halign} was represented by a list of seven characters. A -complete version of \TeX\ was designed and coded by the author in late -1977 and early 1978; that program, like its prototype, was written in the -{\mc SAIL} language, for which an excellent debugging system was -available. Preliminary plans to convert the {\mc SAIL} code into a form -somewhat like the present ``web'' were developed by Luis Trabb~Pardo and -@^Trabb Pardo, Luis Isidoro@> -the author at the beginning of 1979, and a complete implementation was -created by Ignacio~A. Zabala in 1979 and 1980. The \TeX82 program, which -@^Zabala Salelles, Ignacio Andr\'es@> -was written by the author during the latter part of 1981 and the early -part of 1982, also incorporates ideas from the 1979 implementation of -@^Guibas, Leonidas Ioannis@> -@^Sedgewick, Robert@> -@^Wyatt, Douglas Kirk@> -\TeX\ in {\mc MESA} that was written by Leonidas Guibas, Robert Sedgewick, -and Douglas Wyatt at the Xerox Palo Alto Research Center. Several hundred -refinements were introduced into \TeX82 based on the experiences gained with -the original implementations, so that essentially every part of the system -has been substantially improved. After the appearance of ``Version 0'' in -September 1982, this program benefited greatly from the comments of -many other people, notably David~R. Fuchs and Howard~W. Trickey. -A final revision in September 1989 extended the input character set to -eight-bit codes and introduced the ability to hyphenate words from -different languages, based on some ideas of Michael~J. Ferguson. -@^Fuchs, David Raymond@> -@^Trickey, Howard Wellington@> -@^Ferguson, Michael John@> - -No doubt there still is plenty of room for improvement, but the author -is firmly committed to keeping \TeX82 ``frozen'' from now on; stability -and reliability are to be its main virtues. - -On the other hand, the \.{WEB} description can be extended without changing -the core of \TeX82 itself, and the program has been designed so that such -extensions are not extremely difficult to make. -The |banner| string defined here should be changed whenever \TeX\ -undergoes any modifications, so that it will be clear which version of -\TeX\ might be the guilty party when a problem arises. -@^extensions to \TeX@> -@^system dependencies@> - -If this program is changed, the resulting system should not be called -`\TeX'; the official name `\TeX' by itself is reserved -for software systems that are fully compatible with each other. -A special test suite called the ``\.{TRIP} test'' is available for -helping to determine whether a particular implementation deserves to be -known as `\TeX' [cf.~Stanford Computer Science report CS1027, -November 1984]. - -@d banner=='This is TeX, Version 3.141592653' {printed when \TeX\ starts} - -@ Different \PASCAL s have slightly different conventions, and the present -@!@:PASCAL H}{\ph@> -program expresses \TeX\ in terms of the \PASCAL\ that was -available to the author in 1982. Constructions that apply to -this particular compiler, which we shall call \ph, should help the -reader see how to make an appropriate interface for other systems -if necessary. (\ph\ is Charles Hedrick's modification of a compiler -@^Hedrick, Charles Locke@> -for the DECsystem-10 that was originally developed at the University of -Hamburg; cf.\ {\sl Software---Practice and Experience \bf6} (1976), -29--42. The \TeX\ program below is intended to be adaptable, without -extensive changes, to most other versions of \PASCAL, so it does not fully -use the admirable features of \ph. Indeed, a conscious effort has been -made here to avoid using several idiosyncratic features of standard -\PASCAL\ itself, so that most of the code can be translated mechanically -into other high-level languages. For example, the `\&{with}' and `\\{new}' -features are not used, nor are pointer types, set types, or enumerated -scalar types; there are no `\&{var}' parameters, except in the case of files; -there are no tag fields on variant records; there are no assignments -|real:=integer|; no procedures are declared local to other procedures.) - -The portions of this program that involve system-dependent code, where -changes might be necessary because of differences between \PASCAL\ compilers -and/or differences between -operating systems, can be identified by looking at the sections whose -numbers are listed under `system dependencies' in the index. Furthermore, -the index entries for `dirty \PASCAL' list all places where the restrictions -of \PASCAL\ have not been followed perfectly, for one reason or another. -@!@^system dependencies@> -@!@^dirty \PASCAL@> - -Incidentally, \PASCAL's standard |round| function can be problematical, -because it disagrees with the IEEE floating-point standard. -Many implementors have -therefore chosen to substitute their own home-grown rounding procedure. - -@ The program begins with a normal \PASCAL\ program heading, whose -components will be filled in later, using the conventions of \.{WEB}. -@.WEB@> -For example, the portion of the program called `\X\glob:Global -variables\X' below will be replaced by a sequence of variable declarations -that starts in $\section\glob$ of this documentation. In this way, we are able -to define each individual global variable when we are prepared to -understand what it means; we do not have to define all of the globals at -once. Cross references in $\section\glob$, where it says ``See also -sections \gglob, \dots,'' also make it possible to look at the set of -all global variables, if desired. Similar remarks apply to the other -portions of the program heading. - -Actually the heading shown here is not quite normal: The |program| line -does not mention any |output| file, because \ph\ would ask the \TeX\ user -to specify a file name if |output| were specified here. -@:PASCAL H}{\ph@> -@^system dependencies@> - -@d mtype==t@&y@&p@&e {this is a \.{WEB} coding trick:} -@f mtype==type {`\&{mtype}' will be equivalent to `\&{type}'} -@f type==true {but `|type|' will not be treated as a reserved word} - -@p @t\4@>@<Compiler directives@>@/ -program TEX; {all file names are defined dynamically} -label @<Labels in the outer block@>@/ -const @<Constants in the outer block@>@/ -mtype @<Types in the outer block@>@/ -var @<Global variables@>@/ -@# -procedure initialize; {this procedure gets things started properly} - var @<Local variables for initialization@>@/ - begin @<Initialize whatever \TeX\ might access@>@; - end;@# -@t\4@>@<Basic printing procedures@>@/ -@t\4@>@<Error handling procedures@>@/ - -@ The overall \TeX\ program begins with the heading just shown, after which -comes a bunch of procedure declarations and function declarations. -Finally we will get to the main program, which begins with the -comment `|start_here|'. If you want to skip down to the -main program now, you can look up `|start_here|' in the index. -But the author suggests that the best way to understand this program -is to follow pretty much the order of \TeX's components as they appear in the -\.{WEB} description you are now reading, since the present ordering is -intended to combine the advantages of the ``bottom up'' and ``top down'' -approaches to the problem of understanding a somewhat complicated system. - -@ Three labels must be declared in the main program, so we give them -symbolic names. - -@d start_of_TEX=1 {go here when \TeX's variables are initialized} -@d end_of_TEX=9998 {go here to close files and terminate gracefully} -@d final_end=9999 {this label marks the ending of the program} - -@<Labels in the out...@>= -start_of_TEX@t\hskip-2pt@>, end_of_TEX@t\hskip-2pt@>,@,final_end; - {key control points} - -@ Some of the code below is intended to be used only when diagnosing the -strange behavior that sometimes occurs when \TeX\ is being installed or -when system wizards are fooling around with \TeX\ without quite knowing -what they are doing. Such code will not normally be compiled; it is -delimited by the codewords `$|debug|\ldots|gubed|$', with apologies -to people who wish to preserve the purity of English. - -Similarly, there is some conditional code delimited by -`$|stat|\ldots|tats|$' that is intended for use when statistics are to be -kept about \TeX's memory usage. The |stat| $\ldots$ |tats| code also -implements diagnostic information for \.{\\tracingparagraphs}, -\.{\\tracingpages}, and \.{\\tracingrestores}. -@^debugging@> - -@d debug==@{ {change this to `$\\{debug}\equiv\null$' when debugging} -@d gubed==@t@>@} {change this to `$\\{gubed}\equiv\null$' when debugging} -@f debug==begin -@f gubed==end -@# -@d stat==@{ {change this to `$\\{stat}\equiv\null$' when gathering - usage statistics} -@d tats==@t@>@} {change this to `$\\{tats}\equiv\null$' when gathering - usage statistics} -@f stat==begin -@f tats==end - -@ This program has two important variations: (1) There is a long and slow -version called \.{INITEX}, which does the extra calculations needed to -@.INITEX@> -initialize \TeX's internal tables; and (2)~there is a shorter and faster -production version, which cuts the initialization to a bare minimum. -Parts of the program that are needed in (1) but not in (2) are delimited by -the codewords `$|init|\ldots|tini|$'. - -@d init== {change this to `$\\{init}\equiv\.{@@\{}$' in the production version} -@d tini== {change this to `$\\{tini}\equiv\.{@@\}}$' in the production version} -@f init==begin -@f tini==end - -@<Initialize whatever...@>= -@<Set initial values of key variables@>@/ -@!init @<Initialize table entries (done by \.{INITEX} only)@>@;@+tini - -@ If the first character of a \PASCAL\ comment is a dollar sign, -\ph\ treats the comment as a list of ``compiler directives'' that will -affect the translation of this program into machine language. The -directives shown below specify full checking and inclusion of the \PASCAL\ -debugger when \TeX\ is being debugged, but they cause range checking and other -redundant code to be eliminated when the production system is being generated. -Arithmetic overflow will be detected in all cases. -@:PASCAL H}{\ph@> -@^system dependencies@> -@^overflow in arithmetic@> - -@<Compiler directives@>= -@{@&$C-,A+,D-@} {no range check, catch arithmetic overflow, no debug overhead} -@!debug @{@&$C+,D+@}@+ gubed {but turn everything on when debugging} - -@ This \TeX\ implementation conforms to the rules of the {\sl Pascal User -@:PASCAL}{\PASCAL@> -@^system dependencies@> -Manual} published by Jensen and Wirth in 1975, except where system-dependent -@^Wirth, Niklaus@> -@^Jensen, Kathleen@> -code is necessary to make a useful system program, and except in another -respect where such conformity would unnecessarily obscure the meaning -and clutter up the code: We assume that |case| statements may include a -default case that applies if no matching label is found. Thus, we shall use -constructions like -$$\vbox{\halign{\ignorespaces#\hfil\cr -|case x of|\cr -1: $\langle\,$code for $x=1\,\rangle$;\cr -3: $\langle\,$code for $x=3\,\rangle$;\cr -|othercases| $\langle\,$code for |x<>1| and |x<>3|$\,\rangle$\cr -|endcases|\cr}}$$ -since most \PASCAL\ compilers have plugged this hole in the language by -incorporating some sort of default mechanism. For example, the \ph\ -compiler allows `|others|:' as a default label, and other \PASCAL s allow -syntaxes like `\&{else}' or `\&{otherwise}' or `\\{otherwise}:', etc. The -definitions of |othercases| and |endcases| should be changed to agree with -local conventions. Note that no semicolon appears before |endcases| in -this program, so the definition of |endcases| should include a semicolon -if the compiler wants one. (Of course, if no default mechanism is -available, the |case| statements of \TeX\ will have to be laboriously -extended by listing all remaining cases. People who are stuck with such -\PASCAL s have, in fact, done this, successfully but not happily!) -@:PASCAL H}{\ph@> - -@d othercases == others: {default for cases not listed explicitly} -@d endcases == @+end {follows the default case in an extended |case| statement} -@f othercases == else -@f endcases == end - -@ The following parameters can be changed at compile time to extend or -reduce \TeX's capacity. They may have different values in \.{INITEX} and -in production versions of \TeX. -@.INITEX@> -@^system dependencies@> - -@<Constants...@>= -@!mem_max=30000; {greatest index in \TeX's internal |mem| array; - must be strictly less than |max_halfword|; - must be equal to |mem_top| in \.{INITEX}, otherwise |>=mem_top|} -@!mem_min=0; {smallest index in \TeX's internal |mem| array; - must be |min_halfword| or more; - must be equal to |mem_bot| in \.{INITEX}, otherwise |<=mem_bot|} -@!buf_size=500; {maximum number of characters simultaneously present in - current lines of open files and in control sequences between - \.{\\csname} and \.{\\endcsname}; must not exceed |max_halfword|} -@!error_line=72; {width of context lines on terminal error messages} -@!half_error_line=42; {width of first lines of contexts in terminal - error messages; should be between 30 and |error_line-15|} -@!max_print_line=79; {width of longest text lines output; should be at least 60} -@!stack_size=200; {maximum number of simultaneous input sources} -@!max_in_open=6; {maximum number of input files and error insertions that - can be going on simultaneously} -@!font_max=75; {maximum internal font number; must not exceed |max_quarterword| - and must be at most |font_base+256|} -@!font_mem_size=20000; {number of words of |font_info| for all fonts} -@!param_size=60; {maximum number of simultaneous macro parameters} -@!nest_size=40; {maximum number of semantic levels simultaneously active} -@!max_strings=3000; {maximum number of strings; must not exceed |max_halfword|} -@!string_vacancies=8000; {the minimum number of characters that should be - available for the user's control sequences and font names, - after \TeX's own error messages are stored} -@!pool_size=32000; {maximum number of characters in strings, including all - error messages and help texts, and the names of all fonts and - control sequences; must exceed |string_vacancies| by the total - length of \TeX's own strings, which is currently about 23000} -@!save_size=600; {space for saving values outside of current group; must be - at most |max_halfword|} -@!trie_size=8000; {space for hyphenation patterns; should be larger for - \.{INITEX} than it is in production versions of \TeX} -@!trie_op_size=500; {space for ``opcodes'' in the hyphenation patterns} -@!dvi_buf_size=800; {size of the output buffer; must be a multiple of 8} -@!file_name_size=40; {file names shouldn't be longer than this} -@!pool_name='TeXformats:TEX.POOL '; - {string of length |file_name_size|; tells where the string pool appears} -@.TeXformats@> - -@ Like the preceding parameters, the following quantities can be changed -at compile time to extend or reduce \TeX's capacity. But if they are changed, -it is necessary to rerun the initialization program \.{INITEX} -@.INITEX@> -to generate new tables for the production \TeX\ program. -One can't simply make helter-skelter changes to the following constants, -since certain rather complex initialization -numbers are computed from them. They are defined here using -\.{WEB} macros, instead of being put into \PASCAL's |const| list, in order to -emphasize this distinction. - -@d mem_bot=0 {smallest index in the |mem| array dumped by \.{INITEX}; - must not be less than |mem_min|} -@d mem_top==30000 {largest index in the |mem| array dumped by \.{INITEX}; - must be substantially larger than |mem_bot| - and not greater than |mem_max|} -@d font_base=0 {smallest internal font number; must not be less - than |min_quarterword|} -@d hash_size=2100 {maximum number of control sequences; it should be at most - about |(mem_max-mem_min)/10|} -@d hash_prime=1777 {a prime number equal to about 85\pct! of |hash_size|} -@d hyph_size=307 {another prime; the number of \.{\\hyphenation} exceptions} -@^system dependencies@> - -@ In case somebody has inadvertently made bad settings of the ``constants,'' -\TeX\ checks them using a global variable called |bad|. - -This is the first of many sections of \TeX\ where global variables are -defined. - -@<Glob...@>= -@!bad:integer; {is some ``constant'' wrong?} - -@ Later on we will say `\ignorespaces|if mem_max>=max_halfword then bad:=14|', -or something similar. (We can't do that until |max_halfword| has been defined.) - -@<Check the ``constant'' values for consistency@>= -bad:=0; -if (half_error_line<30)or(half_error_line>error_line-15) then bad:=1; -if max_print_line<60 then bad:=2; -if dvi_buf_size mod 8<>0 then bad:=3; -if mem_bot+1100>mem_top then bad:=4; -if hash_prime>hash_size then bad:=5; -if max_in_open>=128 then bad:=6; -if mem_top<256+11 then bad:=7; {we will want |null_list>255|} - -@ Labels are given symbolic names by the following definitions, so that -occasional |goto| statements will be meaningful. We insert the label -`|exit|' just before the `\ignorespaces|end|\unskip' of a procedure in -which we have used the `|return|' statement defined below; the label -`|restart|' is occasionally used at the very beginning of a procedure; and -the label `|reswitch|' is occasionally used just prior to a |case| -statement in which some cases change the conditions and we wish to branch -to the newly applicable case. Loops that are set up with the |loop| -construction defined below are commonly exited by going to `|done|' or to -`|found|' or to `|not_found|', and they are sometimes repeated by going to -`|continue|'. If two or more parts of a subroutine start differently but -end up the same, the shared code may be gathered together at -`|common_ending|'. - -Incidentally, this program never declares a label that isn't actually used, -because some fussy \PASCAL\ compilers will complain about redundant labels. - -@d exit=10 {go here to leave a procedure} -@d restart=20 {go here to start a procedure again} -@d reswitch=21 {go here to start a case statement again} -@d continue=22 {go here to resume a loop} -@d done=30 {go here to exit a loop} -@d done1=31 {like |done|, when there is more than one loop} -@d done2=32 {for exiting the second loop in a long block} -@d done3=33 {for exiting the third loop in a very long block} -@d done4=34 {for exiting the fourth loop in an extremely long block} -@d done5=35 {for exiting the fifth loop in an immense block} -@d done6=36 {for exiting the sixth loop in a block} -@d found=40 {go here when you've found it} -@d found1=41 {like |found|, when there's more than one per routine} -@d found2=42 {like |found|, when there's more than two per routine} -@d not_found=45 {go here when you've found nothing} -@d common_ending=50 {go here when you want to merge with another branch} - -@ Here are some macros for common programming idioms. - -@d incr(#) == #:=#+1 {increase a variable by unity} -@d decr(#) == #:=#-1 {decrease a variable by unity} -@d negate(#) == #:=-# {change the sign of a variable} -@d loop == @+ while true do@+ {repeat over and over until a |goto| happens} -@f loop == xclause - {\.{WEB}'s |xclause| acts like `\ignorespaces|while true do|\unskip'} -@d do_nothing == {empty statement} -@d return == goto exit {terminate a procedure call} -@f return == nil -@d empty=0 {symbolic name for a null constant} - -@* \[2] The character set. -In order to make \TeX\ readily portable to a wide variety of -computers, all of its input text is converted to an internal eight-bit -code that includes standard ASCII, the ``American Standard Code for -Information Interchange.'' This conversion is done immediately when each -character is read in. Conversely, characters are converted from ASCII to -the user's external representation just before they are output to a -text file. - -Such an internal code is relevant to users of \TeX\ primarily because it -governs the positions of characters in the fonts. For example, the -character `\.A' has ASCII code $65=@'101$, and when \TeX\ typesets -this letter it specifies character number 65 in the current font. -If that font actually has `\.A' in a different position, \TeX\ doesn't -know what the real position is; the program that does the actual printing from -\TeX's device-independent files is responsible for converting from ASCII to -a particular font encoding. -@^ASCII code@> - -\TeX's internal code also defines the value of constants -that begin with a reverse apostrophe; and it provides an index to the -\.{\\catcode}, \.{\\mathcode}, \.{\\uccode}, \.{\\lccode}, and \.{\\delcode} -tables. - -@ Characters of text that have been converted to \TeX's internal form -are said to be of type |ASCII_code|, which is a subrange of the integers. - -@<Types...@>= -@!ASCII_code=0..255; {eight-bit numbers} - -@ The original \PASCAL\ compiler was designed in the late 60s, when six-bit -character sets were common, so it did not make provision for lowercase -letters. Nowadays, of course, we need to deal with both capital and small -letters in a convenient way, especially in a program for typesetting; -so the present specification of \TeX\ has been written under the assumption -that the \PASCAL\ compiler and run-time system permit the use of text files -with more than 64 distinguishable characters. More precisely, we assume that -the character set contains at least the letters and symbols associated -with ASCII codes @'40 through @'176; all of these characters are now -available on most computer terminals. - -Since we are dealing with more characters than were present in the first -\PASCAL\ compilers, we have to decide what to call the associated data -type. Some \PASCAL s use the original name |char| for the -characters in text files, even though there now are more than 64 such -characters, while other \PASCAL s consider |char| to be a 64-element -subrange of a larger data type that has some other name. - -In order to accommodate this difference, we shall use the name |text_char| -to stand for the data type of the characters that are converted to and -from |ASCII_code| when they are input and output. We shall also assume -that |text_char| consists of the elements |chr(first_text_char)| through -|chr(last_text_char)|, inclusive. The following definitions should be -adjusted if necessary. -@^system dependencies@> - -@d text_char == char {the data type of characters in text files} -@d first_text_char=0 {ordinal number of the smallest element of |text_char|} -@d last_text_char=255 {ordinal number of the largest element of |text_char|} - -@<Local variables for init...@>= -@!i:integer; - -@ The \TeX\ processor converts between ASCII code and -the user's external character set by means of arrays |xord| and |xchr| -that are analogous to \PASCAL's |ord| and |chr| functions. - -@<Glob...@>= -@!xord: array [text_char] of ASCII_code; - {specifies conversion of input characters} -@!xchr: array [ASCII_code] of text_char; - {specifies conversion of output characters} - -@ Since we are assuming that our \PASCAL\ system is able to read and -write the visible characters of standard ASCII (although not -necessarily using the ASCII codes to represent them), the following -assignment statements initialize the standard part of the |xchr| array -properly, without needing any system-dependent changes. On the other -hand, it is possible to implement \TeX\ with less complete character -sets, and in such cases it will be necessary to change something here. -@^system dependencies@> - -@<Set init...@>= -xchr[@'40]:=' '; -xchr[@'41]:='!'; -xchr[@'42]:='"'; -xchr[@'43]:='#'; -xchr[@'44]:='$'; -xchr[@'45]:='%'; -xchr[@'46]:='&'; -xchr[@'47]:='''';@/ -xchr[@'50]:='('; -xchr[@'51]:=')'; -xchr[@'52]:='*'; -xchr[@'53]:='+'; -xchr[@'54]:=','; -xchr[@'55]:='-'; -xchr[@'56]:='.'; -xchr[@'57]:='/';@/ -xchr[@'60]:='0'; -xchr[@'61]:='1'; -xchr[@'62]:='2'; -xchr[@'63]:='3'; -xchr[@'64]:='4'; -xchr[@'65]:='5'; -xchr[@'66]:='6'; -xchr[@'67]:='7';@/ -xchr[@'70]:='8'; -xchr[@'71]:='9'; -xchr[@'72]:=':'; -xchr[@'73]:=';'; -xchr[@'74]:='<'; -xchr[@'75]:='='; -xchr[@'76]:='>'; -xchr[@'77]:='?';@/ -xchr[@'100]:='@@'; -xchr[@'101]:='A'; -xchr[@'102]:='B'; -xchr[@'103]:='C'; -xchr[@'104]:='D'; -xchr[@'105]:='E'; -xchr[@'106]:='F'; -xchr[@'107]:='G';@/ -xchr[@'110]:='H'; -xchr[@'111]:='I'; -xchr[@'112]:='J'; -xchr[@'113]:='K'; -xchr[@'114]:='L'; -xchr[@'115]:='M'; -xchr[@'116]:='N'; -xchr[@'117]:='O';@/ -xchr[@'120]:='P'; -xchr[@'121]:='Q'; -xchr[@'122]:='R'; -xchr[@'123]:='S'; -xchr[@'124]:='T'; -xchr[@'125]:='U'; -xchr[@'126]:='V'; -xchr[@'127]:='W';@/ -xchr[@'130]:='X'; -xchr[@'131]:='Y'; -xchr[@'132]:='Z'; -xchr[@'133]:='['; -xchr[@'134]:='\'; -xchr[@'135]:=']'; -xchr[@'136]:='^'; -xchr[@'137]:='_';@/ -xchr[@'140]:='`'; -xchr[@'141]:='a'; -xchr[@'142]:='b'; -xchr[@'143]:='c'; -xchr[@'144]:='d'; -xchr[@'145]:='e'; -xchr[@'146]:='f'; -xchr[@'147]:='g';@/ -xchr[@'150]:='h'; -xchr[@'151]:='i'; -xchr[@'152]:='j'; -xchr[@'153]:='k'; -xchr[@'154]:='l'; -xchr[@'155]:='m'; -xchr[@'156]:='n'; -xchr[@'157]:='o';@/ -xchr[@'160]:='p'; -xchr[@'161]:='q'; -xchr[@'162]:='r'; -xchr[@'163]:='s'; -xchr[@'164]:='t'; -xchr[@'165]:='u'; -xchr[@'166]:='v'; -xchr[@'167]:='w';@/ -xchr[@'170]:='x'; -xchr[@'171]:='y'; -xchr[@'172]:='z'; -xchr[@'173]:='{'; -xchr[@'174]:='|'; -xchr[@'175]:='}'; -xchr[@'176]:='~';@/ - -@ Some of the ASCII codes without visible characters have been given symbolic -names in this program because they are used with a special meaning. - -@d null_code=@'0 {ASCII code that might disappear} -@d carriage_return=@'15 {ASCII code used at end of line} -@d invalid_code=@'177 {ASCII code that many systems prohibit in text files} - -@ The ASCII code is ``standard'' only to a certain extent, since many -computer installations have found it advantageous to have ready access -to more than 94 printing characters. Appendix~C of {\sl The \TeX book\/} -gives a complete specification of the intended correspondence between -characters and \TeX's internal representation. -@:TeXbook}{\sl The \TeX book@> - -If \TeX\ is being used -on a garden-variety \PASCAL\ for which only standard ASCII -codes will appear in the input and output files, it doesn't really matter -what codes are specified in |xchr[0..@'37]|, but the safest policy is to -blank everything out by using the code shown below. - -However, other settings of |xchr| will make \TeX\ more friendly on -computers that have an extended character set, so that users can type things -like `\.^^Z' instead of `\.{\\ne}'. People with extended character sets can -assign codes arbitrarily, giving an |xchr| equivalent to whatever -characters the users of \TeX\ are allowed to have in their input files. -It is best to make the codes correspond to the intended interpretations as -shown in Appendix~C whenever possible; but this is not necessary. For -example, in countries with an alphabet of more than 26 letters, it is -usually best to map the additional letters into codes less than~@'40. -To get the most ``permissive'' character set, change |' '| on the -right of these assignment statements to |chr(i)|. -@^character set dependencies@> -@^system dependencies@> - -@<Set init...@>= -for i:=0 to @'37 do xchr[i]:=' '; -for i:=@'177 to @'377 do xchr[i]:=' '; - -@ The following system-independent code makes the |xord| array contain a -suitable inverse to the information in |xchr|. Note that if |xchr[i]=xchr[j]| -where |i<j<@'177|, the value of |xord[xchr[i]]| will turn out to be -|j| or more; hence, standard ASCII code numbers will be used instead of -codes below @'40 in case there is a coincidence. - -@<Set init...@>= -for i:=first_text_char to last_text_char do xord[chr(i)]:=invalid_code; -for i:=@'200 to @'377 do xord[xchr[i]]:=i; -for i:=0 to @'176 do xord[xchr[i]]:=i; - -@* \[3] Input and output. -The bane of portability is the fact that different operating systems treat -input and output quite differently, perhaps because computer scientists -have not given sufficient attention to this problem. People have felt somehow -that input and output are not part of ``real'' programming. Well, it is true -that some kinds of programming are more fun than others. With existing -input/output conventions being so diverse and so messy, the only sources of -joy in such parts of the code are the rare occasions when one can find a -way to make the program a little less bad than it might have been. We have -two choices, either to attack I/O now and get it over with, or to postpone -I/O until near the end. Neither prospect is very attractive, so let's -get it over with. - -The basic operations we need to do are (1)~inputting and outputting of -text, to or from a file or the user's terminal; (2)~inputting and -outputting of eight-bit bytes, to or from a file; (3)~instructing the -operating system to initiate (``open'') or to terminate (``close'') input or -output from a specified file; (4)~testing whether the end of an input -file has been reached. - -\TeX\ needs to deal with two kinds of files. -We shall use the term |alpha_file| for a file that contains textual data, -and the term |byte_file| for a file that contains eight-bit binary information. -These two types turn out to be the same on many computers, but -sometimes there is a significant distinction, so we shall be careful to -distinguish between them. Standard protocols for transferring -such files from computer to computer, via high-speed networks, are -now becoming available to more and more communities of users. - -The program actually makes use also of a third kind of file, called a -|word_file|, when dumping and reloading base information for its own -initialization. We shall define a word file later; but it will be possible -for us to specify simple operations on word files before they are defined. - -@<Types...@>= -@!eight_bits=0..255; {unsigned one-byte quantity} -@!alpha_file=packed file of text_char; {files that contain textual data} -@!byte_file=packed file of eight_bits; {files that contain binary data} - -@ Most of what we need to do with respect to input and output can be handled -by the I/O facilities that are standard in \PASCAL, i.e., the routines -called |get|, |put|, |eof|, and so on. But -standard \PASCAL\ does not allow file variables to be associated with file -names that are determined at run time, so it cannot be used to implement -\TeX; some sort of extension to \PASCAL's ordinary |reset| and |rewrite| -is crucial for our purposes. We shall assume that |name_of_file| is a variable -of an appropriate type such that the \PASCAL\ run-time system being used to -implement \TeX\ can open a file whose external name is specified by -|name_of_file|. -@^system dependencies@> - -@<Glob...@>= -@!name_of_file:packed array[1..file_name_size] of char;@;@/ - {on some systems this may be a \&{record} variable} -@!name_length:0..file_name_size;@/{this many characters are actually - relevant in |name_of_file| (the rest are blank)} - -@ The \ph\ compiler with which the present version of \TeX\ was prepared has -extended the rules of \PASCAL\ in a very convenient way. To open file~|f|, -we can write -$$\vbox{\halign{#\hfil\qquad&#\hfil\cr -|reset(f,@t\\{name}@>,'/O')|&for input;\cr -|rewrite(f,@t\\{name}@>,'/O')|&for output.\cr}}$$ -The `\\{name}' parameter, which is of type `{\bf packed array -$[\langle\\{any}\rangle]$ of \\{char}}', stands for the name of -the external file that is being opened for input or output. -Blank spaces that might appear in \\{name} are ignored. - -The `\.{/O}' parameter tells the operating system not to issue its own -error messages if something goes wrong. If a file of the specified name -cannot be found, or if such a file cannot be opened for some other reason -(e.g., someone may already be trying to write the same file), we will have -|@!erstat(f)<>0| after an unsuccessful |reset| or |rewrite|. This allows -\TeX\ to undertake appropriate corrective action. -@:PASCAL H}{\ph@> -@^system dependencies@> - -\TeX's file-opening procedures return |false| if no file identified by -|name_of_file| could be opened. - -@d reset_OK(#)==erstat(#)=0 -@d rewrite_OK(#)==erstat(#)=0 - -@p function a_open_in(var f:alpha_file):boolean; - {open a text file for input} -begin reset(f,name_of_file,'/O'); a_open_in:=reset_OK(f); -end; -@# -function a_open_out(var f:alpha_file):boolean; - {open a text file for output} -begin rewrite(f,name_of_file,'/O'); a_open_out:=rewrite_OK(f); -end; -@# -function b_open_in(var f:byte_file):boolean; - {open a binary file for input} -begin reset(f,name_of_file,'/O'); b_open_in:=reset_OK(f); -end; -@# -function b_open_out(var f:byte_file):boolean; - {open a binary file for output} -begin rewrite(f,name_of_file,'/O'); b_open_out:=rewrite_OK(f); -end; -@# -function w_open_in(var f:word_file):boolean; - {open a word file for input} -begin reset(f,name_of_file,'/O'); w_open_in:=reset_OK(f); -end; -@# -function w_open_out(var f:word_file):boolean; - {open a word file for output} -begin rewrite(f,name_of_file,'/O'); w_open_out:=rewrite_OK(f); -end; - -@ Files can be closed with the \ph\ routine `|close(f)|', which -@:PASCAL H}{\ph@> -@^system dependencies@> -should be used when all input or output with respect to |f| has been completed. -This makes |f| available to be opened again, if desired; and if |f| was used for -output, the |close| operation makes the corresponding external file appear -on the user's area, ready to be read. - -These procedures should not generate error messages if a file is -being closed before it has been successfully opened. - -@p procedure a_close(var f:alpha_file); {close a text file} -begin close(f); -end; -@# -procedure b_close(var f:byte_file); {close a binary file} -begin close(f); -end; -@# -procedure w_close(var f:word_file); {close a word file} -begin close(f); -end; - -@ Binary input and output are done with \PASCAL's ordinary |get| and |put| -procedures, so we don't have to make any other special arrangements for -binary~I/O. Text output is also easy to do with standard \PASCAL\ routines. -The treatment of text input is more difficult, however, because -of the necessary translation to |ASCII_code| values. -\TeX's conventions should be efficient, and they should -blend nicely with the user's operating environment. - -@ Input from text files is read one line at a time, using a routine called -|input_ln|. This function is defined in terms of global variables called -|buffer|, |first|, and |last| that will be described in detail later; for -now, it suffices for us to know that |buffer| is an array of |ASCII_code| -values, and that |first| and |last| are indices into this array -representing the beginning and ending of a line of text. - -@<Glob...@>= -@!buffer:array[0..buf_size] of ASCII_code; {lines of characters being read} -@!first:0..buf_size; {the first unused position in |buffer|} -@!last:0..buf_size; {end of the line just input to |buffer|} -@!max_buf_stack:0..buf_size; {largest index used in |buffer|} - -@ The |input_ln| function brings the next line of input from the specified -file into available positions of the buffer array and returns the value -|true|, unless the file has already been entirely read, in which case it -returns |false| and sets |last:=first|. In general, the |ASCII_code| -numbers that represent the next line of the file are input into -|buffer[first]|, |buffer[first+1]|, \dots, |buffer[last-1]|; and the -global variable |last| is set equal to |first| plus the length of the -line. Trailing blanks are removed from the line; thus, either |last=first| -(in which case the line was entirely blank) or |buffer[last-1]<>" "|. - -An overflow error is given, however, if the normal actions of |input_ln| -would make |last>=buf_size|; this is done so that other parts of \TeX\ -can safely look at the contents of |buffer[last+1]| without overstepping -the bounds of the |buffer| array. Upon entry to |input_ln|, the condition -|first<buf_size| will always hold, so that there is always room for an -``empty'' line. - -The variable |max_buf_stack|, which is used to keep track of how large -the |buf_size| parameter must be to accommodate the present job, is -also kept up to date by |input_ln|. - -If the |bypass_eoln| parameter is |true|, |input_ln| will do a |get| -before looking at the first character of the line; this skips over -an |eoln| that was in |f^|. The procedure does not do a |get| when it -reaches the end of the line; therefore it can be used to acquire input -from the user's terminal as well as from ordinary text files. - -Standard \PASCAL\ says that a file should have |eoln| immediately -before |eof|, but \TeX\ needs only a weaker restriction: If |eof| -occurs in the middle of a line, the system function |eoln| should return -a |true| result (even though |f^| will be undefined). - -Since the inner loop of |input_ln| is part of \TeX's ``inner loop''---each -character of input comes in at this place---it is wise to reduce system -overhead by making use of special routines that read in an entire array -of characters at once, if such routines are available. The following -code uses standard \PASCAL\ to illustrate what needs to be done, but -finer tuning is often possible at well-developed \PASCAL\ sites. -@^inner loop@> - -@p function input_ln(var f:alpha_file;@!bypass_eoln:boolean):boolean; - {inputs the next line or returns |false|} -var last_nonblank:0..buf_size; {|last| with trailing blanks removed} -begin if bypass_eoln then if not eof(f) then get(f); - {input the first character of the line into |f^|} -last:=first; {cf.\ Matthew 19\thinspace:\thinspace30} -if eof(f) then input_ln:=false -else begin last_nonblank:=first; - while not eoln(f) do - begin if last>=max_buf_stack then - begin max_buf_stack:=last+1; - if max_buf_stack=buf_size then - @<Report overflow of the input buffer, and abort@>; - end; - buffer[last]:=xord[f^]; get(f); incr(last); - if buffer[last-1]<>" " then last_nonblank:=last; - end; - last:=last_nonblank; input_ln:=true; - end; -end; - -@ The user's terminal acts essentially like other files of text, except -that it is used both for input and for output. When the terminal is -considered an input file, the file variable is called |term_in|, and when it -is considered an output file the file variable is |term_out|. -@^system dependencies@> - -@<Glob...@>= -@!term_in:alpha_file; {the terminal as an input file} -@!term_out:alpha_file; {the terminal as an output file} - -@ Here is how to open the terminal files -in \ph. The `\.{/I}' switch suppresses the first |get|. -@:PASCAL H}{\ph@> -@^system dependencies@> - -@d t_open_in==reset(term_in,'TTY:','/O/I') {open the terminal for text input} -@d t_open_out==rewrite(term_out,'TTY:','/O') {open the terminal for text output} - -@ Sometimes it is necessary to synchronize the input/output mixture that -happens on the user's terminal, and three system-dependent -procedures are used for this -purpose. The first of these, |update_terminal|, is called when we want -to make sure that everything we have output to the terminal so far has -actually left the computer's internal buffers and been sent. -The second, |clear_terminal|, is called when we wish to cancel any -input that the user may have typed ahead (since we are about to -issue an unexpected error message). The third, |wake_up_terminal|, -is supposed to revive the terminal if the user has disabled it by -some instruction to the operating system. The following macros show how -these operations can be specified in \ph: -@:PASCAL H}{\ph@> -@^system dependencies@> - -@d update_terminal == break(term_out) {empty the terminal output buffer} -@d clear_terminal == break_in(term_in,true) {clear the terminal input buffer} -@d wake_up_terminal == do_nothing {cancel the user's cancellation of output} - -@ We need a special routine to read the first line of \TeX\ input from -the user's terminal. This line is different because it is read before we -have opened the transcript file; there is sort of a ``chicken and -egg'' problem here. If the user types `\.{\\input paper}' on the first -line, or if some macro invoked by that line does such an \.{\\input}, -the transcript file will be named `\.{paper.log}'; but if no \.{\\input} -commands are performed during the first line of terminal input, the transcript -file will acquire its default name `\.{texput.log}'. (The transcript file -will not contain error messages generated by the first line before the -first \.{\\input} command.) -@.texput@> - -The first line is even more special if we are lucky enough to have an operating -system that treats \TeX\ differently from a run-of-the-mill \PASCAL\ object -program. It's nice to let the user start running a \TeX\ job by typing -a command line like `\.{tex paper}'; in such a case, \TeX\ will operate -as if the first line of input were `\.{paper}', i.e., the first line will -consist of the remainder of the command line, after the part that invoked -\TeX. - -The first line is special also because it may be read before \TeX\ has -input a format file. In such cases, normal error messages cannot yet -be given. The following code uses concepts that will be explained later. -(If the \PASCAL\ compiler does not support non-local |@!goto|\unskip, the -@^system dependencies@> -statement `|goto final_end|' should be replaced by something that -quietly terminates the program.) - -@<Report overflow of the input buffer, and abort@>= -if format_ident=0 then - begin write_ln(term_out,'Buffer size exceeded!'); goto final_end; -@.Buffer size exceeded@> - end -else begin cur_input.loc_field:=first; cur_input.limit_field:=last-1; - overflow("buffer size",buf_size); -@:TeX capacity exceeded buffer size}{\quad buffer size@> - end - -@ Different systems have different ways to get started. But regardless of -what conventions are adopted, the routine that initializes the terminal -should satisfy the following specifications: - -\yskip\textindent{1)}It should open file |term_in| for input from the - terminal. (The file |term_out| will already be open for output to the - terminal.) - -\textindent{2)}If the user has given a command line, this line should be - considered the first line of terminal input. Otherwise the - user should be prompted with `\.{**}', and the first line of input - should be whatever is typed in response. - -\textindent{3)}The first line of input, which might or might not be a - command line, should appear in locations |first| to |last-1| of the - |buffer| array. - -\textindent{4)}The global variable |loc| should be set so that the - character to be read next by \TeX\ is in |buffer[loc]|. This - character should not be blank, and we should have |loc<last|. - -\yskip\noindent(It may be necessary to prompt the user several times -before a non-blank line comes in. The prompt is `\.{**}' instead of the -later `\.*' because the meaning is slightly different: `\.{\\input}' need -not be typed immediately after~`\.{**}'.) - -@d loc==cur_input.loc_field {location of first unread character in |buffer|} - -@ The following program does the required initialization -without retrieving a possible command line. -It should be clear how to modify this routine to deal with command lines, -if the system permits them. -@^system dependencies@> - -@p function init_terminal:boolean; {gets the terminal input started} -label exit; -begin t_open_in; -loop@+begin wake_up_terminal; write(term_out,'**'); update_terminal; -@.**@> - if not input_ln(term_in,true) then {this shouldn't happen} - begin write_ln(term_out); - write(term_out,'! End of file on the terminal... why?'); -@.End of file on the terminal@> - init_terminal:=false; return; - end; - loc:=first; - while (loc<last)and(buffer[loc]=" ") do incr(loc); - if loc<last then - begin init_terminal:=true; - return; {return unless the line was all blank} - end; - write_ln(term_out,'Please type the name of your input file.'); - end; -exit:end; - -@* \[4] String handling. -Control sequence names and diagnostic messages are variable-length strings -of eight-bit characters. Since \PASCAL\ does not have a well-developed string -mechanism, \TeX\ does all of its string processing by homegrown methods. - -Elaborate facilities for dynamic strings are not needed, so all of the -necessary operations can be handled with a simple data structure. -The array |str_pool| contains all of the (eight-bit) ASCII codes in all -of the strings, and the array |str_start| contains indices of the starting -points of each string. Strings are referred to by integer numbers, so that -string number |s| comprises the characters |str_pool[j]| for -|str_start[s]<=j<str_start[s+1]|. Additional integer variables -|pool_ptr| and |str_ptr| indicate the number of entries used so far -in |str_pool| and |str_start|, respectively; locations -|str_pool[pool_ptr]| and |str_start[str_ptr]| are -ready for the next string to be allocated. - -String numbers 0 to 255 are reserved for strings that correspond to single -ASCII characters. This is in accordance with the conventions of \.{WEB}, -@.WEB@> -which converts single-character strings into the ASCII code number of the -single character involved, while it converts other strings into integers -and builds a string pool file. Thus, when the string constant \.{"."} appears -in the program below, \.{WEB} converts it into the integer 46, which is the -ASCII code for a period, while \.{WEB} will convert a string like \.{"hello"} -into some integer greater than~255. String number 46 will presumably be the -single character `\..'; but some ASCII codes have no standard visible -representation, and \TeX\ sometimes needs to be able to print an arbitrary -ASCII character, so the first 256 strings are used to specify exactly what -should be printed for each of the 256 possibilities. - -Elements of the |str_pool| array must be ASCII codes that can actually -be printed; i.e., they must have an |xchr| equivalent in the local -character set. (This restriction applies only to preloaded strings, -not to those generated dynamically by the user.) - -Some \PASCAL\ compilers won't pack integers into a single byte unless the -integers lie in the range |-128..127|. To accommodate such systems -we access the string pool only via macros that can easily be redefined. -@^system dependencies@> - -@d si(#) == # {convert from |ASCII_code| to |packed_ASCII_code|} -@d so(#) == # {convert from |packed_ASCII_code| to |ASCII_code|} - -@<Types...@>= -@!pool_pointer = 0..pool_size; {for variables that point into |str_pool|} -@!str_number = 0..max_strings; {for variables that point into |str_start|} -@!packed_ASCII_code = 0..255; {elements of |str_pool| array} - -@ @<Glob...@>= -@!str_pool:packed array[pool_pointer] of packed_ASCII_code; {the characters} -@!str_start : array[str_number] of pool_pointer; {the starting pointers} -@!pool_ptr : pool_pointer; {first unused position in |str_pool|} -@!str_ptr : str_number; {number of the current string being created} -@!init_pool_ptr : pool_pointer; {the starting value of |pool_ptr|} -@!init_str_ptr : str_number; {the starting value of |str_ptr|} - -@ Several of the elementary string operations are performed using \.{WEB} -macros instead of \PASCAL\ procedures, because many of the -operations are done quite frequently and we want to avoid the -overhead of procedure calls. For example, here is -a simple macro that computes the length of a string. -@.WEB@> - -@d length(#)==(str_start[#+1]-str_start[#]) {the number of characters - in string number \#} - -@ The length of the current string is called |cur_length|: - -@d cur_length == (pool_ptr - str_start[str_ptr]) - -@ Strings are created by appending character codes to |str_pool|. -The |append_char| macro, defined here, does not check to see if the -value of |pool_ptr| has gotten too high; this test is supposed to be -made before |append_char| is used. There is also a |flush_char| -macro, which erases the last character appended. - -To test if there is room to append |l| more characters to |str_pool|, -we shall write |str_room(l)|, which aborts \TeX\ and gives an -apologetic error message if there isn't enough room. - -@d append_char(#) == {put |ASCII_code| \# at the end of |str_pool|} -begin str_pool[pool_ptr]:=si(#); incr(pool_ptr); -end -@d flush_char == decr(pool_ptr) {forget the last character in the pool} -@d str_room(#) == {make sure that the pool hasn't overflowed} - begin if pool_ptr+# > pool_size then - overflow("pool size",pool_size-init_pool_ptr); -@:TeX capacity exceeded pool size}{\quad pool size@> - end - -@ Once a sequence of characters has been appended to |str_pool|, it -officially becomes a string when the function |make_string| is called. -This function returns the identification number of the new string as its -value. - -@p function make_string : str_number; {current string enters the pool} -begin if str_ptr=max_strings then - overflow("number of strings",max_strings-init_str_ptr); -@:TeX capacity exceeded number of strings}{\quad number of strings@> -incr(str_ptr); str_start[str_ptr]:=pool_ptr; -make_string:=str_ptr-1; -end; - -@ To destroy the most recently made string, we say |flush_string|. - -@d flush_string==begin decr(str_ptr); pool_ptr:=str_start[str_ptr]; - end - -@ The following subroutine compares string |s| with another string of the -same length that appears in |buffer| starting at position |k|; -the result is |true| if and only if the strings are equal. -Empirical tests indicate that |str_eq_buf| is used in such a way that -it tends to return |true| about 80 percent of the time. - -@p function str_eq_buf(@!s:str_number;@!k:integer):boolean; - {test equality of strings} -label not_found; {loop exit} -var j: pool_pointer; {running index} -@!result: boolean; {result of comparison} -begin j:=str_start[s]; -while j<str_start[s+1] do - begin if so(str_pool[j])<>buffer[k] then - begin result:=false; goto not_found; - end; - incr(j); incr(k); - end; -result:=true; -not_found: str_eq_buf:=result; -end; - -@ Here is a similar routine, but it compares two strings in the string pool, -and it does not assume that they have the same length. - -@p function str_eq_str(@!s,@!t:str_number):boolean; - {test equality of strings} -label not_found; {loop exit} -var j,@!k: pool_pointer; {running indices} -@!result: boolean; {result of comparison} -begin result:=false; -if length(s)<>length(t) then goto not_found; -j:=str_start[s]; k:=str_start[t]; -while j<str_start[s+1] do - begin if str_pool[j]<>str_pool[k] then goto not_found; - incr(j); incr(k); - end; -result:=true; -not_found: str_eq_str:=result; -end; - -@ The initial values of |str_pool|, |str_start|, |pool_ptr|, -and |str_ptr| are computed by the \.{INITEX} program, based in part -on the information that \.{WEB} has output while processing \TeX. -@.INITEX@> -@^string pool@> - -@p @!init function get_strings_started:boolean; {initializes the string pool, - but returns |false| if something goes wrong} -label done,exit; -var k,@!l:0..255; {small indices or counters} -@!m,@!n:text_char; {characters input from |pool_file|} -@!g:str_number; {garbage} -@!a:integer; {accumulator for check sum} -@!c:boolean; {check sum has been checked} -begin pool_ptr:=0; str_ptr:=0; str_start[0]:=0; -@<Make the first 256 strings@>; -@<Read the other strings from the \.{TEX.POOL} file and return |true|, - or give an error message and return |false|@>; -exit:end; -tini - -@ @d app_lc_hex(#)==l:=#; - if l<10 then append_char(l+"0")@+else append_char(l-10+"a") - -@<Make the first 256...@>= -for k:=0 to 255 do - begin if (@<Character |k| cannot be printed@>) then - begin append_char("^"); append_char("^"); - if k<@'100 then append_char(k+@'100) - else if k<@'200 then append_char(k-@'100) - else begin app_lc_hex(k div 16); app_lc_hex(k mod 16); - end; - end - else append_char(k); - g:=make_string; - end - -@ The first 128 strings will contain 95 standard ASCII characters, and the -other 33 characters will be printed in three-symbol form like `\.{\^\^A}' -unless a system-dependent change is made here. Installations that have -an extended character set, where for example |xchr[@'32]=@t\.{\'^^Z\'}@>|, -would like string @'32 to be the single character @'32 instead of the -three characters @'136, @'136, @'132 (\.{\^\^Z}). On the other hand, -even people with an extended character set will want to represent string -@'15 by \.{\^\^M}, since @'15 is |carriage_return|; the idea is to -produce visible strings instead of tabs or line-feeds or carriage-returns -or bell-rings or characters that are treated anomalously in text files. - -Unprintable characters of codes 128--255 are, similarly, rendered -\.{\^\^80}--\.{\^\^ff}. - -The boolean expression defined here should be |true| unless \TeX\ -internal code number~|k| corresponds to a non-troublesome visible -symbol in the local character set. An appropriate formula for the -extended character set recommended in {\sl The \TeX book\/} would, for -example, be `|k in [0,@'10..@'12,@'14,@'15,@'33,@'177..@'377]|'. -If character |k| cannot be printed, and |k<@'200|, then character |k+@'100| or -|k-@'100| must be printable; moreover, ASCII codes |[@'41..@'46, -@'60..@'71, @'136, @'141..@'146, @'160..@'171]| must be printable. -Thus, at least 80 printable characters are needed. -@:TeXbook}{\sl The \TeX book@> -@^character set dependencies@> -@^system dependencies@> - -@<Character |k| cannot be printed@>= - (k<" ")or(k>"~") - -@ When the \.{WEB} system program called \.{TANGLE} processes the \.{TEX.WEB} -description that you are now reading, it outputs the \PASCAL\ program -\.{TEX.PAS} and also a string pool file called \.{TEX.POOL}. The \.{INITEX} -@.WEB@>@.INITEX@> -program reads the latter file, where each string appears as a two-digit decimal -length followed by the string itself, and the information is recorded in -\TeX's string memory. - -@<Glob...@>= -@!init @!pool_file:alpha_file; {the string-pool file output by \.{TANGLE}} -tini - -@ @d bad_pool(#)==begin wake_up_terminal; write_ln(term_out,#); - a_close(pool_file); get_strings_started:=false; return; - end -@<Read the other strings...@>= -name_of_file:=pool_name; {we needn't set |name_length|} -if a_open_in(pool_file) then - begin c:=false; - repeat @<Read one string, but return |false| if the - string memory space is getting too tight for comfort@>; - until c; - a_close(pool_file); get_strings_started:=true; - end -else bad_pool('! I can''t read TEX.POOL.') -@.I can't read TEX.POOL@> - -@ @<Read one string...@>= -begin if eof(pool_file) then bad_pool('! TEX.POOL has no check sum.'); -@.TEX.POOL has no check sum@> -read(pool_file,m,n); {read two digits of string length} -if m='*' then @<Check the pool check sum@> -else begin if (xord[m]<"0")or(xord[m]>"9")or@| - (xord[n]<"0")or(xord[n]>"9") then - bad_pool('! TEX.POOL line doesn''t begin with two digits.'); -@.TEX.POOL line doesn't...@> - l:=xord[m]*10+xord[n]-"0"*11; {compute the length} - if pool_ptr+l+string_vacancies>pool_size then - bad_pool('! You have to increase POOLSIZE.'); -@.You have to increase POOLSIZE@> - for k:=1 to l do - begin if eoln(pool_file) then m:=' '@+else read(pool_file,m); - append_char(xord[m]); - end; - read_ln(pool_file); g:=make_string; - end; -end - -@ The \.{WEB} operation \.{@@\$} denotes the value that should be at the -end of this \.{TEX.POOL} file; any other value means that the wrong pool -file has been loaded. -@^check sum@> - -@<Check the pool check sum@>= -begin a:=0; k:=1; -loop@+ begin if (xord[n]<"0")or(xord[n]>"9") then - bad_pool('! TEX.POOL check sum doesn''t have nine digits.'); -@.TEX.POOL check sum...@> - a:=10*a+xord[n]-"0"; - if k=9 then goto done; - incr(k); read(pool_file,n); - end; -done: if a<>@$ then bad_pool('! TEX.POOL doesn''t match; TANGLE me again.'); -@.TEX.POOL doesn't match@> -c:=true; -end - -@* \[5] On-line and off-line printing. -Messages that are sent to a user's terminal and to the transcript-log file -are produced by several `|print|' procedures. These procedures will -direct their output to a variety of places, based on the setting of -the global variable |selector|, which has the following possible -values: - -\yskip -\hang |term_and_log|, the normal setting, prints on the terminal and on the - transcript file. - -\hang |log_only|, prints only on the transcript file. - -\hang |term_only|, prints only on the terminal. - -\hang |no_print|, doesn't print at all. This is used only in rare cases - before the transcript file is open. - -\hang |pseudo|, puts output into a cyclic buffer that is used - by the |show_context| routine; when we get to that routine we shall discuss - the reasoning behind this curious mode. - -\hang |new_string|, appends the output to the current string in the - string pool. - -\hang 0 to 15, prints on one of the sixteen files for \.{\\write} output. - -\yskip -\noindent The symbolic names `|term_and_log|', etc., have been assigned -numeric codes that satisfy the convenient relations |no_print+1=term_only|, -|no_print+2=log_only|, |term_only+2=log_only+1=term_and_log|. - -Three additional global variables, |tally| and |term_offset| and -|file_offset|, record the number of characters that have been printed -since they were most recently cleared to zero. We use |tally| to record -the length of (possibly very long) stretches of printing; |term_offset| -and |file_offset|, on the other hand, keep track of how many characters -have appeared so far on the current line that has been output to the -terminal or to the transcript file, respectively. - -@d no_print=16 {|selector| setting that makes data disappear} -@d term_only=17 {printing is destined for the terminal only} -@d log_only=18 {printing is destined for the transcript file only} -@d term_and_log=19 {normal |selector| setting} -@d pseudo=20 {special |selector| setting for |show_context|} -@d new_string=21 {printing is deflected to the string pool} -@d max_selector=21 {highest selector setting} - -@<Glob...@>= -@!log_file : alpha_file; {transcript of \TeX\ session} -@!selector : 0..max_selector; {where to print a message} -@!dig : array[0..22] of 0..15; {digits in a number being output} -@!tally : integer; {the number of characters recently printed} -@!term_offset : 0..max_print_line; - {the number of characters on the current terminal line} -@!file_offset : 0..max_print_line; - {the number of characters on the current file line} -@!trick_buf:array[0..error_line] of ASCII_code; {circular buffer for - pseudoprinting} -@!trick_count: integer; {threshold for pseudoprinting, explained later} -@!first_count: integer; {another variable for pseudoprinting} - -@ @<Initialize the output routines@>= -selector:=term_only; tally:=0; term_offset:=0; file_offset:=0; - -@ Macro abbreviations for output to the terminal and to the log file are -defined here for convenience. Some systems need special conventions -for terminal output, and it is possible to adhere to those conventions -by changing |wterm|, |wterm_ln|, and |wterm_cr| in this section. -@^system dependencies@> - -@d wterm(#)==write(term_out,#) -@d wterm_ln(#)==write_ln(term_out,#) -@d wterm_cr==write_ln(term_out) -@d wlog(#)==write(log_file,#) -@d wlog_ln(#)==write_ln(log_file,#) -@d wlog_cr==write_ln(log_file) - -@ To end a line of text output, we call |print_ln|. - -@<Basic print...@>= -procedure print_ln; {prints an end-of-line} -begin case selector of -term_and_log: begin wterm_cr; wlog_cr; - term_offset:=0; file_offset:=0; - end; -log_only: begin wlog_cr; file_offset:=0; - end; -term_only: begin wterm_cr; term_offset:=0; - end; -no_print,pseudo,new_string: do_nothing; -othercases write_ln(write_file[selector]) -endcases;@/ -end; {|tally| is not affected} - -@ The |print_char| procedure sends one character to the desired destination, -using the |xchr| array to map it into an external character compatible with -|input_ln|. All printing comes through |print_ln| or |print_char|. - -@<Basic printing...@>= -procedure print_char(@!s:ASCII_code); {prints a single character} -label exit; -begin if @<Character |s| is the current new-line character@> then - if selector<pseudo then - begin print_ln; return; - end; -case selector of -term_and_log: begin wterm(xchr[s]); wlog(xchr[s]); - incr(term_offset); incr(file_offset); - if term_offset=max_print_line then - begin wterm_cr; term_offset:=0; - end; - if file_offset=max_print_line then - begin wlog_cr; file_offset:=0; - end; - end; -log_only: begin wlog(xchr[s]); incr(file_offset); - if file_offset=max_print_line then print_ln; - end; -term_only: begin wterm(xchr[s]); incr(term_offset); - if term_offset=max_print_line then print_ln; - end; -no_print: do_nothing; -pseudo: if tally<trick_count then trick_buf[tally mod error_line]:=s; -new_string: begin if pool_ptr<pool_size then append_char(s); - end; {we drop characters if the string space is full} -othercases write(write_file[selector],xchr[s]) -endcases;@/ -incr(tally); -exit:end; - -@ An entire string is output by calling |print|. Note that if we are outputting -the single standard ASCII character \.c, we could call |print("c")|, since -|"c"=99| is the number of a single-character string, as explained above. But -|print_char("c")| is quicker, so \TeX\ goes directly to the |print_char| -routine when it knows that this is safe. (The present implementation -assumes that it is always safe to print a visible ASCII character.) -@^system dependencies@> - -@<Basic print...@>= -procedure print(@!s:integer); {prints string |s|} -label exit; -var j:pool_pointer; {current character code position} -@!nl:integer; {new-line character to restore} -begin if s>=str_ptr then s:="???" {this can't happen} -@.???@> -else if s<256 then - if s<0 then s:="???" {can't happen} - else begin if selector>pseudo then - begin print_char(s); return; {internal strings are not expanded} - end; - if (@<Character |s| is the current new-line character@>) then - if selector<pseudo then - begin print_ln; return; - end; - nl:=new_line_char; new_line_char:=-1; - {temporarily disable new-line character} - j:=str_start[s]; - while j<str_start[s+1] do - begin print_char(so(str_pool[j])); incr(j); - end; - new_line_char:=nl; return; - end; -j:=str_start[s]; -while j<str_start[s+1] do - begin print_char(so(str_pool[j])); incr(j); - end; -exit:end; - -@ Control sequence names, file names, and strings constructed with -\.{\\string} might contain |ASCII_code| values that can't -be printed using |print_char|. Therefore we use |slow_print| for them: - -@<Basic print...@>= -procedure slow_print(@!s:integer); {prints string |s|} -var j:pool_pointer; {current character code position} -begin if (s>=str_ptr) or (s<256) then print(s) -else begin j:=str_start[s]; - while j<str_start[s+1] do - begin print(so(str_pool[j])); incr(j); - end; - end; -end; - -@ Here is the very first thing that \TeX\ prints: a headline that identifies -the version number and format package. The |term_offset| variable is temporarily -incorrect, but the discrepancy is not serious since we assume that this -part of the program is system dependent. -@^system dependencies@> - -@<Initialize the output...@>= -wterm(banner); -if format_ident=0 then wterm_ln(' (no format preloaded)') -else begin slow_print(format_ident); print_ln; - end; -update_terminal; - -@ The procedure |print_nl| is like |print|, but it makes sure that the -string appears at the beginning of a new line. - -@<Basic print...@>= -procedure print_nl(@!s:str_number); {prints string |s| at beginning of line} -begin if ((term_offset>0)and(odd(selector)))or@| - ((file_offset>0)and(selector>=log_only)) then print_ln; -print(s); -end; - -@ The procedure |print_esc| prints a string that is preceded by -the user's escape character (which is usually a backslash). - -@<Basic print...@>= -procedure print_esc(@!s:str_number); {prints escape character, then |s|} -var c:integer; {the escape character code} -begin @<Set variable |c| to the current escape character@>; -if c>=0 then if c<256 then print(c); -slow_print(s); -end; - -@ An array of digits in the range |0..15| is printed by |print_the_digs|. - -@<Basic print...@>= -procedure print_the_digs(@!k:eight_bits); - {prints |dig[k-1]|$\,\ldots\,$|dig[0]|} -begin while k>0 do - begin decr(k); - if dig[k]<10 then print_char("0"+dig[k]) - else print_char("A"-10+dig[k]); - end; -end; - -@ The following procedure, which prints out the decimal representation of a -given integer |n|, has been written carefully so that it works properly -if |n=0| or if |(-n)| would cause overflow. It does not apply |mod| or |div| -to negative arguments, since such operations are not implemented consistently -by all \PASCAL\ compilers. - -@<Basic print...@>= -procedure print_int(@!n:integer); {prints an integer in decimal form} -var k:0..23; {index to current digit; we assume that $\vert n\vert<10^{23}$} -@!m:integer; {used to negate |n| in possibly dangerous cases} -begin k:=0; -if n<0 then - begin print_char("-"); - if n>-100000000 then negate(n) - else begin m:=-1-n; n:=m div 10; m:=(m mod 10)+1; k:=1; - if m<10 then dig[0]:=m - else begin dig[0]:=0; incr(n); - end; - end; - end; -repeat dig[k]:=n mod 10; n:=n div 10; incr(k); -until n=0; -print_the_digs(k); -end; - -@ Here is a trivial procedure to print two digits; it is usually called with -a parameter in the range |0<=n<=99|. - -@p procedure print_two(@!n:integer); {prints two least significant digits} -begin n:=abs(n) mod 100; print_char("0"+(n div 10)); -print_char("0"+(n mod 10)); -end; - -@ Hexadecimal printing of nonnegative integers is accomplished by |print_hex|. - -@p procedure print_hex(@!n:integer); - {prints a positive integer in hexadecimal form} -var k:0..22; {index to current digit; we assume that $0\L n<16^{22}$} -begin k:=0; print_char(""""); -repeat dig[k]:=n mod 16; n:=n div 16; incr(k); -until n=0; -print_the_digs(k); -end; - -@ Old versions of \TeX\ needed a procedure called |print_ASCII| whose function -is now subsumed by |print|. We retain the old name here as a possible aid to -future software arch\ae ologists. - -@d print_ASCII == print - -@ Roman numerals are produced by the |print_roman_int| routine. Readers -who like puzzles might enjoy trying to figure out how this tricky code -works; therefore no explanation will be given. Notice that 1990 yields -\.{mcmxc}, not \.{mxm}. - -@p procedure print_roman_int(@!n:integer); -label exit; -var j,@!k: pool_pointer; {mysterious indices into |str_pool|} -@!u,@!v: nonnegative_integer; {mysterious numbers} -begin j:=str_start["m2d5c2l5x2v5i"]; v:=1000; -loop@+ begin while n>=v do - begin print_char(so(str_pool[j])); n:=n-v; - end; - if n<=0 then return; {nonpositive input produces no output} - k:=j+2; u:=v div (so(str_pool[k-1])-"0"); - if str_pool[k-1]=si("2") then - begin k:=k+2; u:=u div (so(str_pool[k-1])-"0"); - end; - if n+u>=v then - begin print_char(so(str_pool[k])); n:=n+u; - end - else begin j:=j+2; v:=v div (so(str_pool[j-1])-"0"); - end; - end; -exit:end; - -@ The |print| subroutine will not print a string that is still being -created. The following procedure will. - -@p procedure print_current_string; {prints a yet-unmade string} -var j:pool_pointer; {points to current character code} -begin j:=str_start[str_ptr]; -while j<pool_ptr do - begin print_char(so(str_pool[j])); incr(j); - end; -end; - -@ Here is a procedure that asks the user to type a line of input, -assuming that the |selector| setting is either |term_only| or |term_and_log|. -The input is placed into locations |first| through |last-1| of the -|buffer| array, and echoed on the transcript file if appropriate. - -This procedure is never called when |interaction<scroll_mode|. - -@d prompt_input(#)==begin wake_up_terminal; print(#); term_input; - end {prints a string and gets a line of input} - -@p procedure term_input; {gets a line from the terminal} -var k:0..buf_size; {index into |buffer|} -begin update_terminal; {now the user sees the prompt for sure} -if not input_ln(term_in,true) then fatal_error("End of file on the terminal!"); -@.End of file on the terminal@> -term_offset:=0; {the user's line ended with \<\rm return>} -decr(selector); {prepare to echo the input} -if last<>first then for k:=first to last-1 do print(buffer[k]); -print_ln; incr(selector); {restore previous status} -end; - -@* \[6] Reporting errors. -When something anomalous is detected, \TeX\ typically does something like this: -$$\vbox{\halign{#\hfil\cr -|print_err("Something anomalous has been detected");|\cr -|help3("This is the first line of my offer to help.")|\cr -|("This is the second line. I'm trying to")|\cr -|("explain the best way for you to proceed.");|\cr -|error;|\cr}}$$ -A two-line help message would be given using |help2|, etc.; these informal -helps should use simple vocabulary that complements the words used in the -official error message that was printed. (Outside the U.S.A., the help -messages should preferably be translated into the local vernacular. Each -line of help is at most 60 characters long, in the present implementation, -so that |max_print_line| will not be exceeded.) - -The |print_err| procedure supplies a `\.!' before the official message, -and makes sure that the terminal is awake if a stop is going to occur. -The |error| procedure supplies a `\..' after the official message, then it -shows the location of the error; and if |interaction=error_stop_mode|, -it also enters into a dialog with the user, during which time the help -message may be printed. -@^system dependencies@> - -@ The global variable |interaction| has four settings, representing increasing -amounts of user interaction: - -@d batch_mode=0 {omits all stops and omits terminal output} -@d nonstop_mode=1 {omits all stops} -@d scroll_mode=2 {omits error stops} -@d error_stop_mode=3 {stops at every opportunity to interact} -@d print_err(#)==begin if interaction=error_stop_mode then wake_up_terminal; - print_nl("! "); print(#); - end - -@<Glob...@>= -@!interaction:batch_mode..error_stop_mode; {current level of interaction} - -@ @<Set init...@>=interaction:=error_stop_mode; - -@ \TeX\ is careful not to call |error| when the print |selector| setting -might be unusual. The only possible values of |selector| at the time of -error messages are - -\yskip\hang|no_print| (when |interaction=batch_mode| - and |log_file| not yet open); - -\hang|term_only| (when |interaction>batch_mode| and |log_file| not yet open); - -\hang|log_only| (when |interaction=batch_mode| and |log_file| is open); - -\hang|term_and_log| (when |interaction>batch_mode| and |log_file| is open). - -@<Initialize the print |selector| based on |interaction|@>= -if interaction=batch_mode then selector:=no_print@+else selector:=term_only - -@ A global variable |deletions_allowed| is set |false| if the |get_next| -routine is active when |error| is called; this ensures that |get_next| -and related routines like |get_token| will never be called recursively. -A similar interlock is provided by |set_box_allowed|. -@^recursion@> - -The global variable |history| records the worst level of error that -has been detected. It has four possible values: |spotless|, |warning_issued|, -|error_message_issued|, and |fatal_error_stop|. - -Another global variable, |error_count|, is increased by one when an -|error| occurs without an interactive dialog, and it is reset to zero at -the end of every paragraph. If |error_count| reaches 100, \TeX\ decides -that there is no point in continuing further. - -@d spotless=0 {|history| value when nothing has been amiss yet} -@d warning_issued=1 {|history| value when |begin_diagnostic| has been called} -@d error_message_issued=2 {|history| value when |error| has been called} -@d fatal_error_stop=3 {|history| value when termination was premature} - -@<Glob...@>= -@!deletions_allowed:boolean; {is it safe for |error| to call |get_token|?} -@!set_box_allowed:boolean; {is it safe to do a \.{\\setbox} assignment?} -@!history:spotless..fatal_error_stop; {has the source input been clean so far?} -@!error_count:-1..100; {the number of scrolled errors since the - last paragraph ended} - -@ The value of |history| is initially |fatal_error_stop|, but it will -be changed to |spotless| if \TeX\ survives the initialization process. - -@<Set init...@>= -deletions_allowed:=true; set_box_allowed:=true; -error_count:=0; {|history| is initialized elsewhere} - -@ Since errors can be detected almost anywhere in \TeX, we want to declare the -error procedures near the beginning of the program. But the error procedures -in turn use some other procedures, which need to be declared |forward| -before we get to |error| itself. - -It is possible for |error| to be called recursively if some error arises -when |get_token| is being used to delete a token, and/or if some fatal error -occurs while \TeX\ is trying to fix a non-fatal one. But such recursion -@^recursion@> -is never more than two levels deep. - -@<Error handling...@>= -procedure@?normalize_selector; forward;@t\2@>@/ -procedure@?get_token; forward;@t\2@>@/ -procedure@?term_input; forward;@t\2@>@/ -procedure@?show_context; forward;@t\2@>@/ -procedure@?begin_file_reading; forward;@t\2@>@/ -procedure@?open_log_file; forward;@t\2@>@/ -procedure@?close_files_and_terminate; forward;@t\2@>@/ -procedure@?clear_for_error_prompt; forward;@t\2@>@/ -procedure@?give_err_help; forward;@t\2@>@/ -@t\4\hskip-\fontdimen2\font@>@;@+@!debug@+procedure@?debug_help; - forward;@;@+gubed - -@ Individual lines of help are recorded in the array |help_line|, which -contains entries in positions |0..(help_ptr-1)|. They should be printed -in reverse order, i.e., with |help_line[0]| appearing last. - -@d hlp1(#)==help_line[0]:=#;@+end -@d hlp2(#)==help_line[1]:=#; hlp1 -@d hlp3(#)==help_line[2]:=#; hlp2 -@d hlp4(#)==help_line[3]:=#; hlp3 -@d hlp5(#)==help_line[4]:=#; hlp4 -@d hlp6(#)==help_line[5]:=#; hlp5 -@d help0==help_ptr:=0 {sometimes there might be no help} -@d help1==@+begin help_ptr:=1; hlp1 {use this with one help line} -@d help2==@+begin help_ptr:=2; hlp2 {use this with two help lines} -@d help3==@+begin help_ptr:=3; hlp3 {use this with three help lines} -@d help4==@+begin help_ptr:=4; hlp4 {use this with four help lines} -@d help5==@+begin help_ptr:=5; hlp5 {use this with five help lines} -@d help6==@+begin help_ptr:=6; hlp6 {use this with six help lines} - -@<Glob...@>= -@!help_line:array[0..5] of str_number; {helps for the next |error|} -@!help_ptr:0..6; {the number of help lines present} -@!use_err_help:boolean; {should the |err_help| list be shown?} - -@ @<Set init...@>= -help_ptr:=0; use_err_help:=false; - -@ The |jump_out| procedure just cuts across all active procedure levels and -goes to |end_of_TEX|. This is the only nontrivial |@!goto| statement in the -whole program. It is used when there is no recovery from a particular error. - -Some \PASCAL\ compilers do not implement non-local |goto| statements. -@^system dependencies@> -In such cases the body of |jump_out| should simply be -`|close_files_and_terminate|;\thinspace' followed by a call on some system -procedure that quietly terminates the program. - -@<Error hand...@>= -procedure jump_out; -begin goto end_of_TEX; -end; - -@ Here now is the general |error| routine. - -@<Error hand...@>= -procedure error; {completes the job of error reporting} -label continue,exit; -var c:ASCII_code; {what the user types} -@!s1,@!s2,@!s3,@!s4:integer; - {used to save global variables when deleting tokens} -begin if history<error_message_issued then history:=error_message_issued; -print_char("."); show_context; -if interaction=error_stop_mode then - @<Get user's advice and |return|@>; -incr(error_count); -if error_count=100 then - begin print_nl("(That makes 100 errors; please try again.)"); -@.That makes 100 errors...@> - history:=fatal_error_stop; jump_out; - end; -@<Put help message on the transcript file@>; -exit:end; - -@ @<Get user's advice...@>= -loop@+begin continue: if interaction<>error_stop_mode then return; - clear_for_error_prompt; prompt_input("? "); -@.?\relax@> - if last=first then return; - c:=buffer[first]; - if c>="a" then c:=c+"A"-"a"; {convert to uppercase} - @<Interpret code |c| and |return| if done@>; - end - -@ It is desirable to provide an `\.E' option here that gives the user -an easy way to return from \TeX\ to the system editor, with the offending -line ready to be edited. But such an extension requires some system -wizardry, so the present implementation simply types out the name of the -file that should be -edited and the relevant line number. -@^system dependencies@> - -There is a secret `\.D' option available when the debugging routines haven't -been commented~out. -@^debugging@> - -@<Interpret code |c| and |return| if done@>= -case c of -"0","1","2","3","4","5","6","7","8","9": if deletions_allowed then - @<Delete \(c)|c-"0"| tokens and |goto continue|@>; -@t\4\4@>@;@+@!debug "D": begin debug_help; goto continue;@+end;@+gubed@/ -"E": if base_ptr>0 then if input_stack[base_ptr].name_field>=256 then - begin print_nl("You want to edit file "); -@.You want to edit file x@> - slow_print(input_stack[base_ptr].name_field); - print(" at line "); print_int(line); - interaction:=scroll_mode; jump_out; - end; -"H": @<Print the help information and |goto continue|@>; -"I":@<Introduce new material from the terminal and |return|@>; -"Q","R","S":@<Change the interaction level and |return|@>; -"X":begin interaction:=scroll_mode; jump_out; - end; -othercases do_nothing -endcases;@/ -@<Print the menu of available options@> - -@ @<Print the menu...@>= -begin print("Type <return> to proceed, S to scroll future error messages,");@/ -@.Type <return> to proceed...@> -print_nl("R to run without stopping, Q to run quietly,");@/ -print_nl("I to insert something, "); -if base_ptr>0 then if input_stack[base_ptr].name_field>=256 then - print("E to edit your file,"); -if deletions_allowed then - print_nl("1 or ... or 9 to ignore the next 1 to 9 tokens of input,"); -print_nl("H for help, X to quit."); -end - -@ Here the author of \TeX\ apologizes for making use of the numerical -relation between |"Q"|, |"R"|, |"S"|, and the desired interaction settings -|batch_mode|, |nonstop_mode|, |scroll_mode|. -@^Knuth, Donald Ervin@> - -@<Change the interaction...@>= -begin error_count:=0; interaction:=batch_mode+c-"Q"; -print("OK, entering "); -case c of -"Q":begin print_esc("batchmode"); decr(selector); - end; -"R":print_esc("nonstopmode"); -"S":print_esc("scrollmode"); -end; {there are no other cases} -print("..."); print_ln; update_terminal; return; -end - -@ When the following code is executed, |buffer[(first+1)..(last-1)]| may -contain the material inserted by the user; otherwise another prompt will -be given. In order to understand this part of the program fully, you need -to be familiar with \TeX's input stacks. - -@<Introduce new material...@>= -begin begin_file_reading; {enter a new syntactic level for terminal input} -{now |state=mid_line|, so an initial blank space will count as a blank} -if last>first+1 then - begin loc:=first+1; buffer[first]:=" "; - end -else begin prompt_input("insert>"); loc:=first; -@.insert>@> - end; -first:=last; -cur_input.limit_field:=last-1; {no |end_line_char| ends this line} -return; -end - -@ We allow deletion of up to 99 tokens at a time. - -@<Delete \(c)|c-"0"| tokens...@>= -begin s1:=cur_tok; s2:=cur_cmd; s3:=cur_chr; s4:=align_state; -align_state:=1000000; OK_to_interrupt:=false; -if (last>first+1) and (buffer[first+1]>="0")and(buffer[first+1]<="9") then - c:=c*10+buffer[first+1]-"0"*11 -else c:=c-"0"; -while c>0 do - begin get_token; {one-level recursive call of |error| is possible} - decr(c); - end; -cur_tok:=s1; cur_cmd:=s2; cur_chr:=s3; align_state:=s4; OK_to_interrupt:=true; -help2("I have just deleted some text, as you asked.")@/ -("You can now delete more, or insert, or whatever."); -show_context; goto continue; -end - -@ @<Print the help info...@>= -begin if use_err_help then - begin give_err_help; use_err_help:=false; - end -else begin if help_ptr=0 then - help2("Sorry, I don't know how to help in this situation.")@/ - @t\kern1em@>("Maybe you should try asking a human?"); - repeat decr(help_ptr); print(help_line[help_ptr]); print_ln; - until help_ptr=0; - end; -help4("Sorry, I already gave what help I could...")@/ - ("Maybe you should try asking a human?")@/ - ("An error might have occurred before I noticed any problems.")@/ - ("``If all else fails, read the instructions.''");@/ -goto continue; -end - -@ @<Put help message on the transcript file@>= -if interaction>batch_mode then decr(selector); {avoid terminal output} -if use_err_help then - begin print_ln; give_err_help; - end -else while help_ptr>0 do - begin decr(help_ptr); print_nl(help_line[help_ptr]); - end; -print_ln; -if interaction>batch_mode then incr(selector); {re-enable terminal output} -print_ln - -@ A dozen or so error messages end with a parenthesized integer, so we -save a teeny bit of program space by declaring the following procedure: - -@p procedure int_error(@!n:integer); -begin print(" ("); print_int(n); print_char(")"); error; -end; - -@ In anomalous cases, the print selector might be in an unknown state; -the following subroutine is called to fix things just enough to keep -running a bit longer. - -@p procedure normalize_selector; -begin if log_opened then selector:=term_and_log -else selector:=term_only; -if job_name=0 then open_log_file; -if interaction=batch_mode then decr(selector); -end; - -@ The following procedure prints \TeX's last words before dying. - -@d succumb==begin if interaction=error_stop_mode then - interaction:=scroll_mode; {no more interaction} - if log_opened then error; - @!debug if interaction>batch_mode then debug_help;@+gubed@;@/ - history:=fatal_error_stop; jump_out; {irrecoverable error} - end - -@<Error hand...@>= -procedure fatal_error(@!s:str_number); {prints |s|, and that's it} -begin normalize_selector;@/ -print_err("Emergency stop"); help1(s); succumb; -@.Emergency stop@> -end; - -@ Here is the most dreaded error message. - -@<Error hand...@>= -procedure overflow(@!s:str_number;@!n:integer); {stop due to finiteness} -begin normalize_selector; -print_err("TeX capacity exceeded, sorry ["); -@.TeX capacity exceeded ...@> -print(s); print_char("="); print_int(n); print_char("]"); -help2("If you really absolutely need more capacity,")@/ - ("you can ask a wizard to enlarge me."); -succumb; -end; - -@ The program might sometime run completely amok, at which point there is -no choice but to stop. If no previous error has been detected, that's bad -news; a message is printed that is really intended for the \TeX\ -maintenance person instead of the user (unless the user has been -particularly diabolical). The index entries for `this can't happen' may -help to pinpoint the problem. -@^dry rot@> - -@<Error hand...@>= -procedure confusion(@!s:str_number); - {consistency check violated; |s| tells where} -begin normalize_selector; -if history<error_message_issued then - begin print_err("This can't happen ("); print(s); print_char(")"); -@.This can't happen@> - help1("I'm broken. Please show this to someone who can fix can fix"); - end -else begin print_err("I can't go on meeting you like this"); -@.I can't go on...@> - help2("One of your faux pas seems to have wounded me deeply...")@/ - ("in fact, I'm barely conscious. Please fix it and try again."); - end; -succumb; -end; - -@ Users occasionally want to interrupt \TeX\ while it's running. -If the \PASCAL\ runtime system allows this, one can implement -a routine that sets the global variable |interrupt| to some nonzero value -when such an interrupt is signalled. Otherwise there is probably at least -a way to make |interrupt| nonzero using the \PASCAL\ debugger. -@^system dependencies@> -@^debugging@> - -@d check_interrupt==begin if interrupt<>0 then pause_for_instructions; - end - -@<Global...@>= -@!interrupt:integer; {should \TeX\ pause for instructions?} -@!OK_to_interrupt:boolean; {should interrupts be observed?} - -@ @<Set init...@>= -interrupt:=0; OK_to_interrupt:=true; - -@ When an interrupt has been detected, the program goes into its -highest interaction level and lets the user have nearly the full flexibility of -the |error| routine. \TeX\ checks for interrupts only at times when it is -safe to do this. - -@p procedure pause_for_instructions; -begin if OK_to_interrupt then - begin interaction:=error_stop_mode; - if (selector=log_only)or(selector=no_print) then - incr(selector); - print_err("Interruption"); -@.Interruption@> - help3("You rang?")@/ - ("Try to insert an instruction for me (e.g., `I\showlists'),")@/ - ("unless you just want to quit by typing `X'."); - deletions_allowed:=false; error; deletions_allowed:=true; - interrupt:=0; - end; -end; - -@* \[7] Arithmetic with scaled dimensions. -The principal computations performed by \TeX\ are done entirely in terms of -integers less than $2^{31}$ in magnitude; and divisions are done only when both -dividend and divisor are nonnegative. Thus, the arithmetic specified in this -program can be carried out in exactly the same way on a wide variety of -computers, including some small ones. Why? Because the arithmetic -calculations need to be spelled out precisely in order to guarantee that -\TeX\ will produce identical output on different machines. If some -quantities were rounded differently in different implementations, we would -find that line breaks and even page breaks might occur in different places. -Hence the arithmetic of \TeX\ has been designed with care, and systems that -claim to be implementations of \TeX82 should follow precisely the -@:TeX82}{\TeX82@> -calculations as they appear in the present program. - -(Actually there are three places where \TeX\ uses |div| with a possibly negative -numerator. These are harmless; see |div| in the index. Also if the user -sets the \.{\\time} or the \.{\\year} to a negative value, some diagnostic -information will involve negative-numerator division. The same remarks -apply for |mod| as well as for |div|.) - -@ Here is a routine that calculates half of an integer, using an -unambiguous convention with respect to signed odd numbers. - -@p function half(@!x:integer):integer; -begin if odd(x) then half:=(x+1) div 2 -else half:=x @!div 2; -end; - -@ Fixed-point arithmetic is done on {\sl scaled integers\/} that are multiples -of $2^{-16}$. In other words, a binary point is assumed to be sixteen bit -positions from the right end of a binary computer word. - -@d unity == @'200000 {$2^{16}$, represents 1.00000} -@d two == @'400000 {$2^{17}$, represents 2.00000} - -@<Types...@>= -@!scaled = integer; {this type is used for scaled integers} -@!nonnegative_integer=0..@'17777777777; {$0\L x<2^{31}$} -@!small_number=0..63; {this type is self-explanatory} - -@ The following function is used to create a scaled integer from a given decimal -fraction $(.d_0d_1\ldots d_{k-1})$, where |0<=k<=17|. The digit $d_i$ is -given in |dig[i]|, and the calculation produces a correctly rounded result. - -@p function round_decimals(@!k:small_number) : scaled; - {converts a decimal fraction} -var a:integer; {the accumulator} -begin a:=0; -while k>0 do - begin decr(k); a:=(a+dig[k]*two) div 10; - end; -round_decimals:=(a+1) div 2; -end; - -@ Conversely, here is a procedure analogous to |print_int|. If the output -of this procedure is subsequently read by \TeX\ and converted by the -|round_decimals| routine above, it turns out that the original value will -be reproduced exactly; the ``simplest'' such decimal number is output, -but there is always at least one digit following the decimal point. - -The invariant relation in the \&{repeat} loop is that a sequence of -decimal digits yet to be printed will yield the original number if and only if -they form a fraction~$f$ in the range $s-\delta\L10\cdot2^{16}f<s$. -We can stop if and only if $f=0$ satisfies this condition; the loop will -terminate before $s$ can possibly become zero. - -@p procedure print_scaled(@!s:scaled); {prints scaled real, rounded to five - digits} -var delta:scaled; {amount of allowable inaccuracy} -begin if s<0 then - begin print_char("-"); negate(s); {print the sign, if negative} - end; -print_int(s div unity); {print the integer part} -print_char("."); -s:=10*(s mod unity)+5; delta:=10; -repeat if delta>unity then s:=s+@'100000-50000; {round the last digit} -print_char("0"+(s div unity)); s:=10*(s mod unity); delta:=delta*10; -until s<=delta; -end; - -@ Physical sizes that a \TeX\ user specifies for portions of documents are -represented internally as scaled points. Thus, if we define an `sp' (scaled -@^sp@> -point) as a unit equal to $2^{-16}$ printer's points, every dimension -inside of \TeX\ is an integer number of sp. There are exactly -4,736,286.72 sp per inch. Users are not allowed to specify dimensions -larger than $2^{30}-1$ sp, which is a distance of about 18.892 feet (5.7583 -meters); two such quantities can be added without overflow on a 32-bit -computer. - -The present implementation of \TeX\ does not check for overflow when -@^overflow in arithmetic@> -dimensions are added or subtracted. This could be done by inserting a -few dozen tests of the form `\ignorespaces|if x>=@'10000000000 then -@t\\{report\_overflow}@>|', but the chance of overflow is so remote that -such tests do not seem worthwhile. - -\TeX\ needs to do only a few arithmetic operations on scaled quantities, -other than addition and subtraction, and the following subroutines do most of -the work. A single computation might use several subroutine calls, and it is -desirable to avoid producing multiple error messages in case of arithmetic -overflow; so the routines set the global variable |arith_error| to |true| -instead of reporting errors directly to the user. Another global variable, -|remainder|, holds the remainder after a division. - -@<Glob...@>= -@!arith_error:boolean; {has arithmetic overflow occurred recently?} -@!remainder:scaled; {amount subtracted to get an exact division} - -@ The first arithmetical subroutine we need computes $nx+y$, where |x| -and~|y| are |scaled| and |n| is an integer. We will also use it to -multiply integers. - -@d nx_plus_y(#)==mult_and_add(#,@'7777777777) -@d mult_integers(#)==mult_and_add(#,0,@'17777777777) - -@p function mult_and_add(@!n:integer;@!x,@!y,@!max_answer:scaled):scaled; -begin if n<0 then - begin negate(x); negate(n); - end; -if n=0 then mult_and_add:=y -else if ((x<=(max_answer-y) div n)and(-x<=(max_answer+y) div n)) then - mult_and_add:=n*x+y -else begin arith_error:=true; mult_and_add:=0; - end; -end; - -@ We also need to divide scaled dimensions by integers. - -@p function x_over_n(@!x:scaled;@!n:integer):scaled; -var negative:boolean; {should |remainder| be negated?} -begin negative:=false; -if n=0 then - begin arith_error:=true; x_over_n:=0; remainder:=x; - end -else begin if n<0 then - begin negate(x); negate(n); negative:=true; - end; - if x>=0 then - begin x_over_n:=x div n; remainder:=x mod n; - end - else begin x_over_n:=-((-x) div n); remainder:=-((-x) mod n); - end; - end; -if negative then negate(remainder); -end; - -@ Then comes the multiplication of a scaled number by a fraction |n/d|, -where |n| and |d| are nonnegative integers |<=@t$2^{16}$@>| and |d| is -positive. It would be too dangerous to multiply by~|n| and then divide -by~|d|, in separate operations, since overflow might well occur; and it -would be too inaccurate to divide by |d| and then multiply by |n|. Hence -this subroutine simulates 1.5-precision arithmetic. - -@p function xn_over_d(@!x:scaled; @!n,@!d:integer):scaled; -var positive:boolean; {was |x>=0|?} -@!t,@!u,@!v:nonnegative_integer; {intermediate quantities} -begin if x>=0 then positive:=true -else begin negate(x); positive:=false; - end; -t:=(x mod @'100000)*n; -u:=(x div @'100000)*n+(t div @'100000); -v:=(u mod d)*@'100000 + (t mod @'100000); -if u div d>=@'100000 then arith_error:=true -else u:=@'100000*(u div d) + (v div d); -if positive then - begin xn_over_d:=u; remainder:=v mod d; - end -else begin xn_over_d:=-u; remainder:=-(v mod d); - end; -end; - -@ The next subroutine is used to compute the ``badness'' of glue, when a -total~|t| is supposed to be made from amounts that sum to~|s|. According -to {\sl The \TeX book}, the badness of this situation is $100(t/s)^3$; -however, badness is simply a heuristic, so we need not squeeze out the -last drop of accuracy when computing it. All we really want is an -approximation that has similar properties. -@:TeXbook}{\sl The \TeX book@> - -The actual method used to compute the badness is easier to read from the -program than to describe in words. It produces an integer value that is a -reasonably close approximation to $100(t/s)^3$, and all implementations -of \TeX\ should use precisely this method. Any badness of $2^{13}$ or more is -treated as infinitely bad, and represented by 10000. - -It is not difficult to prove that $$\hbox{|badness(t+1,s)>=badness(t,s) ->=badness(t,s+1)|}.$$ The badness function defined here is capable of -computing at most 1095 distinct values, but that is plenty. - -@d inf_bad = 10000 {infinitely bad value} - -@p function badness(@!t,@!s:scaled):halfword; {compute badness, given |t>=0|} -var r:integer; {approximation to $\alpha t/s$, where $\alpha^3\approx - 100\cdot2^{18}$} -begin if t=0 then badness:=0 -else if s<=0 then badness:=inf_bad -else begin if t<=7230584 then r:=(t*297) div s {$297^3=99.94\times2^{18}$} - else if s>=1663497 then r:=t div (s div 297) - else r:=t; - if r>1290 then badness:=inf_bad {$1290^3<2^{31}<1291^3$} - else badness:=(r*r*r+@'400000) div @'1000000; - end; {that was $r^3/2^{18}$, rounded to the nearest integer} -end; - -@ When \TeX\ ``packages'' a list into a box, it needs to calculate the -proportionality ratio by which the glue inside the box should stretch -or shrink. This calculation does not affect \TeX's decision making, -so the precise details of rounding, etc., in the glue calculation are not -of critical importance for the consistency of results on different computers. - -We shall use the type |glue_ratio| for such proportionality ratios. -A glue ratio should take the same amount of memory as an -|integer| (usually 32 bits) if it is to blend smoothly with \TeX's -other data structures. Thus |glue_ratio| should be equivalent to -|short_real| in some implementations of \PASCAL. Alternatively, -it is possible to deal with glue ratios using nothing but fixed-point -arithmetic; see {\sl TUGboat \bf3},1 (March 1982), 10--27. (But the -routines cited there must be modified to allow negative glue ratios.) -@^system dependencies@> - -@d set_glue_ratio_zero(#) == #:=0.0 {store the representation of zero ratio} -@d set_glue_ratio_one(#) == #:=1.0 {store the representation of unit ratio} -@d float(#) == # {convert from |glue_ratio| to type |real|} -@d unfloat(#) == # {convert from |real| to type |glue_ratio|} -@d float_constant(#) == #.0 {convert |integer| constant to |real|} - -@<Types...@>= -@!glue_ratio=real; {one-word representation of a glue expansion factor} - -@* \[8] Packed data. -In order to make efficient use of storage space, \TeX\ bases its major data -structures on a |memory_word|, which contains either a (signed) integer, -possibly scaled, or a (signed) |glue_ratio|, or a small number of -fields that are one half or one quarter of the size used for storing -integers. - -If |x| is a variable of type |memory_word|, it contains up to four -fields that can be referred to as follows: -$$\vbox{\halign{\hfil#&#\hfil&#\hfil\cr -|x|&.|int|&(an |integer|)\cr -|x|&.|sc|\qquad&(a |scaled| integer)\cr -|x|&.|gr|&(a |glue_ratio|)\cr -|x.hh.lh|, |x.hh|&.|rh|&(two halfword fields)\cr -|x.hh.b0|, |x.hh.b1|, |x.hh|&.|rh|&(two quarterword fields, one halfword - field)\cr -|x.qqqq.b0|, |x.qqqq.b1|, |x.qqqq|&.|b2|, |x.qqqq.b3|\hskip-100pt - &\qquad\qquad\qquad(four quarterword fields)\cr}}$$ -This is somewhat cumbersome to write, and not very readable either, but -macros will be used to make the notation shorter and more transparent. -The \PASCAL\ code below gives a formal definition of |memory_word| and -its subsidiary types, using packed variant records. \TeX\ makes no -assumptions about the relative positions of the fields within a word. - -Since we are assuming 32-bit integers, a halfword must contain at least -16 bits, and a quarterword must contain at least 8 bits. -@^system dependencies@> -But it doesn't hurt to have more bits; for example, with enough 36-bit -words you might be able to have |mem_max| as large as 262142, which is -eight times as much memory as anybody had during the first four years of -\TeX's existence. - -N.B.: Valuable memory space will be dreadfully wasted unless \TeX\ is compiled -by a \PASCAL\ that packs all of the |memory_word| variants into -the space of a single integer. This means, for example, that |glue_ratio| -words should be |short_real| instead of |real| on some computers. Some -\PASCAL\ compilers will pack an integer whose subrange is `|0..255|' into -an eight-bit field, but others insist on allocating space for an additional -sign bit; on such systems you can get 256 values into a quarterword only -if the subrange is `|-128..127|'. - -The present implementation tries to accommodate as many variations as possible, -so it makes few assumptions. If integers having the subrange -`|min_quarterword..max_quarterword|' can be packed into a quarterword, -and if integers having the subrange `|min_halfword..max_halfword|' -can be packed into a halfword, everything should work satisfactorily. - -It is usually most efficient to have |min_quarterword=min_halfword=0|, -so one should try to achieve this unless it causes a severe problem. -The values defined here are recommended for most 32-bit computers. - -@d min_quarterword=0 {smallest allowable value in a |quarterword|} -@d max_quarterword=255 {largest allowable value in a |quarterword|} -@d min_halfword==0 {smallest allowable value in a |halfword|} -@d max_halfword==65535 {largest allowable value in a |halfword|} - -@ Here are the inequalities that the quarterword and halfword values -must satisfy (or rather, the inequalities that they mustn't satisfy): - -@<Check the ``constant''...@>= -init if (mem_min<>mem_bot)or(mem_max<>mem_top) then bad:=10;@+tini@;@/ -if (mem_min>mem_bot)or(mem_max<mem_top) then bad:=10; -if (min_quarterword>0)or(max_quarterword<127) then bad:=11; -if (min_halfword>0)or(max_halfword<32767) then bad:=12; -if (min_quarterword<min_halfword)or@| - (max_quarterword>max_halfword) then bad:=13; -if (mem_min<min_halfword)or(mem_max>=max_halfword)or@| - (mem_bot-mem_min>max_halfword+1) then bad:=14; -if (font_base<min_quarterword)or(font_max>max_quarterword) then bad:=15; -if font_max>font_base+256 then bad:=16; -if (save_size>max_halfword)or(max_strings>max_halfword) then bad:=17; -if buf_size>max_halfword then bad:=18; -if max_quarterword-min_quarterword<255 then bad:=19; - -@ The operation of adding or subtracting |min_quarterword| occurs quite -frequently in \TeX, so it is convenient to abbreviate this operation -by using the macros |qi| and |qo| for input and output to and from -quarterword format. - -The inner loop of \TeX\ will run faster with respect to compilers -that don't optimize expressions like `|x+0|' and `|x-0|', if these -macros are simplified in the obvious way when |min_quarterword=0|. -@^inner loop@>@^system dependencies@> - -@d qi(#)==#+min_quarterword - {to put an |eight_bits| item into a quarterword} -@d qo(#)==#-min_quarterword - {to take an |eight_bits| item out of a quarterword} -@d hi(#)==#+min_halfword - {to put a sixteen-bit item into a halfword} -@d ho(#)==#-min_halfword - {to take a sixteen-bit item from a halfword} - -@ The reader should study the following definitions closely: -@^system dependencies@> - -@d sc==int {|scaled| data is equivalent to |integer|} - -@<Types...@>= -@!quarterword = min_quarterword..max_quarterword; {1/4 of a word} -@!halfword=min_halfword..max_halfword; {1/2 of a word} -@!two_choices = 1..2; {used when there are two variants in a record} -@!four_choices = 1..4; {used when there are four variants in a record} -@!two_halves = packed record@;@/ - @!rh:halfword; - case two_choices of - 1: (@!lh:halfword); - 2: (@!b0:quarterword; @!b1:quarterword); - end; -@!four_quarters = packed record@;@/ - @!b0:quarterword; - @!b1:quarterword; - @!b2:quarterword; - @!b3:quarterword; - end; -@!memory_word = record@;@/ - case four_choices of - 1: (@!int:integer); - 2: (@!gr:glue_ratio); - 3: (@!hh:two_halves); - 4: (@!qqqq:four_quarters); - end; -@!word_file = file of memory_word; - -@ When debugging, we may want to print a |memory_word| without knowing -what type it is; so we print it in all modes. -@^dirty \PASCAL@>@^debugging@> - -@p @!debug procedure print_word(@!w:memory_word); - {prints |w| in all ways} -begin print_int(w.int); print_char(" ");@/ -print_scaled(w.sc); print_char(" ");@/ -print_scaled(round(unity*float(w.gr))); print_ln;@/ -@^real multiplication@> -print_int(w.hh.lh); print_char("="); print_int(w.hh.b0); print_char(":"); -print_int(w.hh.b1); print_char(";"); print_int(w.hh.rh); print_char(" ");@/ -print_int(w.qqqq.b0); print_char(":"); print_int(w.qqqq.b1); print_char(":"); -print_int(w.qqqq.b2); print_char(":"); print_int(w.qqqq.b3); -end; -gubed - -@* \[9] Dynamic memory allocation. -The \TeX\ system does nearly all of its own memory allocation, so that it -can readily be transported into environments that do not have automatic -facilities for strings, garbage collection, etc., and so that it can be in -control of what error messages the user receives. The dynamic storage -requirements of \TeX\ are handled by providing a large array |mem| in -which consecutive blocks of words are used as nodes by the \TeX\ routines. - -Pointer variables are indices into this array, or into another array -called |eqtb| that will be explained later. A pointer variable might -also be a special flag that lies outside the bounds of |mem|, so we -allow pointers to assume any |halfword| value. The minimum halfword -value represents a null pointer. \TeX\ does not assume that |mem[null]| exists. - -@d pointer==halfword {a flag or a location in |mem| or |eqtb|} -@d null==min_halfword {the null pointer} - -@<Glob...@>= -@!temp_ptr:pointer; {a pointer variable for occasional emergency use} - -@ The |mem| array is divided into two regions that are allocated separately, -but the dividing line between these two regions is not fixed; they grow -together until finding their ``natural'' size in a particular job. -Locations less than or equal to |lo_mem_max| are used for storing -variable-length records consisting of two or more words each. This region -is maintained using an algorithm similar to the one described in exercise -2.5--19 of {\sl The Art of Computer Programming}. However, no size field -appears in the allocated nodes; the program is responsible for knowing the -relevant size when a node is freed. Locations greater than or equal to -|hi_mem_min| are used for storing one-word records; a conventional -\.{AVAIL} stack is used for allocation in this region. - -Locations of |mem| between |mem_bot| and |mem_top| may be dumped as part -of preloaded format files, by the \.{INITEX} preprocessor. -@.INITEX@> -Production versions of \TeX\ may extend the memory at both ends in order to -provide more space; locations between |mem_min| and |mem_bot| are always -used for variable-size nodes, and locations between |mem_top| and |mem_max| -are always used for single-word nodes. - -The key pointers that govern |mem| allocation have a prescribed order: -$$\advance\thickmuskip-2mu -\hbox{|null<=mem_min<=mem_bot<lo_mem_max< - hi_mem_min<mem_top<=mem_end<=mem_max|.}$$ - -Empirical tests show that the present implementation of \TeX\ tends to -spend about 9\pct! of its running time allocating nodes, and about 6\pct! -deallocating them after their use. - -@<Glob...@>= -@!mem : array[mem_min..mem_max] of memory_word; {the big dynamic storage area} -@!lo_mem_max : pointer; {the largest location of variable-size memory in use} -@!hi_mem_min : pointer; {the smallest location of one-word memory in use} - -@ In order to study the memory requirements of particular applications, it -is possible to prepare a version of \TeX\ that keeps track of current and -maximum memory usage. When code between the delimiters |@!stat| $\ldots$ -|tats| is not ``commented out,'' \TeX\ will run a bit slower but it will -report these statistics when |tracing_stats| is sufficiently large. - -@<Glob...@>= -@!var_used, @!dyn_used : integer; {how much memory is in use} - -@ Let's consider the one-word memory region first, since it's the -simplest. The pointer variable |mem_end| holds the highest-numbered location -of |mem| that has ever been used. The free locations of |mem| that -occur between |hi_mem_min| and |mem_end|, inclusive, are of type -|two_halves|, and we write |info(p)| and |link(p)| for the |lh| -and |rh| fields of |mem[p]| when it is of this type. The single-word -free locations form a linked list -$$|avail|,\;\hbox{|link(avail)|},\;\hbox{|link(link(avail))|},\;\ldots$$ -terminated by |null|. - -@d link(#) == mem[#].hh.rh {the |link| field of a memory word} -@d info(#) == mem[#].hh.lh {the |info| field of a memory word} - -@<Glob...@>= -@!avail : pointer; {head of the list of available one-word nodes} -@!mem_end : pointer; {the last one-word node used in |mem|} - -@ If memory is exhausted, it might mean that the user has forgotten -a right brace. We will define some procedures later that try to help -pinpoint the trouble. - -@p @<Declare the procedure called |show_token_list|@>@/ -@<Declare the procedure called |runaway|@> - -@ The function |get_avail| returns a pointer to a new one-word node whose -|link| field is null. However, \TeX\ will halt if there is no more room left. -@^inner loop@> - -If the available-space list is empty, i.e., if |avail=null|, -we try first to increase |mem_end|. If that cannot be done, i.e., if -|mem_end=mem_max|, we try to decrease |hi_mem_min|. If that cannot be -done, i.e., if |hi_mem_min=lo_mem_max+1|, we have to quit. - -@p function get_avail : pointer; {single-word node allocation} -var p:pointer; {the new node being got} -begin p:=avail; {get top location in the |avail| stack} -if p<>null then avail:=link(avail) {and pop it off} -else if mem_end<mem_max then {or go into virgin territory} - begin incr(mem_end); p:=mem_end; - end -else begin decr(hi_mem_min); p:=hi_mem_min; - if hi_mem_min<=lo_mem_max then - begin runaway; {if memory is exhausted, display possible runaway text} - overflow("main memory size",mem_max+1-mem_min); - {quit; all one-word nodes are busy} -@:TeX capacity exceeded main memory size}{\quad main memory size@> - end; - end; -link(p):=null; {provide an oft-desired initialization of the new node} -@!stat incr(dyn_used);@+tats@;{maintain statistics} -get_avail:=p; -end; - -@ Conversely, a one-word node is recycled by calling |free_avail|. -This routine is part of \TeX's ``inner loop,'' so we want it to be fast. -@^inner loop@> - -@d free_avail(#)== {single-word node liberation} - begin link(#):=avail; avail:=#; - @!stat decr(dyn_used);@+tats@/ - end - -@ There's also a |fast_get_avail| routine, which saves the procedure-call -overhead at the expense of extra programming. This routine is used in -the places that would otherwise account for the most calls of |get_avail|. -@^inner loop@> - -@d fast_get_avail(#)==@t@>@;@/ - begin #:=avail; {avoid |get_avail| if possible, to save time} - if #=null then #:=get_avail - else begin avail:=link(#); link(#):=null; - @!stat incr(dyn_used);@+tats@/ - end; - end - -@ The procedure |flush_list(p)| frees an entire linked list of -one-word nodes that starts at position |p|. -@^inner loop@> - -@p procedure flush_list(@!p:pointer); {makes list of single-word nodes - available} -var @!q,@!r:pointer; {list traversers} -begin if p<>null then - begin r:=p; - repeat q:=r; r:=link(r); @!stat decr(dyn_used);@+tats@/ - until r=null; {now |q| is the last node on the list} - link(q):=avail; avail:=p; - end; -end; - -@ The available-space list that keeps track of the variable-size portion -of |mem| is a nonempty, doubly-linked circular list of empty nodes, -pointed to by the roving pointer |rover|. - -Each empty node has size 2 or more; the first word contains the special -value |max_halfword| in its |link| field and the size in its |info| field; -the second word contains the two pointers for double linking. - -Each nonempty node also has size 2 or more. Its first word is of type -|two_halves|\kern-1pt, and its |link| field is never equal to |max_halfword|. -Otherwise there is complete flexibility with respect to the contents -of its other fields and its other words. - -(We require |mem_max<max_halfword| because terrible things can happen -when |max_halfword| appears in the |link| field of a nonempty node.) - -@d empty_flag == max_halfword {the |link| of an empty variable-size node} -@d is_empty(#) == (link(#)=empty_flag) {tests for empty node} -@d node_size == info {the size field in empty variable-size nodes} -@d llink(#) == info(#+1) {left link in doubly-linked list of empty nodes} -@d rlink(#) == link(#+1) {right link in doubly-linked list of empty nodes} - -@<Glob...@>= -@!rover : pointer; {points to some node in the list of empties} - -@ A call to |get_node| with argument |s| returns a pointer to a new node -of size~|s|, which must be 2~or more. The |link| field of the first word -of this new node is set to null. An overflow stop occurs if no suitable -space exists. - -If |get_node| is called with $s=2^{30}$, it simply merges adjacent free -areas and returns the value |max_halfword|. - -@p function get_node(@!s:integer):pointer; {variable-size node allocation} -label found,exit,restart; -var p:pointer; {the node currently under inspection} -@!q:pointer; {the node physically after node |p|} -@!r:integer; {the newly allocated node, or a candidate for this honor} -@!t:integer; {temporary register} -begin restart: p:=rover; {start at some free node in the ring} -repeat @<Try to allocate within node |p| and its physical successors, - and |goto found| if allocation was possible@>; -@^inner loop@> -p:=rlink(p); {move to the next node in the ring} -until p=rover; {repeat until the whole list has been traversed} -if s=@'10000000000 then - begin get_node:=max_halfword; return; - end; -if lo_mem_max+2<hi_mem_min then if lo_mem_max+2<=mem_bot+max_halfword then - @<Grow more variable-size memory and |goto restart|@>; -overflow("main memory size",mem_max+1-mem_min); - {sorry, nothing satisfactory is left} -@:TeX capacity exceeded main memory size}{\quad main memory size@> -found: link(r):=null; {this node is now nonempty} -@!stat var_used:=var_used+s; {maintain usage statistics} -tats@;@/ -get_node:=r; -exit:end; - -@ The lower part of |mem| grows by 1000 words at a time, unless -we are very close to going under. When it grows, we simply link -a new node into the available-space list. This method of controlled -growth helps to keep the |mem| usage consecutive when \TeX\ is -implemented on ``virtual memory'' systems. -@^virtual memory@> - -@<Grow more variable-size memory and |goto restart|@>= -begin if hi_mem_min-lo_mem_max>=1998 then t:=lo_mem_max+1000 -else t:=lo_mem_max+1+(hi_mem_min-lo_mem_max) div 2; - {|lo_mem_max+2<=t<hi_mem_min|} -p:=llink(rover); q:=lo_mem_max; rlink(p):=q; llink(rover):=q;@/ -if t>mem_bot+max_halfword then t:=mem_bot+max_halfword; -rlink(q):=rover; llink(q):=p; link(q):=empty_flag; node_size(q):=t-lo_mem_max;@/ -lo_mem_max:=t; link(lo_mem_max):=null; info(lo_mem_max):=null; -rover:=q; goto restart; -end - -@ Empirical tests show that the routine in this section performs a -node-merging operation about 0.75 times per allocation, on the average, -after which it finds that |r>p+1| about 95\pct! of the time. - -@<Try to allocate...@>= -q:=p+node_size(p); {find the physical successor} -@^inner loop@> -while is_empty(q) do {merge node |p| with node |q|} - begin t:=rlink(q); - if q=rover then rover:=t; - llink(t):=llink(q); rlink(llink(q)):=t;@/ - q:=q+node_size(q); - end; -r:=q-s; -if r>p+1 then @<Allocate from the top of node |p| and |goto found|@>; -if r=p then if rlink(p)<>p then - @<Allocate entire node |p| and |goto found|@>; -node_size(p):=q-p {reset the size in case it grew} - -@ @<Allocate from the top...@>= -begin node_size(p):=r-p; {store the remaining size} -@^inner loop@> -rover:=p; {start searching here next time} -goto found; -end - -@ Here we delete node |p| from the ring, and let |rover| rove around. - -@<Allocate entire...@>= -begin rover:=rlink(p); t:=llink(p); -llink(rover):=t; rlink(t):=rover; -goto found; -end - -@ Conversely, when some variable-size node |p| of size |s| is no longer needed, -the operation |free_node(p,s)| will make its words available, by inserting -|p| as a new empty node just before where |rover| now points. -@^inner loop@> - -@p procedure free_node(@!p:pointer; @!s:halfword); {variable-size node - liberation} -var q:pointer; {|llink(rover)|} -begin node_size(p):=s; link(p):=empty_flag; -q:=llink(rover); llink(p):=q; rlink(p):=rover; {set both links} -llink(rover):=p; rlink(q):=p; {insert |p| into the ring} -@!stat var_used:=var_used-s;@+tats@;{maintain statistics} -end; - -@ Just before \.{INITEX} writes out the memory, it sorts the doubly linked -available space list. The list is probably very short at such times, so a -simple insertion sort is used. The smallest available location will be -pointed to by |rover|, the next-smallest by |rlink(rover)|, etc. - -@p @!init procedure sort_avail; {sorts the available variable-size nodes - by location} -var p,@!q,@!r: pointer; {indices into |mem|} -@!old_rover:pointer; {initial |rover| setting} -begin p:=get_node(@'10000000000); {merge adjacent free areas} -p:=rlink(rover); rlink(rover):=max_halfword; old_rover:=rover; -while p<>old_rover do @<Sort \(p)|p| into the list starting at |rover| - and advance |p| to |rlink(p)|@>; -p:=rover; -while rlink(p)<>max_halfword do - begin llink(rlink(p)):=p; p:=rlink(p); - end; -rlink(p):=rover; llink(rover):=p; -end; -tini - -@ The following |while| loop is guaranteed to -terminate, since the list that starts at -|rover| ends with |max_halfword| during the sorting procedure. - -@<Sort \(p)|p|...@>= -if p<rover then - begin q:=p; p:=rlink(q); rlink(q):=rover; rover:=q; - end -else begin q:=rover; - while rlink(q)<p do q:=rlink(q); - r:=rlink(p); rlink(p):=rlink(q); rlink(q):=p; p:=r; - end - -@* \[10] Data structures for boxes and their friends. -From the computer's standpoint, \TeX's chief mission is to create -horizontal and vertical lists. We shall now investigate how the elements -of these lists are represented internally as nodes in the dynamic memory. - -A horizontal or vertical list is linked together by |link| fields in -the first word of each node. Individual nodes represent boxes, glue, -penalties, or special things like discretionary hyphens; because of this -variety, some nodes are longer than others, and we must distinguish different -kinds of nodes. We do this by putting a `|type|' field in the first word, -together with the link and an optional `|subtype|'. - -@d type(#) == mem[#].hh.b0 {identifies what kind of node this is} -@d subtype(#) == mem[#].hh.b1 {secondary identification in some cases} - -@ A |@!char_node|, which represents a single character, is the most important -kind of node because it accounts for the vast majority of all boxes. -Special precautions are therefore taken to ensure that a |char_node| does -not take up much memory space. Every such node is one word long, and in fact -it is identifiable by this property, since other kinds of nodes have at least -two words, and they appear in |mem| locations less than |hi_mem_min|. -This makes it possible to omit the |type| field in a |char_node|, leaving -us room for two bytes that identify a |font| and a |character| within -that font. - -Note that the format of a |char_node| allows for up to 256 different -fonts and up to 256 characters per font; but most implementations will -probably limit the total number of fonts to fewer than 75 per job, -and most fonts will stick to characters whose codes are -less than 128 (since higher codes -are more difficult to access on most keyboards). - -Extensions of \TeX\ intended for oriental languages will need even more -than $256\times256$ possible characters, when we consider different sizes -@^oriental characters@>@^Chinese characters@>@^Japanese characters@> -and styles of type. It is suggested that Chinese and Japanese fonts be -handled by representing such characters in two consecutive |char_node| -entries: The first of these has |font=font_base|, and its |link| points -to the second; -the second identifies the font and the character dimensions. -The saving feature about oriental characters is that most of them have -the same box dimensions. The |character| field of the first |char_node| -is a ``\\{charext}'' that distinguishes between graphic symbols whose -dimensions are identical for typesetting purposes. (See the \MF\ manual.) -Such an extension of \TeX\ would not be difficult; further details are -left to the reader. - -In order to make sure that the |character| code fits in a quarterword, -\TeX\ adds the quantity |min_quarterword| to the actual code. - -Character nodes appear only in horizontal lists, never in vertical lists. - -@d is_char_node(#) == (#>=hi_mem_min) - {does the argument point to a |char_node|?} -@d font == type {the font code in a |char_node|} -@d character == subtype {the character code in a |char_node|} - -@ An |hlist_node| stands for a box that was made from a horizontal list. -Each |hlist_node| is seven words long, and contains the following fields -(in addition to the mandatory |type| and |link|, which we shall not -mention explicitly when discussing the other node types): The |height| and -|width| and |depth| are scaled integers denoting the dimensions of the -box. There is also a |shift_amount| field, a scaled integer indicating -how much this box should be lowered (if it appears in a horizontal list), -or how much it should be moved to the right (if it appears in a vertical -list). There is a |list_ptr| field, which points to the beginning of the -list from which this box was fabricated; if |list_ptr| is |null|, the box -is empty. Finally, there are three fields that represent the setting of -the glue: |glue_set(p)| is a word of type |glue_ratio| that represents -the proportionality constant for glue setting; |glue_sign(p)| is -|stretching| or |shrinking| or |normal| depending on whether or not the -glue should stretch or shrink or remain rigid; and |glue_order(p)| -specifies the order of infinity to which glue setting applies (|normal|, -|fil|, |fill|, or |filll|). The |subtype| field is not used. - -@d hlist_node=0 {|type| of hlist nodes} -@d box_node_size=7 {number of words to allocate for a box node} -@d width_offset=1 {position of |width| field in a box node} -@d depth_offset=2 {position of |depth| field in a box node} -@d height_offset=3 {position of |height| field in a box node} -@d width(#) == mem[#+width_offset].sc {width of the box, in sp} -@d depth(#) == mem[#+depth_offset].sc {depth of the box, in sp} -@d height(#) == mem[#+height_offset].sc {height of the box, in sp} -@d shift_amount(#) == mem[#+4].sc {repositioning distance, in sp} -@d list_offset=5 {position of |list_ptr| field in a box node} -@d list_ptr(#) == link(#+list_offset) {beginning of the list inside the box} -@d glue_order(#) == subtype(#+list_offset) {applicable order of infinity} -@d glue_sign(#) == type(#+list_offset) {stretching or shrinking} -@d normal=0 {the most common case when several cases are named} -@d stretching = 1 {glue setting applies to the stretch components} -@d shrinking = 2 {glue setting applies to the shrink components} -@d glue_offset = 6 {position of |glue_set| in a box node} -@d glue_set(#) == mem[#+glue_offset].gr - {a word of type |glue_ratio| for glue setting} - -@ The |new_null_box| function returns a pointer to an |hlist_node| in -which all subfields have the values corresponding to `\.{\\hbox\{\}}'. -(The |subtype| field is set to |min_quarterword|, for historic reasons -that are no longer relevant.) - -@p function new_null_box:pointer; {creates a new box node} -var p:pointer; {the new node} -begin p:=get_node(box_node_size); type(p):=hlist_node; -subtype(p):=min_quarterword; -width(p):=0; depth(p):=0; height(p):=0; shift_amount(p):=0; list_ptr(p):=null; -glue_sign(p):=normal; glue_order(p):=normal; set_glue_ratio_zero(glue_set(p)); -new_null_box:=p; -end; - -@ A |vlist_node| is like an |hlist_node| in all respects except that it -contains a vertical list. - -@d vlist_node=1 {|type| of vlist nodes} - -@ A |rule_node| stands for a solid black rectangle; it has |width|, -|depth|, and |height| fields just as in an |hlist_node|. However, if -any of these dimensions is $-2^{30}$, the actual value will be determined -by running the rule up to the boundary of the innermost enclosing box. -This is called a ``running dimension.'' The |width| is never running in -an hlist; the |height| and |depth| are never running in a~vlist. - -@d rule_node=2 {|type| of rule nodes} -@d rule_node_size=4 {number of words to allocate for a rule node} -@d null_flag==-@'10000000000 {$-2^{30}$, signifies a missing item} -@d is_running(#) == (#=null_flag) {tests for a running dimension} - -@ A new rule node is delivered by the |new_rule| function. It -makes all the dimensions ``running,'' so you have to change the -ones that are not allowed to run. - -@p function new_rule:pointer; -var p:pointer; {the new node} -begin p:=get_node(rule_node_size); type(p):=rule_node; -subtype(p):=0; {the |subtype| is not used} -width(p):=null_flag; depth(p):=null_flag; height(p):=null_flag; -new_rule:=p; -end; - -@ Insertions are represented by |ins_node| records, where the |subtype| -indicates the corresponding box number. For example, `\.{\\insert 250}' -leads to an |ins_node| whose |subtype| is |250+min_quarterword|. -The |height| field of an |ins_node| is slightly misnamed; it actually holds -the natural height plus depth of the vertical list being inserted. -The |depth| field holds the |split_max_depth| to be used in case this -insertion is split, and the |split_top_ptr| points to the corresponding -|split_top_skip|. The |float_cost| field holds the |floating_penalty| that -will be used if this insertion floats to a subsequent page after a -split insertion of the same class. There is one more field, the -|ins_ptr|, which points to the beginning of the vlist for the insertion. - -@d ins_node=3 {|type| of insertion nodes} -@d ins_node_size=5 {number of words to allocate for an insertion} -@d float_cost(#)==mem[#+1].int {the |floating_penalty| to be used} -@d ins_ptr(#)==info(#+4) {the vertical list to be inserted} -@d split_top_ptr(#)==link(#+4) {the |split_top_skip| to be used} - -@ A |mark_node| has a |mark_ptr| field that points to the reference count -of a token list that contains the user's \.{\\mark} text. -This field occupies a full word instead of a halfword, because -there's nothing to put in the other halfword; it is easier in \PASCAL\ to -use the full word than to risk leaving garbage in the unused half. - -@d mark_node=4 {|type| of a mark node} -@d small_node_size=2 {number of words to allocate for most node types} -@d mark_ptr(#)==mem[#+1].int {head of the token list for a mark} - -@ An |adjust_node|, which occurs only in horizontal lists, -specifies material that will be moved out into the surrounding -vertical list; i.e., it is used to implement \TeX's `\.{\\vadjust}' -operation. The |adjust_ptr| field points to the vlist containing this -material. - -@d adjust_node=5 {|type| of an adjust node} -@d adjust_ptr==mark_ptr {vertical list to be moved out of horizontal list} - -@ A |ligature_node|, which occurs only in horizontal lists, specifies -a character that was fabricated from the interaction of two or more -actual characters. The second word of the node, which is called the -|lig_char| word, contains |font| and |character| fields just as in a -|char_node|. The characters that generated the ligature have not been -forgotten, since they are needed for diagnostic messages and for -hyphenation; the |lig_ptr| field points to a linked list of character -nodes for all original characters that have been deleted. (This list -might be empty if the characters that generated the ligature were -retained in other nodes.) - -The |subtype| field is 0, plus 2 and/or 1 if the original source of the -ligature included implicit left and/or right boundaries. - -@d ligature_node=6 {|type| of a ligature node} -@d lig_char(#)==#+1 {the word where the ligature is to be found} -@d lig_ptr(#)==link(lig_char(#)) {the list of characters} - -@ The |new_ligature| function creates a ligature node having given -contents of the |font|, |character|, and |lig_ptr| fields. We also have -a |new_lig_item| function, which returns a two-word node having a given -|character| field. Such nodes are used for temporary processing as ligatures -are being created. - -@p function new_ligature(@!f,@!c:quarterword; @!q:pointer):pointer; -var p:pointer; {the new node} -begin p:=get_node(small_node_size); type(p):=ligature_node; -font(lig_char(p)):=f; character(lig_char(p)):=c; lig_ptr(p):=q; -subtype(p):=0; new_ligature:=p; -end; -@# -function new_lig_item(@!c:quarterword):pointer; -var p:pointer; {the new node} -begin p:=get_node(small_node_size); character(p):=c; lig_ptr(p):=null; -new_lig_item:=p; -end; - -@ A |disc_node|, which occurs only in horizontal lists, specifies a -``dis\-cretion\-ary'' line break. If such a break occurs at node |p|, the text -that starts at |pre_break(p)| will precede the break, the text that starts at -|post_break(p)| will follow the break, and text that appears in the next -|replace_count(p)| nodes will be ignored. For example, an ordinary -discretionary hyphen, indicated by `\.{\\-}', yields a |disc_node| with -|pre_break| pointing to a |char_node| containing a hyphen, |post_break=null|, -and |replace_count=0|. All three of the discretionary texts must be -lists that consist entirely of character, kern, box, rule, and ligature nodes. - -If |pre_break(p)=null|, the |ex_hyphen_penalty| will be charged for this -break. Otherwise the |hyphen_penalty| will be charged. The texts will -actually be substituted into the list by the line-breaking algorithm if it -decides to make the break, and the discretionary node will disappear at -that time; thus, the output routine sees only discretionaries that were -not chosen. - -@d disc_node=7 {|type| of a discretionary node} -@d replace_count==subtype {how many subsequent nodes to replace} -@d pre_break==llink {text that precedes a discretionary break} -@d post_break==rlink {text that follows a discretionary break} - -@p function new_disc:pointer; {creates an empty |disc_node|} -var p:pointer; {the new node} -begin p:=get_node(small_node_size); type(p):=disc_node; -replace_count(p):=0; pre_break(p):=null; post_break(p):=null; -new_disc:=p; -end; - -@ A |whatsit_node| is a wild card reserved for extensions to \TeX. The -|subtype| field in its first word says what `\\{whatsit}' it is, and -implicitly determines the node size (which must be 2 or more) and the -format of the remaining words. When a |whatsit_node| is encountered -in a list, special actions are invoked; knowledgeable people who are -careful not to mess up the rest of \TeX\ are able to make \TeX\ do new -things by adding code at the end of the program. For example, there -might be a `\TeX nicolor' extension to specify different colors of ink, -@^extensions to \TeX@> -and the whatsit node might contain the desired parameters. - -The present implementation of \TeX\ treats the features associated with -`\.{\\write}' and `\.{\\special}' as if they were extensions, in order to -illustrate how such routines might be coded. We shall defer further -discussion of extensions until the end of this program. - -@d whatsit_node=8 {|type| of special extension nodes} - -@ A |math_node|, which occurs only in horizontal lists, appears before and -after mathematical formulas. The |subtype| field is |before| before the -formula and |after| after it. There is a |width| field, which represents -the amount of surrounding space inserted by \.{\\mathsurround}. - -@d math_node=9 {|type| of a math node} -@d before=0 {|subtype| for math node that introduces a formula} -@d after=1 {|subtype| for math node that winds up a formula} - -@p function new_math(@!w:scaled;@!s:small_number):pointer; -var p:pointer; {the new node} -begin p:=get_node(small_node_size); type(p):=math_node; -subtype(p):=s; width(p):=w; new_math:=p; -end; - -@ \TeX\ makes use of the fact that |hlist_node|, |vlist_node|, -|rule_node|, |ins_node|, |mark_node|, |adjust_node|, |ligature_node|, -|disc_node|, |whatsit_node|, and |math_node| are at the low end of the -type codes, by permitting a break at glue in a list if and only if the -|type| of the previous node is less than |math_node|. Furthermore, a -node is discarded after a break if its type is |math_node| or~more. - -@d precedes_break(#)==(type(#)<math_node) -@d non_discardable(#)==(type(#)<math_node) - -@ A |glue_node| represents glue in a list. However, it is really only -a pointer to a separate glue specification, since \TeX\ makes use of the -fact that many essentially identical nodes of glue are usually present. -If |p| points to a |glue_node|, |glue_ptr(p)| points to -another packet of words that specify the stretch and shrink components, etc. - -Glue nodes also serve to represent leaders; the |subtype| is used to -distinguish between ordinary glue (which is called |normal|) and the three -kinds of leaders (which are called |a_leaders|, |c_leaders|, and |x_leaders|). -The |leader_ptr| field points to a rule node or to a box node containing the -leaders; it is set to |null| in ordinary glue nodes. - -Many kinds of glue are computed from \TeX's ``skip'' parameters, and -it is helpful to know which parameter has led to a particular glue node. -Therefore the |subtype| is set to indicate the source of glue, whenever -it originated as a parameter. We will be defining symbolic names for the -parameter numbers later (e.g., |line_skip_code=0|, |baseline_skip_code=1|, -etc.); it suffices for now to say that the |subtype| of parametric glue -will be the same as the parameter number, plus~one. - -In math formulas there are two more possibilities for the |subtype| in a -glue node: |mu_glue| denotes an \.{\\mskip} (where the units are scaled \.{mu} -instead of scaled \.{pt}); and |cond_math_glue| denotes the `\.{\\nonscript}' -feature that cancels the glue node immediately following if it appears -in a subscript. - -@d glue_node=10 {|type| of node that points to a glue specification} -@d cond_math_glue=98 {special |subtype| to suppress glue in the next node} -@d mu_glue=99 {|subtype| for math glue} -@d a_leaders=100 {|subtype| for aligned leaders} -@d c_leaders=101 {|subtype| for centered leaders} -@d x_leaders=102 {|subtype| for expanded leaders} -@d glue_ptr==llink {pointer to a glue specification} -@d leader_ptr==rlink {pointer to box or rule node for leaders} - -@ A glue specification has a halfword reference count in its first word, -@^reference counts@> -representing |null| plus the number of glue nodes that point to it (less one). -Note that the reference count appears in the same position as -the |link| field in list nodes; this is the field that is initialized -to |null| when a node is allocated, and it is also the field that is flagged -by |empty_flag| in empty nodes. - -Glue specifications also contain three |scaled| fields, for the |width|, -|stretch|, and |shrink| dimensions. Finally, there are two one-byte -fields called |stretch_order| and |shrink_order|; these contain the -orders of infinity (|normal|, |fil|, |fill|, or |filll|) -corresponding to the stretch and shrink values. - -@d glue_spec_size=4 {number of words to allocate for a glue specification} -@d glue_ref_count(#) == link(#) {reference count of a glue specification} -@d stretch(#) == mem[#+2].sc {the stretchability of this glob of glue} -@d shrink(#) == mem[#+3].sc {the shrinkability of this glob of glue} -@d stretch_order == type {order of infinity for stretching} -@d shrink_order == subtype {order of infinity for shrinking} -@d fil=1 {first-order infinity} -@d fill=2 {second-order infinity} -@d filll=3 {third-order infinity} - -@<Types...@>= -@!glue_ord=normal..filll; {infinity to the 0, 1, 2, or 3 power} - -@ Here is a function that returns a pointer to a copy of a glue spec. -The reference count in the copy is |null|, because there is assumed -to be exactly one reference to the new specification. - -@p function new_spec(@!p:pointer):pointer; {duplicates a glue specification} -var q:pointer; {the new spec} -begin q:=get_node(glue_spec_size);@/ -mem[q]:=mem[p]; glue_ref_count(q):=null;@/ -width(q):=width(p); stretch(q):=stretch(p); shrink(q):=shrink(p); -new_spec:=q; -end; - -@ And here's a function that creates a glue node for a given parameter -identified by its code number; for example, -|new_param_glue(line_skip_code)| returns a pointer to a glue node for the -current \.{\\lineskip}. - -@p function new_param_glue(@!n:small_number):pointer; -var p:pointer; {the new node} -@!q:pointer; {the glue specification} -begin p:=get_node(small_node_size); type(p):=glue_node; subtype(p):=n+1; -leader_ptr(p):=null;@/ -q:=@<Current |mem| equivalent of glue parameter number |n|@>@t@>; -glue_ptr(p):=q; incr(glue_ref_count(q)); -new_param_glue:=p; -end; - -@ Glue nodes that are more or less anonymous are created by |new_glue|, -whose argument points to a glue specification. - -@p function new_glue(@!q:pointer):pointer; -var p:pointer; {the new node} -begin p:=get_node(small_node_size); type(p):=glue_node; subtype(p):=normal; -leader_ptr(p):=null; glue_ptr(p):=q; incr(glue_ref_count(q)); -new_glue:=p; -end; - -@ Still another subroutine is needed: This one is sort of a combination -of |new_param_glue| and |new_glue|. It creates a glue node for one of -the current glue parameters, but it makes a fresh copy of the glue -specification, since that specification will probably be subject to change, -while the parameter will stay put. The global variable |temp_ptr| is -set to the address of the new spec. - -@p function new_skip_param(@!n:small_number):pointer; -var p:pointer; {the new node} -begin temp_ptr:=new_spec(@<Current |mem| equivalent of glue parameter...@>); -p:=new_glue(temp_ptr); glue_ref_count(temp_ptr):=null; subtype(p):=n+1; -new_skip_param:=p; -end; - -@ A |kern_node| has a |width| field to specify a (normally negative) -amount of spacing. This spacing correction appears in horizontal lists -between letters like A and V when the font designer said that it looks -better to move them closer together or further apart. A kern node can -also appear in a vertical list, when its `|width|' denotes additional -spacing in the vertical direction. The |subtype| is either |normal| (for -kerns inserted from font information or math mode calculations) or |explicit| -(for kerns inserted from \.{\\kern} and \.{\\/} commands) or |acc_kern| -(for kerns inserted from non-math accents) or |mu_glue| (for kerns -inserted from \.{\\mkern} specifications in math formulas). - -@d kern_node=11 {|type| of a kern node} -@d explicit=1 {|subtype| of kern nodes from \.{\\kern} and \.{\\/}} -@d acc_kern=2 {|subtype| of kern nodes from accents} - -@ The |new_kern| function creates a kern node having a given width. - -@p function new_kern(@!w:scaled):pointer; -var p:pointer; {the new node} -begin p:=get_node(small_node_size); type(p):=kern_node; -subtype(p):=normal; -width(p):=w; -new_kern:=p; -end; - -@ A |penalty_node| specifies the penalty associated with line or page -breaking, in its |penalty| field. This field is a fullword integer, but -the full range of integer values is not used: Any penalty |>=10000| is -treated as infinity, and no break will be allowed for such high values. -Similarly, any penalty |<=-10000| is treated as negative infinity, and a -break will be forced. - -@d penalty_node=12 {|type| of a penalty node} -@d inf_penalty=inf_bad {``infinite'' penalty value} -@d eject_penalty=-inf_penalty {``negatively infinite'' penalty value} -@d penalty(#) == mem[#+1].int {the added cost of breaking a list here} - -@ Anyone who has been reading the last few sections of the program will -be able to guess what comes next. - -@p function new_penalty(@!m:integer):pointer; -var p:pointer; {the new node} -begin p:=get_node(small_node_size); type(p):=penalty_node; -subtype(p):=0; {the |subtype| is not used} -penalty(p):=m; new_penalty:=p; -end; - -@ You might think that we have introduced enough node types by now. Well, -almost, but there is one more: An |unset_node| has nearly the same format -as an |hlist_node| or |vlist_node|; it is used for entries in \.{\\halign} -or \.{\\valign} that are not yet in their final form, since the box -dimensions are their ``natural'' sizes before any glue adjustment has been -made. The |glue_set| word is not present; instead, we have a |glue_stretch| -field, which contains the total stretch of order |glue_order| that is -present in the hlist or vlist being boxed. -Similarly, the |shift_amount| field is replaced by a |glue_shrink| field, -containing the total shrink of order |glue_sign| that is present. -The |subtype| field is called |span_count|; an unset box typically -contains the data for |qo(span_count)+1| columns. -Unset nodes will be changed to box nodes when alignment is completed. - -@d unset_node=13 {|type| for an unset node} -@d glue_stretch(#)==mem[#+glue_offset].sc {total stretch in an unset node} -@d glue_shrink==shift_amount {total shrink in an unset node} -@d span_count==subtype {indicates the number of spanned columns} - -@ In fact, there are still more types coming. When we get to math formula -processing we will see that a |style_node| has |type=14|; and a number -of larger type codes will also be defined, for use in math mode only. - -@ Warning: If any changes are made to these data structure layouts, such as -changing any of the node sizes or even reordering the words of nodes, -the |copy_node_list| procedure and the memory initialization code -below may have to be changed. Such potentially dangerous parts of the -program are listed in the index under `data structure assumptions'. -@!@^data structure assumptions@> -However, other references to the nodes are made symbolically in terms of -the \.{WEB} macro definitions above, so that format changes will leave -\TeX's other algorithms intact. -@^system dependencies@> - -@* \[11] Memory layout. -Some areas of |mem| are dedicated to fixed usage, since static allocation is -more efficient than dynamic allocation when we can get away with it. For -example, locations |mem_bot| to |mem_bot+3| are always used to store the -specification for glue that is `\.{0pt plus 0pt minus 0pt}'. The -following macro definitions accomplish the static allocation by giving -symbolic names to the fixed positions. Static variable-size nodes appear -in locations |mem_bot| through |lo_mem_stat_max|, and static single-word nodes -appear in locations |hi_mem_stat_min| through |mem_top|, inclusive. It is -harmless to let |lig_trick| and |garbage| share the same location of |mem|. - -@d zero_glue==mem_bot {specification for \.{0pt plus 0pt minus 0pt}} -@d fil_glue==zero_glue+glue_spec_size {\.{0pt plus 1fil minus 0pt}} -@d fill_glue==fil_glue+glue_spec_size {\.{0pt plus 1fill minus 0pt}} -@d ss_glue==fill_glue+glue_spec_size {\.{0pt plus 1fil minus 1fil}} -@d fil_neg_glue==ss_glue+glue_spec_size {\.{0pt plus -1fil minus 0pt}} -@d lo_mem_stat_max==fil_neg_glue+glue_spec_size-1 {largest statically - allocated word in the variable-size |mem|} -@# -@d page_ins_head==mem_top {list of insertion data for current page} -@d contrib_head==mem_top-1 {vlist of items not yet on current page} -@d page_head==mem_top-2 {vlist for current page} -@d temp_head==mem_top-3 {head of a temporary list of some kind} -@d hold_head==mem_top-4 {head of a temporary list of another kind} -@d adjust_head==mem_top-5 {head of adjustment list returned by |hpack|} -@d active==mem_top-7 {head of active list in |line_break|, needs two words} -@d align_head==mem_top-8 {head of preamble list for alignments} -@d end_span==mem_top-9 {tail of spanned-width lists} -@d omit_template==mem_top-10 {a constant token list} -@d null_list==mem_top-11 {permanently empty list} -@d lig_trick==mem_top-12 {a ligature masquerading as a |char_node|} -@d garbage==mem_top-12 {used for scrap information} -@d backup_head==mem_top-13 {head of token list built by |scan_keyword|} -@d hi_mem_stat_min==mem_top-13 {smallest statically allocated word in - the one-word |mem|} -@d hi_mem_stat_usage=14 {the number of one-word nodes always present} - -@ The following code gets |mem| off to a good start, when \TeX\ is -initializing itself the slow~way. - -@<Local variables for init...@>= -@!k:integer; {index into |mem|, |eqtb|, etc.} - -@ @<Initialize table entries...@>= -for k:=mem_bot+1 to lo_mem_stat_max do mem[k].sc:=0; - {all glue dimensions are zeroed} -@^data structure assumptions@> -k:=mem_bot;@+while k<=lo_mem_stat_max do - {set first words of glue specifications} - begin glue_ref_count(k):=null+1; - stretch_order(k):=normal; shrink_order(k):=normal; - k:=k+glue_spec_size; - end; -stretch(fil_glue):=unity; stretch_order(fil_glue):=fil;@/ -stretch(fill_glue):=unity; stretch_order(fill_glue):=fill;@/ -stretch(ss_glue):=unity; stretch_order(ss_glue):=fil;@/ -shrink(ss_glue):=unity; shrink_order(ss_glue):=fil;@/ -stretch(fil_neg_glue):=-unity; stretch_order(fil_neg_glue):=fil;@/ -rover:=lo_mem_stat_max+1; -link(rover):=empty_flag; {now initialize the dynamic memory} -node_size(rover):=1000; {which is a 1000-word available node} -llink(rover):=rover; rlink(rover):=rover;@/ -lo_mem_max:=rover+1000; link(lo_mem_max):=null; info(lo_mem_max):=null;@/ -for k:=hi_mem_stat_min to mem_top do - mem[k]:=mem[lo_mem_max]; {clear list heads} -@<Initialize the special list heads and constant nodes@>; -avail:=null; mem_end:=mem_top; -hi_mem_min:=hi_mem_stat_min; {initialize the one-word memory} -var_used:=lo_mem_stat_max+1-mem_bot; dyn_used:=hi_mem_stat_usage; - {initialize statistics} - -@ If \TeX\ is extended improperly, the |mem| array might get screwed up. -For example, some pointers might be wrong, or some ``dead'' nodes might not -have been freed when the last reference to them disappeared. Procedures -|check_mem| and |search_mem| are available to help diagnose such -problems. These procedures make use of two arrays called |free| and -|was_free| that are present only if \TeX's debugging routines have -been included. (You may want to decrease the size of |mem| while you -@^debugging@> -are debugging.) - -@<Glob...@>= -@!debug @!free: packed array [mem_min..mem_max] of boolean; {free cells} -@t\hskip10pt@>@!was_free: packed array [mem_min..mem_max] of boolean; - {previously free cells} -@t\hskip10pt@>@!was_mem_end,@!was_lo_max,@!was_hi_min: pointer; - {previous |mem_end|, |lo_mem_max|, and |hi_mem_min|} -@t\hskip10pt@>@!panicking:boolean; {do we want to check memory constantly?} -gubed - -@ @<Set initial...@>= -@!debug was_mem_end:=mem_min; {indicate that everything was previously free} -was_lo_max:=mem_min; was_hi_min:=mem_max; -panicking:=false; -gubed - -@ Procedure |check_mem| makes sure that the available space lists of -|mem| are well formed, and it optionally prints out all locations -that are reserved now but were free the last time this procedure was called. - -@p @!debug procedure check_mem(@!print_locs : boolean); -label done1,done2; {loop exits} -var p,@!q:pointer; {current locations of interest in |mem|} -@!clobbered:boolean; {is something amiss?} -begin for p:=mem_min to lo_mem_max do free[p]:=false; {you can probably - do this faster} -for p:=hi_mem_min to mem_end do free[p]:=false; {ditto} -@<Check single-word |avail| list@>; -@<Check variable-size |avail| list@>; -@<Check flags of unavailable nodes@>; -if print_locs then @<Print newly busy locations@>; -for p:=mem_min to lo_mem_max do was_free[p]:=free[p]; -for p:=hi_mem_min to mem_end do was_free[p]:=free[p]; - {|was_free:=free| might be faster} -was_mem_end:=mem_end; was_lo_max:=lo_mem_max; was_hi_min:=hi_mem_min; -end; -gubed - -@ @<Check single-word...@>= -p:=avail; q:=null; clobbered:=false; -while p<>null do - begin if (p>mem_end)or(p<hi_mem_min) then clobbered:=true - else if free[p] then clobbered:=true; - if clobbered then - begin print_nl("AVAIL list clobbered at "); -@.AVAIL list clobbered...@> - print_int(q); goto done1; - end; - free[p]:=true; q:=p; p:=link(q); - end; -done1: - -@ @<Check variable-size...@>= -p:=rover; q:=null; clobbered:=false; -repeat if (p>=lo_mem_max)or(p<mem_min) then clobbered:=true - else if (rlink(p)>=lo_mem_max)or(rlink(p)<mem_min) then clobbered:=true - else if not(is_empty(p))or(node_size(p)<2)or@| - (p+node_size(p)>lo_mem_max)or@| (llink(rlink(p))<>p) then clobbered:=true; - if clobbered then - begin print_nl("Double-AVAIL list clobbered at "); - print_int(q); goto done2; - end; -for q:=p to p+node_size(p)-1 do {mark all locations free} - begin if free[q] then - begin print_nl("Doubly free location at "); -@.Doubly free location...@> - print_int(q); goto done2; - end; - free[q]:=true; - end; -q:=p; p:=rlink(p); -until p=rover; -done2: - -@ @<Check flags...@>= -p:=mem_min; -while p<=lo_mem_max do {node |p| should not be empty} - begin if is_empty(p) then - begin print_nl("Bad flag at "); print_int(p); -@.Bad flag...@> - end; - while (p<=lo_mem_max) and not free[p] do incr(p); - while (p<=lo_mem_max) and free[p] do incr(p); - end - -@ @<Print newly busy...@>= -begin print_nl("New busy locs:"); -for p:=mem_min to lo_mem_max do - if not free[p] and ((p>was_lo_max) or was_free[p]) then - begin print_char(" "); print_int(p); - end; -for p:=hi_mem_min to mem_end do - if not free[p] and - ((p<was_hi_min) or (p>was_mem_end) or was_free[p]) then - begin print_char(" "); print_int(p); - end; -end - -@ The |search_mem| procedure attempts to answer the question ``Who points -to node~|p|?'' In doing so, it fetches |link| and |info| fields of |mem| -that might not be of type |two_halves|. Strictly speaking, this is -@^dirty \PASCAL@> -undefined in \PASCAL, and it can lead to ``false drops'' (words that seem to -point to |p| purely by coincidence). But for debugging purposes, we want -to rule out the places that do {\sl not\/} point to |p|, so a few false -drops are tolerable. - -@p @!debug procedure search_mem(@!p:pointer); {look for pointers to |p|} -var q:integer; {current position being searched} -begin for q:=mem_min to lo_mem_max do - begin if link(q)=p then - begin print_nl("LINK("); print_int(q); print_char(")"); - end; - if info(q)=p then - begin print_nl("INFO("); print_int(q); print_char(")"); - end; - end; -for q:=hi_mem_min to mem_end do - begin if link(q)=p then - begin print_nl("LINK("); print_int(q); print_char(")"); - end; - if info(q)=p then - begin print_nl("INFO("); print_int(q); print_char(")"); - end; - end; -@<Search |eqtb| for equivalents equal to |p|@>; -@<Search |save_stack| for equivalents that point to |p|@>; -@<Search |hyph_list| for pointers to |p|@>; -end; -gubed - -@* \[12] Displaying boxes. -We can reinforce our knowledge of the data structures just introduced -by considering two procedures that display a list in symbolic form. -The first of these, called |short_display|, is used in ``overfull box'' -messages to give the top-level description of a list. The other one, -called |show_node_list|, prints a detailed description of exactly what -is in the data structure. - -The philosophy of |short_display| is to ignore the fine points about exactly -what is inside boxes, except that ligatures and discretionary breaks are -expanded. As a result, |short_display| is a recursive procedure, but the -recursion is never more than one level deep. -@^recursion@> - -A global variable |font_in_short_display| keeps track of the font code that -is assumed to be present when |short_display| begins; deviations from this -font will be printed. - -@<Glob...@>= -@!font_in_short_display:integer; {an internal font number} - -@ Boxes, rules, inserts, whatsits, marks, and things in general that are -sort of ``complicated'' are indicated only by printing `\.{[]}'. - -@p procedure short_display(@!p:integer); {prints highlights of list |p|} -var n:integer; {for replacement counts} -begin while p>mem_min do - begin if is_char_node(p) then - begin if p<=mem_end then - begin if font(p)<>font_in_short_display then - begin if (font(p)<font_base)or(font(p)>font_max) then - print_char("*") -@.*\relax@> - else @<Print the font identifier for |font(p)|@>; - print_char(" "); font_in_short_display:=font(p); - end; - print_ASCII(qo(character(p))); - end; - end - else @<Print a short indication of the contents of node |p|@>; - p:=link(p); - end; -end; - -@ @<Print a short indication of the contents of node |p|@>= -case type(p) of -hlist_node,vlist_node,ins_node,whatsit_node,mark_node,adjust_node, - unset_node: print("[]"); -rule_node: print_char("|"); -glue_node: if glue_ptr(p)<>zero_glue then print_char(" "); -math_node: print_char("$"); -ligature_node: short_display(lig_ptr(p)); -disc_node: begin short_display(pre_break(p)); - short_display(post_break(p));@/ - n:=replace_count(p); - while n>0 do - begin if link(p)<>null then p:=link(p); - decr(n); - end; - end; -othercases do_nothing -endcases - -@ The |show_node_list| routine requires some auxiliary subroutines: one to -print a font-and-character combination, one to print a token list without -its reference count, and one to print a rule dimension. - -@p procedure print_font_and_char(@!p:integer); {prints |char_node| data} -begin if p>mem_end then print_esc("CLOBBERED.") -else begin if (font(p)<font_base)or(font(p)>font_max) then print_char("*") -@.*\relax@> - else @<Print the font identifier for |font(p)|@>; - print_char(" "); print_ASCII(qo(character(p))); - end; -end; -@# -procedure print_mark(@!p:integer); {prints token list data in braces} -begin print_char("{"); -if (p<hi_mem_min)or(p>mem_end) then print_esc("CLOBBERED.") -else show_token_list(link(p),null,max_print_line-10); -print_char("}"); -end; -@# -procedure print_rule_dimen(@!d:scaled); {prints dimension in rule node} -begin if is_running(d) then print_char("*") else print_scaled(d); -@.*\relax@> -end; - -@ Then there is a subroutine that prints glue stretch and shrink, possibly -followed by the name of finite units: - -@p procedure print_glue(@!d:scaled;@!order:integer;@!s:str_number); - {prints a glue component} -begin print_scaled(d); -if (order<normal)or(order>filll) then print("foul") -else if order>normal then - begin print("fil"); - while order>fil do - begin print_char("l"); decr(order); - end; - end -else if s<>0 then print(s); -end; - -@ The next subroutine prints a whole glue specification. - -@p procedure print_spec(@!p:integer;@!s:str_number); - {prints a glue specification} -begin if (p<mem_min)or(p>=lo_mem_max) then print_char("*") -@.*\relax@> -else begin print_scaled(width(p)); - if s<>0 then print(s); - if stretch(p)<>0 then - begin print(" plus "); print_glue(stretch(p),stretch_order(p),s); - end; - if shrink(p)<>0 then - begin print(" minus "); print_glue(shrink(p),shrink_order(p),s); - end; - end; -end; - -@ We also need to declare some procedures that appear later in this -documentation. - -@p @<Declare procedures needed for displaying the elements of mlists@>@; -@<Declare the procedure called |print_skip_param|@> - -@ Since boxes can be inside of boxes, |show_node_list| is inherently recursive, -@^recursion@> -up to a given maximum number of levels. The history of nesting is indicated -by the current string, which will be printed at the beginning of each line; -the length of this string, namely |cur_length|, is the depth of nesting. - -Recursive calls on |show_node_list| therefore use the following pattern: - -@d node_list_display(#)== - begin append_char("."); show_node_list(#); flush_char; - end {|str_room| need not be checked; see |show_box| below} - -@ A global variable called |depth_threshold| is used to record the maximum -depth of nesting for which |show_node_list| will show information. If we -have |depth_threshold=0|, for example, only the top level information will -be given and no sublists will be traversed. Another global variable, called -|breadth_max|, tells the maximum number of items to show at each level; -|breadth_max| had better be positive, or you won't see anything. - -@<Glob...@>= -@!depth_threshold : integer; {maximum nesting depth in box displays} -@!breadth_max : integer; {maximum number of items shown at the same list level} - -@ Now we are ready for |show_node_list| itself. This procedure has been -written to be ``extra robust'' in the sense that it should not crash or get -into a loop even if the data structures have been messed up by bugs in -the rest of the program. You can safely call its parent routine -|show_box(p)| for arbitrary values of |p| when you are debugging \TeX. -However, in the presence of bad data, the procedure may -@^dirty \PASCAL@>@^debugging@> -fetch a |memory_word| whose variant is different from the way it was stored; -for example, it might try to read |mem[p].hh| when |mem[p]| -contains a scaled integer, if |p| is a pointer that has been -clobbered or chosen at random. - -@p procedure show_node_list(@!p:integer); {prints a node list symbolically} -label exit; -var n:integer; {the number of items already printed at this level} -@!g:real; {a glue ratio, as a floating point number} -begin if cur_length>depth_threshold then - begin if p>null then print(" []"); - {indicate that there's been some truncation} - return; - end; -n:=0; -while p>mem_min do - begin print_ln; print_current_string; {display the nesting history} - if p>mem_end then {pointer out of range} - begin print("Bad link, display aborted."); return; -@.Bad link...@> - end; - incr(n); if n>breadth_max then {time to stop} - begin print("etc."); return; -@.etc@> - end; - @<Display node |p|@>; - p:=link(p); - end; -exit: -end; - -@ @<Display node |p|@>= -if is_char_node(p) then print_font_and_char(p) -else case type(p) of - hlist_node,vlist_node,unset_node: @<Display box |p|@>; - rule_node: @<Display rule |p|@>; - ins_node: @<Display insertion |p|@>; - whatsit_node: @<Display the whatsit node |p|@>; - glue_node: @<Display glue |p|@>; - kern_node: @<Display kern |p|@>; - math_node: @<Display math node |p|@>; - ligature_node: @<Display ligature |p|@>; - penalty_node: @<Display penalty |p|@>; - disc_node: @<Display discretionary |p|@>; - mark_node: @<Display mark |p|@>; - adjust_node: @<Display adjustment |p|@>; - @t\4@>@<Cases of |show_node_list| that arise in mlists only@>@; - othercases print("Unknown node type!") - endcases - -@ @<Display box |p|@>= -begin if type(p)=hlist_node then print_esc("h") -else if type(p)=vlist_node then print_esc("v") -else print_esc("unset"); -print("box("); print_scaled(height(p)); print_char("+"); -print_scaled(depth(p)); print(")x"); print_scaled(width(p)); -if type(p)=unset_node then - @<Display special fields of the unset node |p|@> -else begin @<Display the value of |glue_set(p)|@>; - if shift_amount(p)<>0 then - begin print(", shifted "); print_scaled(shift_amount(p)); - end; - end; -node_list_display(list_ptr(p)); {recursive call} -end - -@ @<Display special fields of the unset node |p|@>= -begin if span_count(p)<>min_quarterword then - begin print(" ("); print_int(qo(span_count(p))+1); - print(" columns)"); - end; -if glue_stretch(p)<>0 then - begin print(", stretch "); print_glue(glue_stretch(p),glue_order(p),0); - end; -if glue_shrink(p)<>0 then - begin print(", shrink "); print_glue(glue_shrink(p),glue_sign(p),0); - end; -end - -@ The code will have to change in this place if |glue_ratio| is -a structured type instead of an ordinary |real|. Note that this routine -should avoid arithmetic errors even if the |glue_set| field holds an -arbitrary random value. The following code assumes that a properly -formed nonzero |real| number has absolute value $2^{20}$ or more when -it is regarded as an integer; this precaution was adequate to prevent -floating point underflow on the author's computer. -@^system dependencies@> -@^dirty \PASCAL@> - -@<Display the value of |glue_set(p)|@>= -g:=float(glue_set(p)); -if (g<>float_constant(0))and(glue_sign(p)<>normal) then - begin print(", glue set "); - if glue_sign(p)=shrinking then print("- "); - if abs(mem[p+glue_offset].int)<@'4000000 then print("?.?") - else if abs(g)>float_constant(20000) then - begin if g>float_constant(0) then print_char(">") - else print("< -"); - print_glue(20000*unity,glue_order(p),0); - end - else print_glue(round(unity*g),glue_order(p),0); -@^real multiplication@> - end - -@ @<Display rule |p|@>= -begin print_esc("rule("); print_rule_dimen(height(p)); print_char("+"); -print_rule_dimen(depth(p)); print(")x"); print_rule_dimen(width(p)); -end - -@ @<Display insertion |p|@>= -begin print_esc("insert"); print_int(qo(subtype(p))); -print(", natural size "); print_scaled(height(p)); -print("; split("); print_spec(split_top_ptr(p),0); -print_char(","); print_scaled(depth(p)); -print("); float cost "); print_int(float_cost(p)); -node_list_display(ins_ptr(p)); {recursive call} -end - -@ @<Display glue |p|@>= -if subtype(p)>=a_leaders then @<Display leaders |p|@> -else begin print_esc("glue"); - if subtype(p)<>normal then - begin print_char("("); - if subtype(p)<cond_math_glue then - print_skip_param(subtype(p)-1) - else if subtype(p)=cond_math_glue then print_esc("nonscript") - else print_esc("mskip"); - print_char(")"); - end; - if subtype(p)<>cond_math_glue then - begin print_char(" "); - if subtype(p)<cond_math_glue then print_spec(glue_ptr(p),0) - else print_spec(glue_ptr(p),"mu"); - end; - end - -@ @<Display leaders |p|@>= -begin print_esc(""); -if subtype(p)=c_leaders then print_char("c") -else if subtype(p)=x_leaders then print_char("x"); -print("leaders "); print_spec(glue_ptr(p),0); -node_list_display(leader_ptr(p)); {recursive call} -end - -@ An ``explicit'' kern value is indicated implicitly by an explicit space. - -@<Display kern |p|@>= -if subtype(p)<>mu_glue then - begin print_esc("kern"); - if subtype(p)<>normal then print_char(" "); - print_scaled(width(p)); - if subtype(p)=acc_kern then print(" (for accent)"); -@.for accent@> - end -else begin print_esc("mkern"); print_scaled(width(p)); print("mu"); - end - -@ @<Display math node |p|@>= -begin print_esc("math"); -if subtype(p)=before then print("on") -else print("off"); -if width(p)<>0 then - begin print(", surrounded "); print_scaled(width(p)); - end; -end - -@ @<Display ligature |p|@>= -begin print_font_and_char(lig_char(p)); print(" (ligature "); -if subtype(p)>1 then print_char("|"); -font_in_short_display:=font(lig_char(p)); short_display(lig_ptr(p)); -if odd(subtype(p)) then print_char("|"); -print_char(")"); -end - -@ @<Display penalty |p|@>= -begin print_esc("penalty "); print_int(penalty(p)); -end - -@ The |post_break| list of a discretionary node is indicated by a prefixed -`\.{\char'174}' instead of the `\..' before the |pre_break| list. - -@<Display discretionary |p|@>= -begin print_esc("discretionary"); -if replace_count(p)>0 then - begin print(" replacing "); print_int(replace_count(p)); - end; -node_list_display(pre_break(p)); {recursive call} -append_char("|"); show_node_list(post_break(p)); flush_char; {recursive call} -end - -@ @<Display mark |p|@>= -begin print_esc("mark"); print_mark(mark_ptr(p)); -end - -@ @<Display adjustment |p|@>= -begin print_esc("vadjust"); node_list_display(adjust_ptr(p)); {recursive call} -end - -@ The recursive machinery is started by calling |show_box|. -@^recursion@> - -@p procedure show_box(@!p:pointer); -begin @<Assign the values |depth_threshold:=show_box_depth| and - |breadth_max:=show_box_breadth|@>; -if breadth_max<=0 then breadth_max:=5; -if pool_ptr+depth_threshold>=pool_size then - depth_threshold:=pool_size-pool_ptr-1; - {now there's enough room for prefix string} -show_node_list(p); {the show starts at |p|} -print_ln; -end; - -@* \[13] Destroying boxes. -When we are done with a node list, we are obliged to return it to free -storage, including all of its sublists. The recursive procedure -|flush_node_list| does this for us. - -@ First, however, we shall consider two non-recursive procedures that do -simpler tasks. The first of these, |delete_token_ref|, is called when -a pointer to a token list's reference count is being removed. This means -that the token list should disappear if the reference count was |null|, -otherwise the count should be decreased by one. -@^reference counts@> - -@d token_ref_count(#) == info(#) {reference count preceding a token list} - -@p procedure delete_token_ref(@!p:pointer); {|p| points to the reference count - of a token list that is losing one reference} -begin if token_ref_count(p)=null then flush_list(p) -else decr(token_ref_count(p)); -end; - -@ Similarly, |delete_glue_ref| is called when a pointer to a glue -specification is being withdrawn. -@^reference counts@> -@d fast_delete_glue_ref(#)==@t@>@;@/ - begin if glue_ref_count(#)=null then free_node(#,glue_spec_size) - else decr(glue_ref_count(#)); - end - -@p procedure delete_glue_ref(@!p:pointer); {|p| points to a glue specification} -fast_delete_glue_ref(p); - -@ Now we are ready to delete any node list, recursively. -In practice, the nodes deleted are usually charnodes (about 2/3 of the time), -and they are glue nodes in about half of the remaining cases. -@^recursion@> - -@p procedure flush_node_list(@!p:pointer); {erase list of nodes starting at |p|} -label done; {go here when node |p| has been freed} -var q:pointer; {successor to node |p|} -begin while p<>null do -@^inner loop@> - begin q:=link(p); - if is_char_node(p) then free_avail(p) - else begin case type(p) of - hlist_node,vlist_node,unset_node: begin flush_node_list(list_ptr(p)); - free_node(p,box_node_size); goto done; - end; - rule_node: begin free_node(p,rule_node_size); goto done; - end; - ins_node: begin flush_node_list(ins_ptr(p)); - delete_glue_ref(split_top_ptr(p)); - free_node(p,ins_node_size); goto done; - end; - whatsit_node: @<Wipe out the whatsit node |p| and |goto done|@>; - glue_node: begin fast_delete_glue_ref(glue_ptr(p)); - if leader_ptr(p)<>null then flush_node_list(leader_ptr(p)); - end; - kern_node,math_node,penalty_node: do_nothing; - ligature_node: flush_node_list(lig_ptr(p)); - mark_node: delete_token_ref(mark_ptr(p)); - disc_node: begin flush_node_list(pre_break(p)); - flush_node_list(post_break(p)); - end; - adjust_node: flush_node_list(adjust_ptr(p)); - @t\4@>@<Cases of |flush_node_list| that arise in mlists only@>@; - othercases confusion("flushing") -@:this can't happen flushing}{\quad flushing@> - endcases;@/ - free_node(p,small_node_size); - done:end; - p:=q; - end; -end; - -@* \[14] Copying boxes. -Another recursive operation that acts on boxes is sometimes needed: The -procedure |copy_node_list| returns a pointer to another node list that has -the same structure and meaning as the original. Note that since glue -specifications and token lists have reference counts, we need not make -copies of them. Reference counts can never get too large to fit in a -halfword, since each pointer to a node is in a different memory address, -and the total number of memory addresses fits in a halfword. -@^recursion@> -@^reference counts@> - -(Well, there actually are also references from outside |mem|; if the -|save_stack| is made arbitrarily large, it would theoretically be possible -to break \TeX\ by overflowing a reference count. But who would want to do that?) - -@d add_token_ref(#)==incr(token_ref_count(#)) {new reference to a token list} -@d add_glue_ref(#)==incr(glue_ref_count(#)) {new reference to a glue spec} - -@ The copying procedure copies words en masse without bothering -to look at their individual fields. If the node format changes---for -example, if the size is altered, or if some link field is moved to another -relative position---then this code may need to be changed too. -@^data structure assumptions@> - -@p function copy_node_list(@!p:pointer):pointer; {makes a duplicate of the - node list that starts at |p| and returns a pointer to the new list} -var h:pointer; {temporary head of copied list} -@!q:pointer; {previous position in new list} -@!r:pointer; {current node being fabricated for new list} -@!words:0..5; {number of words remaining to be copied} -begin h:=get_avail; q:=h; -while p<>null do - begin @<Make a copy of node |p| in node |r|@>; - link(q):=r; q:=r; p:=link(p); - end; -link(q):=null; q:=link(h); free_avail(h); -copy_node_list:=q; -end; - -@ @<Make a copy of node |p|...@>= -words:=1; {this setting occurs in more branches than any other} -if is_char_node(p) then r:=get_avail -else @<Case statement to copy different types and set |words| to the number - of initial words not yet copied@>; -while words>0 do - begin decr(words); mem[r+words]:=mem[p+words]; - end - -@ @<Case statement to copy...@>= -case type(p) of -hlist_node,vlist_node,unset_node: begin r:=get_node(box_node_size); - mem[r+6]:=mem[p+6]; mem[r+5]:=mem[p+5]; {copy the last two words} - list_ptr(r):=copy_node_list(list_ptr(p)); {this affects |mem[r+5]|} - words:=5; - end; -rule_node: begin r:=get_node(rule_node_size); words:=rule_node_size; - end; -ins_node: begin r:=get_node(ins_node_size); mem[r+4]:=mem[p+4]; - add_glue_ref(split_top_ptr(p)); - ins_ptr(r):=copy_node_list(ins_ptr(p)); {this affects |mem[r+4]|} - words:=ins_node_size-1; - end; -whatsit_node:@<Make a partial copy of the whatsit node |p| and make |r| - point to it; set |words| to the number of initial words not yet copied@>; -glue_node: begin r:=get_node(small_node_size); add_glue_ref(glue_ptr(p)); - glue_ptr(r):=glue_ptr(p); leader_ptr(r):=copy_node_list(leader_ptr(p)); - end; -kern_node,math_node,penalty_node: begin r:=get_node(small_node_size); - words:=small_node_size; - end; -ligature_node: begin r:=get_node(small_node_size); - mem[lig_char(r)]:=mem[lig_char(p)]; {copy |font| and |character|} - lig_ptr(r):=copy_node_list(lig_ptr(p)); - end; -disc_node: begin r:=get_node(small_node_size); - pre_break(r):=copy_node_list(pre_break(p)); - post_break(r):=copy_node_list(post_break(p)); - end; -mark_node: begin r:=get_node(small_node_size); add_token_ref(mark_ptr(p)); - words:=small_node_size; - end; -adjust_node: begin r:=get_node(small_node_size); - adjust_ptr(r):=copy_node_list(adjust_ptr(p)); - end; {|words=1=small_node_size-1|} -othercases confusion("copying") -@:this can't happen copying}{\quad copying@> -endcases - -@* \[15] The command codes. -Before we can go any further, we need to define symbolic names for the internal -code numbers that represent the various commands obeyed by \TeX. These codes -are somewhat arbitrary, but not completely so. For example, the command -codes for character types are fixed by the language, since a user says, -e.g., `\.{\\catcode \`\\\${} = 3}' to make \.{\char'44} a math delimiter, -and the command code |math_shift| is equal to~3. Some other codes have -been made adjacent so that |case| statements in the program need not consider -cases that are widely spaced, or so that |case| statements can be replaced -by |if| statements. - -At any rate, here is the list, for future reference. First come the -``catcode'' commands, several of which share their numeric codes with -ordinary commands when the catcode cannot emerge from \TeX's scanning routine. - -@d escape=0 {escape delimiter (called \.\\ in {\sl The \TeX book\/})} -@:TeXbook}{\sl The \TeX book@> -@d relax=0 {do nothing ( \.{\\relax} )} -@d left_brace=1 {beginning of a group ( \.\{ )} -@d right_brace=2 {ending of a group ( \.\} )} -@d math_shift=3 {mathematics shift character ( \.\$ )} -@d tab_mark=4 {alignment delimiter ( \.\&, \.{\\span} )} -@d car_ret=5 {end of line ( |carriage_return|, \.{\\cr}, \.{\\crcr} )} -@d out_param=5 {output a macro parameter} -@d mac_param=6 {macro parameter symbol ( \.\# )} -@d sup_mark=7 {superscript ( \.{\char'136} )} -@d sub_mark=8 {subscript ( \.{\char'137} )} -@d ignore=9 {characters to ignore ( \.{\^\^@@} )} -@d endv=9 {end of \<v_j> list in alignment template} -@d spacer=10 {characters equivalent to blank space ( \.{\ } )} -@d letter=11 {characters regarded as letters ( \.{A..Z}, \.{a..z} )} -@d other_char=12 {none of the special character types} -@d active_char=13 {characters that invoke macros ( \.{\char`\~} )} -@d par_end=13 {end of paragraph ( \.{\\par} )} -@d match=13 {match a macro parameter} -@d comment=14 {characters that introduce comments ( \.\% )} -@d end_match=14 {end of parameters to macro} -@d stop=14 {end of job ( \.{\\end}, \.{\\dump} )} -@d invalid_char=15 {characters that shouldn't appear ( \.{\^\^?} )} -@d delim_num=15 {specify delimiter numerically ( \.{\\delimiter} )} -@d max_char_code=15 {largest catcode for individual characters} - -@ Next are the ordinary run-of-the-mill command codes. Codes that are -|min_internal| or more represent internal quantities that might be -expanded by `\.{\\the}'. - -@d char_num=16 {character specified numerically ( \.{\\char} )} -@d math_char_num=17 {explicit math code ( \.{\\mathchar} )} -@d mark=18 {mark definition ( \.{\\mark} )} -@d xray=19 {peek inside of \TeX\ ( \.{\\show}, \.{\\showbox}, etc.~)} -@d make_box=20 {make a box ( \.{\\box}, \.{\\copy}, \.{\\hbox}, etc.~)} -@d hmove=21 {horizontal motion ( \.{\\moveleft}, \.{\\moveright} )} -@d vmove=22 {vertical motion ( \.{\\raise}, \.{\\lower} )} -@d un_hbox=23 {unglue a box ( \.{\\unhbox}, \.{\\unhcopy} )} -@d un_vbox=24 {unglue a box ( \.{\\unvbox}, \.{\\unvcopy} )} -@d remove_item=25 {nullify last item ( \.{\\unpenalty}, - \.{\\unkern}, \.{\\unskip} )} -@d hskip=26 {horizontal glue ( \.{\\hskip}, \.{\\hfil}, etc.~)} -@d vskip=27 {vertical glue ( \.{\\vskip}, \.{\\vfil}, etc.~)} -@d mskip=28 {math glue ( \.{\\mskip} )} -@d kern=29 {fixed space ( \.{\\kern} )} -@d mkern=30 {math kern ( \.{\\mkern} )} -@d leader_ship=31 {use a box ( \.{\\shipout}, \.{\\leaders}, etc.~)} -@d halign=32 {horizontal table alignment ( \.{\\halign} )} -@d valign=33 {vertical table alignment ( \.{\\valign} )} -@d no_align=34 {temporary escape from alignment ( \.{\\noalign} )} -@d vrule=35 {vertical rule ( \.{\\vrule} )} -@d hrule=36 {horizontal rule ( \.{\\hrule} )} -@d insert=37 {vlist inserted in box ( \.{\\insert} )} -@d vadjust=38 {vlist inserted in enclosing paragraph ( \.{\\vadjust} )} -@d ignore_spaces=39 {gobble |spacer| tokens ( \.{\\ignorespaces} )} -@d after_assignment=40 {save till assignment is done ( \.{\\afterassignment} )} -@d after_group=41 {save till group is done ( \.{\\aftergroup} )} -@d break_penalty=42 {additional badness ( \.{\\penalty} )} -@d start_par=43 {begin paragraph ( \.{\\indent}, \.{\\noindent} )} -@d ital_corr=44 {italic correction ( \.{\\/} )} -@d accent=45 {attach accent in text ( \.{\\accent} )} -@d math_accent=46 {attach accent in math ( \.{\\mathaccent} )} -@d discretionary=47 {discretionary texts ( \.{\\-}, \.{\\discretionary} )} -@d eq_no=48 {equation number ( \.{\\eqno}, \.{\\leqno} )} -@d left_right=49 {variable delimiter ( \.{\\left}, \.{\\right} )} -@d math_comp=50 {component of formula ( \.{\\mathbin}, etc.~)} -@d limit_switch=51 {diddle limit conventions ( \.{\\displaylimits}, etc.~)} -@d above=52 {generalized fraction ( \.{\\above}, \.{\\atop}, etc.~)} -@d math_style=53 {style specification ( \.{\\displaystyle}, etc.~)} -@d math_choice=54 {choice specification ( \.{\\mathchoice} )} -@d non_script=55 {conditional math glue ( \.{\\nonscript} )} -@d vcenter=56 {vertically center a vbox ( \.{\\vcenter} )} -@d case_shift=57 {force specific case ( \.{\\lowercase}, \.{\\uppercase}~)} -@d message=58 {send to user ( \.{\\message}, \.{\\errmessage} )} -@d extension=59 {extensions to \TeX\ ( \.{\\write}, \.{\\special}, etc.~)} -@d in_stream=60 {files for reading ( \.{\\openin}, \.{\\closein} )} -@d begin_group=61 {begin local grouping ( \.{\\begingroup} )} -@d end_group=62 {end local grouping ( \.{\\endgroup} )} -@d omit=63 {omit alignment template ( \.{\\omit} )} -@d ex_space=64 {explicit space ( \.{\\\ } )} -@d no_boundary=65 {suppress boundary ligatures ( \.{\\noboundary} )} -@d radical=66 {square root and similar signs ( \.{\\radical} )} -@d end_cs_name=67 {end control sequence ( \.{\\endcsname} )} -@d min_internal=68 {the smallest code that can follow \.{\\the}} -@d char_given=68 {character code defined by \.{\\chardef}} -@d math_given=69 {math code defined by \.{\\mathchardef}} -@d last_item=70 {most recent item ( \.{\\lastpenalty}, - \.{\\lastkern}, \.{\\lastskip} )} -@d max_non_prefixed_command=70 {largest command code that can't be \.{\\global}} - -@ The next codes are special; they all relate to mode-independent -assignment of values to \TeX's internal registers or tables. -Codes that are |max_internal| or less represent internal quantities -that might be expanded by `\.{\\the}'. - -@d toks_register=71 {token list register ( \.{\\toks} )} -@d assign_toks=72 {special token list ( \.{\\output}, \.{\\everypar}, etc.~)} -@d assign_int=73 {user-defined integer ( \.{\\tolerance}, \.{\\day}, etc.~)} -@d assign_dimen=74 {user-defined length ( \.{\\hsize}, etc.~)} -@d assign_glue=75 {user-defined glue ( \.{\\baselineskip}, etc.~)} -@d assign_mu_glue=76 {user-defined muglue ( \.{\\thinmuskip}, etc.~)} -@d assign_font_dimen=77 {user-defined font dimension ( \.{\\fontdimen} )} -@d assign_font_int=78 {user-defined font integer ( \.{\\hyphenchar}, - \.{\\skewchar} )} -@d set_aux=79 {specify state info ( \.{\\spacefactor}, \.{\\prevdepth} )} -@d set_prev_graf=80 {specify state info ( \.{\\prevgraf} )} -@d set_page_dimen=81 {specify state info ( \.{\\pagegoal}, etc.~)} -@d set_page_int=82 {specify state info ( \.{\\deadcycles}, - \.{\\insertpenalties} )} -@d set_box_dimen=83 {change dimension of box ( \.{\\wd}, \.{\\ht}, \.{\\dp} )} -@d set_shape=84 {specify fancy paragraph shape ( \.{\\parshape} )} -@d def_code=85 {define a character code ( \.{\\catcode}, etc.~)} -@d def_family=86 {declare math fonts ( \.{\\textfont}, etc.~)} -@d set_font=87 {set current font ( font identifiers )} -@d def_font=88 {define a font file ( \.{\\font} )} -@d register=89 {internal register ( \.{\\count}, \.{\\dimen}, etc.~)} -@d max_internal=89 {the largest code that can follow \.{\\the}} -@d advance=90 {advance a register or parameter ( \.{\\advance} )} -@d multiply=91 {multiply a register or parameter ( \.{\\multiply} )} -@d divide=92 {divide a register or parameter ( \.{\\divide} )} -@d prefix=93 {qualify a definition ( \.{\\global}, \.{\\long}, \.{\\outer} )} -@d let=94 {assign a command code ( \.{\\let}, \.{\\futurelet} )} -@d shorthand_def=95 {code definition ( \.{\\chardef}, \.{\\countdef}, etc.~)} -@d read_to_cs=96 {read into a control sequence ( \.{\\read} )} -@d def=97 {macro definition ( \.{\\def}, \.{\\gdef}, \.{\\xdef}, \.{\\edef} )} -@d set_box=98 {set a box ( \.{\\setbox} )} -@d hyph_data=99 {hyphenation data ( \.{\\hyphenation}, \.{\\patterns} )} -@d set_interaction=100 {define level of interaction ( \.{\\batchmode}, etc.~)} -@d max_command=100 {the largest command code seen at |big_switch|} - -@ The remaining command codes are extra special, since they cannot get through -\TeX's scanner to the main control routine. They have been given values higher -than |max_command| so that their special nature is easily discernible. -The ``expandable'' commands come first. - -@d undefined_cs=max_command+1 {initial state of most |eq_type| fields} -@d expand_after=max_command+2 {special expansion ( \.{\\expandafter} )} -@d no_expand=max_command+3 {special nonexpansion ( \.{\\noexpand} )} -@d input=max_command+4 {input a source file ( \.{\\input}, \.{\\endinput} )} -@d if_test=max_command+5 {conditional text ( \.{\\if}, \.{\\ifcase}, etc.~)} -@d fi_or_else=max_command+6 {delimiters for conditionals ( \.{\\else}, etc.~)} -@d cs_name=max_command+7 {make a control sequence from tokens ( \.{\\csname} )} -@d convert=max_command+8 {convert to text ( \.{\\number}, \.{\\string}, etc.~)} -@d the=max_command+9 {expand an internal quantity ( \.{\\the} )} -@d top_bot_mark=max_command+10 {inserted mark ( \.{\\topmark}, etc.~)} -@d call=max_command+11 {non-long, non-outer control sequence} -@d long_call=max_command+12 {long, non-outer control sequence} -@d outer_call=max_command+13 {non-long, outer control sequence} -@d long_outer_call=max_command+14 {long, outer control sequence} -@d end_template=max_command+15 {end of an alignment template} -@d dont_expand=max_command+16 {the following token was marked by \.{\\noexpand}} -@d glue_ref=max_command+17 {the equivalent points to a glue specification} -@d shape_ref=max_command+18 {the equivalent points to a parshape specification} -@d box_ref=max_command+19 {the equivalent points to a box node, or is |null|} -@d data=max_command+20 {the equivalent is simply a halfword number} - -@* \[16] The semantic nest. -\TeX\ is typically in the midst of building many lists at once. For example, -when a math formula is being processed, \TeX\ is in math mode and -working on an mlist; this formula has temporarily interrupted \TeX\ from -being in horizontal mode and building the hlist of a paragraph; and this -paragraph has temporarily interrupted \TeX\ from being in vertical mode -and building the vlist for the next page of a document. Similarly, when a -\.{\\vbox} occurs inside of an \.{\\hbox}, \TeX\ is temporarily -interrupted from working in restricted horizontal mode, and it enters -internal vertical mode. The ``semantic nest'' is a stack that -keeps track of what lists and modes are currently suspended. - -At each level of processing we are in one of six modes: - -\yskip\hang|vmode| stands for vertical mode (the page builder); - -\hang|hmode| stands for horizontal mode (the paragraph builder); - -\hang|mmode| stands for displayed formula mode; - -\hang|-vmode| stands for internal vertical mode (e.g., in a \.{\\vbox}); - -\hang|-hmode| stands for restricted horizontal mode (e.g., in an \.{\\hbox}); - -\hang|-mmode| stands for math formula mode (not displayed). - -\yskip\noindent The mode is temporarily set to zero while processing \.{\\write} -texts. - -Numeric values are assigned to |vmode|, |hmode|, and |mmode| so that -\TeX's ``big semantic switch'' can select the appropriate thing to -do by computing the value |abs(mode)+cur_cmd|, where |mode| is the current -mode and |cur_cmd| is the current command code. - -@d vmode=1 {vertical mode} -@d hmode=vmode+max_command+1 {horizontal mode} -@d mmode=hmode+max_command+1 {math mode} - -@p procedure print_mode(@!m:integer); {prints the mode represented by |m|} -begin if m>0 then - case m div (max_command+1) of - 0:print("vertical"); - 1:print("horizontal"); - 2:print("display math"); - end -else if m=0 then print("no") -else case (-m) div (max_command+1) of - 0:print("internal vertical"); - 1:print("restricted horizontal"); - 2:print("math"); - end; -print(" mode"); -end; - -@ The state of affairs at any semantic level can be represented by -five values: - -\yskip\hang|mode| is the number representing the semantic mode, as -just explained. - -\yskip\hang|head| is a |pointer| to a list head for the list being built; -|link(head)| therefore points to the first element of the list, or -to |null| if the list is empty. - -\yskip\hang|tail| is a |pointer| to the final node of the list being -built; thus, |tail=head| if and only if the list is empty. - -\yskip\hang|prev_graf| is the number of lines of the current paragraph that -have already been put into the present vertical list. - -\yskip\hang|aux| is an auxiliary |memory_word| that gives further information -that is needed to characterize the situation. - -\yskip\noindent -In vertical mode, |aux| is also known as |prev_depth|; it is the scaled -value representing the depth of the previous box, for use in baseline -calculations, or it is |<=-1000|pt if the next box on the vertical list is to -be exempt from baseline calculations. In horizontal mode, |aux| is also -known as |space_factor| and |clang|; it holds the current space factor used in -spacing calculations, and the current language used for hyphenation. -(The value of |clang| is undefined in restricted horizontal mode.) -In math mode, |aux| is also known as |incompleat_noad|; if -not |null|, it points to a record that represents the numerator of a -generalized fraction for which the denominator is currently being formed -in the current list. - -There is also a sixth quantity, |mode_line|, which correlates -the semantic nest with the user's input; |mode_line| contains the source -line number at which the current level of nesting was entered. The negative -of this line number is the |mode_line| at the level of the -user's output routine. - -In horizontal mode, the |prev_graf| field is used for initial language data. - -The semantic nest is an array called |nest| that holds the |mode|, |head|, -|tail|, |prev_graf|, |aux|, and |mode_line| values for all semantic levels -below the currently active one. Information about the currently active -level is kept in the global quantities |mode|, |head|, |tail|, |prev_graf|, -|aux|, and |mode_line|, which live in a \PASCAL\ record that is ready to -be pushed onto |nest| if necessary. - -@d ignore_depth==-65536000 {|prev_depth| value that is ignored} - -@<Types...@>= -@!list_state_record=record@!mode_field:-mmode..mmode;@+ - @!head_field,@!tail_field: pointer; - @!pg_field,@!ml_field: integer;@+ - @!aux_field: memory_word; - end; - -@ @d mode==cur_list.mode_field {current mode} -@d head==cur_list.head_field {header node of current list} -@d tail==cur_list.tail_field {final node on current list} -@d prev_graf==cur_list.pg_field {number of paragraph lines accumulated} -@d aux==cur_list.aux_field {auxiliary data about the current list} -@d prev_depth==aux.sc {the name of |aux| in vertical mode} -@d space_factor==aux.hh.lh {part of |aux| in horizontal mode} -@d clang==aux.hh.rh {the other part of |aux| in horizontal mode} -@d incompleat_noad==aux.int {the name of |aux| in math mode} -@d mode_line==cur_list.ml_field {source file line number at beginning of list} - -@<Glob...@>= -@!nest:array[0..nest_size] of list_state_record; -@!nest_ptr:0..nest_size; {first unused location of |nest|} -@!max_nest_stack:0..nest_size; {maximum of |nest_ptr| when pushing} -@!cur_list:list_state_record; {the ``top'' semantic state} -@!shown_mode:-mmode..mmode; {most recent mode shown by \.{\\tracingcommands}} - -@ Here is a common way to make the current list grow: - -@d tail_append(#)==begin link(tail):=#; tail:=link(tail); - end - -@ We will see later that the vertical list at the bottom semantic level is split -into two parts; the ``current page'' runs from |page_head| to |page_tail|, -and the ``contribution list'' runs from |contrib_head| to |tail| of -semantic level zero. The idea is that contributions are first formed in -vertical mode, then ``contributed'' to the current page (during which time -the page-breaking decisions are made). For now, we don't need to know -any more details about the page-building process. - -@<Set init...@>= -nest_ptr:=0; max_nest_stack:=0; -mode:=vmode; head:=contrib_head; tail:=contrib_head; -prev_depth:=ignore_depth; mode_line:=0; -prev_graf:=0; shown_mode:=0; -@<Start a new current page@>; - -@ When \TeX's work on one level is interrupted, the state is saved by -calling |push_nest|. This routine changes |head| and |tail| so that -a new (empty) list is begun; it does not change |mode| or |aux|. - -@p procedure push_nest; {enter a new semantic level, save the old} -begin if nest_ptr>max_nest_stack then - begin max_nest_stack:=nest_ptr; - if nest_ptr=nest_size then overflow("semantic nest size",nest_size); -@:TeX capacity exceeded semantic nest size}{\quad semantic nest size@> - end; -nest[nest_ptr]:=cur_list; {stack the record} -incr(nest_ptr); head:=get_avail; tail:=head; prev_graf:=0; mode_line:=line; -end; - -@ Conversely, when \TeX\ is finished on the current level, the former -state is restored by calling |pop_nest|. This routine will never be -called at the lowest semantic level, nor will it be called unless |head| -is a node that should be returned to free memory. - -@p procedure pop_nest; {leave a semantic level, re-enter the old} -begin free_avail(head); decr(nest_ptr); cur_list:=nest[nest_ptr]; -end; - -@ Here is a procedure that displays what \TeX\ is working on, at all levels. - -@p procedure@?print_totals; forward;@t\2@> -procedure show_activities; -var p:0..nest_size; {index into |nest|} -@!m:-mmode..mmode; {mode} -@!a:memory_word; {auxiliary} -@!q,@!r:pointer; {for showing the current page} -@!t:integer; {ditto} -begin nest[nest_ptr]:=cur_list; {put the top level into the array} -print_nl(""); print_ln; -for p:=nest_ptr downto 0 do - begin m:=nest[p].mode_field; a:=nest[p].aux_field; - print_nl("### "); print_mode(m); - print(" entered at line "); print_int(abs(nest[p].ml_field)); - if m=hmode then if nest[p].pg_field <> @'40600000 then - begin print(" (language"); print_int(nest[p].pg_field mod @'200000); - print(":hyphenmin"); print_int(nest[p].pg_field div @'20000000); - print_char(","); print_int((nest[p].pg_field div @'200000) mod @'100); - print_char(")"); - end; - if nest[p].ml_field<0 then print(" (\output routine)"); - if p=0 then - begin @<Show the status of the current page@>; - if link(contrib_head)<>null then - print_nl("### recent contributions:"); - end; - show_box(link(nest[p].head_field)); - @<Show the auxiliary field, |a|@>; - end; -end; - -@ @<Show the auxiliary...@>= -case abs(m) div (max_command+1) of -0: begin print_nl("prevdepth "); - if a.sc<=ignore_depth then print("ignored") - else print_scaled(a.sc); - if nest[p].pg_field<>0 then - begin print(", prevgraf "); - print_int(nest[p].pg_field); print(" line"); - if nest[p].pg_field<>1 then print_char("s"); - end; - end; -1: begin print_nl("spacefactor "); print_int(a.hh.lh); - if m>0 then@+ if a.hh.rh>0 then - begin print(", current language "); print_int(a.hh.rh);@+ - end; - end; -2: if a.int<>null then - begin print("this will begin denominator of:"); show_box(a.int);@+ - end; -end {there are no other cases} - -@* \[17] The table of equivalents. -Now that we have studied the data structures for \TeX's semantic routines, -we ought to consider the data structures used by its syntactic routines. In -other words, our next concern will be -the tables that \TeX\ looks at when it is scanning -what the user has written. - -The biggest and most important such table is called |eqtb|. It holds the -current ``equivalents'' of things; i.e., it explains what things mean -or what their current values are, for all quantities that are subject to -the nesting structure provided by \TeX's grouping mechanism. There are six -parts to |eqtb|: - -\yskip\hangg 1) |eqtb[active_base..(hash_base-1)]| holds the current -equivalents of single-character control sequences. - -\yskip\hangg 2) |eqtb[hash_base..(glue_base-1)]| holds the current -equivalents of multiletter control sequences. - -\yskip\hangg 3) |eqtb[glue_base..(local_base-1)]| holds the current -equivalents of glue parameters like the current baselineskip. - -\yskip\hangg 4) |eqtb[local_base..(int_base-1)]| holds the current -equivalents of local halfword quantities like the current box registers, -the current ``catcodes,'' the current font, and a pointer to the current -paragraph shape. - -\yskip\hangg 5) |eqtb[int_base..(dimen_base-1)]| holds the current -equivalents of fullword integer parameters like the current hyphenation -penalty. - -\yskip\hangg 6) |eqtb[dimen_base..eqtb_size]| holds the current equivalents -of fullword dimension parameters like the current hsize or amount of -hanging indentation. - -\yskip\noindent Note that, for example, the current amount of -baselineskip glue is determined by the setting of a particular location -in region~3 of |eqtb|, while the current meaning of the control sequence -`\.{\\baselineskip}' (which might have been changed by \.{\\def} or -\.{\\let}) appears in region~2. - -@ Each entry in |eqtb| is a |memory_word|. Most of these words are of type -|two_halves|, and subdivided into three fields: - -\yskip\hangg 1) The |eq_level| (a quarterword) is the level of grouping at -which this equivalent was defined. If the level is |level_zero|, the -equivalent has never been defined; |level_one| refers to the outer level -(outside of all groups), and this level is also used for global -definitions that never go away. Higher levels are for equivalents that -will disappear at the end of their group. @^global definitions@> - -\yskip\hangg 2) The |eq_type| (another quarterword) specifies what kind of -entry this is. There are many types, since each \TeX\ primitive like -\.{\\hbox}, \.{\\def}, etc., has its own special code. The list of -command codes above includes all possible settings of the |eq_type| field. - -\yskip\hangg 3) The |equiv| (a halfword) is the current equivalent value. -This may be a font number, a pointer into |mem|, or a variety of other -things. - -@d eq_level_field(#)==#.hh.b1 -@d eq_type_field(#)==#.hh.b0 -@d equiv_field(#)==#.hh.rh -@d eq_level(#)==eq_level_field(eqtb[#]) {level of definition} -@d eq_type(#)==eq_type_field(eqtb[#]) {command code for equivalent} -@d equiv(#)==equiv_field(eqtb[#]) {equivalent value} -@d level_zero=min_quarterword {level for undefined quantities} -@d level_one=level_zero+1 {outermost level for defined quantities} - -@ Many locations in |eqtb| have symbolic names. The purpose of the next -paragraphs is to define these names, and to set up the initial values of the -equivalents. - -In the first region we have 256 equivalents for ``active characters'' that -act as control sequences, followed by 256 equivalents for single-character -control sequences. - -Then comes region~2, which corresponds to the hash table that we will -define later. The maximum address in this region is used for a dummy -control sequence that is perpetually undefined. There also are several -locations for control sequences that are perpetually defined -(since they are used in error recovery). - -@d active_base=1 {beginning of region 1, for active character equivalents} -@d single_base=active_base+256 {equivalents of one-character control sequences} -@d null_cs=single_base+256 {equivalent of \.{\\csname\\endcsname}} -@d hash_base=null_cs+1 {beginning of region 2, for the hash table} -@d frozen_control_sequence=hash_base+hash_size {for error recovery} -@d frozen_protection=frozen_control_sequence {inaccessible but definable} -@d frozen_cr=frozen_control_sequence+1 {permanent `\.{\\cr}'} -@d frozen_end_group=frozen_control_sequence+2 {permanent `\.{\\endgroup}'} -@d frozen_right=frozen_control_sequence+3 {permanent `\.{\\right}'} -@d frozen_fi=frozen_control_sequence+4 {permanent `\.{\\fi}'} -@d frozen_end_template=frozen_control_sequence+5 {permanent `\.{\\endtemplate}'} -@d frozen_endv=frozen_control_sequence+6 {second permanent `\.{\\endtemplate}'} -@d frozen_relax=frozen_control_sequence+7 {permanent `\.{\\relax}'} -@d end_write=frozen_control_sequence+8 {permanent `\.{\\endwrite}'} -@d frozen_dont_expand=frozen_control_sequence+9 - {permanent `\.{\\notexpanded:}'} -@d frozen_null_font=frozen_control_sequence+10 - {permanent `\.{\\nullfont}'} -@d font_id_base=frozen_null_font-font_base - {begins table of 257 permanent font identifiers} -@d undefined_control_sequence=frozen_null_font+257 {dummy location} -@d glue_base=undefined_control_sequence+1 {beginning of region 3} - -@<Initialize table entries...@>= -eq_type(undefined_control_sequence):=undefined_cs; -equiv(undefined_control_sequence):=null; -eq_level(undefined_control_sequence):=level_zero; -for k:=active_base to undefined_control_sequence-1 do - eqtb[k]:=eqtb[undefined_control_sequence]; - -@ Here is a routine that displays the current meaning of an |eqtb| entry -in region 1 or~2. (Similar routines for the other regions will appear -below.) - -@<Show equivalent |n|, in region 1 or 2@>= -begin sprint_cs(n); print_char("="); print_cmd_chr(eq_type(n),equiv(n)); -if eq_type(n)>=call then - begin print_char(":"); show_token_list(link(equiv(n)),null,32); - end; -end - -@ Region 3 of |eqtb| contains the 256 \.{\\skip} registers, as well as the -glue parameters defined here. It is important that the ``muskip'' -parameters have larger numbers than the others. - -@d line_skip_code=0 {interline glue if |baseline_skip| is infeasible} -@d baseline_skip_code=1 {desired glue between baselines} -@d par_skip_code=2 {extra glue just above a paragraph} -@d above_display_skip_code=3 {extra glue just above displayed math} -@d below_display_skip_code=4 {extra glue just below displayed math} -@d above_display_short_skip_code=5 - {glue above displayed math following short lines} -@d below_display_short_skip_code=6 - {glue below displayed math following short lines} -@d left_skip_code=7 {glue at left of justified lines} -@d right_skip_code=8 {glue at right of justified lines} -@d top_skip_code=9 {glue at top of main pages} -@d split_top_skip_code=10 {glue at top of split pages} -@d tab_skip_code=11 {glue between aligned entries} -@d space_skip_code=12 {glue between words (if not |zero_glue|)} -@d xspace_skip_code=13 {glue after sentences (if not |zero_glue|)} -@d par_fill_skip_code=14 {glue on last line of paragraph} -@d thin_mu_skip_code=15 {thin space in math formula} -@d med_mu_skip_code=16 {medium space in math formula} -@d thick_mu_skip_code=17 {thick space in math formula} -@d glue_pars=18 {total number of glue parameters} -@d skip_base=glue_base+glue_pars {table of 256 ``skip'' registers} -@d mu_skip_base=skip_base+256 {table of 256 ``muskip'' registers} -@d local_base=mu_skip_base+256 {beginning of region 4} -@# -@d skip(#)==equiv(skip_base+#) {|mem| location of glue specification} -@d mu_skip(#)==equiv(mu_skip_base+#) {|mem| location of math glue spec} -@d glue_par(#)==equiv(glue_base+#) {|mem| location of glue specification} -@d line_skip==glue_par(line_skip_code) -@d baseline_skip==glue_par(baseline_skip_code) -@d par_skip==glue_par(par_skip_code) -@d above_display_skip==glue_par(above_display_skip_code) -@d below_display_skip==glue_par(below_display_skip_code) -@d above_display_short_skip==glue_par(above_display_short_skip_code) -@d below_display_short_skip==glue_par(below_display_short_skip_code) -@d left_skip==glue_par(left_skip_code) -@d right_skip==glue_par(right_skip_code) -@d top_skip==glue_par(top_skip_code) -@d split_top_skip==glue_par(split_top_skip_code) -@d tab_skip==glue_par(tab_skip_code) -@d space_skip==glue_par(space_skip_code) -@d xspace_skip==glue_par(xspace_skip_code) -@d par_fill_skip==glue_par(par_fill_skip_code) -@d thin_mu_skip==glue_par(thin_mu_skip_code) -@d med_mu_skip==glue_par(med_mu_skip_code) -@d thick_mu_skip==glue_par(thick_mu_skip_code) - -@<Current |mem| equivalent of glue parameter number |n|@>=glue_par(n) - -@ Sometimes we need to convert \TeX's internal code numbers into symbolic -form. The |print_skip_param| routine gives the symbolic name of a glue -parameter. - -@<Declare the procedure called |print_skip_param|@>= -procedure print_skip_param(@!n:integer); -begin case n of -line_skip_code: print_esc("lineskip"); -baseline_skip_code: print_esc("baselineskip"); -par_skip_code: print_esc("parskip"); -above_display_skip_code: print_esc("abovedisplayskip"); -below_display_skip_code: print_esc("belowdisplayskip"); -above_display_short_skip_code: print_esc("abovedisplayshortskip"); -below_display_short_skip_code: print_esc("belowdisplayshortskip"); -left_skip_code: print_esc("leftskip"); -right_skip_code: print_esc("rightskip"); -top_skip_code: print_esc("topskip"); -split_top_skip_code: print_esc("splittopskip"); -tab_skip_code: print_esc("tabskip"); -space_skip_code: print_esc("spaceskip"); -xspace_skip_code: print_esc("xspaceskip"); -par_fill_skip_code: print_esc("parfillskip"); -thin_mu_skip_code: print_esc("thinmuskip"); -med_mu_skip_code: print_esc("medmuskip"); -thick_mu_skip_code: print_esc("thickmuskip"); -othercases print("[unknown glue parameter!]") -endcases; -end; - -@ The symbolic names for glue parameters are put into \TeX's hash table -by using the routine called |primitive|, defined below. Let us enter them -now, so that we don't have to list all those parameter names anywhere else. - -@<Put each of \TeX's primitives into the hash table@>= -primitive("lineskip",assign_glue,glue_base+line_skip_code);@/ -@!@:line_skip_}{\.{\\lineskip} primitive@> -primitive("baselineskip",assign_glue,glue_base+baseline_skip_code);@/ -@!@:baseline_skip_}{\.{\\baselineskip} primitive@> -primitive("parskip",assign_glue,glue_base+par_skip_code);@/ -@!@:par_skip_}{\.{\\parskip} primitive@> -primitive("abovedisplayskip",assign_glue,glue_base+above_display_skip_code);@/ -@!@:above_display_skip_}{\.{\\abovedisplayskip} primitive@> -primitive("belowdisplayskip",assign_glue,glue_base+below_display_skip_code);@/ -@!@:below_display_skip_}{\.{\\belowdisplayskip} primitive@> -primitive("abovedisplayshortskip", - assign_glue,glue_base+above_display_short_skip_code);@/ -@!@:above_display_short_skip_}{\.{\\abovedisplayshortskip} primitive@> -primitive("belowdisplayshortskip", - assign_glue,glue_base+below_display_short_skip_code);@/ -@!@:below_display_short_skip_}{\.{\\belowdisplayshortskip} primitive@> -primitive("leftskip",assign_glue,glue_base+left_skip_code);@/ -@!@:left_skip_}{\.{\\leftskip} primitive@> -primitive("rightskip",assign_glue,glue_base+right_skip_code);@/ -@!@:right_skip_}{\.{\\rightskip} primitive@> -primitive("topskip",assign_glue,glue_base+top_skip_code);@/ -@!@:top_skip_}{\.{\\topskip} primitive@> -primitive("splittopskip",assign_glue,glue_base+split_top_skip_code);@/ -@!@:split_top_skip_}{\.{\\splittopskip} primitive@> -primitive("tabskip",assign_glue,glue_base+tab_skip_code);@/ -@!@:tab_skip_}{\.{\\tabskip} primitive@> -primitive("spaceskip",assign_glue,glue_base+space_skip_code);@/ -@!@:space_skip_}{\.{\\spaceskip} primitive@> -primitive("xspaceskip",assign_glue,glue_base+xspace_skip_code);@/ -@!@:xspace_skip_}{\.{\\xspaceskip} primitive@> -primitive("parfillskip",assign_glue,glue_base+par_fill_skip_code);@/ -@!@:par_fill_skip_}{\.{\\parfillskip} primitive@> -primitive("thinmuskip",assign_mu_glue,glue_base+thin_mu_skip_code);@/ -@!@:thin_mu_skip_}{\.{\\thinmuskip} primitive@> -primitive("medmuskip",assign_mu_glue,glue_base+med_mu_skip_code);@/ -@!@:med_mu_skip_}{\.{\\medmuskip} primitive@> -primitive("thickmuskip",assign_mu_glue,glue_base+thick_mu_skip_code);@/ -@!@:thick_mu_skip_}{\.{\\thickmuskip} primitive@> - -@ @<Cases of |print_cmd_chr| for symbolic printing of primitives@>= -assign_glue,assign_mu_glue: if chr_code<skip_base then - print_skip_param(chr_code-glue_base) - else if chr_code<mu_skip_base then - begin print_esc("skip"); print_int(chr_code-skip_base); - end - else begin print_esc("muskip"); print_int(chr_code-mu_skip_base); - end; - -@ All glue parameters and registers are initially `\.{0pt plus0pt minus0pt}'. - -@<Initialize table entries...@>= -equiv(glue_base):=zero_glue; eq_level(glue_base):=level_one; -eq_type(glue_base):=glue_ref; -for k:=glue_base+1 to local_base-1 do eqtb[k]:=eqtb[glue_base]; -glue_ref_count(zero_glue):=glue_ref_count(zero_glue)+local_base-glue_base; - -@ @<Show equivalent |n|, in region 3@>= -if n<skip_base then - begin print_skip_param(n-glue_base); print_char("="); - if n<glue_base+thin_mu_skip_code then print_spec(equiv(n),"pt") - else print_spec(equiv(n),"mu"); - end -else if n<mu_skip_base then - begin print_esc("skip"); print_int(n-skip_base); print_char("="); - print_spec(equiv(n),"pt"); - end -else begin print_esc("muskip"); print_int(n-mu_skip_base); print_char("="); - print_spec(equiv(n),"mu"); - end - -@ Region 4 of |eqtb| contains the local quantities defined here. The -bulk of this region is taken up by five tables that are indexed by eight-bit -characters; these tables are important to both the syntactic and semantic -portions of \TeX. There are also a bunch of special things like font and -token parameters, as well as the tables of \.{\\toks} and \.{\\box} -registers. - -@d par_shape_loc=local_base {specifies paragraph shape} -@d output_routine_loc=local_base+1 {points to token list for \.{\\output}} -@d every_par_loc=local_base+2 {points to token list for \.{\\everypar}} -@d every_math_loc=local_base+3 {points to token list for \.{\\everymath}} -@d every_display_loc=local_base+4 {points to token list for \.{\\everydisplay}} -@d every_hbox_loc=local_base+5 {points to token list for \.{\\everyhbox}} -@d every_vbox_loc=local_base+6 {points to token list for \.{\\everyvbox}} -@d every_job_loc=local_base+7 {points to token list for \.{\\everyjob}} -@d every_cr_loc=local_base+8 {points to token list for \.{\\everycr}} -@d err_help_loc=local_base+9 {points to token list for \.{\\errhelp}} -@d toks_base=local_base+10 {table of 256 token list registers} -@d box_base=toks_base+256 {table of 256 box registers} -@d cur_font_loc=box_base+256 {internal font number outside math mode} -@d math_font_base=cur_font_loc+1 {table of 48 math font numbers} -@d cat_code_base=math_font_base+48 - {table of 256 command codes (the ``catcodes'')} -@d lc_code_base=cat_code_base+256 {table of 256 lowercase mappings} -@d uc_code_base=lc_code_base+256 {table of 256 uppercase mappings} -@d sf_code_base=uc_code_base+256 {table of 256 spacefactor mappings} -@d math_code_base=sf_code_base+256 {table of 256 math mode mappings} -@d int_base=math_code_base+256 {beginning of region 5} -@# -@d par_shape_ptr==equiv(par_shape_loc) -@d output_routine==equiv(output_routine_loc) -@d every_par==equiv(every_par_loc) -@d every_math==equiv(every_math_loc) -@d every_display==equiv(every_display_loc) -@d every_hbox==equiv(every_hbox_loc) -@d every_vbox==equiv(every_vbox_loc) -@d every_job==equiv(every_job_loc) -@d every_cr==equiv(every_cr_loc) -@d err_help==equiv(err_help_loc) -@d toks(#)==equiv(toks_base+#) -@d box(#)==equiv(box_base+#) -@d cur_font==equiv(cur_font_loc) -@d fam_fnt(#)==equiv(math_font_base+#) -@d cat_code(#)==equiv(cat_code_base+#) -@d lc_code(#)==equiv(lc_code_base+#) -@d uc_code(#)==equiv(uc_code_base+#) -@d sf_code(#)==equiv(sf_code_base+#) -@d math_code(#)==equiv(math_code_base+#) - {Note: |math_code(c)| is the true math code plus |min_halfword|} - -@<Put each...@>= -primitive("output",assign_toks,output_routine_loc); -@!@:output_}{\.{\\output} primitive@> -primitive("everypar",assign_toks,every_par_loc); -@!@:every_par_}{\.{\\everypar} primitive@> -primitive("everymath",assign_toks,every_math_loc); -@!@:every_math_}{\.{\\everymath} primitive@> -primitive("everydisplay",assign_toks,every_display_loc); -@!@:every_display_}{\.{\\everydisplay} primitive@> -primitive("everyhbox",assign_toks,every_hbox_loc); -@!@:every_hbox_}{\.{\\everyhbox} primitive@> -primitive("everyvbox",assign_toks,every_vbox_loc); -@!@:every_vbox_}{\.{\\everyvbox} primitive@> -primitive("everyjob",assign_toks,every_job_loc); -@!@:every_job_}{\.{\\everyjob} primitive@> -primitive("everycr",assign_toks,every_cr_loc); -@!@:every_cr_}{\.{\\everycr} primitive@> -primitive("errhelp",assign_toks,err_help_loc); -@!@:err_help_}{\.{\\errhelp} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -assign_toks: if chr_code>=toks_base then - begin print_esc("toks"); print_int(chr_code-toks_base); - end -else case chr_code of - output_routine_loc: print_esc("output"); - every_par_loc: print_esc("everypar"); - every_math_loc: print_esc("everymath"); - every_display_loc: print_esc("everydisplay"); - every_hbox_loc: print_esc("everyhbox"); - every_vbox_loc: print_esc("everyvbox"); - every_job_loc: print_esc("everyjob"); - every_cr_loc: print_esc("everycr"); - othercases print_esc("errhelp") - endcases; - -@ We initialize most things to null or undefined values. An undefined font -is represented by the internal code |font_base|. - -However, the character code tables are given initial values based on the -conventional interpretation of ASCII code. These initial values should -not be changed when \TeX\ is adapted for use with non-English languages; -all changes to the initialization conventions should be made in format -packages, not in \TeX\ itself, so that global interchange of formats is -possible. - -@d null_font==font_base -@d var_code==@'70000 {math code meaning ``use the current family''} - -@<Initialize table entries...@>= -par_shape_ptr:=null; eq_type(par_shape_loc):=shape_ref; -eq_level(par_shape_loc):=level_one;@/ -for k:=output_routine_loc to toks_base+255 do - eqtb[k]:=eqtb[undefined_control_sequence]; -box(0):=null; eq_type(box_base):=box_ref; eq_level(box_base):=level_one; -for k:=box_base+1 to box_base+255 do eqtb[k]:=eqtb[box_base]; -cur_font:=null_font; eq_type(cur_font_loc):=data; -eq_level(cur_font_loc):=level_one;@/ -for k:=math_font_base to math_font_base+47 do eqtb[k]:=eqtb[cur_font_loc]; -equiv(cat_code_base):=0; eq_type(cat_code_base):=data; -eq_level(cat_code_base):=level_one;@/ -for k:=cat_code_base+1 to int_base-1 do eqtb[k]:=eqtb[cat_code_base]; -for k:=0 to 255 do - begin cat_code(k):=other_char; math_code(k):=hi(k); sf_code(k):=1000; - end; -cat_code(carriage_return):=car_ret; cat_code(" "):=spacer; -cat_code("\"):=escape; cat_code("%"):=comment; -cat_code(invalid_code):=invalid_char; cat_code(null_code):=ignore; -for k:="0" to "9" do math_code(k):=hi(k+var_code); -for k:="A" to "Z" do - begin cat_code(k):=letter; cat_code(k+"a"-"A"):=letter;@/ - math_code(k):=hi(k+var_code+@"100); - math_code(k+"a"-"A"):=hi(k+"a"-"A"+var_code+@"100);@/ - lc_code(k):=k+"a"-"A"; lc_code(k+"a"-"A"):=k+"a"-"A";@/ - uc_code(k):=k; uc_code(k+"a"-"A"):=k;@/ - sf_code(k):=999; - end; - -@ @<Show equivalent |n|, in region 4@>= -if n=par_shape_loc then - begin print_esc("parshape"); print_char("="); - if par_shape_ptr=null then print_char("0") - else print_int(info(par_shape_ptr)); - end -else if n<toks_base then - begin print_cmd_chr(assign_toks,n); print_char("="); - if equiv(n)<>null then show_token_list(link(equiv(n)),null,32); - end -else if n<box_base then - begin print_esc("toks"); print_int(n-toks_base); print_char("="); - if equiv(n)<>null then show_token_list(link(equiv(n)),null,32); - end -else if n<cur_font_loc then - begin print_esc("box"); print_int(n-box_base); print_char("="); - if equiv(n)=null then print("void") - else begin depth_threshold:=0; breadth_max:=1; show_node_list(equiv(n)); - end; - end -else if n<cat_code_base then @<Show the font identifier in |eqtb[n]|@> -else @<Show the halfword code in |eqtb[n]|@> - -@ @<Show the font identifier in |eqtb[n]|@>= -begin if n=cur_font_loc then print("current font") -else if n<math_font_base+16 then - begin print_esc("textfont"); print_int(n-math_font_base); - end -else if n<math_font_base+32 then - begin print_esc("scriptfont"); print_int(n-math_font_base-16); - end -else begin print_esc("scriptscriptfont"); print_int(n-math_font_base-32); - end; -print_char("=");@/ -print_esc(hash[font_id_base+equiv(n)].rh); - {that's |font_id_text(equiv(n))|} -end - -@ @<Show the halfword code in |eqtb[n]|@>= -if n<math_code_base then - begin if n<lc_code_base then - begin print_esc("catcode"); print_int(n-cat_code_base); - end - else if n<uc_code_base then - begin print_esc("lccode"); print_int(n-lc_code_base); - end - else if n<sf_code_base then - begin print_esc("uccode"); print_int(n-uc_code_base); - end - else begin print_esc("sfcode"); print_int(n-sf_code_base); - end; - print_char("="); print_int(equiv(n)); - end -else begin print_esc("mathcode"); print_int(n-math_code_base); - print_char("="); print_int(ho(equiv(n))); - end - -@ Region 5 of |eqtb| contains the integer parameters and registers defined -here, as well as the |del_code| table. The latter table differs from the -|cat_code..math_code| tables that precede it, since delimiter codes are -fullword integers while the other kinds of codes occupy at most a -halfword. This is what makes region~5 different from region~4. We will -store the |eq_level| information in an auxiliary array of quarterwords -that will be defined later. - -@d pretolerance_code=0 {badness tolerance before hyphenation} -@d tolerance_code=1 {badness tolerance after hyphenation} -@d line_penalty_code=2 {added to the badness of every line} -@d hyphen_penalty_code=3 {penalty for break after discretionary hyphen} -@d ex_hyphen_penalty_code=4 {penalty for break after explicit hyphen} -@d club_penalty_code=5 {penalty for creating a club line} -@d widow_penalty_code=6 {penalty for creating a widow line} -@d display_widow_penalty_code=7 {ditto, just before a display} -@d broken_penalty_code=8 {penalty for breaking a page at a broken line} -@d bin_op_penalty_code=9 {penalty for breaking after a binary operation} -@d rel_penalty_code=10 {penalty for breaking after a relation} -@d pre_display_penalty_code=11 - {penalty for breaking just before a displayed formula} -@d post_display_penalty_code=12 - {penalty for breaking just after a displayed formula} -@d inter_line_penalty_code=13 {additional penalty between lines} -@d double_hyphen_demerits_code=14 {demerits for double hyphen break} -@d final_hyphen_demerits_code=15 {demerits for final hyphen break} -@d adj_demerits_code=16 {demerits for adjacent incompatible lines} -@d mag_code=17 {magnification ratio} -@d delimiter_factor_code=18 {ratio for variable-size delimiters} -@d looseness_code=19 {change in number of lines for a paragraph} -@d time_code=20 {current time of day} -@d day_code=21 {current day of the month} -@d month_code=22 {current month of the year} -@d year_code=23 {current year of our Lord} -@d show_box_breadth_code=24 {nodes per level in |show_box|} -@d show_box_depth_code=25 {maximum level in |show_box|} -@d hbadness_code=26 {hboxes exceeding this badness will be shown by |hpack|} -@d vbadness_code=27 {vboxes exceeding this badness will be shown by |vpack|} -@d pausing_code=28 {pause after each line is read from a file} -@d tracing_online_code=29 {show diagnostic output on terminal} -@d tracing_macros_code=30 {show macros as they are being expanded} -@d tracing_stats_code=31 {show memory usage if \TeX\ knows it} -@d tracing_paragraphs_code=32 {show line-break calculations} -@d tracing_pages_code=33 {show page-break calculations} -@d tracing_output_code=34 {show boxes when they are shipped out} -@d tracing_lost_chars_code=35 {show characters that aren't in the font} -@d tracing_commands_code=36 {show command codes at |big_switch|} -@d tracing_restores_code=37 {show equivalents when they are restored} -@d uc_hyph_code=38 {hyphenate words beginning with a capital letter} -@d output_penalty_code=39 {penalty found at current page break} -@d max_dead_cycles_code=40 {bound on consecutive dead cycles of output} -@d hang_after_code=41 {hanging indentation changes after this many lines} -@d floating_penalty_code=42 {penalty for insertions held over after a split} -@d global_defs_code=43 {override \.{\\global} specifications} -@d cur_fam_code=44 {current family} -@d escape_char_code=45 {escape character for token output} -@d default_hyphen_char_code=46 {value of \.{\\hyphenchar} when a font is loaded} -@d default_skew_char_code=47 {value of \.{\\skewchar} when a font is loaded} -@d end_line_char_code=48 {character placed at the right end of the buffer} -@d new_line_char_code=49 {character that prints as |print_ln|} -@d language_code=50 {current hyphenation table} -@d left_hyphen_min_code=51 {minimum left hyphenation fragment size} -@d right_hyphen_min_code=52 {minimum right hyphenation fragment size} -@d holding_inserts_code=53 {do not remove insertion nodes from \.{\\box255}} -@d error_context_lines_code=54 {maximum intermediate line pairs shown} -@d int_pars=55 {total number of integer parameters} -@d count_base=int_base+int_pars {256 user \.{\\count} registers} -@d del_code_base=count_base+256 {256 delimiter code mappings} -@d dimen_base=del_code_base+256 {beginning of region 6} -@# -@d del_code(#)==eqtb[del_code_base+#].int -@d count(#)==eqtb[count_base+#].int -@d int_par(#)==eqtb[int_base+#].int {an integer parameter} -@d pretolerance==int_par(pretolerance_code) -@d tolerance==int_par(tolerance_code) -@d line_penalty==int_par(line_penalty_code) -@d hyphen_penalty==int_par(hyphen_penalty_code) -@d ex_hyphen_penalty==int_par(ex_hyphen_penalty_code) -@d club_penalty==int_par(club_penalty_code) -@d widow_penalty==int_par(widow_penalty_code) -@d display_widow_penalty==int_par(display_widow_penalty_code) -@d broken_penalty==int_par(broken_penalty_code) -@d bin_op_penalty==int_par(bin_op_penalty_code) -@d rel_penalty==int_par(rel_penalty_code) -@d pre_display_penalty==int_par(pre_display_penalty_code) -@d post_display_penalty==int_par(post_display_penalty_code) -@d inter_line_penalty==int_par(inter_line_penalty_code) -@d double_hyphen_demerits==int_par(double_hyphen_demerits_code) -@d final_hyphen_demerits==int_par(final_hyphen_demerits_code) -@d adj_demerits==int_par(adj_demerits_code) -@d mag==int_par(mag_code) -@d delimiter_factor==int_par(delimiter_factor_code) -@d looseness==int_par(looseness_code) -@d time==int_par(time_code) -@d day==int_par(day_code) -@d month==int_par(month_code) -@d year==int_par(year_code) -@d show_box_breadth==int_par(show_box_breadth_code) -@d show_box_depth==int_par(show_box_depth_code) -@d hbadness==int_par(hbadness_code) -@d vbadness==int_par(vbadness_code) -@d pausing==int_par(pausing_code) -@d tracing_online==int_par(tracing_online_code) -@d tracing_macros==int_par(tracing_macros_code) -@d tracing_stats==int_par(tracing_stats_code) -@d tracing_paragraphs==int_par(tracing_paragraphs_code) -@d tracing_pages==int_par(tracing_pages_code) -@d tracing_output==int_par(tracing_output_code) -@d tracing_lost_chars==int_par(tracing_lost_chars_code) -@d tracing_commands==int_par(tracing_commands_code) -@d tracing_restores==int_par(tracing_restores_code) -@d uc_hyph==int_par(uc_hyph_code) -@d output_penalty==int_par(output_penalty_code) -@d max_dead_cycles==int_par(max_dead_cycles_code) -@d hang_after==int_par(hang_after_code) -@d floating_penalty==int_par(floating_penalty_code) -@d global_defs==int_par(global_defs_code) -@d cur_fam==int_par(cur_fam_code) -@d escape_char==int_par(escape_char_code) -@d default_hyphen_char==int_par(default_hyphen_char_code) -@d default_skew_char==int_par(default_skew_char_code) -@d end_line_char==int_par(end_line_char_code) -@d new_line_char==int_par(new_line_char_code) -@d language==int_par(language_code) -@d left_hyphen_min==int_par(left_hyphen_min_code) -@d right_hyphen_min==int_par(right_hyphen_min_code) -@d holding_inserts==int_par(holding_inserts_code) -@d error_context_lines==int_par(error_context_lines_code) - -@<Assign the values |depth_threshold:=show_box_depth|...@>= -depth_threshold:=show_box_depth; -breadth_max:=show_box_breadth - -@ We can print the symbolic name of an integer parameter as follows. - -@p procedure print_param(@!n:integer); -begin case n of -pretolerance_code:print_esc("pretolerance"); -tolerance_code:print_esc("tolerance"); -line_penalty_code:print_esc("linepenalty"); -hyphen_penalty_code:print_esc("hyphenpenalty"); -ex_hyphen_penalty_code:print_esc("exhyphenpenalty"); -club_penalty_code:print_esc("clubpenalty"); -widow_penalty_code:print_esc("widowpenalty"); -display_widow_penalty_code:print_esc("displaywidowpenalty"); -broken_penalty_code:print_esc("brokenpenalty"); -bin_op_penalty_code:print_esc("binoppenalty"); -rel_penalty_code:print_esc("relpenalty"); -pre_display_penalty_code:print_esc("predisplaypenalty"); -post_display_penalty_code:print_esc("postdisplaypenalty"); -inter_line_penalty_code:print_esc("interlinepenalty"); -double_hyphen_demerits_code:print_esc("doublehyphendemerits"); -final_hyphen_demerits_code:print_esc("finalhyphendemerits"); -adj_demerits_code:print_esc("adjdemerits"); -mag_code:print_esc("mag"); -delimiter_factor_code:print_esc("delimiterfactor"); -looseness_code:print_esc("looseness"); -time_code:print_esc("time"); -day_code:print_esc("day"); -month_code:print_esc("month"); -year_code:print_esc("year"); -show_box_breadth_code:print_esc("showboxbreadth"); -show_box_depth_code:print_esc("showboxdepth"); -hbadness_code:print_esc("hbadness"); -vbadness_code:print_esc("vbadness"); -pausing_code:print_esc("pausing"); -tracing_online_code:print_esc("tracingonline"); -tracing_macros_code:print_esc("tracingmacros"); -tracing_stats_code:print_esc("tracingstats"); -tracing_paragraphs_code:print_esc("tracingparagraphs"); -tracing_pages_code:print_esc("tracingpages"); -tracing_output_code:print_esc("tracingoutput"); -tracing_lost_chars_code:print_esc("tracinglostchars"); -tracing_commands_code:print_esc("tracingcommands"); -tracing_restores_code:print_esc("tracingrestores"); -uc_hyph_code:print_esc("uchyph"); -output_penalty_code:print_esc("outputpenalty"); -max_dead_cycles_code:print_esc("maxdeadcycles"); -hang_after_code:print_esc("hangafter"); -floating_penalty_code:print_esc("floatingpenalty"); -global_defs_code:print_esc("globaldefs"); -cur_fam_code:print_esc("fam"); -escape_char_code:print_esc("escapechar"); -default_hyphen_char_code:print_esc("defaulthyphenchar"); -default_skew_char_code:print_esc("defaultskewchar"); -end_line_char_code:print_esc("endlinechar"); -new_line_char_code:print_esc("newlinechar"); -language_code:print_esc("language"); -left_hyphen_min_code:print_esc("lefthyphenmin"); -right_hyphen_min_code:print_esc("righthyphenmin"); -holding_inserts_code:print_esc("holdinginserts"); -error_context_lines_code:print_esc("errorcontextlines"); -othercases print("[unknown integer parameter!]") -endcases; -end; - -@ The integer parameter names must be entered into the hash table. - -@<Put each...@>= -primitive("pretolerance",assign_int,int_base+pretolerance_code);@/ -@!@:pretolerance_}{\.{\\pretolerance} primitive@> -primitive("tolerance",assign_int,int_base+tolerance_code);@/ -@!@:tolerance_}{\.{\\tolerance} primitive@> -primitive("linepenalty",assign_int,int_base+line_penalty_code);@/ -@!@:line_penalty_}{\.{\\linepenalty} primitive@> -primitive("hyphenpenalty",assign_int,int_base+hyphen_penalty_code);@/ -@!@:hyphen_penalty_}{\.{\\hyphenpenalty} primitive@> -primitive("exhyphenpenalty",assign_int,int_base+ex_hyphen_penalty_code);@/ -@!@:ex_hyphen_penalty_}{\.{\\exhyphenpenalty} primitive@> -primitive("clubpenalty",assign_int,int_base+club_penalty_code);@/ -@!@:club_penalty_}{\.{\\clubpenalty} primitive@> -primitive("widowpenalty",assign_int,int_base+widow_penalty_code);@/ -@!@:widow_penalty_}{\.{\\widowpenalty} primitive@> -primitive("displaywidowpenalty", - assign_int,int_base+display_widow_penalty_code);@/ -@!@:display_widow_penalty_}{\.{\\displaywidowpenalty} primitive@> -primitive("brokenpenalty",assign_int,int_base+broken_penalty_code);@/ -@!@:broken_penalty_}{\.{\\brokenpenalty} primitive@> -primitive("binoppenalty",assign_int,int_base+bin_op_penalty_code);@/ -@!@:bin_op_penalty_}{\.{\\binoppenalty} primitive@> -primitive("relpenalty",assign_int,int_base+rel_penalty_code);@/ -@!@:rel_penalty_}{\.{\\relpenalty} primitive@> -primitive("predisplaypenalty",assign_int,int_base+pre_display_penalty_code);@/ -@!@:pre_display_penalty_}{\.{\\predisplaypenalty} primitive@> -primitive("postdisplaypenalty",assign_int,int_base+post_display_penalty_code);@/ -@!@:post_display_penalty_}{\.{\\postdisplaypenalty} primitive@> -primitive("interlinepenalty",assign_int,int_base+inter_line_penalty_code);@/ -@!@:inter_line_penalty_}{\.{\\interlinepenalty} primitive@> -primitive("doublehyphendemerits", - assign_int,int_base+double_hyphen_demerits_code);@/ -@!@:double_hyphen_demerits_}{\.{\\doublehyphendemerits} primitive@> -primitive("finalhyphendemerits", - assign_int,int_base+final_hyphen_demerits_code);@/ -@!@:final_hyphen_demerits_}{\.{\\finalhyphendemerits} primitive@> -primitive("adjdemerits",assign_int,int_base+adj_demerits_code);@/ -@!@:adj_demerits_}{\.{\\adjdemerits} primitive@> -primitive("mag",assign_int,int_base+mag_code);@/ -@!@:mag_}{\.{\\mag} primitive@> -primitive("delimiterfactor",assign_int,int_base+delimiter_factor_code);@/ -@!@:delimiter_factor_}{\.{\\delimiterfactor} primitive@> -primitive("looseness",assign_int,int_base+looseness_code);@/ -@!@:looseness_}{\.{\\looseness} primitive@> -primitive("time",assign_int,int_base+time_code);@/ -@!@:time_}{\.{\\time} primitive@> -primitive("day",assign_int,int_base+day_code);@/ -@!@:day_}{\.{\\day} primitive@> -primitive("month",assign_int,int_base+month_code);@/ -@!@:month_}{\.{\\month} primitive@> -primitive("year",assign_int,int_base+year_code);@/ -@!@:year_}{\.{\\year} primitive@> -primitive("showboxbreadth",assign_int,int_base+show_box_breadth_code);@/ -@!@:show_box_breadth_}{\.{\\showboxbreadth} primitive@> -primitive("showboxdepth",assign_int,int_base+show_box_depth_code);@/ -@!@:show_box_depth_}{\.{\\showboxdepth} primitive@> -primitive("hbadness",assign_int,int_base+hbadness_code);@/ -@!@:hbadness_}{\.{\\hbadness} primitive@> -primitive("vbadness",assign_int,int_base+vbadness_code);@/ -@!@:vbadness_}{\.{\\vbadness} primitive@> -primitive("pausing",assign_int,int_base+pausing_code);@/ -@!@:pausing_}{\.{\\pausing} primitive@> -primitive("tracingonline",assign_int,int_base+tracing_online_code);@/ -@!@:tracing_online_}{\.{\\tracingonline} primitive@> -primitive("tracingmacros",assign_int,int_base+tracing_macros_code);@/ -@!@:tracing_macros_}{\.{\\tracingmacros} primitive@> -primitive("tracingstats",assign_int,int_base+tracing_stats_code);@/ -@!@:tracing_stats_}{\.{\\tracingstats} primitive@> -primitive("tracingparagraphs",assign_int,int_base+tracing_paragraphs_code);@/ -@!@:tracing_paragraphs_}{\.{\\tracingparagraphs} primitive@> -primitive("tracingpages",assign_int,int_base+tracing_pages_code);@/ -@!@:tracing_pages_}{\.{\\tracingpages} primitive@> -primitive("tracingoutput",assign_int,int_base+tracing_output_code);@/ -@!@:tracing_output_}{\.{\\tracingoutput} primitive@> -primitive("tracinglostchars",assign_int,int_base+tracing_lost_chars_code);@/ -@!@:tracing_lost_chars_}{\.{\\tracinglostchars} primitive@> -primitive("tracingcommands",assign_int,int_base+tracing_commands_code);@/ -@!@:tracing_commands_}{\.{\\tracingcommands} primitive@> -primitive("tracingrestores",assign_int,int_base+tracing_restores_code);@/ -@!@:tracing_restores_}{\.{\\tracingrestores} primitive@> -primitive("uchyph",assign_int,int_base+uc_hyph_code);@/ -@!@:uc_hyph_}{\.{\\uchyph} primitive@> -primitive("outputpenalty",assign_int,int_base+output_penalty_code);@/ -@!@:output_penalty_}{\.{\\outputpenalty} primitive@> -primitive("maxdeadcycles",assign_int,int_base+max_dead_cycles_code);@/ -@!@:max_dead_cycles_}{\.{\\maxdeadcycles} primitive@> -primitive("hangafter",assign_int,int_base+hang_after_code);@/ -@!@:hang_after_}{\.{\\hangafter} primitive@> -primitive("floatingpenalty",assign_int,int_base+floating_penalty_code);@/ -@!@:floating_penalty_}{\.{\\floatingpenalty} primitive@> -primitive("globaldefs",assign_int,int_base+global_defs_code);@/ -@!@:global_defs_}{\.{\\globaldefs} primitive@> -primitive("fam",assign_int,int_base+cur_fam_code);@/ -@!@:fam_}{\.{\\fam} primitive@> -primitive("escapechar",assign_int,int_base+escape_char_code);@/ -@!@:escape_char_}{\.{\\escapechar} primitive@> -primitive("defaulthyphenchar",assign_int,int_base+default_hyphen_char_code);@/ -@!@:default_hyphen_char_}{\.{\\defaulthyphenchar} primitive@> -primitive("defaultskewchar",assign_int,int_base+default_skew_char_code);@/ -@!@:default_skew_char_}{\.{\\defaultskewchar} primitive@> -primitive("endlinechar",assign_int,int_base+end_line_char_code);@/ -@!@:end_line_char_}{\.{\\endlinechar} primitive@> -primitive("newlinechar",assign_int,int_base+new_line_char_code);@/ -@!@:new_line_char_}{\.{\\newlinechar} primitive@> -primitive("language",assign_int,int_base+language_code);@/ -@!@:language_}{\.{\\language} primitive@> -primitive("lefthyphenmin",assign_int,int_base+left_hyphen_min_code);@/ -@!@:left_hyphen_min_}{\.{\\lefthyphenmin} primitive@> -primitive("righthyphenmin",assign_int,int_base+right_hyphen_min_code);@/ -@!@:right_hyphen_min_}{\.{\\righthyphenmin} primitive@> -primitive("holdinginserts",assign_int,int_base+holding_inserts_code);@/ -@!@:holding_inserts_}{\.{\\holdinginserts} primitive@> -primitive("errorcontextlines",assign_int,int_base+error_context_lines_code);@/ -@!@:error_context_lines_}{\.{\\errorcontextlines} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -assign_int: if chr_code<count_base then print_param(chr_code-int_base) - else begin print_esc("count"); print_int(chr_code-count_base); - end; - -@ The integer parameters should really be initialized by a macro package; -the following initialization does the minimum to keep \TeX\ from -complete failure. -@^null delimiter@> - -@<Initialize table entries...@>= -for k:=int_base to del_code_base-1 do eqtb[k].int:=0; -mag:=1000; tolerance:=10000; hang_after:=1; max_dead_cycles:=25; -escape_char:="\"; end_line_char:=carriage_return; -for k:=0 to 255 do del_code(k):=-1; -del_code("."):=0; {this null delimiter is used in error recovery} - -@ The following procedure, which is called just before \TeX\ initializes its -input and output, establishes the initial values of the date and time. -@^system dependencies@> -Since standard \PASCAL\ cannot provide such information, something special -is needed. The program here simply assumes that suitable values appear in -the global variables \\{sys\_time}, \\{sys\_day}, \\{sys\_month}, and -\\{sys\_year} (which are initialized to noon on 4 July 1776, -in case the implementor is careless). - -@p procedure fix_date_and_time; -begin sys_time:=12*60; -sys_day:=4; sys_month:=7; sys_year:=1776; {self-evident truths} -time:=sys_time; {minutes since midnight} -day:=sys_day; {day of the month} -month:=sys_month; {month of the year} -year:=sys_year; {Anno Domini} -end; - -@ @<Show equivalent |n|, in region 5@>= -begin if n<count_base then print_param(n-int_base) -else if n<del_code_base then - begin print_esc("count"); print_int(n-count_base); - end -else begin print_esc("delcode"); print_int(n-del_code_base); - end; -print_char("="); print_int(eqtb[n].int); -end - -@ @<Set variable |c| to the current escape character@>=c:=escape_char - -@ @<Character |s| is the current new-line character@>=s=new_line_char - -@ \TeX\ is occasionally supposed to print diagnostic information that -goes only into the transcript file, unless |tracing_online| is positive. -Here are two routines that adjust the destination of print commands: - -@p procedure begin_diagnostic; {prepare to do some tracing} -begin old_setting:=selector; -if (tracing_online<=0)and(selector=term_and_log) then - begin decr(selector); - if history=spotless then history:=warning_issued; - end; -end; -@# -procedure end_diagnostic(@!blank_line:boolean); - {restore proper conditions after tracing} -begin print_nl(""); -if blank_line then print_ln; -selector:=old_setting; -end; - -@ Of course we had better declare a few more global variables, if the previous -routines are going to work. - -@<Glob...@>= -@!old_setting:0..max_selector; -@!sys_time,@!sys_day,@!sys_month,@!sys_year:integer; - {date and time supplied by external system} - -@ The final region of |eqtb| contains the dimension parameters defined -here, and the 256 \.{\\dimen} registers. - -@d par_indent_code=0 {indentation of paragraphs} -@d math_surround_code=1 {space around math in text} -@d line_skip_limit_code=2 {threshold for |line_skip| instead of |baseline_skip|} -@d hsize_code=3 {line width in horizontal mode} -@d vsize_code=4 {page height in vertical mode} -@d max_depth_code=5 {maximum depth of boxes on main pages} -@d split_max_depth_code=6 {maximum depth of boxes on split pages} -@d box_max_depth_code=7 {maximum depth of explicit vboxes} -@d hfuzz_code=8 {tolerance for overfull hbox messages} -@d vfuzz_code=9 {tolerance for overfull vbox messages} -@d delimiter_shortfall_code=10 {maximum amount uncovered by variable delimiters} -@d null_delimiter_space_code=11 {blank space in null delimiters} -@d script_space_code=12 {extra space after subscript or superscript} -@d pre_display_size_code=13 {length of text preceding a display} -@d display_width_code=14 {length of line for displayed equation} -@d display_indent_code=15 {indentation of line for displayed equation} -@d overfull_rule_code=16 {width of rule that identifies overfull hboxes} -@d hang_indent_code=17 {amount of hanging indentation} -@d h_offset_code=18 {amount of horizontal offset when shipping pages out} -@d v_offset_code=19 {amount of vertical offset when shipping pages out} -@d emergency_stretch_code=20 {reduces badnesses on final pass of line-breaking} -@d dimen_pars=21 {total number of dimension parameters} -@d scaled_base=dimen_base+dimen_pars - {table of 256 user-defined \.{\\dimen} registers} -@d eqtb_size=scaled_base+255 {largest subscript of |eqtb|} -@# -@d dimen(#)==eqtb[scaled_base+#].sc -@d dimen_par(#)==eqtb[dimen_base+#].sc {a scaled quantity} -@d par_indent==dimen_par(par_indent_code) -@d math_surround==dimen_par(math_surround_code) -@d line_skip_limit==dimen_par(line_skip_limit_code) -@d hsize==dimen_par(hsize_code) -@d vsize==dimen_par(vsize_code) -@d max_depth==dimen_par(max_depth_code) -@d split_max_depth==dimen_par(split_max_depth_code) -@d box_max_depth==dimen_par(box_max_depth_code) -@d hfuzz==dimen_par(hfuzz_code) -@d vfuzz==dimen_par(vfuzz_code) -@d delimiter_shortfall==dimen_par(delimiter_shortfall_code) -@d null_delimiter_space==dimen_par(null_delimiter_space_code) -@d script_space==dimen_par(script_space_code) -@d pre_display_size==dimen_par(pre_display_size_code) -@d display_width==dimen_par(display_width_code) -@d display_indent==dimen_par(display_indent_code) -@d overfull_rule==dimen_par(overfull_rule_code) -@d hang_indent==dimen_par(hang_indent_code) -@d h_offset==dimen_par(h_offset_code) -@d v_offset==dimen_par(v_offset_code) -@d emergency_stretch==dimen_par(emergency_stretch_code) - -@p procedure print_length_param(@!n:integer); -begin case n of -par_indent_code:print_esc("parindent"); -math_surround_code:print_esc("mathsurround"); -line_skip_limit_code:print_esc("lineskiplimit"); -hsize_code:print_esc("hsize"); -vsize_code:print_esc("vsize"); -max_depth_code:print_esc("maxdepth"); -split_max_depth_code:print_esc("splitmaxdepth"); -box_max_depth_code:print_esc("boxmaxdepth"); -hfuzz_code:print_esc("hfuzz"); -vfuzz_code:print_esc("vfuzz"); -delimiter_shortfall_code:print_esc("delimitershortfall"); -null_delimiter_space_code:print_esc("nulldelimiterspace"); -script_space_code:print_esc("scriptspace"); -pre_display_size_code:print_esc("predisplaysize"); -display_width_code:print_esc("displaywidth"); -display_indent_code:print_esc("displayindent"); -overfull_rule_code:print_esc("overfullrule"); -hang_indent_code:print_esc("hangindent"); -h_offset_code:print_esc("hoffset"); -v_offset_code:print_esc("voffset"); -emergency_stretch_code:print_esc("emergencystretch"); -othercases print("[unknown dimen parameter!]") -endcases; -end; - -@ @<Put each...@>= -primitive("parindent",assign_dimen,dimen_base+par_indent_code);@/ -@!@:par_indent_}{\.{\\parindent} primitive@> -primitive("mathsurround",assign_dimen,dimen_base+math_surround_code);@/ -@!@:math_surround_}{\.{\\mathsurround} primitive@> -primitive("lineskiplimit",assign_dimen,dimen_base+line_skip_limit_code);@/ -@!@:line_skip_limit_}{\.{\\lineskiplimit} primitive@> -primitive("hsize",assign_dimen,dimen_base+hsize_code);@/ -@!@:hsize_}{\.{\\hsize} primitive@> -primitive("vsize",assign_dimen,dimen_base+vsize_code);@/ -@!@:vsize_}{\.{\\vsize} primitive@> -primitive("maxdepth",assign_dimen,dimen_base+max_depth_code);@/ -@!@:max_depth_}{\.{\\maxdepth} primitive@> -primitive("splitmaxdepth",assign_dimen,dimen_base+split_max_depth_code);@/ -@!@:split_max_depth_}{\.{\\splitmaxdepth} primitive@> -primitive("boxmaxdepth",assign_dimen,dimen_base+box_max_depth_code);@/ -@!@:box_max_depth_}{\.{\\boxmaxdepth} primitive@> -primitive("hfuzz",assign_dimen,dimen_base+hfuzz_code);@/ -@!@:hfuzz_}{\.{\\hfuzz} primitive@> -primitive("vfuzz",assign_dimen,dimen_base+vfuzz_code);@/ -@!@:vfuzz_}{\.{\\vfuzz} primitive@> -primitive("delimitershortfall", - assign_dimen,dimen_base+delimiter_shortfall_code);@/ -@!@:delimiter_shortfall_}{\.{\\delimitershortfall} primitive@> -primitive("nulldelimiterspace", - assign_dimen,dimen_base+null_delimiter_space_code);@/ -@!@:null_delimiter_space_}{\.{\\nulldelimiterspace} primitive@> -primitive("scriptspace",assign_dimen,dimen_base+script_space_code);@/ -@!@:script_space_}{\.{\\scriptspace} primitive@> -primitive("predisplaysize",assign_dimen,dimen_base+pre_display_size_code);@/ -@!@:pre_display_size_}{\.{\\predisplaysize} primitive@> -primitive("displaywidth",assign_dimen,dimen_base+display_width_code);@/ -@!@:display_width_}{\.{\\displaywidth} primitive@> -primitive("displayindent",assign_dimen,dimen_base+display_indent_code);@/ -@!@:display_indent_}{\.{\\displayindent} primitive@> -primitive("overfullrule",assign_dimen,dimen_base+overfull_rule_code);@/ -@!@:overfull_rule_}{\.{\\overfullrule} primitive@> -primitive("hangindent",assign_dimen,dimen_base+hang_indent_code);@/ -@!@:hang_indent_}{\.{\\hangindent} primitive@> -primitive("hoffset",assign_dimen,dimen_base+h_offset_code);@/ -@!@:h_offset_}{\.{\\hoffset} primitive@> -primitive("voffset",assign_dimen,dimen_base+v_offset_code);@/ -@!@:v_offset_}{\.{\\voffset} primitive@> -primitive("emergencystretch",assign_dimen,dimen_base+emergency_stretch_code);@/ -@!@:emergency_stretch_}{\.{\\emergencystretch} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -assign_dimen: if chr_code<scaled_base then - print_length_param(chr_code-dimen_base) - else begin print_esc("dimen"); print_int(chr_code-scaled_base); - end; - -@ @<Initialize table entries...@>= -for k:=dimen_base to eqtb_size do eqtb[k].sc:=0; - -@ @<Show equivalent |n|, in region 6@>= -begin if n<scaled_base then print_length_param(n-dimen_base) -else begin print_esc("dimen"); print_int(n-scaled_base); - end; -print_char("="); print_scaled(eqtb[n].sc); print("pt"); -end - -@ Here is a procedure that displays the contents of |eqtb[n]| -symbolically. - -@p@t\4@>@<Declare the procedure called |print_cmd_chr|@>@;@/ -@!stat procedure show_eqtb(@!n:pointer); -begin if n<active_base then print_char("?") {this can't happen} -else if n<glue_base then @<Show equivalent |n|, in region 1 or 2@> -else if n<local_base then @<Show equivalent |n|, in region 3@> -else if n<int_base then @<Show equivalent |n|, in region 4@> -else if n<dimen_base then @<Show equivalent |n|, in region 5@> -else if n<=eqtb_size then @<Show equivalent |n|, in region 6@> -else print_char("?"); {this can't happen either} -end; -tats - -@ The last two regions of |eqtb| have fullword values instead of the -three fields |eq_level|, |eq_type|, and |equiv|. An |eq_type| is unnecessary, -but \TeX\ needs to store the |eq_level| information in another array -called |xeq_level|. - -@<Glob...@>= -@!eqtb:array[active_base..eqtb_size] of memory_word; -@!xeq_level:array[int_base..eqtb_size] of quarterword; - -@ @<Set init...@>= -for k:=int_base to eqtb_size do xeq_level[k]:=level_one; - -@ When the debugging routine |search_mem| is looking for pointers having a -given value, it is interested only in regions 1 to~3 of~|eqtb|, and in the -first part of region~4. - -@<Search |eqtb| for equivalents equal to |p|@>= -for q:=active_base to box_base+255 do - begin if equiv(q)=p then - begin print_nl("EQUIV("); print_int(q); print_char(")"); - end; - end - -@* \[18] The hash table. -Control sequences are stored and retrieved by means of a fairly standard hash -table algorithm called the method of ``coalescing lists'' (cf.\ Algorithm 6.4C -in {\sl The Art of Computer Programming\/}). Once a control sequence enters the -table, it is never removed, because there are complicated situations -involving \.{\\gdef} where the removal of a control sequence at the end of -a group would be a mistake preventable only by the introduction of a -complicated reference-count mechanism. - -The actual sequence of letters forming a control sequence identifier is -stored in the |str_pool| array together with all the other strings. An -auxiliary array |hash| consists of items with two halfword fields per -word. The first of these, called |next(p)|, points to the next identifier -belonging to the same coalesced list as the identifier corresponding to~|p|; -and the other, called |text(p)|, points to the |str_start| entry for -|p|'s identifier. If position~|p| of the hash table is empty, we have -|text(p)=0|; if position |p| is either empty or the end of a coalesced -hash list, we have |next(p)=0|. An auxiliary pointer variable called -|hash_used| is maintained in such a way that all locations |p>=hash_used| -are nonempty. The global variable |cs_count| tells how many multiletter -control sequences have been defined, if statistics are being kept. - -A global boolean variable called |no_new_control_sequence| is set to -|true| during the time that new hash table entries are forbidden. - -@d next(#) == hash[#].lh {link for coalesced lists} -@d text(#) == hash[#].rh {string number for control sequence name} -@d hash_is_full == (hash_used=hash_base) {test if all positions are occupied} -@d font_id_text(#) == text(font_id_base+#) {a frozen font identifier's name} - -@<Glob...@>= -@!hash: array[hash_base..undefined_control_sequence-1] of two_halves; - {the hash table} -@!hash_used:pointer; {allocation pointer for |hash|} -@!no_new_control_sequence:boolean; {are new identifiers legal?} -@!cs_count:integer; {total number of known identifiers} - -@ @<Set init...@>= -no_new_control_sequence:=true; {new identifiers are usually forbidden} -next(hash_base):=0; text(hash_base):=0; -for k:=hash_base+1 to undefined_control_sequence-1 do hash[k]:=hash[hash_base]; - -@ @<Initialize table entries...@>= -hash_used:=frozen_control_sequence; {nothing is used} -cs_count:=0; -eq_type(frozen_dont_expand):=dont_expand; -text(frozen_dont_expand):="notexpanded:"; -@.notexpanded:@> - -@ Here is the subroutine that searches the hash table for an identifier -that matches a given string of length |l>1| appearing in |buffer[j.. -(j+l-1)]|. If the identifier is found, the corresponding hash table address -is returned. Otherwise, if the global variable |no_new_control_sequence| -is |true|, the dummy address |undefined_control_sequence| is returned. -Otherwise the identifier is inserted into the hash table and its location -is returned. - -@p function id_lookup(@!j,@!l:integer):pointer; {search the hash table} -label found; {go here if you found it} -var h:integer; {hash code} -@!d:integer; {number of characters in incomplete current string} -@!p:pointer; {index in |hash| array} -@!k:pointer; {index in |buffer| array} -begin @<Compute the hash code |h|@>; -p:=h+hash_base; {we start searching here; note that |0<=h<hash_prime|} -loop@+begin if text(p)>0 then if length(text(p))=l then - if str_eq_buf(text(p),j) then goto found; - if next(p)=0 then - begin if no_new_control_sequence then - p:=undefined_control_sequence - else @<Insert a new control sequence after |p|, then make - |p| point to it@>; - goto found; - end; - p:=next(p); - end; -found: id_lookup:=p; -end; - -@ @<Insert a new control...@>= -begin if text(p)>0 then - begin repeat if hash_is_full then overflow("hash size",hash_size); -@:TeX capacity exceeded hash size}{\quad hash size@> - decr(hash_used); - until text(hash_used)=0; {search for an empty location in |hash|} - next(p):=hash_used; p:=hash_used; - end; -str_room(l); d:=cur_length; -while pool_ptr>str_start[str_ptr] do - begin decr(pool_ptr); str_pool[pool_ptr+l]:=str_pool[pool_ptr]; - end; {move current string up to make room for another} -for k:=j to j+l-1 do append_char(buffer[k]); -text(p):=make_string; pool_ptr:=pool_ptr+d; -@!stat incr(cs_count);@+tats@;@/ -end - -@ The value of |hash_prime| should be roughly 85\pct! of |hash_size|, and it -should be a prime number. The theory of hashing tells us to expect fewer -than two table probes, on the average, when the search is successful. -[See J.~S. Vitter, {\sl Journal of the ACM\/ \bf30} (1983), 231--258.] -@^Vitter, Jeffrey Scott@> - -@<Compute the hash code |h|@>= -h:=buffer[j]; -for k:=j+1 to j+l-1 do - begin h:=h+h+buffer[k]; - while h>=hash_prime do h:=h-hash_prime; - end - -@ Single-character control sequences do not need to be looked up in a hash -table, since we can use the character code itself as a direct address. -The procedure |print_cs| prints the name of a control sequence, given -a pointer to its address in |eqtb|. A space is printed after the name -unless it is a single nonletter or an active character. This procedure -might be invoked with invalid data, so it is ``extra robust.'' The -individual characters must be printed one at a time using |print|, since -they may be unprintable. - -@<Basic printing...@>= -procedure print_cs(@!p:integer); {prints a purported control sequence} -begin if p<hash_base then {single character} - if p>=single_base then - if p=null_cs then - begin print_esc("csname"); print_esc("endcsname"); print_char(" "); - end - else begin print_esc(p-single_base); - if cat_code(p-single_base)=letter then print_char(" "); - end - else if p<active_base then print_esc("IMPOSSIBLE.") -@.IMPOSSIBLE@> - else print(p-active_base) -else if p>=undefined_control_sequence then print_esc("IMPOSSIBLE.") -else if (text(p)<0)or(text(p)>=str_ptr) then print_esc("NONEXISTENT.") -@.NONEXISTENT@> -else begin print_esc(text(p)); - print_char(" "); - end; -end; - -@ Here is a similar procedure; it avoids the error checks, and it never -prints a space after the control sequence. - -@<Basic printing procedures@>= -procedure sprint_cs(@!p:pointer); {prints a control sequence} -begin if p<hash_base then - if p<single_base then print(p-active_base) - else if p<null_cs then print_esc(p-single_base) - else begin print_esc("csname"); print_esc("endcsname"); - end -else print_esc(text(p)); -end; - -@ We need to put \TeX's ``primitive'' control sequences into the hash -table, together with their command code (which will be the |eq_type|) -and an operand (which will be the |equiv|). The |primitive| procedure -does this, in a way that no \TeX\ user can. The global value |cur_val| -contains the new |eqtb| pointer after |primitive| has acted. - -@p @!init procedure primitive(@!s:str_number;@!c:quarterword;@!o:halfword); -var k:pool_pointer; {index into |str_pool|} -@!j:small_number; {index into |buffer|} -@!l:small_number; {length of the string} -begin if s<256 then cur_val:=s+single_base -else begin k:=str_start[s]; l:=str_start[s+1]-k; - {we will move |s| into the (empty) |buffer|} - for j:=0 to l-1 do buffer[j]:=so(str_pool[k+j]); - cur_val:=id_lookup(0,l); {|no_new_control_sequence| is |false|} - flush_string; text(cur_val):=s; {we don't want to have the string twice} - end; -eq_level(cur_val):=level_one; eq_type(cur_val):=c; equiv(cur_val):=o; -end; -tini - -@ Many of \TeX's primitives need no |equiv|, since they are identifiable -by their |eq_type| alone. These primitives are loaded into the hash table -as follows: - -@<Put each of \TeX's primitives into the hash table@>= -primitive(" ",ex_space,0);@/ -@!@:Single-character primitives /}{\quad\.{\\\ }@> -primitive("/",ital_corr,0);@/ -@!@:Single-character primitives /}{\quad\.{\\/}@> -primitive("accent",accent,0);@/ -@!@:accent_}{\.{\\accent} primitive@> -primitive("advance",advance,0);@/ -@!@:advance_}{\.{\\advance} primitive@> -primitive("afterassignment",after_assignment,0);@/ -@!@:after_assignment_}{\.{\\afterassignment} primitive@> -primitive("aftergroup",after_group,0);@/ -@!@:after_group_}{\.{\\aftergroup} primitive@> -primitive("begingroup",begin_group,0);@/ -@!@:begin_group_}{\.{\\begingroup} primitive@> -primitive("char",char_num,0);@/ -@!@:char_}{\.{\\char} primitive@> -primitive("csname",cs_name,0);@/ -@!@:cs_name_}{\.{\\csname} primitive@> -primitive("delimiter",delim_num,0);@/ -@!@:delimiter_}{\.{\\delimiter} primitive@> -primitive("divide",divide,0);@/ -@!@:divide_}{\.{\\divide} primitive@> -primitive("endcsname",end_cs_name,0);@/ -@!@:end_cs_name_}{\.{\\endcsname} primitive@> -primitive("endgroup",end_group,0); -@!@:end_group_}{\.{\\endgroup} primitive@> -text(frozen_end_group):="endgroup"; eqtb[frozen_end_group]:=eqtb[cur_val];@/ -primitive("expandafter",expand_after,0);@/ -@!@:expand_after_}{\.{\\expandafter} primitive@> -primitive("font",def_font,0);@/ -@!@:font_}{\.{\\font} primitive@> -primitive("fontdimen",assign_font_dimen,0);@/ -@!@:font_dimen_}{\.{\\fontdimen} primitive@> -primitive("halign",halign,0);@/ -@!@:halign_}{\.{\\halign} primitive@> -primitive("hrule",hrule,0);@/ -@!@:hrule_}{\.{\\hrule} primitive@> -primitive("ignorespaces",ignore_spaces,0);@/ -@!@:ignore_spaces_}{\.{\\ignorespaces} primitive@> -primitive("insert",insert,0);@/ -@!@:insert_}{\.{\\insert} primitive@> -primitive("mark",mark,0);@/ -@!@:mark_}{\.{\\mark} primitive@> -primitive("mathaccent",math_accent,0);@/ -@!@:math_accent_}{\.{\\mathaccent} primitive@> -primitive("mathchar",math_char_num,0);@/ -@!@:math_char_}{\.{\\mathchar} primitive@> -primitive("mathchoice",math_choice,0);@/ -@!@:math_choice_}{\.{\\mathchoice} primitive@> -primitive("multiply",multiply,0);@/ -@!@:multiply_}{\.{\\multiply} primitive@> -primitive("noalign",no_align,0);@/ -@!@:no_align_}{\.{\\noalign} primitive@> -primitive("noboundary",no_boundary,0);@/ -@!@:no_boundary_}{\.{\\noboundary} primitive@> -primitive("noexpand",no_expand,0);@/ -@!@:no_expand_}{\.{\\noexpand} primitive@> -primitive("nonscript",non_script,0);@/ -@!@:non_script_}{\.{\\nonscript} primitive@> -primitive("omit",omit,0);@/ -@!@:omit_}{\.{\\omit} primitive@> -primitive("parshape",set_shape,0);@/ -@!@:par_shape_}{\.{\\parshape} primitive@> -primitive("penalty",break_penalty,0);@/ -@!@:penalty_}{\.{\\penalty} primitive@> -primitive("prevgraf",set_prev_graf,0);@/ -@!@:prev_graf_}{\.{\\prevgraf} primitive@> -primitive("radical",radical,0);@/ -@!@:radical_}{\.{\\radical} primitive@> -primitive("read",read_to_cs,0);@/ -@!@:read_}{\.{\\read} primitive@> -primitive("relax",relax,256); {cf.\ |scan_file_name|} -@!@:relax_}{\.{\\relax} primitive@> -text(frozen_relax):="relax"; eqtb[frozen_relax]:=eqtb[cur_val];@/ -primitive("setbox",set_box,0);@/ -@!@:set_box_}{\.{\\setbox} primitive@> -primitive("the",the,0);@/ -@!@:the_}{\.{\\the} primitive@> -primitive("toks",toks_register,0);@/ -@!@:toks_}{\.{\\toks} primitive@> -primitive("vadjust",vadjust,0);@/ -@!@:vadjust_}{\.{\\vadjust} primitive@> -primitive("valign",valign,0);@/ -@!@:valign_}{\.{\\valign} primitive@> -primitive("vcenter",vcenter,0);@/ -@!@:vcenter_}{\.{\\vcenter} primitive@> -primitive("vrule",vrule,0);@/ -@!@:vrule_}{\.{\\vrule} primitive@> - -@ Each primitive has a corresponding inverse, so that it is possible to -display the cryptic numeric contents of |eqtb| in symbolic form. -Every call of |primitive| in this program is therefore accompanied by some -straightforward code that forms part of the |print_cmd_chr| routine -below. - -@<Cases of |print_cmd_chr|...@>= -accent: print_esc("accent"); -advance: print_esc("advance"); -after_assignment: print_esc("afterassignment"); -after_group: print_esc("aftergroup"); -assign_font_dimen: print_esc("fontdimen"); -begin_group: print_esc("begingroup"); -break_penalty: print_esc("penalty"); -char_num: print_esc("char"); -cs_name: print_esc("csname"); -def_font: print_esc("font"); -delim_num: print_esc("delimiter"); -divide: print_esc("divide"); -end_cs_name: print_esc("endcsname"); -end_group: print_esc("endgroup"); -ex_space: print_esc(" "); -expand_after: print_esc("expandafter"); -halign: print_esc("halign"); -hrule: print_esc("hrule"); -ignore_spaces: print_esc("ignorespaces"); -insert: print_esc("insert"); -ital_corr: print_esc("/"); -mark: print_esc("mark"); -math_accent: print_esc("mathaccent"); -math_char_num: print_esc("mathchar"); -math_choice: print_esc("mathchoice"); -multiply: print_esc("multiply"); -no_align: print_esc("noalign"); -no_boundary:print_esc("noboundary"); -no_expand: print_esc("noexpand"); -non_script: print_esc("nonscript"); -omit: print_esc("omit"); -radical: print_esc("radical"); -read_to_cs: print_esc("read"); -relax: print_esc("relax"); -set_box: print_esc("setbox"); -set_prev_graf: print_esc("prevgraf"); -set_shape: print_esc("parshape"); -the: print_esc("the"); -toks_register: print_esc("toks"); -vadjust: print_esc("vadjust"); -valign: print_esc("valign"); -vcenter: print_esc("vcenter"); -vrule: print_esc("vrule"); - -@ We will deal with the other primitives later, at some point in the program -where their |eq_type| and |equiv| values are more meaningful. For example, -the primitives for math mode will be loaded when we consider the routines -that deal with formulas. It is easy to find where each particular -primitive was treated by looking in the index at the end; for example, the -section where |"radical"| entered |eqtb| is listed under `\.{\\radical} -primitive'. (Primitives consisting of a single nonalphabetic character, -@!like `\.{\\/}', are listed under `Single-character primitives'.) -@!@^Single-character primitives@> - -Meanwhile, this is a convenient place to catch up on something we were unable -to do before the hash table was defined: - -@<Print the font identifier for |font(p)|@>= -print_esc(font_id_text(font(p))) - -@* \[19] Saving and restoring equivalents. -The nested structure provided by `$\.{\char'173}\ldots\.{\char'175}$' groups -in \TeX\ means that |eqtb| entries valid in outer groups should be saved -and restored later if they are overridden inside the braces. When a new |eqtb| -value is being assigned, the program therefore checks to see if the previous -entry belongs to an outer level. In such a case, the old value is placed -on the |save_stack| just before the new value enters |eqtb|. At the -end of a grouping level, i.e., when the right brace is sensed, the -|save_stack| is used to restore the outer values, and the inner ones are -destroyed. - -Entries on the |save_stack| are of type |memory_word|. The top item on -this stack is |save_stack[p]|, where |p=save_ptr-1|; it contains three -fields called |save_type|, |save_level|, and |save_index|, and it is -interpreted in one of four ways: - -\yskip\hangg 1) If |save_type(p)=restore_old_value|, then -|save_index(p)| is a location in |eqtb| whose current value should -be destroyed at the end of the current group and replaced by |save_stack[p-1]|. -Furthermore if |save_index(p)>=int_base|, then |save_level(p)| -should replace the corresponding entry in |xeq_level|. - -\yskip\hangg 2) If |save_type(p)=restore_zero|, then |save_index(p)| -is a location in |eqtb| whose current value should be destroyed at the end -of the current group, when it should be -replaced by the value of |eqtb[undefined_control_sequence]|. - -\yskip\hangg 3) If |save_type(p)=insert_token|, then |save_index(p)| -is a token that should be inserted into \TeX's input when the current -group ends. - -\yskip\hangg 4) If |save_type(p)=level_boundary|, then |save_level(p)| -is a code explaining what kind of group we were previously in, and -|save_index(p)| points to the level boundary word at the bottom of -the entries for that group. - -@d save_type(#)==save_stack[#].hh.b0 {classifies a |save_stack| entry} -@d save_level(#)==save_stack[#].hh.b1 - {saved level for regions 5 and 6, or group code} -@d save_index(#)==save_stack[#].hh.rh - {|eqtb| location or token or |save_stack| location} -@d restore_old_value=0 {|save_type| when a value should be restored later} -@d restore_zero=1 {|save_type| when an undefined entry should be restored} -@d insert_token=2 {|save_type| when a token is being saved for later use} -@d level_boundary=3 {|save_type| corresponding to beginning of group} - -@ Here are the group codes that are used to discriminate between different -kinds of groups. They allow \TeX\ to decide what special actions, if any, -should be performed when a group ends. -\def\grp{\.{\char'173...\char'175}} - -Some groups are not supposed to be ended by right braces. For example, -the `\.\$' that begins a math formula causes a |math_shift_group| to -be started, and this should be terminated by a matching `\.\$'. Similarly, -a group that starts with \.{\\left} should end with \.{\\right}, and -one that starts with \.{\\begingroup} should end with \.{\\endgroup}. - -@d bottom_level=0 {group code for the outside world} -@d simple_group=1 {group code for local structure only} -@d hbox_group=2 {code for `\.{\\hbox}\grp'} -@d adjusted_hbox_group=3 {code for `\.{\\hbox}\grp' in vertical mode} -@d vbox_group=4 {code for `\.{\\vbox}\grp'} -@d vtop_group=5 {code for `\.{\\vtop}\grp'} -@d align_group=6 {code for `\.{\\halign}\grp', `\.{\\valign}\grp'} -@d no_align_group=7 {code for `\.{\\noalign}\grp'} -@d output_group=8 {code for output routine} -@d math_group=9 {code for, e.g., `\.{\char'136}\grp'} -@d disc_group=10 {code for `\.{\\discretionary}\grp\grp\grp'} -@d insert_group=11 {code for `\.{\\insert}\grp', `\.{\\vadjust}\grp'} -@d vcenter_group=12 {code for `\.{\\vcenter}\grp'} -@d math_choice_group=13 {code for `\.{\\mathchoice}\grp\grp\grp\grp'} -@d semi_simple_group=14 {code for `\.{\\begingroup...\\endgroup}'} -@d math_shift_group=15 {code for `\.{\$...\$}'} -@d math_left_group=16 {code for `\.{\\left...\\right}'} -@d max_group_code=16 - -@<Types...@>= -@!group_code=0..max_group_code; {|save_level| for a level boundary} - -@ The global variable |cur_group| keeps track of what sort of group we are -currently in. Another global variable, |cur_boundary|, points to the -topmost |level_boundary| word. And |cur_level| is the current depth of -nesting. The routines are designed to preserve the condition that no entry -in the |save_stack| or in |eqtb| ever has a level greater than |cur_level|. - -@ @<Glob...@>= -@!save_stack : array[0..save_size] of memory_word; -@!save_ptr : 0..save_size; {first unused entry on |save_stack|} -@!max_save_stack:0..save_size; {maximum usage of save stack} -@!cur_level: quarterword; {current nesting level for groups} -@!cur_group: group_code; {current group type} -@!cur_boundary: 0..save_size; {where the current level begins} - -@ At this time it might be a good idea for the reader to review the introduction -to |eqtb| that was given above just before the long lists of parameter names. -Recall that the ``outer level'' of the program is |level_one|, since -undefined control sequences are assumed to be ``defined'' at |level_zero|. - -@<Set init...@>= -save_ptr:=0; cur_level:=level_one; cur_group:=bottom_level; cur_boundary:=0; -max_save_stack:=0; - -@ The following macro is used to test if there is room for up to six more -entries on |save_stack|. By making a conservative test like this, we can -get by with testing for overflow in only a few places. - -@d check_full_save_stack==if save_ptr>max_save_stack then - begin max_save_stack:=save_ptr; - if max_save_stack>save_size-6 then overflow("save size",save_size); -@:TeX capacity exceeded save size}{\quad save size@> - end - -@ Procedure |new_save_level| is called when a group begins. The -argument is a group identification code like `|hbox_group|'. After -calling this routine, it is safe to put five more entries on |save_stack|. - -In some cases integer-valued items are placed onto the -|save_stack| just below a |level_boundary| word, because this is a -convenient place to keep information that is supposed to ``pop up'' just -when the group has finished. -For example, when `\.{\\hbox to 100pt}\grp' is being treated, the 100pt -dimension is stored on |save_stack| just before |new_save_level| is -called. - -We use the notation |saved(k)| to stand for an integer item that -appears in location |save_ptr+k| of the save stack. - -@d saved(#)==save_stack[save_ptr+#].int - -@p procedure new_save_level(@!c:group_code); {begin a new level of grouping} -begin check_full_save_stack; -save_type(save_ptr):=level_boundary; save_level(save_ptr):=cur_group; -save_index(save_ptr):=cur_boundary; -if cur_level=max_quarterword then overflow("grouping levels", -@:TeX capacity exceeded grouping levels}{\quad grouping levels@> - max_quarterword-min_quarterword); - {quit if |(cur_level+1)| is too big to be stored in |eqtb|} -cur_boundary:=save_ptr; incr(cur_level); incr(save_ptr); cur_group:=c; -end; - -@ Just before an entry of |eqtb| is changed, the following procedure should -be called to update the other data structures properly. It is important -to keep in mind that reference counts in |mem| include references from -within |save_stack|, so these counts must be handled carefully. -@^reference counts@> - -@p procedure eq_destroy(@!w:memory_word); {gets ready to forget |w|} -var q:pointer; {|equiv| field of |w|} -begin case eq_type_field(w) of -call,long_call,outer_call,long_outer_call: delete_token_ref(equiv_field(w)); -glue_ref: delete_glue_ref(equiv_field(w)); -shape_ref: begin q:=equiv_field(w); {we need to free a \.{\\parshape} block} - if q<>null then free_node(q,info(q)+info(q)+1); - end; {such a block is |2n+1| words long, where |n=info(q)|} -box_ref: flush_node_list(equiv_field(w)); -othercases do_nothing -endcases; -end; - -@ To save a value of |eqtb[p]| that was established at level |l|, we -can use the following subroutine. - -@p procedure eq_save(@!p:pointer;@!l:quarterword); {saves |eqtb[p]|} -begin check_full_save_stack; -if l=level_zero then save_type(save_ptr):=restore_zero -else begin save_stack[save_ptr]:=eqtb[p]; incr(save_ptr); - save_type(save_ptr):=restore_old_value; - end; -save_level(save_ptr):=l; save_index(save_ptr):=p; incr(save_ptr); -end; - -@ The procedure |eq_define| defines an |eqtb| entry having specified -|eq_type| and |equiv| fields, and saves the former value if appropriate. -This procedure is used only for entries in the first four regions of |eqtb|, -i.e., only for entries that have |eq_type| and |equiv| fields. -After calling this routine, it is safe to put four more entries on -|save_stack|, provided that there was room for four more entries before -the call, since |eq_save| makes the necessary test. - -@p procedure eq_define(@!p:pointer;@!t:quarterword;@!e:halfword); - {new data for |eqtb|} -begin if eq_level(p)=cur_level then eq_destroy(eqtb[p]) -else if cur_level>level_one then eq_save(p,eq_level(p)); -eq_level(p):=cur_level; eq_type(p):=t; equiv(p):=e; -end; - -@ The counterpart of |eq_define| for the remaining (fullword) positions in -|eqtb| is called |eq_word_define|. Since |xeq_level[p]>=level_one| for all -|p|, a `|restore_zero|' will never be used in this case. - -@p procedure eq_word_define(@!p:pointer;@!w:integer); -begin if xeq_level[p]<>cur_level then - begin eq_save(p,xeq_level[p]); xeq_level[p]:=cur_level; - end; -eqtb[p].int:=w; -end; - -@ The |eq_define| and |eq_word_define| routines take care of local definitions. -@^global definitions@> -Global definitions are done in almost the same way, but there is no need -to save old values, and the new value is associated with |level_one|. - -@p procedure geq_define(@!p:pointer;@!t:quarterword;@!e:halfword); - {global |eq_define|} -begin eq_destroy(eqtb[p]); -eq_level(p):=level_one; eq_type(p):=t; equiv(p):=e; -end; -@# -procedure geq_word_define(@!p:pointer;@!w:integer); {global |eq_word_define|} -begin eqtb[p].int:=w; xeq_level[p]:=level_one; -end; - -@ Subroutine |save_for_after| puts a token on the stack for save-keeping. - -@p procedure save_for_after(@!t:halfword); -begin if cur_level>level_one then - begin check_full_save_stack; - save_type(save_ptr):=insert_token; save_level(save_ptr):=level_zero; - save_index(save_ptr):=t; incr(save_ptr); - end; -end; - -@ The |unsave| routine goes the other way, taking items off of |save_stack|. -This routine takes care of restoration when a level ends; everything -belonging to the topmost group is cleared off of the save stack. - -@p@t\4@>@<Declare the procedure called |restore_trace|@>@;@/ -procedure@?back_input; forward; @t\2@> -procedure unsave; {pops the top level off the save stack} -label done; -var p:pointer; {position to be restored} -@!l:quarterword; {saved level, if in fullword regions of |eqtb|} -@!t:halfword; {saved value of |cur_tok|} -begin if cur_level>level_one then - begin decr(cur_level); - @<Clear off top level from |save_stack|@>; - end -else confusion("curlevel"); {|unsave| is not used when |cur_group=bottom_level|} -@:this can't happen curlevel}{\quad curlevel@> -end; - -@ @<Clear off...@>= -loop@+begin decr(save_ptr); - if save_type(save_ptr)=level_boundary then goto done; - p:=save_index(save_ptr); - if save_type(save_ptr)=insert_token then - @<Insert token |p| into \TeX's input@> - else begin if save_type(save_ptr)=restore_old_value then - begin l:=save_level(save_ptr); decr(save_ptr); - end - else save_stack[save_ptr]:=eqtb[undefined_control_sequence]; - @<Store \(s)|save_stack[save_ptr]| in |eqtb[p]|, unless - |eqtb[p]| holds a global value@>; - end; - end; -done: cur_group:=save_level(save_ptr); cur_boundary:=save_index(save_ptr) - -@ A global definition, which sets the level to |level_one|, -@^global definitions@> -will not be undone by |unsave|. If at least one global definition of -|eqtb[p]| has been carried out within the group that just ended, the -last such definition will therefore survive. - -@<Store \(s)|save...@>= -if p<int_base then - if eq_level(p)=level_one then - begin eq_destroy(save_stack[save_ptr]); {destroy the saved value} - @!stat if tracing_restores>0 then restore_trace(p,"retaining");@+tats@;@/ - end - else begin eq_destroy(eqtb[p]); {destroy the current value} - eqtb[p]:=save_stack[save_ptr]; {restore the saved value} - @!stat if tracing_restores>0 then restore_trace(p,"restoring");@+tats@;@/ - end -else if xeq_level[p]<>level_one then - begin eqtb[p]:=save_stack[save_ptr]; xeq_level[p]:=l; - @!stat if tracing_restores>0 then restore_trace(p,"restoring");@+tats@;@/ - end -else begin - @!stat if tracing_restores>0 then restore_trace(p,"retaining");@+tats@;@/ - end - -@ @<Declare the procedure called |restore_trace|@>= -@!stat procedure restore_trace(@!p:pointer;@!s:str_number); - {|eqtb[p]| has just been restored or retained} -begin begin_diagnostic; print_char("{"); print(s); print_char(" "); -show_eqtb(p); print_char("}"); -end_diagnostic(false); -end; -tats - -@ When looking for possible pointers to a memory location, it is helpful -to look for references from |eqtb| that might be waiting on the -save stack. Of course, we might find spurious pointers too; but this -routine is merely an aid when debugging, and at such times we are -grateful for any scraps of information, even if they prove to be irrelevant. -@^dirty \PASCAL@> - -@<Search |save_stack| for equivalents that point to |p|@>= -if save_ptr>0 then for q:=0 to save_ptr-1 do - begin if equiv_field(save_stack[q])=p then - begin print_nl("SAVE("); print_int(q); print_char(")"); - end; - end - -@ Most of the parameters kept in |eqtb| can be changed freely, but there's -an exception: The magnification should not be used with two different -values during any \TeX\ job, since a single magnification is applied to an -entire run. The global variable |mag_set| is set to the current magnification -whenever it becomes necessary to ``freeze'' it at a particular value. - -@<Glob...@>= -@!mag_set:integer; {if nonzero, this magnification should be used henceforth} - -@ @<Set init...@>= -mag_set:=0; - -@ The |prepare_mag| subroutine is called whenever \TeX\ wants to use |mag| -for magnification. - -@p procedure prepare_mag; -begin if (mag_set>0)and(mag<>mag_set) then - begin print_err("Incompatible magnification ("); print_int(mag); -@.Incompatible magnification@> - print(");"); print_nl(" the previous value will be retained"); - help2("I can handle only one magnification ratio per job. So I've")@/ - ("reverted to the magnification you used earlier on this run.");@/ - int_error(mag_set); - geq_word_define(int_base+mag_code,mag_set); {|mag:=mag_set|} - end; -if (mag<=0)or(mag>32768) then - begin print_err("Illegal magnification has been changed to 1000");@/ -@.Illegal magnification...@> - help1("The magnification ratio must be between 1 and 32768."); - int_error(mag); geq_word_define(int_base+mag_code,1000); - end; -mag_set:=mag; -end; - -@* \[20] Token lists. -A \TeX\ token is either a character or a control sequence, and it is -@^token@> -represented internally in one of two ways: (1)~A character whose ASCII -code number is |c| and whose command code is |m| is represented as the -number $2^8m+c$; the command code is in the range |1<=m<=14|. (2)~A control -sequence whose |eqtb| address is |p| is represented as the number -|cs_token_flag+p|. Here |cs_token_flag=@t$2^{12}-1$@>| is larger than -$2^8m+c$, yet it is small enough that |cs_token_flag+p< max_halfword|; -thus, a token fits comfortably in a halfword. - -A token |t| represents a |left_brace| command if and only if -|t<left_brace_limit|; it represents a |right_brace| command if and only if -we have |left_brace_limit<=t<right_brace_limit|; and it represents a |match| or -|end_match| command if and only if |match_token<=t<=end_match_token|. -The following definitions take care of these token-oriented constants -and a few others. - -@d cs_token_flag==@'7777 {amount added to the |eqtb| location in a - token that stands for a control sequence; is a multiple of~256, less~1} -@d left_brace_token=@'0400 {$2^8\cdot|left_brace|$} -@d left_brace_limit=@'1000 {$2^8\cdot(|left_brace|+1)$} -@d right_brace_token=@'1000 {$2^8\cdot|right_brace|$} -@d right_brace_limit=@'1400 {$2^8\cdot(|right_brace|+1)$} -@d math_shift_token=@'1400 {$2^8\cdot|math_shift|$} -@d tab_token=@'2000 {$2^8\cdot|tab_mark|$} -@d out_param_token=@'2400 {$2^8\cdot|out_param|$} -@d space_token=@'5040 {$2^8\cdot|spacer|+|" "|$} -@d letter_token=@'5400 {$2^8\cdot|letter|$} -@d other_token=@'6000 {$2^8\cdot|other_char|$} -@d match_token=@'6400 {$2^8\cdot|match|$} -@d end_match_token=@'7000 {$2^8\cdot|end_match|$} - -@ @<Check the ``constant''...@>= -if cs_token_flag+undefined_control_sequence>max_halfword then bad:=21; - -@ A token list is a singly linked list of one-word nodes in |mem|, where -each word contains a token and a link. Macro definitions, output-routine -definitions, marks, \.{\\write} texts, and a few other things -are remembered by \TeX\ in the form -of token lists, usually preceded by a node with a reference count in its -|token_ref_count| field. The token stored in location |p| is called -|info(p)|. - -Three special commands appear in the token lists of macro definitions. -When |m=match|, it means that \TeX\ should scan a parameter -for the current macro; when |m=end_match|, it means that parameter -matching should end and \TeX\ should start reading the macro text; and -when |m=out_param|, it means that \TeX\ should insert parameter -number |c| into the text at this point. - -The enclosing \.{\char'173} and \.{\char'175} characters of a macro -definition are omitted, but an output routine -will be enclosed in braces. - -Here is an example macro definition that illustrates these conventions. -After \TeX\ processes the text -$$\.{\\def\\mac a\#1\#2 \\b \{\#1\\-a \#\#1\#2 \#2\}}$$ -the definition of \.{\\mac} is represented as a token list containing -$$\def\,{\hskip2pt} -\vbox{\halign{\hfil#\hfil\cr -(reference count), |letter|\,\.a, |match|\,\#, |match|\,\#, |spacer|\,\.\ , -\.{\\b}, |end_match|,\cr -|out_param|\,1, \.{\\-}, |letter|\,\.a, |spacer|\,\.\ , |mac_param|\,\#, -|other_char|\,\.1,\cr -|out_param|\,2, |spacer|\,\.\ , |out_param|\,2.\cr}}$$ -The procedure |scan_toks| builds such token lists, and |macro_call| -does the parameter matching. -@^reference counts@> - -Examples such as -$$\.{\\def\\m\{\\def\\m\{a\}\ b\}}$$ -explain why reference counts would be needed even if \TeX\ had no \.{\\let} -operation: When the token list for \.{\\m} is being read, the redefinition of -\.{\\m} changes the |eqtb| entry before the token list has been fully -consumed, so we dare not simply destroy a token list when its -control sequence is being redefined. - -If the parameter-matching part of a definition ends with `\.{\#\{}', -the corresponding token list will have `\.\{' just before the `|end_match|' -and also at the very end. The first `\.\{' is used to delimit the parameter; the -second one keeps the first from disappearing. - -@ The procedure |show_token_list|, which prints a symbolic form of -the token list that starts at a given node |p|, illustrates these -conventions. The token list being displayed should not begin with a reference -count. However, the procedure is intended to be robust, so that if the -memory links are awry or if |p| is not really a pointer to a token list, -nothing catastrophic will happen. - -An additional parameter |q| is also given; this parameter is either null -or it points to a node in the token list where a certain magic computation -takes place that will be explained later. (Basically, |q| is non-null when -we are printing the two-line context information at the time of an error -message; |q| marks the place corresponding to where the second line -should begin.) - -For example, if |p| points to the node containing the first \.a in the -token list above, then |show_token_list| will print the string -$$\hbox{`\.{a\#1\#2\ \\b\ ->\#1\\-a\ \#\#1\#2\ \#2}';}$$ -and if |q| points to the node containing the second \.a, -the magic computation will be performed just before the second \.a is printed. - -The generation will stop, and `\.{\\ETC.}' will be printed, if the length -of printing exceeds a given limit~|l|. Anomalous entries are printed in the -form of control sequences that are not followed by a blank space, e.g., -`\.{\\BAD.}'; this cannot be confused with actual control sequences because -a real control sequence named \.{BAD} would come out `\.{\\BAD\ }'. - -@<Declare the procedure called |show_token_list|@>= -procedure show_token_list(@!p,@!q:integer;@!l:integer); -label exit; -var m,@!c:integer; {pieces of a token} -@!match_chr:ASCII_code; {character used in a `|match|'} -@!n:ASCII_code; {the highest parameter number, as an ASCII digit} -begin match_chr:="#"; n:="0"; tally:=0; -while (p<>null) and (tally<l) do - begin if p=q then @<Do magic computation@>; - @<Display token |p|, and |return| if there are problems@>; - p:=link(p); - end; -if p<>null then print_esc("ETC."); -@.ETC@> -exit: -end; - -@ @<Display token |p|...@>= -if (p<hi_mem_min) or (p>mem_end) then - begin print_esc("CLOBBERED."); return; -@.CLOBBERED@> - end; -if info(p)>=cs_token_flag then print_cs(info(p)-cs_token_flag) -else begin m:=info(p) div @'400; c:=info(p) mod @'400; - if info(p)<0 then print_esc("BAD.") -@.BAD@> - else @<Display the token $(|m|,|c|)$@>; - end - -@ The procedure usually ``learns'' the character code used for macro -parameters by seeing one in a |match| command before it runs into any -|out_param| commands. - -@<Display the token ...@>= -case m of -left_brace,right_brace,math_shift,tab_mark,sup_mark,sub_mark,spacer, - letter,other_char: print(c); -mac_param: begin print(c); print(c); - end; -out_param: begin print(match_chr); - if c<=9 then print_char(c+"0") - else begin print_char("!"); return; - end; - end; -match: begin match_chr:=c; print(c); incr(n); print_char(n); - if n>"9" then return; - end; -end_match: print("->"); -@.->@> -othercases print_esc("BAD.") -@.BAD@> -endcases - -@ Here's the way we sometimes want to display a token list, given a pointer -to its reference count; the pointer may be null. - -@p procedure token_show(@!p:pointer); -begin if p<>null then show_token_list(link(p),null,10000000); -end; - -@ The |print_meaning| subroutine displays |cur_cmd| and |cur_chr| in -symbolic form, including the expansion of a macro or mark. - -@p procedure print_meaning; -begin print_cmd_chr(cur_cmd,cur_chr); -if cur_cmd>=call then - begin print_char(":"); print_ln; token_show(cur_chr); - end -else if cur_cmd=top_bot_mark then - begin print_char(":"); print_ln; - token_show(cur_mark[cur_chr]); - end; -end; - -@* \[21] Introduction to the syntactic routines. -Let's pause a moment now and try to look at the Big Picture. -The \TeX\ program consists of three main parts: syntactic routines, -semantic routines, and output routines. The chief purpose of the -syntactic routines is to deliver the user's input to the semantic routines, -one token at a time. The semantic routines act as an interpreter -responding to these tokens, which may be regarded as commands. And the -output routines are periodically called on to convert box-and-glue -lists into a compact set of instructions that will be sent -to a typesetter. We have discussed the basic data structures and utility -routines of \TeX, so we are good and ready to plunge into the real activity by -considering the syntactic routines. - -Our current goal is to come to grips with the |get_next| procedure, -which is the keystone of \TeX's input mechanism. Each call of |get_next| -sets the value of three variables |cur_cmd|, |cur_chr|, and |cur_cs|, -representing the next input token. -$$\vbox{\halign{#\hfil\cr - \hbox{|cur_cmd| denotes a command code from the long list of codes - given above;}\cr - \hbox{|cur_chr| denotes a character code or other modifier of the command - code;}\cr - \hbox{|cur_cs| is the |eqtb| location of the current control sequence,}\cr - \hbox{\qquad if the current token was a control sequence, - otherwise it's zero.}\cr}}$$ -Underlying this external behavior of |get_next| is all the machinery -necessary to convert from character files to tokens. At a given time we -may be only partially finished with the reading of several files (for -which \.{\\input} was specified), and partially finished with the expansion -of some user-defined macros and/or some macro parameters, and partially -finished with the generation of some text in a template for \.{\\halign}, -and so on. When reading a character file, special characters must be -classified as math delimiters, etc.; comments and extra blank spaces must -be removed, paragraphs must be recognized, and control sequences must be -found in the hash table. Furthermore there are occasions in which the -scanning routines have looked ahead for a word like `\.{plus}' but only -part of that word was found, hence a few characters must be put back -into the input and scanned again. - -To handle these situations, which might all be present simultaneously, -\TeX\ uses various stacks that hold information about the incomplete -activities, and there is a finite state control for each level of the -input mechanism. These stacks record the current state of an implicitly -recursive process, but the |get_next| procedure is not recursive. -Therefore it will not be difficult to translate these algorithms into -low-level languages that do not support recursion. - -@<Glob...@>= -@!cur_cmd: eight_bits; {current command set by |get_next|} -@!cur_chr: halfword; {operand of current command} -@!cur_cs: pointer; {control sequence found here, zero if none found} -@!cur_tok: halfword; {packed representative of |cur_cmd| and |cur_chr|} - -@ The |print_cmd_chr| routine prints a symbolic interpretation of a -command code and its modifier. This is used in certain `\.{You can\'t}' -error messages, and in the implementation of diagnostic routines like -\.{\\show}. - -The body of |print_cmd_chr| is a rather tedious listing of print -commands, and most of it is essentially an inverse to the |primitive| -routine that enters a \TeX\ primitive into |eqtb|. Therefore much of -this procedure appears elsewhere in the program, -together with the corresponding |primitive| calls. - -@d chr_cmd(#)==begin print(#); print_ASCII(chr_code); - end - -@<Declare the procedure called |print_cmd_chr|@>= -procedure print_cmd_chr(@!cmd:quarterword;@!chr_code:halfword); -begin case cmd of -left_brace: chr_cmd("begin-group character "); -right_brace: chr_cmd("end-group character "); -math_shift: chr_cmd("math shift character "); -mac_param: chr_cmd("macro parameter character "); -sup_mark: chr_cmd("superscript character "); -sub_mark: chr_cmd("subscript character "); -endv: print("end of alignment template"); -spacer: chr_cmd("blank space "); -letter: chr_cmd("the letter "); -other_char: chr_cmd("the character "); -@t\4@>@<Cases of |print_cmd_chr| for symbolic printing of primitives@>@/ -othercases print("[unknown command code!]") -endcases; -end; - -@ Here is a procedure that displays the current command. - -@p procedure show_cur_cmd_chr; -begin begin_diagnostic; print_nl("{"); -if mode<>shown_mode then - begin print_mode(mode); print(": "); shown_mode:=mode; - end; -print_cmd_chr(cur_cmd,cur_chr); print_char("}"); -end_diagnostic(false); -end; - -@* \[22] Input stacks and states. -This implementation of -\TeX\ uses two different conventions for representing sequential stacks. -@^stack conventions@>@^conventions for representing stacks@> - -\yskip\hangg 1) If there is frequent access to the top entry, and if the -stack is essentially never empty, then the top entry is kept in a global -variable (even better would be a machine register), and the other entries -appear in the array $\\{stack}[0\to(\\{ptr}-1)]$. For example, the -semantic stack described above is handled this way, and so is the input -stack that we are about to study. - -\yskip\hangg 2) If there is infrequent top access, the entire stack contents -are in the array $\\{stack}[0\to(\\{ptr}-1)]$. For example, the |save_stack| -is treated this way, as we have seen. - -\yskip\noindent -The state of \TeX's input mechanism appears in the input stack, whose -entries are records with six fields, called |state|, |index|, |start|, |loc|, -|limit|, and |name|. This stack is maintained with -convention~(1), so it is declared in the following way: - -@<Types...@>= -@!in_state_record = record - @!state_field, @!index_field: quarterword; - @!start_field,@!loc_field, @!limit_field, @!name_field: halfword; - end; - -@ @<Glob...@>= -@!input_stack : array[0..stack_size] of in_state_record; -@!input_ptr : 0..stack_size; {first unused location of |input_stack|} -@!max_in_stack: 0..stack_size; {largest value of |input_ptr| when pushing} -@!cur_input : in_state_record; - {the ``top'' input state, according to convention (1)} - -@ We've already defined the special variable |loc==cur_input.loc_field| -in our discussion of basic input-output routines. The other components of -|cur_input| are defined in the same way: - -@d state==cur_input.state_field {current scanner state} -@d index==cur_input.index_field {reference for buffer information} -@d start==cur_input.start_field {starting position in |buffer|} -@d limit==cur_input.limit_field {end of current line in |buffer|} -@d name==cur_input.name_field {name of the current file} - -@ Let's look more closely now at the control variables -(|state|,~|index|,~|start|,~|loc|,~|limit|,~|name|), -assuming that \TeX\ is reading a line of characters that have been input -from some file or from the user's terminal. There is an array called -|buffer| that acts as a stack of all lines of characters that are -currently being read from files, including all lines on subsidiary -levels of the input stack that are not yet completed. \TeX\ will return to -the other lines when it is finished with the present input file. - -(Incidentally, on a machine with byte-oriented addressing, it might be -appropriate to combine |buffer| with the |str_pool| array, -letting the buffer entries grow downward from the top of the string pool -and checking that these two tables don't bump into each other.) - -The line we are currently working on begins in position |start| of the -buffer; the next character we are about to read is |buffer[loc]|; and -|limit| is the location of the last character present. If |loc>limit|, -the line has been completely read. Usually |buffer[limit]| is the -|end_line_char|, denoting the end of a line, but this is not -true if the current line is an insertion that was entered on the user's -terminal in response to an error message. - -The |name| variable is a string number that designates the name of -the current file, if we are reading a text file. It is zero if we -are reading from the terminal; it is |n+1| if we are reading from -input stream |n|, where |0<=n<=16|. (Input stream 16 stands for -an invalid stream number; in such cases the input is actually from -the terminal, under control of the procedure |read_toks|.) - -The |state| variable has one of three values, when we are scanning such -files: -$$\baselineskip 15pt\vbox{\halign{#\hfil\cr -1) |state=mid_line| is the normal state.\cr -2) |state=skip_blanks| is like |mid_line|, but blanks are ignored.\cr -3) |state=new_line| is the state at the beginning of a line.\cr}}$$ -These state values are assigned numeric codes so that if we add the state -code to the next character's command code, we get distinct values. For -example, `|mid_line+spacer|' stands for the case that a blank -space character occurs in the middle of a line when it is not being -ignored; after this case is processed, the next value of |state| will -be |skip_blanks|. - -@d mid_line=1 {|state| code when scanning a line of characters} -@d skip_blanks=2+max_char_code {|state| code when ignoring blanks} -@d new_line=3+max_char_code+max_char_code {|state| code at start of line} - -@ Additional information about the current line is available via the -|index| variable, which counts how many lines of characters are present -in the buffer below the current level. We have |index=0| when reading -from the terminal and prompting the user for each line; then if the user types, -e.g., `\.{\\input paper}', we will have |index=1| while reading -the file \.{paper.tex}. However, it does not follow that |index| is the -same as the input stack pointer, since many of the levels on the input -stack may come from token lists. For example, the instruction `\.{\\input -paper}' might occur in a token list. - -The global variable |in_open| is equal to the |index| -value of the highest non-token-list level. Thus, the number of partially read -lines in the buffer is |in_open+1|, and we have |in_open=index| -when we are not reading a token list. - -If we are not currently reading from the terminal, or from an input -stream, we are reading from the file variable |input_file[index]|. We use -the notation |terminal_input| as a convenient abbreviation for |name=0|, -and |cur_file| as an abbreviation for |input_file[index]|. - -The global variable |line| contains the line number in the topmost -open file, for use in error messages. If we are not reading from -the terminal, |line_stack[index]| holds the line number for the -enclosing level, so that |line| can be restored when the current -file has been read. Line numbers should never be negative, since the -negative of the current line number is used to identify the user's output -routine in the |mode_line| field of the semantic nest entries. - -If more information about the input state is needed, it can be -included in small arrays like those shown here. For example, -the current page or segment number in the input file might be -put into a variable |@!page|, maintained for enclosing levels in -`\ignorespaces|@!page_stack:array[1..max_in_open] of integer|\unskip' -by analogy with |line_stack|. -@^system dependencies@> - -@d terminal_input==(name=0) {are we reading from the terminal?} -@d cur_file==input_file[index] {the current |alpha_file| variable} - -@<Glob...@>= -@!in_open : 0..max_in_open; {the number of lines in the buffer, less one} -@!open_parens : 0..max_in_open; {the number of open text files} -@!input_file : array[1..max_in_open] of alpha_file; -@!line : integer; {current line number in the current source file} -@!line_stack : array[1..max_in_open] of integer; - -@ Users of \TeX\ sometimes forget to balance left and right braces properly, -and one of the ways \TeX\ tries to spot such errors is by considering an -input file as broken into subfiles by control sequences that -are declared to be \.{\\outer}. - -A variable called |scanner_status| tells \TeX\ whether or not to complain -when a subfile ends. This variable has six possible values: - -\yskip\hang|normal|, means that a subfile can safely end here without incident. - -\yskip\hang|skipping|, means that a subfile can safely end here, but not a file, -because we're reading past some conditional text that was not selected. - -\yskip\hang|defining|, means that a subfile shouldn't end now because a -macro is being defined. - -\yskip\hang|matching|, means that a subfile shouldn't end now because a -macro is being used and we are searching for the end of its arguments. - -\yskip\hang|aligning|, means that a subfile shouldn't end now because we are -not finished with the preamble of an \.{\\halign} or \.{\\valign}. - -\yskip\hang|absorbing|, means that a subfile shouldn't end now because we are -reading a balanced token list for \.{\\message}, \.{\\write}, etc. - -\yskip\noindent -If the |scanner_status| is not |normal|, the variable |warning_index| points -to the |eqtb| location for the relevant control sequence name to print -in an error message. - -@d skipping=1 {|scanner_status| when passing conditional text} -@d defining=2 {|scanner_status| when reading a macro definition} -@d matching=3 {|scanner_status| when reading macro arguments} -@d aligning=4 {|scanner_status| when reading an alignment preamble} -@d absorbing=5 {|scanner_status| when reading a balanced text} - -@<Glob...@>= -@!scanner_status : normal..absorbing; {can a subfile end now?} -@!warning_index : pointer; {identifier relevant to non-|normal| scanner status} -@!def_ref : pointer; {reference count of token list being defined} - -@ Here is a procedure that uses |scanner_status| to print a warning message -when a subfile has ended, and at certain other crucial times: - -@<Declare the procedure called |runaway|@>= -procedure runaway; -var p:pointer; {head of runaway list} -begin if scanner_status>skipping then - begin print_nl("Runaway "); -@.Runaway...@> - case scanner_status of - defining: begin print("definition"); p:=def_ref; - end; - matching: begin print("argument"); p:=temp_head; - end; - aligning: begin print("preamble"); p:=hold_head; - end; - absorbing: begin print("text"); p:=def_ref; - end; - end; {there are no other cases} - print_char("?");print_ln; show_token_list(link(p),null,error_line-10); - end; -end; - -@ However, all this discussion about input state really applies only to the -case that we are inputting from a file. There is another important case, -namely when we are currently getting input from a token list. In this case -|state=token_list|, and the conventions about the other state variables -are different: - -\yskip\hang|loc| is a pointer to the current node in the token list, i.e., -the node that will be read next. If |loc=null|, the token list has been -fully read. - -\yskip\hang|start| points to the first node of the token list; this node -may or may not contain a reference count, depending on the type of token -list involved. - -\yskip\hang|token_type|, which takes the place of |index| in the -discussion above, is a code number that explains what kind of token list -is being scanned. - -\yskip\hang|name| points to the |eqtb| address of the control sequence -being expanded, if the current token list is a macro. - -\yskip\hang|param_start|, which takes the place of |limit|, tells where -the parameters of the current macro begin in the |param_stack|, if the -current token list is a macro. - -\yskip\noindent The |token_type| can take several values, depending on -where the current token list came from: - -\yskip\hang|parameter|, if a parameter is being scanned; - -\hang|u_template|, if the \<u_j> part of an alignment -template is being scanned; - -\hang|v_template|, if the \<v_j> part of an alignment -template is being scanned; - -\hang|backed_up|, if the token list being scanned has been inserted as -`to be read again'; - -\hang|inserted|, if the token list being scanned has been inserted as -the text expansion of a \.{\\count} or similar variable; - -\hang|macro|, if a user-defined control sequence is being scanned; - -\hang|output_text|, if an \.{\\output} routine is being scanned; - -\hang|every_par_text|, if the text of \.{\\everypar} is being scanned; - -\hang|every_math_text|, if the text of \.{\\everymath} is being scanned; - -\hang|every_display_text|, if the text of \.{\\everydisplay} is being scanned; - -\hang|every_hbox_text|, if the text of \.{\\everyhbox} is being scanned; - -\hang|every_vbox_text|, if the text of \.{\\everyvbox} is being scanned; - -\hang|every_job_text|, if the text of \.{\\everyjob} is being scanned; - -\hang|every_cr_text|, if the text of \.{\\everycr} is being scanned; - -\hang|mark_text|, if the text of a \.{\\mark} is being scanned; - -\hang|write_text|, if the text of a \.{\\write} is being scanned. - -\yskip\noindent -The codes for |output_text|, |every_par_text|, etc., are equal to a constant -plus the corresponding codes for token list parameters |output_routine_loc|, -|every_par_loc|, etc. The token list begins with a reference count if and -only if |token_type>=macro|. -@^reference counts@> - -@d token_list=0 {|state| code when scanning a token list} -@d token_type==index {type of current token list} -@d param_start==limit {base of macro parameters in |param_stack|} -@d parameter=0 {|token_type| code for parameter} -@d u_template=1 {|token_type| code for \<u_j> template} -@d v_template=2 {|token_type| code for \<v_j> template} -@d backed_up=3 {|token_type| code for text to be reread} -@d inserted=4 {|token_type| code for inserted texts} -@d macro=5 {|token_type| code for defined control sequences} -@d output_text=6 {|token_type| code for output routines} -@d every_par_text=7 {|token_type| code for \.{\\everypar}} -@d every_math_text=8 {|token_type| code for \.{\\everymath}} -@d every_display_text=9 {|token_type| code for \.{\\everydisplay}} -@d every_hbox_text=10 {|token_type| code for \.{\\everyhbox}} -@d every_vbox_text=11 {|token_type| code for \.{\\everyvbox}} -@d every_job_text=12 {|token_type| code for \.{\\everyjob}} -@d every_cr_text=13 {|token_type| code for \.{\\everycr}} -@d mark_text=14 {|token_type| code for \.{\\topmark}, etc.} -@d write_text=15 {|token_type| code for \.{\\write}} - -@ The |param_stack| is an auxiliary array used to hold pointers to the token -lists for parameters at the current level and subsidiary levels of input. -This stack is maintained with convention (2), and it grows at a different -rate from the others. - -@<Glob...@>= -@!param_stack:array [0..param_size] of pointer; - {token list pointers for parameters} -@!param_ptr:0..param_size; {first unused entry in |param_stack|} -@!max_param_stack:integer; - {largest value of |param_ptr|, will be |<=param_size+9|} - -@ The input routines must also interact with the processing of -\.{\\halign} and \.{\\valign}, since the appearance of tab marks and -\.{\\cr} in certain places is supposed to trigger the beginning of special -\<v_j> template text in the scanner. This magic is accomplished by an -|align_state| variable that is increased by~1 when a `\.{\char'173}' is -scanned and decreased by~1 when a `\.{\char'175}' is scanned. The |align_state| -is nonzero during the \<u_j> template, after which it is set to zero; the -\<v_j> template begins when a tab mark or \.{\\cr} occurs at a time that -|align_state=0|. - -@<Glob...@>= -@!align_state:integer; {group level with respect to current alignment} - -@ Thus, the ``current input state'' can be very complicated indeed; there -can be many levels and each level can arise in a variety of ways. The -|show_context| procedure, which is used by \TeX's error-reporting routine to -print out the current input state on all levels down to the most recent -line of characters from an input file, illustrates most of these conventions. -The global variable |base_ptr| contains the lowest level that was -displayed by this procedure. - -@<Glob...@>= -@!base_ptr:0..stack_size; {shallowest level shown by |show_context|} - -@ The status at each level is indicated by printing two lines, where the first -line indicates what was read so far and the second line shows what remains -to be read. The context is cropped, if necessary, so that the first line -contains at most |half_error_line| characters, and the second contains -at most |error_line|. Non-current input levels whose |token_type| is -`|backed_up|' are shown only if they have not been fully read. - -@p procedure show_context; {prints where the scanner is} -label done; -var old_setting:0..max_selector; {saved |selector| setting} -@!nn:integer; {number of contexts shown so far, less one} -@!bottom_line:boolean; {have we reached the final context to be shown?} -@<Local variables for formatting calculations@>@/ -begin base_ptr:=input_ptr; input_stack[base_ptr]:=cur_input; - {store current state} -nn:=-1; bottom_line:=false; -loop@+begin cur_input:=input_stack[base_ptr]; {enter into the context} - if (state<>token_list) then - if (name>17) or (base_ptr=0) then bottom_line:=true; - if (base_ptr=input_ptr)or bottom_line or(nn<error_context_lines) then - @<Display the current context@> - else if nn=error_context_lines then - begin print_nl("..."); incr(nn); {omitted if |error_context_lines<0|} - end; - if bottom_line then goto done; - decr(base_ptr); - end; -done: cur_input:=input_stack[input_ptr]; {restore original state} -end; - -@ @<Display the current context@>= -begin if (base_ptr=input_ptr) or (state<>token_list) or - (token_type<>backed_up) or (loc<>null) then - {we omit backed-up token lists that have already been read} - begin tally:=0; {get ready to count characters} - old_setting:=selector; - if state<>token_list then - begin @<Print location of current line@>; - @<Pseudoprint the line@>; - end - else begin @<Print type of token list@>; - @<Pseudoprint the token list@>; - end; - selector:=old_setting; {stop pseudoprinting} - @<Print two lines using the tricky pseudoprinted information@>; - incr(nn); - end; -end - -@ This routine should be changed, if necessary, to give the best possible -indication of where the current line resides in the input file. -For example, on some systems it is best to print both a page and line number. -@^system dependencies@> - -@<Print location of current line@>= -if name<=17 then - if terminal_input then - if base_ptr=0 then print_nl("<*>") else print_nl("<insert> ") - else begin print_nl("<read "); - if name=17 then print_char("*")@+else print_int(name-1); -@.*\relax@> - print_char(">"); - end -else begin print_nl("l."); print_int(line); - end; -print_char(" ") - -@ @<Print type of token list@>= -case token_type of -parameter: print_nl("<argument> "); -u_template,v_template: print_nl("<template> "); -backed_up: if loc=null then print_nl("<recently read> ") - else print_nl("<to be read again> "); -inserted: print_nl("<inserted text> "); -macro: begin print_ln; print_cs(name); - end; -output_text: print_nl("<output> "); -every_par_text: print_nl("<everypar> "); -every_math_text: print_nl("<everymath> "); -every_display_text: print_nl("<everydisplay> "); -every_hbox_text: print_nl("<everyhbox> "); -every_vbox_text: print_nl("<everyvbox> "); -every_job_text: print_nl("<everyjob> "); -every_cr_text: print_nl("<everycr> "); -mark_text: print_nl("<mark> "); -write_text: print_nl("<write> "); -othercases print_nl("?") {this should never happen} -endcases - -@ Here it is necessary to explain a little trick. We don't want to store a long -string that corresponds to a token list, because that string might take up -lots of memory; and we are printing during a time when an error message is -being given, so we dare not do anything that might overflow one of \TeX's -tables. So `pseudoprinting' is the answer: We enter a mode of printing -that stores characters into a buffer of length |error_line|, where character -$k+1$ is placed into \hbox{|trick_buf[k mod error_line]|} if -|k<trick_count|, otherwise character |k| is dropped. Initially we set -|tally:=0| and |trick_count:=1000000|; then when we reach the -point where transition from line 1 to line 2 should occur, we -set |first_count:=tally| and |trick_count:=@tmax@>(error_line, -tally+1+error_line-half_error_line)|. At the end of the -pseudoprinting, the values of |first_count|, |tally|, and -|trick_count| give us all the information we need to print the two lines, -and all of the necessary text is in |trick_buf|. - -Namely, let |l| be the length of the descriptive information that appears -on the first line. The length of the context information gathered for that -line is |k=first_count|, and the length of the context information -gathered for line~2 is $m=\min(|tally|, |trick_count|)-k$. If |l+k<=h|, -where |h=half_error_line|, we print |trick_buf[0..k-1]| after the -descriptive information on line~1, and set |n:=l+k|; here |n| is the -length of line~1. If $l+k>h$, some cropping is necessary, so we set |n:=h| -and print `\.{...}' followed by -$$\hbox{|trick_buf[(l+k-h+3)..k-1]|,}$$ -where subscripts of |trick_buf| are circular modulo |error_line|. The -second line consists of |n|~spaces followed by |trick_buf[k..(k+m-1)]|, -unless |n+m>error_line|; in the latter case, further cropping is done. -This is easier to program than to explain. - -@<Local variables for formatting...@>= -@!i:0..buf_size; {index into |buffer|} -@!j:0..buf_size; {end of current line in |buffer|} -@!l:0..half_error_line; {length of descriptive information on line 1} -@!m:integer; {context information gathered for line 2} -@!n:0..error_line; {length of line 1} -@!p: integer; {starting or ending place in |trick_buf|} -@!q: integer; {temporary index} - -@ The following code sets up the print routines so that they will gather -the desired information. - -@d begin_pseudoprint== - begin l:=tally; tally:=0; selector:=pseudo; - trick_count:=1000000; - end -@d set_trick_count== - begin first_count:=tally; - trick_count:=tally+1+error_line-half_error_line; - if trick_count<error_line then trick_count:=error_line; - end - -@ And the following code uses the information after it has been gathered. - -@<Print two lines using the tricky pseudoprinted information@>= -if trick_count=1000000 then set_trick_count; - {|set_trick_count| must be performed} -if tally<trick_count then m:=tally-first_count -else m:=trick_count-first_count; {context on line 2} -if l+first_count<=half_error_line then - begin p:=0; n:=l+first_count; - end -else begin print("..."); p:=l+first_count-half_error_line+3; - n:=half_error_line; - end; -for q:=p to first_count-1 do print_char(trick_buf[q mod error_line]); -print_ln; -for q:=1 to n do print_char(" "); {print |n| spaces to begin line~2} -if m+n<=error_line then p:=first_count+m else p:=first_count+(error_line-n-3); -for q:=first_count to p-1 do print_char(trick_buf[q mod error_line]); -if m+n>error_line then print("...") - -@ But the trick is distracting us from our current goal, which is to -understand the input state. So let's concentrate on the data structures that -are being pseudoprinted as we finish up the |show_context| procedure. - -@<Pseudoprint the line@>= -begin_pseudoprint; -if buffer[limit]=end_line_char then j:=limit -else j:=limit+1; {determine the effective end of the line} -if j>0 then for i:=start to j-1 do - begin if i=loc then set_trick_count; - print(buffer[i]); - end - -@ @<Pseudoprint the token list@>= -begin_pseudoprint; -if token_type<macro then show_token_list(start,loc,100000) -else show_token_list(link(start),loc,100000) {avoid reference count} - -@ Here is the missing piece of |show_token_list| that is activated when the -token beginning line~2 is about to be shown: - -@<Do magic computation@>=set_trick_count - -@* \[23] Maintaining the input stacks. -The following subroutines change the input status in commonly needed ways. - -First comes |push_input|, which stores the current state and creates a -new level (having, initially, the same properties as the old). - -@d push_input==@t@> {enter a new input level, save the old} - begin if input_ptr>max_in_stack then - begin max_in_stack:=input_ptr; - if input_ptr=stack_size then overflow("input stack size",stack_size); -@:TeX capacity exceeded input stack size}{\quad input stack size@> - end; - input_stack[input_ptr]:=cur_input; {stack the record} - incr(input_ptr); - end - -@ And of course what goes up must come down. - -@d pop_input==@t@> {leave an input level, re-enter the old} - begin decr(input_ptr); cur_input:=input_stack[input_ptr]; - end - -@ Here is a procedure that starts a new level of token-list input, given -a token list |p| and its type |t|. If |t=macro|, the calling routine should -set |name| and |loc|. - -@d back_list(#)==begin_token_list(#,backed_up) {backs up a simple token list} -@d ins_list(#)==begin_token_list(#,inserted) {inserts a simple token list} - -@p procedure begin_token_list(@!p:pointer;@!t:quarterword); -begin push_input; state:=token_list; start:=p; token_type:=t; -if t>=macro then {the token list starts with a reference count} - begin add_token_ref(p); - if t=macro then param_start:=param_ptr - else begin loc:=link(p); - if tracing_macros>1 then - begin begin_diagnostic; print_nl(""); - case t of - mark_text:print_esc("mark"); - write_text:print_esc("write"); - othercases print_cmd_chr(assign_toks,t-output_text+output_routine_loc) - endcases;@/ - print("->"); token_show(p); end_diagnostic(false); - end; - end; - end -else loc:=p; -end; - -@ When a token list has been fully scanned, the following computations -should be done as we leave that level of input. The |token_type| tends -to be equal to either |backed_up| or |inserted| about 2/3 of the time. -@^inner loop@> - -@p procedure end_token_list; {leave a token-list input level} -begin if token_type>=backed_up then {token list to be deleted} - begin if token_type<=inserted then flush_list(start) - else begin delete_token_ref(start); {update reference count} - if token_type=macro then {parameters must be flushed} - while param_ptr>param_start do - begin decr(param_ptr); - flush_list(param_stack[param_ptr]); - end; - end; - end -else if token_type=u_template then - if align_state>500000 then align_state:=0 - else fatal_error("(interwoven alignment preambles are not allowed)"); -@.interwoven alignment preambles...@> -pop_input; -check_interrupt; -end; - -@ Sometimes \TeX\ has read too far and wants to ``unscan'' what it has -seen. The |back_input| procedure takes care of this by putting the token -just scanned back into the input stream, ready to be read again. This -procedure can be used only if |cur_tok| represents the token to be -replaced. Some applications of \TeX\ use this procedure a lot, -so it has been slightly optimized for speed. -@^inner loop@> - -@p procedure back_input; {undoes one token of input} -var p:pointer; {a token list of length one} -begin while (state=token_list)and(loc=null)and(token_type<>v_template) do - end_token_list; {conserve stack space} -p:=get_avail; info(p):=cur_tok; -if cur_tok<right_brace_limit then - if cur_tok<left_brace_limit then decr(align_state) - else incr(align_state); -push_input; state:=token_list; start:=p; token_type:=backed_up; -loc:=p; {that was |back_list(p)|, without procedure overhead} -end; - -@ @<Insert token |p| into \TeX's input@>= -begin t:=cur_tok; cur_tok:=p; back_input; cur_tok:=t; -end - -@ The |back_error| routine is used when we want to replace an offending token -just before issuing an error message. This routine, like |back_input|, -requires that |cur_tok| has been set. We disable interrupts during the -call of |back_input| so that the help message won't be lost. - -@p procedure back_error; {back up one token and call |error|} -begin OK_to_interrupt:=false; back_input; OK_to_interrupt:=true; error; -end; -@# -procedure ins_error; {back up one inserted token and call |error|} -begin OK_to_interrupt:=false; back_input; token_type:=inserted; -OK_to_interrupt:=true; error; -end; - -@ The |begin_file_reading| procedure starts a new level of input for lines -of characters to be read from a file, or as an insertion from the -terminal. It does not take care of opening the file, nor does it set |loc| -or |limit| or |line|. -@^system dependencies@> - -@p procedure begin_file_reading; -begin if in_open=max_in_open then overflow("text input levels",max_in_open); -@:TeX capacity exceeded text input levels}{\quad text input levels@> -if first=buf_size then overflow("buffer size",buf_size); -@:TeX capacity exceeded buffer size}{\quad buffer size@> -incr(in_open); push_input; index:=in_open; -line_stack[index]:=line; start:=first; state:=mid_line; -name:=0; {|terminal_input| is now |true|} -end; - -@ Conversely, the variables must be downdated when such a level of input -is finished: - -@p procedure end_file_reading; -begin first:=start; line:=line_stack[index]; -if name>17 then a_close(cur_file); {forget it} -pop_input; decr(in_open); -end; - -@ In order to keep the stack from overflowing during a long sequence of -inserted `\.{\\show}' commands, the following routine removes completed -error-inserted lines from memory. - -@p procedure clear_for_error_prompt; -begin while (state<>token_list)and terminal_input and@| - (input_ptr>0)and(loc>limit) do end_file_reading; -print_ln; clear_terminal; -end; - -@ To get \TeX's whole input mechanism going, we perform the following -actions. - -@<Initialize the input routines@>= -begin input_ptr:=0; max_in_stack:=0; -in_open:=0; open_parens:=0; max_buf_stack:=0; -param_ptr:=0; max_param_stack:=0; -first:=buf_size; repeat buffer[first]:=0; decr(first); until first=0; -scanner_status:=normal; warning_index:=null; first:=1; -state:=new_line; start:=1; index:=0; line:=0; name:=0; -force_eof:=false; -align_state:=1000000;@/ -if not init_terminal then goto final_end; -limit:=last; first:=last+1; {|init_terminal| has set |loc| and |last|} -end - -@* \[24] Getting the next token. -The heart of \TeX's input mechanism is the |get_next| procedure, which -we shall develop in the next few sections of the program. Perhaps we -shouldn't actually call it the ``heart,'' however, because it really acts -as \TeX's eyes and mouth, reading the source files and gobbling them up. -And it also helps \TeX\ to regurgitate stored token lists that are to be -processed again. -@^eyes and mouth@> - -The main duty of |get_next| is to input one token and to set |cur_cmd| -and |cur_chr| to that token's command code and modifier. Furthermore, if -the input token is a control sequence, the |eqtb| location of that control -sequence is stored in |cur_cs|; otherwise |cur_cs| is set to zero. - -Underlying this simple description is a certain amount of complexity -because of all the cases that need to be handled. -However, the inner loop of |get_next| is reasonably short and fast. - -When |get_next| is asked to get the next token of a \.{\\read} line, -it sets |cur_cmd=cur_chr=cur_cs=0| in the case that no more tokens -appear on that line. (There might not be any tokens at all, if the -|end_line_char| has |ignore| as its catcode.) - -@ The value of |par_loc| is the |eqtb| address of `\.{\\par}'. This quantity -is needed because a blank line of input is supposed to be exactly equivalent -to the appearance of \.{\\par}; we must set |cur_cs:=par_loc| -when detecting a blank line. - -@<Glob...@>= -@!par_loc:pointer; {location of `\.{\\par}' in |eqtb|} -@!par_token:halfword; {token representing `\.{\\par}'} - -@ @<Put each...@>= -primitive("par",par_end,256); {cf.\ |scan_file_name|} -@!@:par_}{\.{\\par} primitive@> -par_loc:=cur_val; par_token:=cs_token_flag+par_loc; - -@ @<Cases of |print_cmd_chr|...@>= -par_end:print_esc("par"); - -@ Before getting into |get_next|, let's consider the subroutine that -is called when an `\.{\\outer}' control sequence has been scanned or -when the end of a file has been reached. These two cases are distinguished -by |cur_cs|, which is zero at the end of a file. - -@p procedure check_outer_validity; -var p:pointer; {points to inserted token list} -@!q:pointer; {auxiliary pointer} -begin if scanner_status<>normal then - begin deletions_allowed:=false; - @<Back up an outer control sequence so that it can be reread@>; - if scanner_status>skipping then - @<Tell the user what has run away and try to recover@> - else begin print_err("Incomplete "); print_cmd_chr(if_test,cur_if); -@.Incomplete \\if...@> - print("; all text was ignored after line "); print_int(skip_line); - help3("A forbidden control sequence occurred in skipped text.")@/ - ("This kind of error happens when you say `\if...' and forget")@/ - ("the matching `\fi'. I've inserted a `\fi'; this might work."); - if cur_cs<>0 then cur_cs:=0 - else help_line[2]:=@| - "The file ended while I was skipping conditional text."; - cur_tok:=cs_token_flag+frozen_fi; ins_error; - end; - deletions_allowed:=true; - end; -end; - -@ An outer control sequence that occurs in a \.{\\read} will not be reread, -since the error recovery for \.{\\read} is not very powerful. - -@<Back up an outer control sequence so that it can be reread@>= -if cur_cs<>0 then - begin if (state=token_list)or(name<1)or(name>17) then - begin p:=get_avail; info(p):=cs_token_flag+cur_cs; - back_list(p); {prepare to read the control sequence again} - end; - cur_cmd:=spacer; cur_chr:=" "; {replace it by a space} - end - -@ @<Tell the user what has run away...@>= -begin runaway; {print a definition, argument, or preamble} -if cur_cs=0 then print_err("File ended") -@.File ended while scanning...@> -else begin cur_cs:=0; print_err("Forbidden control sequence found"); -@.Forbidden control sequence...@> - end; -print(" while scanning "); -@<Print either `\.{definition}' or `\.{use}' or `\.{preamble}' or `\.{text}', - and insert tokens that should lead to recovery@>; -print(" of "); sprint_cs(warning_index); -help4("I suspect you have forgotten a `}', causing me")@/ -("to read past where you wanted me to stop.")@/ -("I'll try to recover; but if the error is serious,")@/ -("you'd better type `E' or `X' now and fix your file.");@/ -error; -end - -@ The recovery procedure can't be fully understood without knowing more -about the \TeX\ routines that should be aborted, but we can sketch the -ideas here: For a runaway definition or a runaway balanced text -we will insert a right brace; for a -runaway preamble, we will insert a special \.{\\cr} token and a right -brace; and for a runaway argument, we will set |long_state| to -|outer_call| and insert \.{\\par}. - -@<Print either `\.{definition}' or ...@>= -p:=get_avail; -case scanner_status of -defining:begin print("definition"); info(p):=right_brace_token+"}"; - end; -matching:begin print("use"); info(p):=par_token; long_state:=outer_call; - end; -aligning:begin print("preamble"); info(p):=right_brace_token+"}"; q:=p; - p:=get_avail; link(p):=q; info(p):=cs_token_flag+frozen_cr; - align_state:=-1000000; - end; -absorbing:begin print("text"); info(p):=right_brace_token+"}"; - end; -end; {there are no other cases} -ins_list(p) - -@ We need to mention a procedure here that may be called by |get_next|. - -@p procedure@?firm_up_the_line; forward; - -@ Now we're ready to take the plunge into |get_next| itself. Parts of -this routine are executed more often than any other instructions of \TeX. -@^mastication@>@^inner loop@> - -@d switch=25 {a label in |get_next|} -@d start_cs=26 {another} - -@p procedure get_next; {sets |cur_cmd|, |cur_chr|, |cur_cs| to next token} -label restart, {go here to get the next input token} - switch, {go here to eat the next character from a file} - reswitch, {go here to digest it again} - start_cs, {go here to start looking for a control sequence} - found, {go here when a control sequence has been found} - exit; {go here when the next input token has been got} -var k:0..buf_size; {an index into |buffer|} -@!t:halfword; {a token} -@!cat:0..max_char_code; {|cat_code(cur_chr)|, usually} -@!c,@!cc:ASCII_code; {constituents of a possible expanded code} -@!d:2..3; {number of excess characters in an expanded code} -begin restart: cur_cs:=0; -if state<>token_list then -@<Input from external file, |goto restart| if no input found@> -else @<Input from token list, |goto restart| if end of list or - if a parameter needs to be expanded@>; -@<If an alignment entry has just ended, take appropriate action@>; -exit:end; - -@ An alignment entry ends when a tab or \.{\\cr} occurs, provided that the -current level of braces is the same as the level that was present at the -beginning of that alignment entry; i.e., provided that |align_state| has -returned to the value it had after the \<u_j> template for that entry. -@^inner loop@> - -@<If an alignment entry has just ended, take appropriate action@>= -if cur_cmd<=car_ret then if cur_cmd>=tab_mark then if align_state=0 then - @<Insert the \(v)\<v_j> template and |goto restart|@> - -@ @<Input from external file, |goto restart| if no input found@>= -@^inner loop@> -begin switch: if loc<=limit then {current line not yet finished} - begin cur_chr:=buffer[loc]; incr(loc); - reswitch: cur_cmd:=cat_code(cur_chr); - @<Change state if necessary, and |goto switch| if the - current character should be ignored, - or |goto reswitch| if the current character - changes to another@>; - end -else begin state:=new_line;@/ - @<Move to next line of file, - or |goto restart| if there is no next line, - or |return| if a \.{\\read} line has finished@>; - check_interrupt; - goto switch; - end; -end - -@ The following 48-way switch accomplishes the scanning quickly, assuming -that a decent \PASCAL\ compiler has translated the code. Note that the numeric -values for |mid_line|, |skip_blanks|, and |new_line| are spaced -apart from each other by |max_char_code+1|, so we can add a character's -command code to the state to get a single number that characterizes both. - -@d any_state_plus(#) == mid_line+#,skip_blanks+#,new_line+# - -@<Change state if necessary...@>= -case state+cur_cmd of -@<Cases where character is ignored@>: goto switch; -any_state_plus(escape): @<Scan a control sequence - and set |state:=skip_blanks| or |mid_line|@>; -any_state_plus(active_char): @<Process an active-character control sequence - and set |state:=mid_line|@>; -any_state_plus(sup_mark): @<If this |sup_mark| starts an expanded character - like~\.{\^\^A} or~\.{\^\^df}, then |goto reswitch|, - otherwise set |state:=mid_line|@>; -any_state_plus(invalid_char): @<Decry the invalid character and - |goto restart|@>; -@t\4@>@<Handle situations involving spaces, braces, changes of state@>@; -othercases do_nothing -endcases - -@ @<Cases where character is ignored@>= -any_state_plus(ignore),skip_blanks+spacer,new_line+spacer - -@ We go to |restart| instead of to |switch|, because |state| might equal -|token_list| after the error has been dealt with -(cf.\ |clear_for_error_prompt|). - -@<Decry the invalid...@>= -begin print_err("Text line contains an invalid character"); -@.Text line contains...@> -help2("A funny symbol that I can't read has just been input.")@/ -("Continue, and I'll forget that it ever happened.");@/ -deletions_allowed:=false; error; deletions_allowed:=true; -goto restart; -end - -@ @d add_delims_to(#)==#+math_shift,#+tab_mark,#+mac_param, - #+sub_mark,#+letter,#+other_char - -@<Handle situations involving spaces, braces, changes of state@>= -mid_line+spacer:@<Enter |skip_blanks| state, emit a space@>; -mid_line+car_ret:@<Finish line, emit a space@>; -skip_blanks+car_ret,any_state_plus(comment): - @<Finish line, |goto switch|@>; -new_line+car_ret:@<Finish line, emit a \.{\\par}@>; -mid_line+left_brace: incr(align_state); -skip_blanks+left_brace,new_line+left_brace: begin - state:=mid_line; incr(align_state); - end; -mid_line+right_brace: decr(align_state); -skip_blanks+right_brace,new_line+right_brace: begin - state:=mid_line; decr(align_state); - end; -add_delims_to(skip_blanks),add_delims_to(new_line): state:=mid_line; - -@ When a character of type |spacer| gets through, its character code is -changed to $\.{"\ "}=@'40$. This means that the ASCII codes for tab and space, -and for the space inserted at the end of a line, will -be treated alike when macro parameters are being matched. We do this -since such characters are indistinguishable on most computer terminal displays. - -@<Finish line, emit a space@>= -begin loc:=limit+1; cur_cmd:=spacer; cur_chr:=" "; -end - -@ The following code is performed only when |cur_cmd=spacer|. - -@<Enter |skip_blanks| state, emit a space@>= -begin state:=skip_blanks; cur_chr:=" "; -end - -@ @<Finish line, |goto switch|@>= -begin loc:=limit+1; goto switch; -end - -@ @<Finish line, emit a \.{\\par}@>= -begin loc:=limit+1; cur_cs:=par_loc; cur_cmd:=eq_type(cur_cs); -cur_chr:=equiv(cur_cs); -if cur_cmd>=outer_call then check_outer_validity; -end - -@ Notice that a code like \.{\^\^8} becomes \.x if not followed by a hex digit. - -@d is_hex(#)==(((#>="0")and(#<="9"))or((#>="a")and(#<="f"))) -@d hex_to_cur_chr== - if c<="9" then cur_chr:=c-"0" @+else cur_chr:=c-"a"+10; - if cc<="9" then cur_chr:=16*cur_chr+cc-"0" - else cur_chr:=16*cur_chr+cc-"a"+10 - -@<If this |sup_mark| starts an expanded character...@>= -begin if cur_chr=buffer[loc] then if loc<limit then - begin c:=buffer[loc+1]; @+if c<@'200 then {yes we have an expanded char} - begin loc:=loc+2; - if is_hex(c) then if loc<=limit then - begin cc:=buffer[loc]; @+if is_hex(cc) then - begin incr(loc); hex_to_cur_chr; goto reswitch; - end; - end; - if c<@'100 then cur_chr:=c+@'100 @+else cur_chr:=c-@'100; - goto reswitch; - end; - end; -state:=mid_line; -end - -@ @<Process an active-character...@>= -begin cur_cs:=cur_chr+active_base; -cur_cmd:=eq_type(cur_cs); cur_chr:=equiv(cur_cs); state:=mid_line; -if cur_cmd>=outer_call then check_outer_validity; -end - -@ Control sequence names are scanned only when they appear in some line of -a file; once they have been scanned the first time, their |eqtb| location -serves as a unique identification, so \TeX\ doesn't need to refer to the -original name any more except when it prints the equivalent in symbolic form. - -The program that scans a control sequence has been written carefully -in order to avoid the blowups that might otherwise occur if a malicious -user tried something like `\.{\\catcode\'15=0}'. The algorithm might -look at |buffer[limit+1]|, but it never looks at |buffer[limit+2]|. - -If expanded characters like `\.{\^\^A}' or `\.{\^\^df}' -appear in or just following -a control sequence name, they are converted to single characters in the -buffer and the process is repeated, slowly but surely. - -@<Scan a control...@>= -begin if loc>limit then cur_cs:=null_cs {|state| is irrelevant in this case} -else begin start_cs: k:=loc; cur_chr:=buffer[k]; cat:=cat_code(cur_chr); - incr(k); - if cat=letter then state:=skip_blanks - else if cat=spacer then state:=skip_blanks - else state:=mid_line; - if (cat=letter)and(k<=limit) then - @<Scan ahead in the buffer until finding a nonletter; - if an expanded code is encountered, reduce it - and |goto start_cs|; otherwise if a multiletter control - sequence is found, adjust |cur_cs| and |loc|, and - |goto found|@> - else @<If an expanded code is present, reduce it and |goto start_cs|@>; - cur_cs:=single_base+buffer[loc]; incr(loc); - end; -found: cur_cmd:=eq_type(cur_cs); cur_chr:=equiv(cur_cs); -if cur_cmd>=outer_call then check_outer_validity; -end - -@ Whenever we reach the following piece of code, we will have -|cur_chr=buffer[k-1]| and |k<=limit+1| and |cat=cat_code(cur_chr)|. If an -expanded code like \.{\^\^A} or \.{\^\^df} appears in |buffer[(k-1)..(k+1)]| -or |buffer[(k-1)..(k+2)]|, we -will store the corresponding code in |buffer[k-1]| and shift the rest of -the buffer left two or three places. - -@<If an expanded...@>= -begin if buffer[k]=cur_chr then @+if cat=sup_mark then @+if k<limit then - begin c:=buffer[k+1]; @+if c<@'200 then {yes, one is indeed present} - begin d:=2; - if is_hex(c) then @+if k+2<=limit then - begin cc:=buffer[k+2]; @+if is_hex(cc) then incr(d); - end; - if d>2 then - begin hex_to_cur_chr; buffer[k-1]:=cur_chr; - end - else if c<@'100 then buffer[k-1]:=c+@'100 - else buffer[k-1]:=c-@'100; - limit:=limit-d; first:=first-d; - while k<=limit do - begin buffer[k]:=buffer[k+d]; incr(k); - end; - goto start_cs; - end; - end; -end - -@ @<Scan ahead in the buffer...@>= -begin repeat cur_chr:=buffer[k]; cat:=cat_code(cur_chr); incr(k); -until (cat<>letter)or(k>limit); -@<If an expanded...@>; -if cat<>letter then decr(k); - {now |k| points to first nonletter} -if k>loc+1 then {multiletter control sequence has been scanned} - begin cur_cs:=id_lookup(loc,k-loc); loc:=k; goto found; - end; -end - -@ Let's consider now what happens when |get_next| is looking at a token list. - -@<Input from token list, |goto restart| if end of list or - if a parameter needs to be expanded@>= -if loc<>null then {list not exhausted} -@^inner loop@> - begin t:=info(loc); loc:=link(loc); {move to next} - if t>=cs_token_flag then {a control sequence token} - begin cur_cs:=t-cs_token_flag; - cur_cmd:=eq_type(cur_cs); cur_chr:=equiv(cur_cs); - if cur_cmd>=outer_call then - if cur_cmd=dont_expand then - @<Get the next token, suppressing expansion@> - else check_outer_validity; - end - else begin cur_cmd:=t div @'400; cur_chr:=t mod @'400; - case cur_cmd of - left_brace: incr(align_state); - right_brace: decr(align_state); - out_param: @<Insert macro parameter and |goto restart|@>; - othercases do_nothing - endcases; - end; - end -else begin {we are done with this token list} - end_token_list; goto restart; {resume previous level} - end - -@ The present point in the program is reached only when the |expand| -routine has inserted a special marker into the input. In this special -case, |info(loc)| is known to be a control sequence token, and |link(loc)=null|. - -@d no_expand_flag=257 {this characterizes a special variant of |relax|} - -@<Get the next token, suppressing expansion@>= -begin cur_cs:=info(loc)-cs_token_flag; loc:=null;@/ -cur_cmd:=eq_type(cur_cs); cur_chr:=equiv(cur_cs); -if cur_cmd>max_command then - begin cur_cmd:=relax; cur_chr:=no_expand_flag; - end; -end - -@ @<Insert macro parameter...@>= -begin begin_token_list(param_stack[param_start+cur_chr-1],parameter); -goto restart; -end - -@ All of the easy branches of |get_next| have now been taken care of. -There is one more branch. - -@d end_line_char_inactive == (end_line_char<0)or(end_line_char>255) - -@<Move to next line of file, or |goto restart|...@>= -if name>17 then @<Read next line of file into |buffer|, or - |goto restart| if the file has ended@> -else begin if not terminal_input then {\.{\\read} line has ended} - begin cur_cmd:=0; cur_chr:=0; return; - end; - if input_ptr>0 then {text was inserted during error recovery} - begin end_file_reading; goto restart; {resume previous level} - end; - if selector<log_only then open_log_file; - if interaction>nonstop_mode then - begin if end_line_char_inactive then incr(limit); - if limit=start then {previous line was empty} - print_nl("(Please type a command or say `\end')"); -@.Please type...@> - print_ln; first:=start; - prompt_input("*"); {input on-line into |buffer|} -@.*\relax@> - limit:=last; - if end_line_char_inactive then decr(limit) - else buffer[limit]:=end_line_char; - first:=limit+1; - loc:=start; - end - else fatal_error("*** (job aborted, no legal \end found)"); -@.job aborted@> - {nonstop mode, which is intended for overnight batch processing, - never waits for on-line input} - end - -@ The global variable |force_eof| is normally |false|; it is set |true| -by an \.{\\endinput} command. - -@<Glob...@>= -@!force_eof:boolean; {should the next \.{\\input} be aborted early?} - -@ @<Read next line of file into |buffer|, or - |goto restart| if the file has ended@>= -begin incr(line); first:=start; -if not force_eof then - begin if input_ln(cur_file,true) then {not end of file} - firm_up_the_line {this sets |limit|} - else force_eof:=true; - end; -if force_eof then - begin print_char(")"); decr(open_parens); - update_terminal; {show user that file has been read} - force_eof:=false; - end_file_reading; {resume previous level} - check_outer_validity; goto restart; - end; -if end_line_char_inactive then decr(limit) -else buffer[limit]:=end_line_char; -first:=limit+1; loc:=start; {ready to read} -end - -@ If the user has set the |pausing| parameter to some positive value, -and if nonstop mode has not been selected, each line of input is displayed -on the terminal and the transcript file, followed by `\.{=>}'. -\TeX\ waits for a response. If the response is simply |carriage_return|, the -line is accepted as it stands, otherwise the line typed is -used instead of the line in the file. - -@p procedure firm_up_the_line; -var k:0..buf_size; {an index into |buffer|} -begin limit:=last; -if pausing>0 then if interaction>nonstop_mode then - begin wake_up_terminal; print_ln; - if start<limit then for k:=start to limit-1 do print(buffer[k]); - first:=limit; prompt_input("=>"); {wait for user response} -@.=>@> - if last>first then - begin for k:=first to last-1 do {move line down in buffer} - buffer[k+start-first]:=buffer[k]; - limit:=start+last-first; - end; - end; -end; - -@ Since |get_next| is used so frequently in \TeX, it is convenient -to define three related procedures that do a little more: - -\yskip\hang|get_token| not only sets |cur_cmd| and |cur_chr|, it -also sets |cur_tok|, a packed halfword version of the current token. - -\yskip\hang|get_x_token|, meaning ``get an expanded token,'' is like -|get_token|, but if the current token turns out to be a user-defined -control sequence (i.e., a macro call), or a conditional, -or something like \.{\\topmark} or \.{\\expandafter} or \.{\\csname}, -it is eliminated from the input by beginning the expansion of the macro -or the evaluation of the conditional. - -\yskip\hang|x_token| is like |get_x_token| except that it assumes that -|get_next| has already been called. - -\yskip\noindent -In fact, these three procedures account for almost every use of |get_next|. - -@ No new control sequences will be defined except during a call of -|get_token|, or when \.{\\csname} compresses a token list, because -|no_new_control_sequence| is always |true| at other times. - -@p procedure get_token; {sets |cur_cmd|, |cur_chr|, |cur_tok|} -begin no_new_control_sequence:=false; get_next; no_new_control_sequence:=true; -@^inner loop@> -if cur_cs=0 then cur_tok:=(cur_cmd*@'400)+cur_chr -else cur_tok:=cs_token_flag+cur_cs; -end; - -@* \[25] Expanding the next token. -Only a dozen or so command codes |>max_command| can possibly be returned by -|get_next|; in increasing order, they are |undefined_cs|, |expand_after|, -|no_expand|, |input|, |if_test|, |fi_or_else|, |cs_name|, |convert|, |the|, -|top_bot_mark|, |call|, |long_call|, |outer_call|, |long_outer_call|, and -|end_template|.{\emergencystretch=40pt\par} - -The |expand| subroutine is used when |cur_cmd>max_command|. It removes a -``call'' or a conditional or one of the other special operations just -listed. It follows that |expand| might invoke itself recursively. In all -cases, |expand| destroys the current token, but it sets things up so that -the next |get_next| will deliver the appropriate next token. The value of -|cur_tok| need not be known when |expand| is called. - -Since several of the basic scanning routines communicate via global variables, -their values are saved as local variables of |expand| so that -recursive calls don't invalidate them. -@^recursion@> - -@p@t\4@>@<Declare the procedure called |macro_call|@>@;@/ -@t\4@>@<Declare the procedure called |insert_relax|@>@;@/ -procedure@?pass_text; forward;@t\2@> -procedure@?start_input; forward;@t\2@> -procedure@?conditional; forward;@t\2@> -procedure@?get_x_token; forward;@t\2@> -procedure@?conv_toks; forward;@t\2@> -procedure@?ins_the_toks; forward;@t\2@> -procedure expand; -var t:halfword; {token that is being ``expanded after''} -@!p,@!q,@!r:pointer; {for list manipulation} -@!j:0..buf_size; {index into |buffer|} -@!cv_backup:integer; {to save the global quantity |cur_val|} -@!cvl_backup,@!radix_backup,@!co_backup:small_number; - {to save |cur_val_level|, etc.} -@!backup_backup:pointer; {to save |link(backup_head)|} -@!save_scanner_status:small_number; {temporary storage of |scanner_status|} -begin cv_backup:=cur_val; cvl_backup:=cur_val_level; radix_backup:=radix; -co_backup:=cur_order; backup_backup:=link(backup_head); -if cur_cmd<call then @<Expand a nonmacro@> -else if cur_cmd<end_template then macro_call -else @<Insert a token containing |frozen_endv|@>; -cur_val:=cv_backup; cur_val_level:=cvl_backup; radix:=radix_backup; -cur_order:=co_backup; link(backup_head):=backup_backup; -end; - -@ @<Expand a nonmacro@>= -begin if tracing_commands>1 then show_cur_cmd_chr; -case cur_cmd of -top_bot_mark:@<Insert the \(a)appropriate mark text into the scanner@>; -expand_after:@<Expand the token after the next token@>; -no_expand:@<Suppress expansion of the next token@>; -cs_name:@<Manufacture a control sequence name@>; -convert:conv_toks; {this procedure is discussed in Part 27 below} -the:ins_the_toks; {this procedure is discussed in Part 27 below} -if_test:conditional; {this procedure is discussed in Part 28 below} -fi_or_else:@<Terminate the current conditional and skip to \.{\\fi}@>; -input:@<Initiate or terminate input from a file@>; -othercases @<Complain about an undefined macro@> -endcases; -end - -@ It takes only a little shuffling to do what \TeX\ calls \.{\\expandafter}. - -@<Expand the token after...@>= -begin get_token; t:=cur_tok; get_token; -if cur_cmd>max_command then expand@+else back_input; -cur_tok:=t; back_input; -end - -@ The implementation of \.{\\noexpand} is a bit trickier, because it is -necessary to insert a special `|dont_expand|' marker into \TeX's reading -mechanism. This special marker is processed by |get_next|, but it does -not slow down the inner loop. - -Since \.{\\outer} macros might arise here, we must also -clear the |scanner_status| temporarily. - -@<Suppress expansion...@>= -begin save_scanner_status:=scanner_status; scanner_status:=normal; -get_token; scanner_status:=save_scanner_status; t:=cur_tok; -back_input; {now |start| and |loc| point to the backed-up token |t|} -if t>=cs_token_flag then - begin p:=get_avail; info(p):=cs_token_flag+frozen_dont_expand; - link(p):=loc; start:=p; loc:=p; - end; -end - -@ @<Complain about an undefined macro@>= -begin print_err("Undefined control sequence"); -@.Undefined control sequence@> -help5("The control sequence at the end of the top line")@/ -("of your error message was never \def'ed. If you have")@/ -("misspelled it (e.g., `\hobx'), type `I' and the correct")@/ -("spelling (e.g., `I\hbox'). Otherwise just continue,")@/ -("and I'll forget about whatever was undefined."); -error; -end - -@ The |expand| procedure and some other routines that construct token -lists find it convenient to use the following macros, which are valid only if -the variables |p| and |q| are reserved for token-list building. - -@d store_new_token(#)==begin q:=get_avail; link(p):=q; info(q):=#; - p:=q; {|link(p)| is |null|} - end -@d fast_store_new_token(#)==begin fast_get_avail(q); link(p):=q; info(q):=#; - p:=q; {|link(p)| is |null|} - end - -@ @<Manufacture a control...@>= -begin r:=get_avail; p:=r; {head of the list of characters} -repeat get_x_token; -if cur_cs=0 then store_new_token(cur_tok); -until cur_cs<>0; -if cur_cmd<>end_cs_name then @<Complain about missing \.{\\endcsname}@>; -@<Look up the characters of list |r| in the hash table, and set |cur_cs|@>; -flush_list(r); -if eq_type(cur_cs)=undefined_cs then - begin eq_define(cur_cs,relax,256); {N.B.: The |save_stack| might change} - end; {the control sequence will now match `\.{\\relax}'} -cur_tok:=cur_cs+cs_token_flag; back_input; -end - -@ @<Complain about missing \.{\\endcsname}@>= -begin print_err("Missing "); print_esc("endcsname"); print(" inserted"); -@.Missing \\endcsname...@> -help2("The control sequence marked <to be read again> should")@/ - ("not appear between \csname and \endcsname."); -back_error; -end - -@ @<Look up the characters of list |r| in the hash table...@>= -j:=first; p:=link(r); -while p<>null do - begin if j>=max_buf_stack then - begin max_buf_stack:=j+1; - if max_buf_stack=buf_size then - overflow("buffer size",buf_size); -@:TeX capacity exceeded buffer size}{\quad buffer size@> - end; - buffer[j]:=info(p) mod @'400; incr(j); p:=link(p); - end; -if j>first+1 then - begin no_new_control_sequence:=false; cur_cs:=id_lookup(first,j-first); - no_new_control_sequence:=true; - end -else if j=first then cur_cs:=null_cs {the list is empty} -else cur_cs:=single_base+buffer[first] {the list has length one} - -@ An |end_template| command is effectively changed to an |endv| command -by the following code. (The reason for this is discussed below; the -|frozen_end_template| at the end of the template has passed the -|check_outer_validity| test, so its mission of error detection has been -accomplished.) - -@<Insert a token containing |frozen_endv|@>= -begin cur_tok:=cs_token_flag+frozen_endv; back_input; -end - -@ The processing of \.{\\input} involves the |start_input| subroutine, -which will be declared later; the processing of \.{\\endinput} is trivial. - -@<Put each...@>= -primitive("input",input,0);@/ -@!@:input_}{\.{\\input} primitive@> -primitive("endinput",input,1);@/ -@!@:end_input_}{\.{\\endinput} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -input: if chr_code=0 then print_esc("input")@+else print_esc("endinput"); - -@ @<Initiate or terminate input...@>= -if cur_chr>0 then force_eof:=true -else if name_in_progress then insert_relax -else start_input - -@ Sometimes the expansion looks too far ahead, so we want to insert -a harmless \.{\\relax} into the user's input. - -@<Declare the procedure called |insert_relax|@>= -procedure insert_relax; -begin cur_tok:=cs_token_flag+cur_cs; back_input; -cur_tok:=cs_token_flag+frozen_relax; back_input; token_type:=inserted; -end; - -@ Here is a recursive procedure that is \TeX's usual way to get the -next token of input. It has been slightly optimized to take account of -common cases. - -@p procedure get_x_token; {sets |cur_cmd|, |cur_chr|, |cur_tok|, - and expands macros} -label restart,done; -begin restart: get_next; -@^inner loop@> -if cur_cmd<=max_command then goto done; -if cur_cmd>=call then - if cur_cmd<end_template then macro_call - else begin cur_cs:=frozen_endv; cur_cmd:=endv; - goto done; {|cur_chr=null_list|} - end -else expand; -goto restart; -done: if cur_cs=0 then cur_tok:=(cur_cmd*@'400)+cur_chr -else cur_tok:=cs_token_flag+cur_cs; -end; - -@ The |get_x_token| procedure is essentially equivalent to two consecutive -procedure calls: |get_next; x_token|. - -@p procedure x_token; {|get_x_token| without the initial |get_next|} -begin while cur_cmd>max_command do - begin expand; - get_next; - end; -if cur_cs=0 then cur_tok:=(cur_cmd*@'400)+cur_chr -else cur_tok:=cs_token_flag+cur_cs; -end; - -@ A control sequence that has been \.{\\def}'ed by the user is expanded by -\TeX's |macro_call| procedure. - -Before we get into the details of |macro_call|, however, let's consider the -treatment of primitives like \.{\\topmark}, since they are essentially -macros without parameters. The token lists for such marks are kept in a -global array of five pointers; we refer to the individual entries of this -array by symbolic names |top_mark|, etc. The value of |top_mark| is either -|null| or a pointer to the reference count of a token list. - -@d top_mark_code=0 {the mark in effect at the previous page break} -@d first_mark_code=1 {the first mark between |top_mark| and |bot_mark|} -@d bot_mark_code=2 {the mark in effect at the current page break} -@d split_first_mark_code=3 {the first mark found by \.{\\vsplit}} -@d split_bot_mark_code=4 {the last mark found by \.{\\vsplit}} -@d top_mark==cur_mark[top_mark_code] -@d first_mark==cur_mark[first_mark_code] -@d bot_mark==cur_mark[bot_mark_code] -@d split_first_mark==cur_mark[split_first_mark_code] -@d split_bot_mark==cur_mark[split_bot_mark_code] - -@<Glob...@>= -@!cur_mark:array[top_mark_code..split_bot_mark_code] of pointer; - {token lists for marks} - -@ @<Set init...@>= -top_mark:=null; first_mark:=null; bot_mark:=null; -split_first_mark:=null; split_bot_mark:=null; - -@ @<Put each...@>= -primitive("topmark",top_bot_mark,top_mark_code); -@!@:top_mark_}{\.{\\topmark} primitive@> -primitive("firstmark",top_bot_mark,first_mark_code); -@!@:first_mark_}{\.{\\firstmark} primitive@> -primitive("botmark",top_bot_mark,bot_mark_code); -@!@:bot_mark_}{\.{\\botmark} primitive@> -primitive("splitfirstmark",top_bot_mark,split_first_mark_code); -@!@:split_first_mark_}{\.{\\splitfirstmark} primitive@> -primitive("splitbotmark",top_bot_mark,split_bot_mark_code); -@!@:split_bot_mark_}{\.{\\splitbotmark} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -top_bot_mark: case chr_code of - first_mark_code: print_esc("firstmark"); - bot_mark_code: print_esc("botmark"); - split_first_mark_code: print_esc("splitfirstmark"); - split_bot_mark_code: print_esc("splitbotmark"); - othercases print_esc("topmark") - endcases; - -@ The following code is activated when |cur_cmd=top_bot_mark| and -when |cur_chr| is a code like |top_mark_code|. - -@<Insert the \(a)appropriate mark text into the scanner@>= -begin if cur_mark[cur_chr]<>null then - begin_token_list(cur_mark[cur_chr],mark_text); -end - -@ Now let's consider |macro_call| itself, which is invoked when \TeX\ is -scanning a control sequence whose |cur_cmd| is either |call|, |long_call|, -|outer_call|, or |long_outer_call|. The control sequence definition -appears in the token list whose reference count is in location |cur_chr| -of |mem|. - -The global variable |long_state| will be set to |call| or to |long_call|, -depending on whether or not the control sequence disallows \.{\\par} -in its parameters. The |get_next| routine will set |long_state| to -|outer_call| and emit \.{\\par}, if a file ends or if an \.{\\outer} -control sequence occurs in the midst of an argument. - -@<Glob...@>= -@!long_state:call..long_outer_call; {governs the acceptance of \.{\\par}} - -@ The parameters, if any, must be scanned before the macro is expanded. -Parameters are token lists without reference counts. They are placed on -an auxiliary stack called |pstack| while they are being scanned, since -the |param_stack| may be losing entries during the matching process. -(Note that |param_stack| can't be gaining entries, since |macro_call| is -the only routine that puts anything onto |param_stack|, and it -is not recursive.) - -@<Glob...@>= -@!pstack:array[0..8] of pointer; {arguments supplied to a macro} - -@ After parameter scanning is complete, the parameters are moved to the -|param_stack|. Then the macro body is fed to the scanner; in other words, -|macro_call| places the defined text of the control sequence at the -top of\/ \TeX's input stack, so that |get_next| will proceed to read it -next. - -The global variable |cur_cs| contains the |eqtb| address of the control sequence -being expanded, when |macro_call| begins. If this control sequence has not been -declared \.{\\long}, i.e., if its command code in the |eq_type| field is -not |long_call| or |long_outer_call|, its parameters are not allowed to contain -the control sequence \.{\\par}. If an illegal \.{\\par} appears, the macro -call is aborted, and the \.{\\par} will be rescanned. - -@<Declare the procedure called |macro_call|@>= -procedure macro_call; {invokes a user-defined control sequence} -label exit, continue, done, done1, found; -var r:pointer; {current node in the macro's token list} -@!p:pointer; {current node in parameter token list being built} -@!q:pointer; {new node being put into the token list} -@!s:pointer; {backup pointer for parameter matching} -@!t:pointer; {cycle pointer for backup recovery} -@!u,@!v:pointer; {auxiliary pointers for backup recovery} -@!rbrace_ptr:pointer; {one step before the last |right_brace| token} -@!n:small_number; {the number of parameters scanned} -@!unbalance:halfword; {unmatched left braces in current parameter} -@!m:halfword; {the number of tokens or groups (usually)} -@!ref_count:pointer; {start of the token list} -@!save_scanner_status:small_number; {|scanner_status| upon entry} -@!save_warning_index:pointer; {|warning_index| upon entry} -@!match_chr:ASCII_code; {character used in parameter} -begin save_scanner_status:=scanner_status; save_warning_index:=warning_index; -warning_index:=cur_cs; ref_count:=cur_chr; r:=link(ref_count); n:=0; -if tracing_macros>0 then @<Show the text of the macro being expanded@>; -if info(r)<>end_match_token then - @<Scan the parameters and make |link(r)| point to the macro body; but - |return| if an illegal \.{\\par} is detected@>; -@<Feed the macro body and its parameters to the scanner@>; -exit:scanner_status:=save_scanner_status; warning_index:=save_warning_index; -end; - -@ Before we put a new token list on the input stack, it is wise to clean off -all token lists that have recently been depleted. Then a user macro that ends -with a call to itself will not require unbounded stack space. - -@<Feed the macro body and its parameters to the scanner@>= -while (state=token_list)and(loc=null)and(token_type<>v_template) do - end_token_list; {conserve stack space} -begin_token_list(ref_count,macro); name:=warning_index; loc:=link(r); -if n>0 then - begin if param_ptr+n>max_param_stack then - begin max_param_stack:=param_ptr+n; - if max_param_stack>param_size then - overflow("parameter stack size",param_size); -@:TeX capacity exceeded parameter stack size}{\quad parameter stack size@> - end; - for m:=0 to n-1 do param_stack[param_ptr+m]:=pstack[m]; - param_ptr:=param_ptr+n; - end - -@ At this point, the reader will find it advisable to review the explanation -of token list format that was presented earlier, since many aspects of that -format are of importance chiefly in the |macro_call| routine. - -The token list might begin with a string of compulsory tokens before the -first |match| or |end_match|. In that case the macro name is supposed to be -followed by those tokens; the following program will set |s=null| to -represent this restriction. Otherwise |s| will be set to the first token of -a string that will delimit the next parameter. - -@<Scan the parameters and make |link(r)| point to the macro body...@>= -begin scanner_status:=matching; unbalance:=0; -long_state:=eq_type(cur_cs); -if long_state>=outer_call then long_state:=long_state-2; -repeat link(temp_head):=null; -if (info(r)>match_token+255)or(info(r)<match_token) then s:=null -else begin match_chr:=info(r)-match_token; s:=link(r); r:=s; - p:=temp_head; m:=0; - end; -@<Scan a parameter until its delimiter string has been found; or, if |s=null|, - simply scan the delimiter string@>;@/ -{now |info(r)| is a token whose command code is either |match| or |end_match|} -until info(r)=end_match_token; -end - -@ If |info(r)| is a |match| or |end_match| command, it cannot be equal to -any token found by |get_token|. Therefore an undelimited parameter---i.e., -a |match| that is immediately followed by |match| or |end_match|---will -always fail the test `|cur_tok=info(r)|' in the following algorithm. - -@<Scan a parameter until its delimiter string has been found; or, ...@>= -continue: get_token; {set |cur_tok| to the next token of input} -if cur_tok=info(r) then - @<Advance \(r)|r|; |goto found| if the parameter delimiter has been - fully matched, otherwise |goto continue|@>; -@<Contribute the recently matched tokens to the current parameter, and - |goto continue| if a partial match is still in effect; - but abort if |s=null|@>; -if cur_tok=par_token then if long_state<>long_call then - @<Report a runaway argument and abort@>; -if cur_tok<right_brace_limit then - if cur_tok<left_brace_limit then - @<Contribute an entire group to the current parameter@> - else @<Report an extra right brace and |goto continue|@> -else @<Store the current token, but |goto continue| if it is - a blank space that would become an undelimited parameter@>; -incr(m); -if info(r)>end_match_token then goto continue; -if info(r)<match_token then goto continue; -found: if s<>null then @<Tidy up the parameter just scanned, and tuck it away@> - -@ @<Store the current token, but |goto continue| if it is...@>= -begin if cur_tok=space_token then - if info(r)<=end_match_token then - if info(r)>=match_token then goto continue; -store_new_token(cur_tok); -end - -@ A slightly subtle point arises here: When the parameter delimiter ends -with `\.{\#\{}', the token list will have a left brace both before and -after the |end_match|\kern-.4pt. Only one of these should affect the -|align_state|, but both will be scanned, so we must make a correction. - -@<Advance \(r)|r|; |goto found| if the parameter delimiter has been fully...@>= -begin r:=link(r); -if (info(r)>=match_token)and(info(r)<=end_match_token) then - begin if cur_tok<left_brace_limit then decr(align_state); - goto found; - end -else goto continue; -end - -@ @<Report an extra right brace and |goto continue|@>= -begin back_input; print_err("Argument of "); sprint_cs(warning_index); -@.Argument of \\x has...@> -print(" has an extra }"); -help6("I've run across a `}' that doesn't seem to match anything.")@/ - ("For example, `\def\a#1{...}' and `\a}' would produce")@/ - ("this error. If you simply proceed now, the `\par' that")@/ - ("I've just inserted will cause me to report a runaway")@/ - ("argument that might be the root of the problem. But if")@/ - ("your `}' was spurious, just type `2' and it will go away."); -incr(align_state); long_state:=call; cur_tok:=par_token; ins_error; -goto continue; -end {a white lie; the \.{\\par} won't always trigger a runaway} - -@ If |long_state=outer_call|, a runaway argument has already been reported. - -@<Report a runaway argument and abort@>= -begin if long_state=call then - begin runaway; print_err("Paragraph ended before "); -@.Paragraph ended before...@> - sprint_cs(warning_index); print(" was complete"); - help3("I suspect you've forgotten a `}', causing me to apply this")@/ - ("control sequence to too much text. How can we recover?")@/ - ("My plan is to forget the whole thing and hope for the best."); - back_error; - end; -pstack[n]:=link(temp_head); align_state:=align_state-unbalance; -for m:=0 to n do flush_list(pstack[m]); -return; -end - -@ When the following code becomes active, we have matched tokens from |s| to -the predecessor of |r|, and we have found that |cur_tok<>info(r)|. An -interesting situation now presents itself: If the parameter is to be -delimited by a string such as `\.{ab}', and if we have scanned `\.{aa}', -we want to contribute one `\.a' to the current parameter and resume -looking for a `\.b'. The program must account for such partial matches and -for others that can be quite complex. But most of the time we have |s=r| -and nothing needs to be done. - -Incidentally, it is possible for \.{\\par} tokens to sneak in to certain -parameters of non-\.{\\long} macros. For example, consider a case like -`\.{\\def\\a\#1\\par!\{...\}}' where the first \.{\\par} is not followed -by an exclamation point. In such situations it does not seem appropriate -to prohibit the \.{\\par}, so \TeX\ keeps quiet about this bending of -the rules. - -@<Contribute the recently matched tokens to the current parameter...@>= -if s<>r then - if s=null then @<Report an improper use of the macro and abort@> - else begin t:=s; - repeat store_new_token(info(t)); incr(m); u:=link(t); v:=s; - loop@+ begin if u=r then - if cur_tok<>info(v) then goto done - else begin r:=link(v); goto continue; - end; - if info(u)<>info(v) then goto done; - u:=link(u); v:=link(v); - end; - done: t:=link(t); - until t=r; - r:=s; {at this point, no tokens are recently matched} - end - -@ @<Report an improper use...@>= -begin print_err("Use of "); sprint_cs(warning_index); -@.Use of x doesn't match...@> -print(" doesn't match its definition"); -help4("If you say, e.g., `\def\a1{...}', then you must always")@/ - ("put `1' after `\a', since control sequence names are")@/ - ("made up of letters only. The macro here has not been")@/ - ("followed by the required stuff, so I'm ignoring it."); -error; return; -end - -@ @<Contribute an entire group to the current parameter@>= -begin unbalance:=1; -@^inner loop@> -loop@+ begin fast_store_new_token(cur_tok); get_token; - if cur_tok=par_token then if long_state<>long_call then - @<Report a runaway argument and abort@>; - if cur_tok<right_brace_limit then - if cur_tok<left_brace_limit then incr(unbalance) - else begin decr(unbalance); - if unbalance=0 then goto done1; - end; - end; -done1: rbrace_ptr:=p; store_new_token(cur_tok); -end - -@ If the parameter consists of a single group enclosed in braces, we must -strip off the enclosing braces. That's why |rbrace_ptr| was introduced. - -@<Tidy up the parameter just scanned, and tuck it away@>= -begin if (m=1)and(info(p)<right_brace_limit) then - begin link(rbrace_ptr):=null; free_avail(p); - p:=link(temp_head); pstack[n]:=link(p); free_avail(p); - end -else pstack[n]:=link(temp_head); -incr(n); -if tracing_macros>0 then - begin begin_diagnostic; print_nl(match_chr); print_int(n); - print("<-"); show_token_list(pstack[n-1],null,1000); - end_diagnostic(false); - end; -end - -@ @<Show the text of the macro being expanded@>= -begin begin_diagnostic; print_ln; print_cs(warning_index); -token_show(ref_count); end_diagnostic(false); -end - -@* \[26] Basic scanning subroutines. -Let's turn now to some procedures that \TeX\ calls upon frequently to digest -certain kinds of patterns in the input. Most of these are quite simple; -some are quite elaborate. Almost all of the routines call |get_x_token|, -which can cause them to be invoked recursively. -@^stomach@> -@^recursion@> - -@ The |scan_left_brace| routine is called when a left brace is supposed to be -the next non-blank token. (The term ``left brace'' means, more precisely, -a character whose catcode is |left_brace|.) \TeX\ allows \.{\\relax} to -appear before the |left_brace|. - -@p procedure scan_left_brace; {reads a mandatory |left_brace|} -begin @<Get the next non-blank non-relax non-call token@>; -if cur_cmd<>left_brace then - begin print_err("Missing { inserted"); -@.Missing \{ inserted@> - help4("A left brace was mandatory here, so I've put one in.")@/ - ("You might want to delete and/or insert some corrections")@/ - ("so that I will find a matching right brace soon.")@/ - ("(If you're confused by all this, try typing `I}' now.)"); - back_error; cur_tok:=left_brace_token+"{"; cur_cmd:=left_brace; - cur_chr:="{"; incr(align_state); - end; -end; - -@ @<Get the next non-blank non-relax non-call token@>= -repeat get_x_token; -until (cur_cmd<>spacer)and(cur_cmd<>relax) - -@ The |scan_optional_equals| routine looks for an optional `\.=' sign preceded -by optional spaces; `\.{\\relax}' is not ignored here. - -@p procedure scan_optional_equals; -begin @<Get the next non-blank non-call token@>; -if cur_tok<>other_token+"=" then back_input; -end; - -@ @<Get the next non-blank non-call token@>= -repeat get_x_token; -until cur_cmd<>spacer - -@ In case you are getting bored, here is a slightly less trivial routine: -Given a string of lowercase letters, like `\.{pt}' or `\.{plus}' or -`\.{width}', the |scan_keyword| routine checks to see whether the next -tokens of input match this string. The match must be exact, except that -uppercase letters will match their lowercase counterparts; uppercase -equivalents are determined by subtracting |"a"-"A"|, rather than using the -|uc_code| table, since \TeX\ uses this routine only for its own limited -set of keywords. - -If a match is found, the characters are effectively removed from the input -and |true| is returned. Otherwise |false| is returned, and the input -is left essentially unchanged (except for the fact that some macros -may have been expanded, etc.). -@^inner loop@> - -@p function scan_keyword(@!s:str_number):boolean; {look for a given string} -label exit; -var p:pointer; {tail of the backup list} -@!q:pointer; {new node being added to the token list via |store_new_token|} -@!k:pool_pointer; {index into |str_pool|} -begin p:=backup_head; link(p):=null; k:=str_start[s]; -while k<str_start[s+1] do - begin get_x_token; {recursion is possible here} -@^recursion@> - if (cur_cs=0)and@| - ((cur_chr=so(str_pool[k]))or(cur_chr=so(str_pool[k])-"a"+"A")) then - begin store_new_token(cur_tok); incr(k); - end - else if (cur_cmd<>spacer)or(p<>backup_head) then - begin back_input; - if p<>backup_head then back_list(link(backup_head)); - scan_keyword:=false; return; - end; - end; -flush_list(link(backup_head)); scan_keyword:=true; -exit:end; - -@ Here is a procedure that sounds an alarm when mu and non-mu units -are being switched. - -@p procedure mu_error; -begin print_err("Incompatible glue units"); -@.Incompatible glue units@> -help1("I'm going to assume that 1mu=1pt when they're mixed."); -error; -end; - -@ The next routine `|scan_something_internal|' is used to fetch internal -numeric quantities like `\.{\\hsize}', and also to handle the `\.{\\the}' -when expanding constructions like `\.{\\the\\toks0}' and -`\.{\\the\\baselineskip}'. Soon we will be considering the |scan_int| -procedure, which calls |scan_something_internal|; on the other hand, -|scan_something_internal| also calls |scan_int|, for constructions like -`\.{\\catcode\`\\\$}' or `\.{\\fontdimen} \.3 \.{\\ff}'. So we -have to declare |scan_int| as a |forward| procedure. A few other -procedures are also declared at this point. - -@p procedure@?scan_int; forward; {scans an integer value} -@t\4\4@>@<Declare procedures that scan restricted classes of integers@>@; -@t\4\4@>@<Declare procedures that scan font-related stuff@> - -@ \TeX\ doesn't know exactly what to expect when |scan_something_internal| -begins. For example, an integer or dimension or glue value could occur -immediately after `\.{\\hskip}'; and one can even say \.{\\the} with -respect to token lists in constructions like -`\.{\\xdef\\o\{\\the\\output\}}'. On the other hand, only integers are -allowed after a construction like `\.{\\count}'. To handle the various -possibilities, |scan_something_internal| has a |level| parameter, which -tells the ``highest'' kind of quantity that |scan_something_internal| is -allowed to produce. Six levels are distinguished, namely |int_val|, -|dimen_val|, |glue_val|, |mu_val|, |ident_val|, and |tok_val|. - -The output of |scan_something_internal| (and of the other routines -|scan_int|, |scan_dimen|, and |scan_glue| below) is put into the global -variable |cur_val|, and its level is put into |cur_val_level|. The highest -values of |cur_val_level| are special: |mu_val| is used only when -|cur_val| points to something in a ``muskip'' register, or to one of the -three parameters \.{\\thinmuskip}, \.{\\medmuskip}, \.{\\thickmuskip}; -|ident_val| is used only when |cur_val| points to a font identifier; -|tok_val| is used only when |cur_val| points to |null| or to the reference -count of a token list. The last two cases are allowed only when -|scan_something_internal| is called with |level=tok_val|. - -If the output is glue, |cur_val| will point to a glue specification, and -the reference count of that glue will have been updated to reflect this -reference; if the output is a nonempty token list, |cur_val| will point to -its reference count, but in this case the count will not have been updated. -Otherwise |cur_val| will contain the integer or scaled value in question. - -@d int_val=0 {integer values} -@d dimen_val=1 {dimension values} -@d glue_val=2 {glue specifications} -@d mu_val=3 {math glue specifications} -@d ident_val=4 {font identifier} -@d tok_val=5 {token lists} - -@<Glob...@>= -@!cur_val:integer; {value returned by numeric scanners} -@!cur_val_level:int_val..tok_val; {the ``level'' of this value} - -@ The hash table is initialized with `\.{\\count}', `\.{\\dimen}', `\.{\\skip}', -and `\.{\\muskip}' all having |register| as their command code; they are -distinguished by the |chr_code|, which is either |int_val|, |dimen_val|, -|glue_val|, or |mu_val|. - -@<Put each...@>= -primitive("count",register,int_val); -@!@:count_}{\.{\\count} primitive@> -primitive("dimen",register,dimen_val); -@!@:dimen_}{\.{\\dimen} primitive@> -primitive("skip",register,glue_val); -@!@:skip_}{\.{\\skip} primitive@> -primitive("muskip",register,mu_val); -@!@:mu_skip_}{\.{\\muskip} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -register: if chr_code=int_val then print_esc("count") - else if chr_code=dimen_val then print_esc("dimen") - else if chr_code=glue_val then print_esc("skip") - else print_esc("muskip"); - -@ OK, we're ready for |scan_something_internal| itself. A second parameter, -|negative|, is set |true| if the value that is found should be negated. -It is assumed that |cur_cmd| and |cur_chr| represent the first token of -the internal quantity to be scanned; an error will be signalled if -|cur_cmd<min_internal| or |cur_cmd>max_internal|. - -@d scanned_result_end(#)==cur_val_level:=#;@+end -@d scanned_result(#)==@+begin cur_val:=#;scanned_result_end - -@p procedure scan_something_internal(@!level:small_number;@!negative:boolean); - {fetch an internal parameter} -var m:halfword; {|chr_code| part of the operand token} -@!p:0..nest_size; {index into |nest|} -begin m:=cur_chr; -case cur_cmd of -def_code: @<Fetch a character code from some table@>; -toks_register,assign_toks,def_family,set_font,def_font: @<Fetch a token list or - font identifier, provided that |level=tok_val|@>; -assign_int: scanned_result(eqtb[m].int)(int_val); -assign_dimen: scanned_result(eqtb[m].sc)(dimen_val); -assign_glue: scanned_result(equiv(m))(glue_val); -assign_mu_glue: scanned_result(equiv(m))(mu_val); -set_aux: @<Fetch the |space_factor| or the |prev_depth|@>; -set_prev_graf: @<Fetch the |prev_graf|@>; -set_page_int:@<Fetch the |dead_cycles| or the |insert_penalties|@>; -set_page_dimen: @<Fetch something on the |page_so_far|@>; -set_shape: @<Fetch the |par_shape| size@>; -set_box_dimen: @<Fetch a box dimension@>; -char_given,math_given: scanned_result(cur_chr)(int_val); -assign_font_dimen: @<Fetch a font dimension@>; -assign_font_int: @<Fetch a font integer@>; -register: @<Fetch a register@>; -last_item: @<Fetch an item in the current node, if appropriate@>; -othercases @<Complain that \.{\\the} can't do this; give zero result@> -endcases;@/ -while cur_val_level>level do @<Convert \(c)|cur_val| to a lower level@>; -@<Fix the reference count, if any, and negate |cur_val| if |negative|@>; -end; - -@ @<Fetch a character code from some table@>= -begin scan_char_num; -if m=math_code_base then scanned_result(ho(math_code(cur_val)))(int_val) -else if m<math_code_base then scanned_result(equiv(m+cur_val))(int_val) -else scanned_result(eqtb[m+cur_val].int)(int_val); -end - -@ @<Fetch a token list...@>= -if level<>tok_val then - begin print_err("Missing number, treated as zero"); -@.Missing number...@> - help3("A number should have been here; I inserted `0'.")@/ - ("(If you can't figure out why I needed to see a number,")@/ - ("look up `weird error' in the index to The TeXbook.)"); -@:TeXbook}{\sl The \TeX book@> - back_error; scanned_result(0)(dimen_val); - end -else if cur_cmd<=assign_toks then - begin if cur_cmd<assign_toks then {|cur_cmd=toks_register|} - begin scan_eight_bit_int; m:=toks_base+cur_val; - end; - scanned_result(equiv(m))(tok_val); - end -else begin back_input; scan_font_ident; - scanned_result(font_id_base+cur_val)(ident_val); - end - -@ Users refer to `\.{\\the\\spacefactor}' only in horizontal -mode, and to `\.{\\the\\prevdepth}' only in vertical mode; so we put the -associated mode in the modifier part of the |set_aux| command. -The |set_page_int| command has modifier 0 or 1, for `\.{\\deadcycles}' and -`\.{\\insertpenalties}', respectively. The |set_box_dimen| command is -modified by either |width_offset|, |height_offset|, or |depth_offset|. -And the |last_item| command is modified by either |int_val|, |dimen_val|, -|glue_val|, |input_line_no_code|, or |badness_code|. - -@d input_line_no_code=glue_val+1 {code for \.{\\inputlineno}} -@d badness_code=glue_val+2 {code for \.{\\badness}} - -@<Put each...@>= -primitive("spacefactor",set_aux,hmode); -@!@:space_factor_}{\.{\\spacefactor} primitive@> -primitive("prevdepth",set_aux,vmode);@/ -@!@:prev_depth_}{\.{\\prevdepth} primitive@> -primitive("deadcycles",set_page_int,0); -@!@:dead_cycles_}{\.{\\deadcycles} primitive@> -primitive("insertpenalties",set_page_int,1); -@!@:insert_penalties_}{\.{\\insertpenalties} primitive@> -primitive("wd",set_box_dimen,width_offset); -@!@:wd_}{\.{\\wd} primitive@> -primitive("ht",set_box_dimen,height_offset); -@!@:ht_}{\.{\\ht} primitive@> -primitive("dp",set_box_dimen,depth_offset); -@!@:dp_}{\.{\\dp} primitive@> -primitive("lastpenalty",last_item,int_val); -@!@:last_penalty_}{\.{\\lastpenalty} primitive@> -primitive("lastkern",last_item,dimen_val); -@!@:last_kern_}{\.{\\lastkern} primitive@> -primitive("lastskip",last_item,glue_val); -@!@:last_skip_}{\.{\\lastskip} primitive@> -primitive("inputlineno",last_item,input_line_no_code); -@!@:input_line_no_}{\.{\\inputlineno} primitive@> -primitive("badness",last_item,badness_code); -@!@:badness_}{\.{\\badness} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -set_aux: if chr_code=vmode then print_esc("prevdepth") -@+else print_esc("spacefactor"); -set_page_int: if chr_code=0 then print_esc("deadcycles") -@+else print_esc("insertpenalties"); -set_box_dimen: if chr_code=width_offset then print_esc("wd") -else if chr_code=height_offset then print_esc("ht") -else print_esc("dp"); -last_item: case chr_code of - int_val: print_esc("lastpenalty"); - dimen_val: print_esc("lastkern"); - glue_val: print_esc("lastskip"); - input_line_no_code: print_esc("inputlineno"); - othercases print_esc("badness") - endcases; - -@ @<Fetch the |space_factor| or the |prev_depth|@>= -if abs(mode)<>m then - begin print_err("Improper "); print_cmd_chr(set_aux,m); -@.Improper \\spacefactor@> -@.Improper \\prevdepth@> - help4("You can refer to \spacefactor only in horizontal mode;")@/ - ("you can refer to \prevdepth only in vertical mode; and")@/ - ("neither of these is meaningful inside \write. So")@/ - ("I'm forgetting what you said and using zero instead."); - error; - if level<>tok_val then scanned_result(0)(dimen_val) - else scanned_result(0)(int_val); - end -else if m=vmode then scanned_result(prev_depth)(dimen_val) -else scanned_result(space_factor)(int_val) - -@ @<Fetch the |dead_cycles| or the |insert_penalties|@>= -begin if m=0 then cur_val:=dead_cycles@+else cur_val:=insert_penalties; -cur_val_level:=int_val; -end - -@ @<Fetch a box dimension@>= -begin scan_eight_bit_int; -if box(cur_val)=null then cur_val:=0 @+else cur_val:=mem[box(cur_val)+m].sc; -cur_val_level:=dimen_val; -end - -@ Inside an \.{\\output} routine, a user may wish to look at the page totals -that were present at the moment when output was triggered. - -@d max_dimen==@'7777777777 {$2^{30}-1$} - -@<Fetch something on the |page_so_far|@>= -begin if (page_contents=empty) and (not output_active) then - if m=0 then cur_val:=max_dimen@+else cur_val:=0 -else cur_val:=page_so_far[m]; -cur_val_level:=dimen_val; -end - -@ @<Fetch the |prev_graf|@>= -if mode=0 then scanned_result(0)(int_val) {|prev_graf=0| within \.{\\write}} -else begin nest[nest_ptr]:=cur_list; p:=nest_ptr; - while abs(nest[p].mode_field)<>vmode do decr(p); - scanned_result(nest[p].pg_field)(int_val); - end - -@ @<Fetch the |par_shape| size@>= -begin if par_shape_ptr=null then cur_val:=0 -else cur_val:=info(par_shape_ptr); -cur_val_level:=int_val; -end - -@ Here is where \.{\\lastpenalty}, \.{\\lastkern}, and \.{\\lastskip} are -implemented. The reference count for \.{\\lastskip} will be updated later. - -We also handle \.{\\inputlineno} and \.{\\badness} here, because they are -legal in similar contexts. - -@<Fetch an item in the current node...@>= -if cur_chr>glue_val then - begin if cur_chr=input_line_no_code then cur_val:=line - else cur_val:=last_badness; {|cur_chr=badness_code|} - cur_val_level:=int_val; - end -else begin if cur_chr=glue_val then cur_val:=zero_glue@+else cur_val:=0; - cur_val_level:=cur_chr; - if not is_char_node(tail)and(mode<>0) then - case cur_chr of - int_val: if type(tail)=penalty_node then cur_val:=penalty(tail); - dimen_val: if type(tail)=kern_node then cur_val:=width(tail); - glue_val: if type(tail)=glue_node then - begin cur_val:=glue_ptr(tail); - if subtype(tail)=mu_glue then cur_val_level:=mu_val; - end; - end {there are no other cases} - else if (mode=vmode)and(tail=head) then - case cur_chr of - int_val: cur_val:=last_penalty; - dimen_val: cur_val:=last_kern; - glue_val: if last_glue<>max_halfword then cur_val:=last_glue; - end; {there are no other cases} - end - -@ @<Fetch a font dimension@>= -begin find_font_dimen(false); font_info[fmem_ptr].sc:=0; -scanned_result(font_info[cur_val].sc)(dimen_val); -end - -@ @<Fetch a font integer@>= -begin scan_font_ident; -if m=0 then scanned_result(hyphen_char[cur_val])(int_val) -else scanned_result(skew_char[cur_val])(int_val); -end - -@ @<Fetch a register@>= -begin scan_eight_bit_int; -case m of -int_val:cur_val:=count(cur_val); -dimen_val:cur_val:=dimen(cur_val); -glue_val: cur_val:=skip(cur_val); -mu_val: cur_val:=mu_skip(cur_val); -end; {there are no other cases} -cur_val_level:=m; -end - -@ @<Complain that \.{\\the} can't do this; give zero result@>= -begin print_err("You can't use `"); print_cmd_chr(cur_cmd,cur_chr); -@.You can't use x after ...@> -print("' after "); print_esc("the"); -help1("I'm forgetting what you said and using zero instead."); -error; -if level<>tok_val then scanned_result(0)(dimen_val) -else scanned_result(0)(int_val); -end - -@ When a |glue_val| changes to a |dimen_val|, we use the width component -of the glue; there is no need to decrease the reference count, since it -has not yet been increased. When a |dimen_val| changes to an |int_val|, -we use scaled points so that the value doesn't actually change. And when a -|mu_val| changes to a |glue_val|, the value doesn't change either. - -@<Convert \(c)|cur_val| to a lower level@>= -begin if cur_val_level=glue_val then cur_val:=width(cur_val) -else if cur_val_level=mu_val then mu_error; -decr(cur_val_level); -end - -@ If |cur_val| points to a glue specification at this point, the reference -count for the glue does not yet include the reference by |cur_val|. -If |negative| is |true|, |cur_val_level| is known to be |<=mu_val|. - -@<Fix the reference count, if any, ...@>= -if negative then - if cur_val_level>=glue_val then - begin cur_val:=new_spec(cur_val); - @<Negate all three glue components of |cur_val|@>; - end - else negate(cur_val) -else if (cur_val_level>=glue_val)and(cur_val_level<=mu_val) then - add_glue_ref(cur_val) - -@ @<Negate all three...@>= -begin negate(width(cur_val)); -negate(stretch(cur_val)); -negate(shrink(cur_val)); -end - -@ Our next goal is to write the |scan_int| procedure, which scans anything that -\TeX\ treats as an integer. But first we might as well look at some simple -applications of |scan_int| that have already been made inside of -|scan_something_internal|. - -@ @<Declare procedures that scan restricted classes of integers@>= -procedure scan_eight_bit_int; -begin scan_int; -if (cur_val<0)or(cur_val>255) then - begin print_err("Bad register code"); -@.Bad register code@> - help2("A register number must be between 0 and 255.")@/ - ("I changed this one to zero."); int_error(cur_val); cur_val:=0; - end; -end; - -@ @<Declare procedures that scan restricted classes of integers@>= -procedure scan_char_num; -begin scan_int; -if (cur_val<0)or(cur_val>255) then - begin print_err("Bad character code"); -@.Bad character code@> - help2("A character number must be between 0 and 255.")@/ - ("I changed this one to zero."); int_error(cur_val); cur_val:=0; - end; -end; - -@ While we're at it, we might as well deal with similar routines that -will be needed later. - -@<Declare procedures that scan restricted classes of integers@>= -procedure scan_four_bit_int; -begin scan_int; -if (cur_val<0)or(cur_val>15) then - begin print_err("Bad number"); -@.Bad number@> - help2("Since I expected to read a number between 0 and 15,")@/ - ("I changed this one to zero."); int_error(cur_val); cur_val:=0; - end; -end; - -@ @<Declare procedures that scan restricted classes of integers@>= -procedure scan_fifteen_bit_int; -begin scan_int; -if (cur_val<0)or(cur_val>@'77777) then - begin print_err("Bad mathchar"); -@.Bad mathchar@> - help2("A mathchar number must be between 0 and 32767.")@/ - ("I changed this one to zero."); int_error(cur_val); cur_val:=0; - end; -end; - -@ @<Declare procedures that scan restricted classes of integers@>= -procedure scan_twenty_seven_bit_int; -begin scan_int; -if (cur_val<0)or(cur_val>@'777777777) then - begin print_err("Bad delimiter code"); -@.Bad delimiter code@> - help2("A numeric delimiter code must be between 0 and 2^{27}-1.")@/ - ("I changed this one to zero."); int_error(cur_val); cur_val:=0; - end; -end; - -@ An integer number can be preceded by any number of spaces and `\.+' or -`\.-' signs. Then comes either a decimal constant (i.e., radix 10), an -octal constant (i.e., radix 8, preceded by~\.\'), a hexadecimal constant -(radix 16, preceded by~\."), an alphabetic constant (preceded by~\.\`), or -an internal variable. After scanning is complete, -|cur_val| will contain the answer, which must be at most -$2^{31}-1=2147483647$ in absolute value. The value of |radix| is set to -10, 8, or 16 in the cases of decimal, octal, or hexadecimal constants, -otherwise |radix| is set to zero. An optional space follows a constant. - -@d octal_token=other_token+"'" {apostrophe, indicates an octal constant} -@d hex_token=other_token+"""" {double quote, indicates a hex constant} -@d alpha_token=other_token+"`" {reverse apostrophe, precedes alpha constants} -@d point_token=other_token+"." {decimal point} -@d continental_point_token=other_token+"," {decimal point, Eurostyle} - -@<Glob...@>= -@!radix:small_number; {|scan_int| sets this to 8, 10, 16, or zero} - -@ We initialize the following global variables just in case |expand| -comes into action before any of the basic scanning routines has assigned -them a value. - -@<Set init...@>= -cur_val:=0; cur_val_level:=int_val; radix:=0; cur_order:=normal; - -@ The |scan_int| routine is used also to scan the integer part of a -fraction; for example, the `\.3' in `\.{3.14159}' will be found by -|scan_int|. The |scan_dimen| routine assumes that |cur_tok=point_token| -after the integer part of such a fraction has been scanned by |scan_int|, -and that the decimal point has been backed up to be scanned again. - -@p procedure scan_int; {sets |cur_val| to an integer} -label done; -var negative:boolean; {should the answer be negated?} -@!m:integer; {|@t$2^{31}$@> div radix|, the threshold of danger} -@!d:small_number; {the digit just scanned} -@!vacuous:boolean; {have no digits appeared?} -@!OK_so_far:boolean; {has an error message been issued?} -begin radix:=0; OK_so_far:=true;@/ -@<Get the next non-blank non-sign token; set |negative| appropriately@>; -if cur_tok=alpha_token then @<Scan an alphabetic character code into |cur_val|@> -else if (cur_cmd>=min_internal)and(cur_cmd<=max_internal) then - scan_something_internal(int_val,false) -else @<Scan a numeric constant@>; -if negative then negate(cur_val); -end; - -@ @<Get the next non-blank non-sign token...@>= -negative:=false; -repeat @<Get the next non-blank non-call token@>; -if cur_tok=other_token+"-" then - begin negative := not negative; cur_tok:=other_token+"+"; - end; -until cur_tok<>other_token+"+" - -@ A space is ignored after an alphabetic character constant, so that -such constants behave like numeric ones. - -@<Scan an alphabetic character code into |cur_val|@>= -begin get_token; {suppress macro expansion} -if cur_tok<cs_token_flag then - begin cur_val:=cur_chr; - if cur_cmd<=right_brace then - if cur_cmd=right_brace then incr(align_state) - else decr(align_state); - end -else if cur_tok<cs_token_flag+single_base then - cur_val:=cur_tok-cs_token_flag-active_base -else cur_val:=cur_tok-cs_token_flag-single_base; -if cur_val>255 then - begin print_err("Improper alphabetic constant"); -@.Improper alphabetic constant@> - help2("A one-character control sequence belongs after a ` mark.")@/ - ("So I'm essentially inserting \0 here."); - cur_val:="0"; back_error; - end -else @<Scan an optional space@>; -end - -@ @<Scan an optional space@>= -begin get_x_token; if cur_cmd<>spacer then back_input; -end - -@ @<Scan a numeric constant@>= -begin radix:=10; m:=214748364; -if cur_tok=octal_token then - begin radix:=8; m:=@'2000000000; get_x_token; - end -else if cur_tok=hex_token then - begin radix:=16; m:=@'1000000000; get_x_token; - end; -vacuous:=true; cur_val:=0;@/ -@<Accumulate the constant until |cur_tok| is not a suitable digit@>; -if vacuous then @<Express astonishment that no number was here@> -else if cur_cmd<>spacer then back_input; -end - -@ @d infinity==@'17777777777 {the largest positive value that \TeX\ knows} -@d zero_token=other_token+"0" {zero, the smallest digit} -@d A_token=letter_token+"A" {the smallest special hex digit} -@d other_A_token=other_token+"A" {special hex digit of type |other_char|} - -@<Accumulate the constant...@>= -loop@+ begin if (cur_tok<zero_token+radix)and(cur_tok>=zero_token)and - (cur_tok<=zero_token+9) then d:=cur_tok-zero_token - else if radix=16 then - if (cur_tok<=A_token+5)and(cur_tok>=A_token) then d:=cur_tok-A_token+10 - else if (cur_tok<=other_A_token+5)and(cur_tok>=other_A_token) then - d:=cur_tok-other_A_token+10 - else goto done - else goto done; - vacuous:=false; - if (cur_val>=m)and((cur_val>m)or(d>7)or(radix<>10)) then - begin if OK_so_far then - begin print_err("Number too big"); -@.Number too big@> - help2("I can only go up to 2147483647='17777777777=""7FFFFFFF,")@/ - ("so I'm using that number instead of yours."); - error; cur_val:=infinity; OK_so_far:=false; - end; - end - else cur_val:=cur_val*radix+d; - get_x_token; - end; -done: - -@ @<Express astonishment...@>= -begin print_err("Missing number, treated as zero"); -@.Missing number...@> -help3("A number should have been here; I inserted `0'.")@/ - ("(If you can't figure out why I needed to see a number,")@/ - ("look up `weird error' in the index to The TeXbook.)"); -@:TeXbook}{\sl The \TeX book@> -back_error; -end - -@ The |scan_dimen| routine is similar to |scan_int|, but it sets |cur_val| to -a |scaled| value, i.e., an integral number of sp. One of its main tasks -is therefore to interpret the abbreviations for various kinds of units and -to convert measurements to scaled points. - -There are three parameters: |mu| is |true| if the finite units must be -`\.{mu}', while |mu| is |false| if `\.{mu}' units are disallowed; -|inf| is |true| if the infinite units `\.{fil}', `\.{fill}', `\.{filll}' -are permitted; and |shortcut| is |true| if |cur_val| already contains -an integer and only the units need to be considered. - -The order of infinity that was found in the case of infinite glue is returned -in the global variable |cur_order|. - -@<Glob...@>= -@!cur_order:glue_ord; {order of infinity found by |scan_dimen|} - -@ Constructions like `\.{-\'77 pt}' are legal dimensions, so |scan_dimen| -may begin with |scan_int|. This explains why it is convenient to use -|scan_int| also for the integer part of a decimal fraction. - -Several branches of |scan_dimen| work with |cur_val| as an integer and -with an auxiliary fraction |f|, so that the actual quantity of interest is -$|cur_val|+|f|/2^{16}$. At the end of the routine, this ``unpacked'' -representation is put into the single word |cur_val|, which suddenly -switches significance from |integer| to |scaled|. - -@d attach_fraction=88 {go here to pack |cur_val| and |f| into |cur_val|} -@d attach_sign=89 {go here when |cur_val| is correct except perhaps for sign} -@d scan_normal_dimen==scan_dimen(false,false,false) - -@p procedure scan_dimen(@!mu,@!inf,@!shortcut:boolean); - {sets |cur_val| to a dimension} -label done, done1, done2, found, not_found, attach_fraction, attach_sign; -var negative:boolean; {should the answer be negated?} -@!f:integer; {numerator of a fraction whose denominator is $2^{16}$} -@<Local variables for dimension calculations@>@; -begin f:=0; arith_error:=false; cur_order:=normal; negative:=false; -if not shortcut then - begin @<Get the next non-blank non-sign...@>; - if (cur_cmd>=min_internal)and(cur_cmd<=max_internal) then - @<Fetch an internal dimension and |goto attach_sign|, - or fetch an internal integer@> - else begin back_input; - if cur_tok=continental_point_token then cur_tok:=point_token; - if cur_tok<>point_token then scan_int - else begin radix:=10; cur_val:=0; - end; - if cur_tok=continental_point_token then cur_tok:=point_token; - if (radix=10)and(cur_tok=point_token) then @<Scan decimal fraction@>; - end; - end; -if cur_val<0 then {in this case |f=0|} - begin negative := not negative; negate(cur_val); - end; -@<Scan units and set |cur_val| to $x\cdot(|cur_val|+f/2^{16})$, where there - are |x| sp per unit; |goto attach_sign| if the units are internal@>; -@<Scan an optional space@>; -attach_sign: if arith_error or(abs(cur_val)>=@'10000000000) then - @<Report that this dimension is out of range@>; -if negative then negate(cur_val); -end; - -@ @<Fetch an internal dimension and |goto attach_sign|...@>= -if mu then - begin scan_something_internal(mu_val,false); - @<Coerce glue to a dimension@>; - if cur_val_level=mu_val then goto attach_sign; - if cur_val_level<>int_val then mu_error; - end -else begin scan_something_internal(dimen_val,false); - if cur_val_level=dimen_val then goto attach_sign; - end - -@ @<Local variables for dimension calculations@>= -@!num,@!denom:1..65536; {conversion ratio for the scanned units} -@!k,@!kk:small_number; {number of digits in a decimal fraction} -@!p,@!q:pointer; {top of decimal digit stack} -@!v:scaled; {an internal dimension} -@!save_cur_val:integer; {temporary storage of |cur_val|} - -@ The following code is executed when |scan_something_internal| was -called asking for |mu_val|, when we really wanted a ``mudimen'' instead -of ``muglue.'' - -@<Coerce glue to a dimension@>= -if cur_val_level>=glue_val then - begin v:=width(cur_val); delete_glue_ref(cur_val); cur_val:=v; - end - -@ When the following code is executed, we have |cur_tok=point_token|, but this -token has been backed up using |back_input|; we must first discard it. - -It turns out that a decimal point all by itself is equivalent to `\.{0.0}'. -Let's hope people don't use that fact. - -@<Scan decimal fraction@>= -begin k:=0; p:=null; get_token; {|point_token| is being re-scanned} -loop@+ begin get_x_token; - if (cur_tok>zero_token+9)or(cur_tok<zero_token) then goto done1; - if k<17 then {digits for |k>=17| cannot affect the result} - begin q:=get_avail; link(q):=p; info(q):=cur_tok-zero_token; - p:=q; incr(k); - end; - end; -done1: for kk:=k downto 1 do - begin dig[kk-1]:=info(p); q:=p; p:=link(p); free_avail(q); - end; -f:=round_decimals(k); -if cur_cmd<>spacer then back_input; -end - -@ Now comes the harder part: At this point in the program, |cur_val| is a -nonnegative integer and $f/2^{16}$ is a nonnegative fraction less than 1; -we want to multiply the sum of these two quantities by the appropriate -factor, based on the specified units, in order to produce a |scaled| -result, and we want to do the calculation with fixed point arithmetic that -does not overflow. - -@<Scan units and set |cur_val| to $x\cdot(|cur_val|+f/2^{16})$...@>= -if inf then @<Scan for \(f)\.{fil} units; |goto attach_fraction| if found@>; -@<Scan for \(u)units that are internal dimensions; - |goto attach_sign| with |cur_val| set if found@>; -if mu then @<Scan for \(m)\.{mu} units and |goto attach_fraction|@>; -if scan_keyword("true") then @<Adjust \(f)for the magnification ratio@>; -@.true@> -if scan_keyword("pt") then goto attach_fraction; {the easy case} -@.pt@> -@<Scan for \(a)all other units and adjust |cur_val| and |f| accordingly; - |goto done| in the case of scaled points@>; -attach_fraction: if cur_val>=@'40000 then arith_error:=true -else cur_val:=cur_val*unity+f; -done: - -@ A specification like `\.{filllll}' or `\.{fill L L L}' will lead to two -error messages (one for each additional keyword \.{"l"}). - -@<Scan for \(f)\.{fil} units...@>= -if scan_keyword("fil") then -@.fil@> - begin cur_order:=fil; - while scan_keyword("l") do - begin if cur_order=filll then - begin print_err("Illegal unit of measure ("); -@.Illegal unit of measure@> - print("replaced by filll)"); - help1("I dddon't go any higher than filll."); error; - end - else incr(cur_order); - end; - goto attach_fraction; - end - -@ @<Scan for \(u)units that are internal dimensions...@>= -save_cur_val:=cur_val; -@<Get the next non-blank non-call...@>; -if (cur_cmd<min_internal)or(cur_cmd>max_internal) then back_input -else begin if mu then - begin scan_something_internal(mu_val,false); @<Coerce glue...@>; - if cur_val_level<>mu_val then mu_error; - end - else scan_something_internal(dimen_val,false); - v:=cur_val; goto found; - end; -if mu then goto not_found; -if scan_keyword("em") then v:=(@<The em width for |cur_font|@>) -@.em@> -else if scan_keyword("ex") then v:=(@<The x-height for |cur_font|@>) -@.ex@> -else goto not_found; -@<Scan an optional space@>; -found:cur_val:=nx_plus_y(save_cur_val,v,xn_over_d(v,f,@'200000)); -goto attach_sign; -not_found: - -@ @<Scan for \(m)\.{mu} units and |goto attach_fraction|@>= -if scan_keyword("mu") then goto attach_fraction -@.mu@> -else begin print_err("Illegal unit of measure ("); print("mu inserted)"); -@.Illegal unit of measure@> - help4("The unit of measurement in math glue must be mu.")@/ - ("To recover gracefully from this error, it's best to")@/ - ("delete the erroneous units; e.g., type `2' to delete")@/ - ("two letters. (See Chapter 27 of The TeXbook.)"); -@:TeXbook}{\sl The \TeX book@> - error; goto attach_fraction; - end - -@ @<Adjust \(f)for the magnification ratio@>= -begin prepare_mag; -if mag<>1000 then - begin cur_val:=xn_over_d(cur_val,1000,mag); - f:=(1000*f+@'200000*remainder) div mag; - cur_val:=cur_val+(f div @'200000); f:=f mod @'200000; - end; -end - -@ The necessary conversion factors can all be specified exactly as -fractions whose numerator and denominator sum to 32768 or less. -According to the definitions here, $\rm2660\,dd\approx1000.33297\,mm$; -this agrees well with the value $\rm1000.333\,mm$ cited by Bosshard -@^Bosshard, Hans Rudolf@> -in {\sl Technische Grundlagen zur Satzherstellung\/} (Bern, 1980). - -@d set_conversion_end(#)== denom:=#; end -@d set_conversion(#)==@+begin num:=#; set_conversion_end - -@<Scan for \(a)all other units and adjust |cur_val| and |f|...@>= -if scan_keyword("in") then set_conversion(7227)(100) -@.in@> -else if scan_keyword("pc") then set_conversion(12)(1) -@.pc@> -else if scan_keyword("cm") then set_conversion(7227)(254) -@.cm@> -else if scan_keyword("mm") then set_conversion(7227)(2540) -@.mm@> -else if scan_keyword("bp") then set_conversion(7227)(7200) -@.bp@> -else if scan_keyword("dd") then set_conversion(1238)(1157) -@.dd@> -else if scan_keyword("cc") then set_conversion(14856)(1157) -@.cc@> -else if scan_keyword("sp") then goto done -@.sp@> -else @<Complain about unknown unit and |goto done2|@>; -cur_val:=xn_over_d(cur_val,num,denom); -f:=(num*f+@'200000*remainder) div denom;@/ -cur_val:=cur_val+(f div @'200000); f:=f mod @'200000; -done2: - -@ @<Complain about unknown unit...@>= -begin print_err("Illegal unit of measure ("); print("pt inserted)"); -@.Illegal unit of measure@> -help6("Dimensions can be in units of em, ex, in, pt, pc,")@/ - ("cm, mm, dd, cc, bp, or sp; but yours is a new one!")@/ - ("I'll assume that you meant to say pt, for printer's points.")@/ - ("To recover gracefully from this error, it's best to")@/ - ("delete the erroneous units; e.g., type `2' to delete")@/ - ("two letters. (See Chapter 27 of The TeXbook.)"); -@:TeXbook}{\sl The \TeX book@> -error; goto done2; -end - - -@ @<Report that this dimension is out of range@>= -begin print_err("Dimension too large"); -@.Dimension too large@> -help2("I can't work with sizes bigger than about 19 feet.")@/ - ("Continue and I'll use the largest value I can.");@/ -error; cur_val:=max_dimen; arith_error:=false; -end - -@ The final member of \TeX's value-scanning trio is |scan_glue|, which -makes |cur_val| point to a glue specification. The reference count of that -glue spec will take account of the fact that |cur_val| is pointing to~it. - -The |level| parameter should be either |glue_val| or |mu_val|. - -Since |scan_dimen| was so much more complex than |scan_int|, we might expect -|scan_glue| to be even worse. But fortunately, it is very simple, since -most of the work has already been done. - -@p procedure scan_glue(@!level:small_number); - {sets |cur_val| to a glue spec pointer} -label exit; -var negative:boolean; {should the answer be negated?} -@!q:pointer; {new glue specification} -@!mu:boolean; {does |level=mu_val|?} -begin mu:=(level=mu_val); @<Get the next non-blank non-sign...@>; -if (cur_cmd>=min_internal)and(cur_cmd<=max_internal) then - begin scan_something_internal(level,negative); - if cur_val_level>=glue_val then - begin if cur_val_level<>level then mu_error; - return; - end; - if cur_val_level=int_val then scan_dimen(mu,false,true) - else if level=mu_val then mu_error; - end -else begin back_input; scan_dimen(mu,false,false); - if negative then negate(cur_val); - end; -@<Create a new glue specification whose width is |cur_val|; scan for its - stretch and shrink components@>; -exit:end; - -@ @<Create a new glue specification whose width is |cur_val|...@>= -q:=new_spec(zero_glue); width(q):=cur_val; -if scan_keyword("plus") then -@.plus@> - begin scan_dimen(mu,true,false); - stretch(q):=cur_val; stretch_order(q):=cur_order; - end; -if scan_keyword("minus") then -@.minus@> - begin scan_dimen(mu,true,false); - shrink(q):=cur_val; shrink_order(q):=cur_order; - end; -cur_val:=q - -@ Here's a similar procedure that returns a pointer to a rule node. This -routine is called just after \TeX\ has seen \.{\\hrule} or \.{\\vrule}; -therefore |cur_cmd| will be either |hrule| or |vrule|. The idea is to store -the default rule dimensions in the node, then to override them if -`\.{height}' or `\.{width}' or `\.{depth}' specifications are -found (in any order). - -@d default_rule=26214 {0.4\thinspace pt} - -@p function scan_rule_spec:pointer; -label reswitch; -var q:pointer; {the rule node being created} -begin q:=new_rule; {|width|, |depth|, and |height| all equal |null_flag| now} -if cur_cmd=vrule then width(q):=default_rule -else begin height(q):=default_rule; depth(q):=0; - end; -reswitch: if scan_keyword("width") then -@.width@> - begin scan_normal_dimen; width(q):=cur_val; goto reswitch; - end; -if scan_keyword("height") then -@.height@> - begin scan_normal_dimen; height(q):=cur_val; goto reswitch; - end; -if scan_keyword("depth") then -@.depth@> - begin scan_normal_dimen; depth(q):=cur_val; goto reswitch; - end; -scan_rule_spec:=q; -end; - -@* \[27] Building token lists. -The token lists for macros and for other things like \.{\\mark} and \.{\\output} -and \.{\\write} are produced by a procedure called |scan_toks|. - -Before we get into the details of |scan_toks|, let's consider a much -simpler task, that of converting the current string into a token list. -The |str_toks| function does this; it classifies spaces as type |spacer| -and everything else as type |other_char|. - -The token list created by |str_toks| begins at |link(temp_head)| and ends -at the value |p| that is returned. (If |p=temp_head|, the list is empty.) - -@p function str_toks(@!b:pool_pointer):pointer; - {converts |str_pool[b..pool_ptr-1]| to a token list} -var p:pointer; {tail of the token list} -@!q:pointer; {new node being added to the token list via |store_new_token|} -@!t:halfword; {token being appended} -@!k:pool_pointer; {index into |str_pool|} -begin str_room(1); -p:=temp_head; link(p):=null; k:=b; -while k<pool_ptr do - begin t:=so(str_pool[k]); - if t=" " then t:=space_token - else t:=other_token+t; - fast_store_new_token(t); - incr(k); - end; -pool_ptr:=b; str_toks:=p; -end; - -@ The main reason for wanting |str_toks| is the next function, -|the_toks|, which has similar input/output characteristics. - -This procedure is supposed to scan something like `\.{\\skip\\count12}', -i.e., whatever can follow `\.{\\the}', and it constructs a token list -containing something like `\.{-3.0pt minus 0.5fill}'. - -@p function the_toks:pointer; -var old_setting:0..max_selector; {holds |selector| setting} -@!p,@!q,@!r:pointer; {used for copying a token list} -@!b:pool_pointer; {base of temporary string} -begin get_x_token; scan_something_internal(tok_val,false); -if cur_val_level>=ident_val then @<Copy the token list@> -else begin old_setting:=selector; selector:=new_string; b:=pool_ptr; - case cur_val_level of - int_val:print_int(cur_val); - dimen_val:begin print_scaled(cur_val); print("pt"); - end; - glue_val: begin print_spec(cur_val,"pt"); delete_glue_ref(cur_val); - end; - mu_val: begin print_spec(cur_val,"mu"); delete_glue_ref(cur_val); - end; - end; {there are no other cases} - selector:=old_setting; the_toks:=str_toks(b); - end; -end; - -@ @<Copy the token list@>= -begin p:=temp_head; link(p):=null; -if cur_val_level=ident_val then store_new_token(cs_token_flag+cur_val) -else if cur_val<>null then - begin r:=link(cur_val); {do not copy the reference count} - while r<>null do - begin fast_store_new_token(info(r)); r:=link(r); - end; - end; -the_toks:=p; -end - -@ Here's part of the |expand| subroutine that we are now ready to complete: - -@p procedure ins_the_toks; -begin link(garbage):=the_toks; ins_list(link(temp_head)); -end; - -@ The primitives \.{\\number}, \.{\\romannumeral}, \.{\\string}, \.{\\meaning}, -\.{\\fontname}, and \.{\\jobname} are defined as follows. - -@d number_code=0 {command code for \.{\\number}} -@d roman_numeral_code=1 {command code for \.{\\romannumeral}} -@d string_code=2 {command code for \.{\\string}} -@d meaning_code=3 {command code for \.{\\meaning}} -@d font_name_code=4 {command code for \.{\\fontname}} -@d job_name_code=5 {command code for \.{\\jobname}} - -@<Put each...@>= -primitive("number",convert,number_code);@/ -@!@:number_}{\.{\\number} primitive@> -primitive("romannumeral",convert,roman_numeral_code);@/ -@!@:roman_numeral_}{\.{\\romannumeral} primitive@> -primitive("string",convert,string_code);@/ -@!@:string_}{\.{\\string} primitive@> -primitive("meaning",convert,meaning_code);@/ -@!@:meaning_}{\.{\\meaning} primitive@> -primitive("fontname",convert,font_name_code);@/ -@!@:font_name_}{\.{\\fontname} primitive@> -primitive("jobname",convert,job_name_code);@/ -@!@:job_name_}{\.{\\jobname} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -convert: case chr_code of - number_code: print_esc("number"); - roman_numeral_code: print_esc("romannumeral"); - string_code: print_esc("string"); - meaning_code: print_esc("meaning"); - font_name_code: print_esc("fontname"); - othercases print_esc("jobname") - endcases; - -@ The procedure |conv_toks| uses |str_toks| to insert the token list -for |convert| functions into the scanner; `\.{\\outer}' control sequences -are allowed to follow `\.{\\string}' and `\.{\\meaning}'. - -@p procedure conv_toks; -var old_setting:0..max_selector; {holds |selector| setting} -@!c:number_code..job_name_code; {desired type of conversion} -@!save_scanner_status:small_number; {|scanner_status| upon entry} -@!b:pool_pointer; {base of temporary string} -begin c:=cur_chr; @<Scan the argument for command |c|@>; -old_setting:=selector; selector:=new_string; b:=pool_ptr; -@<Print the result of command |c|@>; -selector:=old_setting; link(garbage):=str_toks(b); ins_list(link(temp_head)); -end; - -@ @<Scan the argument for command |c|@>= -case c of -number_code,roman_numeral_code: scan_int; -string_code, meaning_code: begin save_scanner_status:=scanner_status; - scanner_status:=normal; get_token; scanner_status:=save_scanner_status; - end; -font_name_code: scan_font_ident; -job_name_code: if job_name=0 then open_log_file; -end {there are no other cases} - -@ @<Print the result of command |c|@>= -case c of -number_code: print_int(cur_val); -roman_numeral_code: print_roman_int(cur_val); -string_code:if cur_cs<>0 then sprint_cs(cur_cs) - else print_char(cur_chr); -meaning_code: print_meaning; -font_name_code: begin print(font_name[cur_val]); - if font_size[cur_val]<>font_dsize[cur_val] then - begin print(" at "); print_scaled(font_size[cur_val]); - print("pt"); - end; - end; -job_name_code: print(job_name); -end {there are no other cases} - -@ Now we can't postpone the difficulties any longer; we must bravely tackle -|scan_toks|. This function returns a pointer to the tail of a new token -list, and it also makes |def_ref| point to the reference count at the -head of that list. - -There are two boolean parameters, |macro_def| and |xpand|. If |macro_def| -is true, the goal is to create the token list for a macro definition; -otherwise the goal is to create the token list for some other \TeX\ -primitive: \.{\\mark}, \.{\\output}, \.{\\everypar}, \.{\\lowercase}, -\.{\\uppercase}, \.{\\message}, \.{\\errmessage}, \.{\\write}, or -\.{\\special}. In the latter cases a left brace must be scanned next; this -left brace will not be part of the token list, nor will the matching right -brace that comes at the end. If |xpand| is false, the token list will -simply be copied from the input using |get_token|. Otherwise all expandable -tokens will be expanded until unexpandable tokens are left, except that -the results of expanding `\.{\\the}' are not expanded further. -If both |macro_def| and |xpand| are true, the expansion applies -only to the macro body (i.e., to the material following the first -|left_brace| character). - -The value of |cur_cs| when |scan_toks| begins should be the |eqtb| -address of the control sequence to display in ``runaway'' error -messages. - -@p function scan_toks(@!macro_def,@!xpand:boolean):pointer; -label found,continue,done,done1,done2; -var t:halfword; {token representing the highest parameter number} -@!s:halfword; {saved token} -@!p:pointer; {tail of the token list being built} -@!q:pointer; {new node being added to the token list via |store_new_token|} -@!unbalance:halfword; {number of unmatched left braces} -@!hash_brace:halfword; {possible `\.{\#\{}' token} -begin if macro_def then scanner_status:=defining -@+else scanner_status:=absorbing; -warning_index:=cur_cs; def_ref:=get_avail; token_ref_count(def_ref):=null; -p:=def_ref; hash_brace:=0; t:=zero_token; -if macro_def then @<Scan and build the parameter part of the macro definition@> -else scan_left_brace; {remove the compulsory left brace} -@<Scan and build the body of the token list; |goto found| when finished@>; -found: scanner_status:=normal; -if hash_brace<>0 then store_new_token(hash_brace); -scan_toks:=p; -end; - -@ @<Scan and build the parameter part...@>= -begin loop begin continue: get_token; {set |cur_cmd|, |cur_chr|, |cur_tok|} - if cur_tok<right_brace_limit then goto done1; - if cur_cmd=mac_param then - @<If the next character is a parameter number, make |cur_tok| - a |match| token; but if it is a left brace, store - `|left_brace|, |end_match|', set |hash_brace|, and |goto done|@>; - store_new_token(cur_tok); - end; -done1: store_new_token(end_match_token); -if cur_cmd=right_brace then - @<Express shock at the missing left brace; |goto found|@>; -done: end - -@ @<Express shock...@>= -begin print_err("Missing { inserted"); incr(align_state); -@.Missing \{ inserted@> -help2("Where was the left brace? You said something like `\def\a}',")@/ - ("which I'm going to interpret as `\def\a{}'."); error; goto found; -end - -@ @<If the next character is a parameter number...@>= -begin s:=match_token+cur_chr; get_token; -if cur_tok<left_brace_limit then - begin hash_brace:=cur_tok; - store_new_token(cur_tok); store_new_token(end_match_token); - goto done; - end; -if t=zero_token+9 then - begin print_err("You already have nine parameters"); -@.You already have nine...@> - help2("I'm going to ignore the # sign you just used,")@/ - ("as well as the token that followed it."); error; goto continue; - end -else begin incr(t); - if cur_tok<>t then - begin print_err("Parameters must be numbered consecutively"); -@.Parameters...consecutively@> - help2("I've inserted the digit you should have used after the #.")@/ - ("Type `1' to delete what you did use."); back_error; - end; - cur_tok:=s; - end; -end - -@ @<Scan and build the body of the token list; |goto found| when finished@>= -unbalance:=1; -loop@+ begin if xpand then @<Expand the next part of the input@> - else get_token; - if cur_tok<right_brace_limit then - if cur_cmd<right_brace then incr(unbalance) - else begin decr(unbalance); - if unbalance=0 then goto found; - end - else if cur_cmd=mac_param then - if macro_def then @<Look for parameter number or \.{\#\#}@>; - store_new_token(cur_tok); - end - -@ Here we insert an entire token list created by |the_toks| without -expanding it further. - -@<Expand the next part of the input@>= -begin loop begin get_next; - if cur_cmd<=max_command then goto done2; - if cur_cmd<>the then expand - else begin q:=the_toks; - if link(temp_head)<>null then - begin link(p):=link(temp_head); p:=q; - end; - end; - end; -done2: x_token -end - -@ @<Look for parameter number...@>= -begin s:=cur_tok; -if xpand then get_x_token else get_token; -if cur_cmd<>mac_param then - if (cur_tok<=zero_token)or(cur_tok>t) then - begin print_err("Illegal parameter number in definition of "); -@.Illegal parameter number...@> - sprint_cs(warning_index); - help3("You meant to type ## instead of #, right?")@/ - ("Or maybe a } was forgotten somewhere earlier, and things")@/ - ("are all screwed up? I'm going to assume that you meant ##."); - back_error; cur_tok:=s; - end - else cur_tok:=out_param_token-"0"+cur_chr; -end - -@ Another way to create a token list is via the \.{\\read} command. The -sixteen files potentially usable for reading appear in the following -global variables. The value of |read_open[n]| will be |closed| if -stream number |n| has not been opened or if it has been fully read; -|just_open| if an \.{\\openin} but not a \.{\\read} has been done; -and |normal| if it is open and ready to read the next line. - -@d closed=2 {not open, or at end of file} -@d just_open=1 {newly opened, first line not yet read} - -@<Glob...@>= -@!read_file:array[0..15] of alpha_file; {used for \.{\\read}} -@!read_open:array[0..16] of normal..closed; {state of |read_file[n]|} - -@ @<Set init...@>= -for k:=0 to 16 do read_open[k]:=closed; - -@ The |read_toks| procedure constructs a token list like that for any -macro definition, and makes |cur_val| point to it. Parameter |r| points -to the control sequence that will receive this token list. - -@p procedure read_toks(@!n:integer;@!r:pointer); -label done; -var p:pointer; {tail of the token list} -@!q:pointer; {new node being added to the token list via |store_new_token|} -@!s:integer; {saved value of |align_state|} -@!m:small_number; {stream number} -begin scanner_status:=defining; warning_index:=r; -def_ref:=get_avail; token_ref_count(def_ref):=null; -p:=def_ref; {the reference count} -store_new_token(end_match_token); -if (n<0)or(n>15) then m:=16@+else m:=n; -s:=align_state; align_state:=1000000; {disable tab marks, etc.} -repeat @<Input and store tokens from the next line of the file@>; -until align_state=1000000; -cur_val:=def_ref; scanner_status:=normal; align_state:=s; -end; - -@ @<Input and store tokens from the next line of the file@>= -begin_file_reading; name:=m+1; -if read_open[m]=closed then @<Input for \.{\\read} from the terminal@> -else if read_open[m]=just_open then @<Input the first line of |read_file[m]|@> -else @<Input the next line of |read_file[m]|@>; -limit:=last; -if end_line_char_inactive then decr(limit) -else buffer[limit]:=end_line_char; -first:=limit+1; loc:=start; state:=new_line;@/ -loop@+ begin get_token; - if cur_tok=0 then goto done; - {|cur_cmd=cur_chr=0| will occur at the end of the line} - if align_state<1000000 then {unmatched `\.\}' aborts the line} - begin repeat get_token; until cur_tok=0; - align_state:=1000000; goto done; - end; - store_new_token(cur_tok); - end; -done: end_file_reading - -@ Here we input on-line into the |buffer| array, prompting the user explicitly -if |n>=0|. The value of |n| is set negative so that additional prompts -will not be given in the case of multi-line input. - -@<Input for \.{\\read} from the terminal@>= -if interaction>nonstop_mode then - if n<0 then prompt_input("") - else begin wake_up_terminal; - print_ln; sprint_cs(r); prompt_input("="); n:=-1; - end -else fatal_error("*** (cannot \read from terminal in nonstop modes)") -@.cannot \\read@> - -@ The first line of a file must be treated specially, since |input_ln| -must be told not to start with |get|. -@^system dependencies@> - -@<Input the first line of |read_file[m]|@>= -if input_ln(read_file[m],false) then read_open[m]:=normal -else begin a_close(read_file[m]); read_open[m]:=closed; - end - -@ An empty line is appended at the end of a |read_file|. -@^empty line at end of file@> - -@<Input the next line of |read_file[m]|@>= -begin if not input_ln(read_file[m],true) then - begin a_close(read_file[m]); read_open[m]:=closed; - if align_state<>1000000 then - begin runaway; - print_err("File ended within "); print_esc("read"); -@.File ended within \\read@> - help1("This \read has unbalanced braces."); - align_state:=1000000; limit:=0; error; - end; - end; -end - -@* \[28] Conditional processing. -We consider now the way \TeX\ handles various kinds of \.{\\if} commands. - -@d if_char_code=0 { `\.{\\if}' } -@d if_cat_code=1 { `\.{\\ifcat}' } -@d if_int_code=2 { `\.{\\ifnum}' } -@d if_dim_code=3 { `\.{\\ifdim}' } -@d if_odd_code=4 { `\.{\\ifodd}' } -@d if_vmode_code=5 { `\.{\\ifvmode}' } -@d if_hmode_code=6 { `\.{\\ifhmode}' } -@d if_mmode_code=7 { `\.{\\ifmmode}' } -@d if_inner_code=8 { `\.{\\ifinner}' } -@d if_void_code=9 { `\.{\\ifvoid}' } -@d if_hbox_code=10 { `\.{\\ifhbox}' } -@d if_vbox_code=11 { `\.{\\ifvbox}' } -@d ifx_code=12 { `\.{\\ifx}' } -@d if_eof_code=13 { `\.{\\ifeof}' } -@d if_true_code=14 { `\.{\\iftrue}' } -@d if_false_code=15 { `\.{\\iffalse}' } -@d if_case_code=16 { `\.{\\ifcase}' } - -@<Put each...@>= -primitive("if",if_test,if_char_code); -@!@:if_char_}{\.{\\if} primitive@> -primitive("ifcat",if_test,if_cat_code); -@!@:if_cat_code_}{\.{\\ifcat} primitive@> -primitive("ifnum",if_test,if_int_code); -@!@:if_int_}{\.{\\ifnum} primitive@> -primitive("ifdim",if_test,if_dim_code); -@!@:if_dim_}{\.{\\ifdim} primitive@> -primitive("ifodd",if_test,if_odd_code); -@!@:if_odd_}{\.{\\ifodd} primitive@> -primitive("ifvmode",if_test,if_vmode_code); -@!@:if_vmode_}{\.{\\ifvmode} primitive@> -primitive("ifhmode",if_test,if_hmode_code); -@!@:if_hmode_}{\.{\\ifhmode} primitive@> -primitive("ifmmode",if_test,if_mmode_code); -@!@:if_mmode_}{\.{\\ifmmode} primitive@> -primitive("ifinner",if_test,if_inner_code); -@!@:if_inner_}{\.{\\ifinner} primitive@> -primitive("ifvoid",if_test,if_void_code); -@!@:if_void_}{\.{\\ifvoid} primitive@> -primitive("ifhbox",if_test,if_hbox_code); -@!@:if_hbox_}{\.{\\ifhbox} primitive@> -primitive("ifvbox",if_test,if_vbox_code); -@!@:if_vbox_}{\.{\\ifvbox} primitive@> -primitive("ifx",if_test,ifx_code); -@!@:ifx_}{\.{\\ifx} primitive@> -primitive("ifeof",if_test,if_eof_code); -@!@:if_eof_}{\.{\\ifeof} primitive@> -primitive("iftrue",if_test,if_true_code); -@!@:if_true_}{\.{\\iftrue} primitive@> -primitive("iffalse",if_test,if_false_code); -@!@:if_false_}{\.{\\iffalse} primitive@> -primitive("ifcase",if_test,if_case_code); -@!@:if_case_}{\.{\\ifcase} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -if_test: case chr_code of - if_cat_code:print_esc("ifcat"); - if_int_code:print_esc("ifnum"); - if_dim_code:print_esc("ifdim"); - if_odd_code:print_esc("ifodd"); - if_vmode_code:print_esc("ifvmode"); - if_hmode_code:print_esc("ifhmode"); - if_mmode_code:print_esc("ifmmode"); - if_inner_code:print_esc("ifinner"); - if_void_code:print_esc("ifvoid"); - if_hbox_code:print_esc("ifhbox"); - if_vbox_code:print_esc("ifvbox"); - ifx_code:print_esc("ifx"); - if_eof_code:print_esc("ifeof"); - if_true_code:print_esc("iftrue"); - if_false_code:print_esc("iffalse"); - if_case_code:print_esc("ifcase"); - othercases print_esc("if") - endcases; - -@ Conditions can be inside conditions, and this nesting has a stack -that is independent of the |save_stack|. - -Four global variables represent the top of the condition stack: -|cond_ptr| points to pushed-down entries, if any; |if_limit| specifies -the largest code of a |fi_or_else| command that is syntactically legal; -|cur_if| is the name of the current type of conditional; and |if_line| -is the line number at which it began. - -If no conditions are currently in progress, the condition stack has the -special state |cond_ptr=null|, |if_limit=normal|, |cur_if=0|, |if_line=0|. -Otherwise |cond_ptr| points to a two-word node; the |type|, |subtype|, and -|link| fields of the first word contain |if_limit|, |cur_if|, and -|cond_ptr| at the next level, and the second word contains the -corresponding |if_line|. - -@d if_node_size=2 {number of words in stack entry for conditionals} -@d if_line_field(#)==mem[#+1].int -@d if_code=1 {code for \.{\\if...} being evaluated} -@d fi_code=2 {code for \.{\\fi}} -@d else_code=3 {code for \.{\\else}} -@d or_code=4 {code for \.{\\or}} - -@<Glob...@>= -@!cond_ptr:pointer; {top of the condition stack} -@!if_limit:normal..or_code; {upper bound on |fi_or_else| codes} -@!cur_if:small_number; {type of conditional being worked on} -@!if_line:integer; {line where that conditional began} - -@ @<Set init...@>= -cond_ptr:=null; if_limit:=normal; cur_if:=0; if_line:=0; - -@ @<Put each...@>= -primitive("fi",fi_or_else,fi_code); -@!@:fi_}{\.{\\fi} primitive@> -text(frozen_fi):="fi"; eqtb[frozen_fi]:=eqtb[cur_val]; -primitive("or",fi_or_else,or_code); -@!@:or_}{\.{\\or} primitive@> -primitive("else",fi_or_else,else_code); -@!@:else_}{\.{\\else} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -fi_or_else: if chr_code=fi_code then print_esc("fi") - else if chr_code=or_code then print_esc("or") - else print_esc("else"); - -@ When we skip conditional text, we keep track of the line number -where skipping began, for use in error messages. - -@<Glob...@>= -@!skip_line:integer; {skipping began here} - -@ Here is a procedure that ignores text until coming to an \.{\\or}, -\.{\\else}, or \.{\\fi} at the current level of $\.{\\if}\ldots\.{\\fi}$ -nesting. After it has acted, |cur_chr| will indicate the token that -was found, but |cur_tok| will not be set (because this makes the -procedure run faster). - -@p procedure pass_text; -label done; -var l:integer; {level of $\.{\\if}\ldots\.{\\fi}$ nesting} -@!save_scanner_status:small_number; {|scanner_status| upon entry} -begin save_scanner_status:=scanner_status; scanner_status:=skipping; l:=0; -skip_line:=line; -loop@+ begin get_next; - if cur_cmd=fi_or_else then - begin if l=0 then goto done; - if cur_chr=fi_code then decr(l); - end - else if cur_cmd=if_test then incr(l); - end; -done: scanner_status:=save_scanner_status; -end; - -@ When we begin to process a new \.{\\if}, we set |if_limit:=if_code|; then -if\/ \.{\\or} or \.{\\else} or \.{\\fi} occurs before the current \.{\\if} -condition has been evaluated, \.{\\relax} will be inserted. -For example, a sequence of commands like `\.{\\ifvoid1\\else...\\fi}' -would otherwise require something after the `\.1'. - -@<Push the condition stack@>= -begin p:=get_node(if_node_size); link(p):=cond_ptr; type(p):=if_limit; -subtype(p):=cur_if; if_line_field(p):=if_line; -cond_ptr:=p; cur_if:=cur_chr; if_limit:=if_code; if_line:=line; -end - -@ @<Pop the condition stack@>= -begin p:=cond_ptr; if_line:=if_line_field(p); -cur_if:=subtype(p); if_limit:=type(p); cond_ptr:=link(p); -free_node(p,if_node_size); -end - -@ Here's a procedure that changes the |if_limit| code corresponding to -a given value of |cond_ptr|. - -@p procedure change_if_limit(@!l:small_number;@!p:pointer); -label exit; -var q:pointer; -begin if p=cond_ptr then if_limit:=l {that's the easy case} -else begin q:=cond_ptr; - loop@+ begin if q=null then confusion("if"); -@:this can't happen if}{\quad if@> - if link(q)=p then - begin type(q):=l; return; - end; - q:=link(q); - end; - end; -exit:end; - -@ A condition is started when the |expand| procedure encounters -an |if_test| command; in that case |expand| reduces to |conditional|, -which is a recursive procedure. -@^recursion@> - -@p procedure conditional; -label exit,common_ending; -var b:boolean; {is the condition true?} -@!r:"<"..">"; {relation to be evaluated} -@!m,@!n:integer; {to be tested against the second operand} -@!p,@!q:pointer; {for traversing token lists in \.{\\ifx} tests} -@!save_scanner_status:small_number; {|scanner_status| upon entry} -@!save_cond_ptr:pointer; {|cond_ptr| corresponding to this conditional} -@!this_if:small_number; {type of this conditional} -begin @<Push the condition stack@>;@+save_cond_ptr:=cond_ptr;this_if:=cur_chr;@/ -@<Either process \.{\\ifcase} or set |b| to the value of a boolean condition@>; -if tracing_commands>1 then @<Display the value of |b|@>; -if b then - begin change_if_limit(else_code,save_cond_ptr); - return; {wait for \.{\\else} or \.{\\fi}} - end; -@<Skip to \.{\\else} or \.{\\fi}, then |goto common_ending|@>; -common_ending: if cur_chr=fi_code then @<Pop the condition stack@> -else if_limit:=fi_code; {wait for \.{\\fi}} -exit:end; - -@ In a construction like `\.{\\if\\iftrue abc\\else d\\fi}', the first -\.{\\else} that we come to after learning that the \.{\\if} is false is -not the \.{\\else} we're looking for. Hence the following curious -logic is needed. - -@ @<Skip to \.{\\else} or \.{\\fi}...@>= -loop@+ begin pass_text; - if cond_ptr=save_cond_ptr then - begin if cur_chr<>or_code then goto common_ending; - print_err("Extra "); print_esc("or"); -@.Extra \\or@> - help1("I'm ignoring this; it doesn't match any \if."); - error; - end - else if cur_chr=fi_code then @<Pop the condition stack@>; - end - -@ @<Either process \.{\\ifcase} or set |b|...@>= -case this_if of -if_char_code, if_cat_code: @<Test if two characters match@>; -if_int_code, if_dim_code: @<Test relation between integers or dimensions@>; -if_odd_code: @<Test if an integer is odd@>; -if_vmode_code: b:=(abs(mode)=vmode); -if_hmode_code: b:=(abs(mode)=hmode); -if_mmode_code: b:=(abs(mode)=mmode); -if_inner_code: b:=(mode<0); -if_void_code, if_hbox_code, if_vbox_code: @<Test box register status@>; -ifx_code: @<Test if two tokens match@>; -if_eof_code: begin scan_four_bit_int; b:=(read_open[cur_val]=closed); - end; -if_true_code: b:=true; -if_false_code: b:=false; -if_case_code: @<Select the appropriate case - and |return| or |goto common_ending|@>; -end {there are no other cases} - -@ @<Display the value of |b|@>= -begin begin_diagnostic; -if b then print("{true}")@+else print("{false}"); -end_diagnostic(false); -end - -@ Here we use the fact that |"<"|, |"="|, and |">"| are consecutive ASCII -codes. -@^ASCII code@> - -@<Test relation between integers or dimensions@>= -begin if this_if=if_int_code then scan_int@+else scan_normal_dimen; -n:=cur_val; @<Get the next non-blank non-call...@>; -if (cur_tok>=other_token+"<")and(cur_tok<=other_token+">") then - r:=cur_tok-other_token -else begin print_err("Missing = inserted for "); -@.Missing = inserted@> - print_cmd_chr(if_test,this_if); - help1("I was expecting to see `<', `=', or `>'. Didn't."); - back_error; r:="="; - end; -if this_if=if_int_code then scan_int@+else scan_normal_dimen; -case r of -"<": b:=(n<cur_val); -"=": b:=(n=cur_val); -">": b:=(n>cur_val); -end; -end - -@ @<Test if an integer is odd@>= -begin scan_int; b:=odd(cur_val); -end - -@ @<Test box register status@>= -begin scan_eight_bit_int; p:=box(cur_val); -if this_if=if_void_code then b:=(p=null) -else if p=null then b:=false -else if this_if=if_hbox_code then b:=(type(p)=hlist_node) -else b:=(type(p)=vlist_node); -end - -@ An active character will be treated as category 13 following -\.{\\if\\noexpand} or following \.{\\ifcat\\noexpand}. We use the fact that -active characters have the smallest tokens, among all control sequences. - -@d get_x_token_or_active_char==@t@>@; - begin get_x_token; - if cur_cmd=relax then if cur_chr=no_expand_flag then - begin cur_cmd:=active_char; - cur_chr:=cur_tok-cs_token_flag-active_base; - end; - end - -@<Test if two characters match@>= -begin get_x_token_or_active_char; -if (cur_cmd>active_char)or(cur_chr>255) then {not a character} - begin m:=relax; n:=256; - end -else begin m:=cur_cmd; n:=cur_chr; - end; -get_x_token_or_active_char; -if (cur_cmd>active_char)or(cur_chr>255) then - begin cur_cmd:=relax; cur_chr:=256; - end; -if this_if=if_char_code then b:=(n=cur_chr)@+else b:=(m=cur_cmd); -end - -@ Note that `\.{\\ifx}' will declare two macros different if one is \\{long} -or \\{outer} and the other isn't, even though the texts of the macros are -the same. - -We need to reset |scanner_status|, since \.{\\outer} control sequences -are allowed, but we might be scanning a macro definition or preamble. - -@<Test if two tokens match@>= -begin save_scanner_status:=scanner_status; scanner_status:=normal; -get_next; n:=cur_cs; p:=cur_cmd; q:=cur_chr; -get_next; if cur_cmd<>p then b:=false -else if cur_cmd<call then b:=(cur_chr=q) -else @<Test if two macro texts match@>; -scanner_status:=save_scanner_status; -end - -@ Note also that `\.{\\ifx}' decides that macros \.{\\a} and \.{\\b} are -different in examples like this: -$$\vbox{\halign{\.{#}\hfil&\qquad\.{#}\hfil\cr - {}\\def\\a\{\\c\}& - {}\\def\\c\{\}\cr - {}\\def\\b\{\\d\}& - {}\\def\\d\{\}\cr}}$$ - -@<Test if two macro texts match@>= -begin p:=link(cur_chr); q:=link(equiv(n)); {omit reference counts} -if p=q then b:=true -else begin while (p<>null)and(q<>null) do - if info(p)<>info(q) then p:=null - else begin p:=link(p); q:=link(q); - end; - b:=((p=null)and(q=null)); - end; -end - -@ @<Select the appropriate case and |return| or |goto common_ending|@>= -begin scan_int; n:=cur_val; {|n| is the number of cases to pass} -if tracing_commands>1 then - begin begin_diagnostic; print("{case "); print_int(n); print_char("}"); - end_diagnostic(false); - end; -while n<>0 do - begin pass_text; - if cond_ptr=save_cond_ptr then - if cur_chr=or_code then decr(n) - else goto common_ending - else if cur_chr=fi_code then @<Pop the condition stack@>; - end; -change_if_limit(or_code,save_cond_ptr); -return; {wait for \.{\\or}, \.{\\else}, or \.{\\fi}} -end - -@ The processing of conditionals is complete except for the following -code, which is actually part of |expand|. It comes into play when -\.{\\or}, \.{\\else}, or \.{\\fi} is scanned. - -@<Terminate the current conditional and skip to \.{\\fi}@>= -if cur_chr>if_limit then - if if_limit=if_code then insert_relax {condition not yet evaluated} - else begin print_err("Extra "); print_cmd_chr(fi_or_else,cur_chr); -@.Extra \\or@> -@.Extra \\else@> -@.Extra \\fi@> - help1("I'm ignoring this; it doesn't match any \if."); - error; - end -else begin while cur_chr<>fi_code do pass_text; {skip to \.{\\fi}} - @<Pop the condition stack@>; - end - -@* \[29] File names. -It's time now to fret about file names. Besides the fact that different -operating systems treat files in different ways, we must cope with the -fact that completely different naming conventions are used by different -groups of people. The following programs show what is required for one -particular operating system; similar routines for other systems are not -difficult to devise. -@^fingers@> -@^system dependencies@> - -\TeX\ assumes that a file name has three parts: the name proper; its -``extension''; and a ``file area'' where it is found in an external file -system. The extension of an input file or a write file is assumed to be -`\.{.tex}' unless otherwise specified; it is `\.{.log}' on the -transcript file that records each run of \TeX; it is `\.{.tfm}' on the font -metric files that describe characters in the fonts \TeX\ uses; it is -`\.{.dvi}' on the output files that specify typesetting information; and it -is `\.{.fmt}' on the format files written by \.{INITEX} to initialize \TeX. -The file area can be arbitrary on input files, but files are usually -output to the user's current area. If an input file cannot be -found on the specified area, \TeX\ will look for it on a special system -area; this special area is intended for commonly used input files like -\.{webmac.tex}. - -Simple uses of \TeX\ refer only to file names that have no explicit -extension or area. For example, a person usually says `\.{\\input} \.{paper}' -or `\.{\\font\\tenrm} \.= \.{helvetica}' instead of `\.{\\input} -\.{paper.new}' or `\.{\\font\\tenrm} \.= \.{<csd.knuth>test}'. Simple file -names are best, because they make the \TeX\ source files portable; -whenever a file name consists entirely of letters and digits, it should be -treated in the same way by all implementations of \TeX. However, users -need the ability to refer to other files in their environment, especially -when responding to error messages concerning unopenable files; therefore -we want to let them use the syntax that appears in their favorite -operating system. - -The following procedures don't allow spaces to be part of -file names; but some users seem to like names that are spaced-out. -System-dependent changes to allow such things should probably -be made with reluctance, and only when an entire file name that -includes spaces is ``quoted'' somehow. - -@ In order to isolate the system-dependent aspects of file names, the -@^system dependencies@> -system-independent parts of \TeX\ are expressed in terms -of three system-dependent -procedures called |begin_name|, |more_name|, and |end_name|. In -essence, if the user-specified characters of the file name are $c_1\ldots c_n$, -the system-independent driver program does the operations -$$|begin_name|;\,|more_name|(c_1);\,\ldots\,;\,|more_name|(c_n); -\,|end_name|.$$ -These three procedures communicate with each other via global variables. -Afterwards the file name will appear in the string pool as three strings -called |cur_name|\penalty10000\hskip-.05em, -|cur_area|, and |cur_ext|; the latter two are null (i.e., -|""|), unless they were explicitly specified by the user. - -Actually the situation is slightly more complicated, because \TeX\ needs -to know when the file name ends. The |more_name| routine is a function -(with side effects) that returns |true| on the calls |more_name|$(c_1)$, -\dots, |more_name|$(c_{n-1})$. The final call |more_name|$(c_n)$ -returns |false|; or, it returns |true| and the token following $c_n$ is -something like `\.{\\hbox}' (i.e., not a character). In other words, -|more_name| is supposed to return |true| unless it is sure that the -file name has been completely scanned; and |end_name| is supposed to be able -to finish the assembly of |cur_name|, |cur_area|, and |cur_ext| regardless of -whether $|more_name|(c_n)$ returned |true| or |false|. - -@<Glob...@>= -@!cur_name:str_number; {name of file just scanned} -@!cur_area:str_number; {file area just scanned, or \.{""}} -@!cur_ext:str_number; {file extension just scanned, or \.{""}} - -@ The file names we shall deal with for illustrative purposes have the -following structure: If the name contains `\.>' or `\.:', the file area -consists of all characters up to and including the final such character; -otherwise the file area is null. If the remaining file name contains -`\..', the file extension consists of all such characters from the first -remaining `\..' to the end, otherwise the file extension is null. -@^system dependencies@> - -We can scan such file names easily by using two global variables that keep track -of the occurrences of area and extension delimiters: - -@<Glob...@>= -@!area_delimiter:pool_pointer; {the most recent `\.>' or `\.:', if any} -@!ext_delimiter:pool_pointer; {the relevant `\..', if any} - -@ Input files that can't be found in the user's area may appear in a standard -system area called |TEX_area|. Font metric files whose areas are not given -explicitly are assumed to appear in a standard system area called -|TEX_font_area|. These system area names will, of course, vary from place -to place. -@^system dependencies@> - -@d TEX_area=="TeXinputs:" -@.TeXinputs@> -@d TEX_font_area=="TeXfonts:" -@.TeXfonts@> - -@ Here now is the first of the system-dependent routines for file name scanning. -@^system dependencies@> - -@p procedure begin_name; -begin area_delimiter:=0; ext_delimiter:=0; -end; - -@ And here's the second. The string pool might change as the file name is -being scanned, since a new \.{\\csname} might be entered; therefore we keep -|area_delimiter| and |ext_delimiter| relative to the beginning of the current -string, instead of assigning an absolute address like |pool_ptr| to them. -@^system dependencies@> - -@p function more_name(@!c:ASCII_code):boolean; -begin if c=" " then more_name:=false -else begin str_room(1); append_char(c); {contribute |c| to the current string} - if (c=">")or(c=":") then - begin area_delimiter:=cur_length; ext_delimiter:=0; - end - else if (c=".")and(ext_delimiter=0) then ext_delimiter:=cur_length; - more_name:=true; - end; -end; - -@ The third. -@^system dependencies@> - -@p procedure end_name; -begin if str_ptr+3>max_strings then - overflow("number of strings",max_strings-init_str_ptr); -@:TeX capacity exceeded number of strings}{\quad number of strings@> -if area_delimiter=0 then cur_area:="" -else begin cur_area:=str_ptr; - str_start[str_ptr+1]:=str_start[str_ptr]+area_delimiter; incr(str_ptr); - end; -if ext_delimiter=0 then - begin cur_ext:=""; cur_name:=make_string; - end -else begin cur_name:=str_ptr; - str_start[str_ptr+1]:=str_start[str_ptr]+ext_delimiter-area_delimiter-1; - incr(str_ptr); cur_ext:=make_string; - end; -end; - -@ Conversely, here is a routine that takes three strings and prints a file -name that might have produced them. (The routine is system dependent, because -some operating systems put the file area last instead of first.) -@^system dependencies@> - -@<Basic printing...@>= -procedure print_file_name(@!n,@!a,@!e:integer); -begin slow_print(a); slow_print(n); slow_print(e); -end; - -@ Another system-dependent routine is needed to convert three internal -\TeX\ strings -into the |name_of_file| value that is used to open files. The present code -allows both lowercase and uppercase letters in the file name. -@^system dependencies@> - -@d append_to_name(#)==begin c:=#; incr(k); - if k<=file_name_size then name_of_file[k]:=xchr[c]; - end - -@p procedure pack_file_name(@!n,@!a,@!e:str_number); -var k:integer; {number of positions filled in |name_of_file|} -@!c: ASCII_code; {character being packed} -@!j:pool_pointer; {index into |str_pool|} -begin k:=0; -for j:=str_start[a] to str_start[a+1]-1 do append_to_name(so(str_pool[j])); -for j:=str_start[n] to str_start[n+1]-1 do append_to_name(so(str_pool[j])); -for j:=str_start[e] to str_start[e+1]-1 do append_to_name(so(str_pool[j])); -if k<=file_name_size then name_length:=k@+else name_length:=file_name_size; -for k:=name_length+1 to file_name_size do name_of_file[k]:=' '; -end; - -@ A messier routine is also needed, since format file names must be scanned -before \TeX's string mechanism has been initialized. We shall use the -global variable |TEX_format_default| to supply the text for default system areas -and extensions related to format files. -@^system dependencies@> - -@d format_default_length=20 {length of the |TEX_format_default| string} -@d format_area_length=11 {length of its area part} -@d format_ext_length=4 {length of its `\.{.fmt}' part} -@d format_extension=".fmt" {the extension, as a \.{WEB} constant} - -@<Glob...@>= -@!TEX_format_default:packed array[1..format_default_length] of char; - -@ @<Set init...@>= -TEX_format_default:='TeXformats:plain.fmt'; -@.TeXformats@> -@.plain@> -@^system dependencies@> - -@ @<Check the ``constant'' values for consistency@>= -if format_default_length>file_name_size then bad:=31; - -@ Here is the messy routine that was just mentioned. It sets |name_of_file| -from the first |n| characters of |TEX_format_default|, followed by -|buffer[a..b]|, followed by the last |format_ext_length| characters of -|TEX_format_default|. - -We dare not give error messages here, since \TeX\ calls this routine before -the |error| routine is ready to roll. Instead, we simply drop excess characters, -since the error will be detected in another way when a strange file name -isn't found. -@^system dependencies@> - -@p procedure pack_buffered_name(@!n:small_number;@!a,@!b:integer); -var k:integer; {number of positions filled in |name_of_file|} -@!c: ASCII_code; {character being packed} -@!j:integer; {index into |buffer| or |TEX_format_default|} -begin if n+b-a+1+format_ext_length>file_name_size then - b:=a+file_name_size-n-1-format_ext_length; -k:=0; -for j:=1 to n do append_to_name(xord[TEX_format_default[j]]); -for j:=a to b do append_to_name(buffer[j]); -for j:=format_default_length-format_ext_length+1 to format_default_length do - append_to_name(xord[TEX_format_default[j]]); -if k<=file_name_size then name_length:=k@+else name_length:=file_name_size; -for k:=name_length+1 to file_name_size do name_of_file[k]:=' '; -end; - -@ Here is the only place we use |pack_buffered_name|. This part of the program -becomes active when a ``virgin'' \TeX\ is trying to get going, just after -the preliminary initialization, or when the user is substituting another -format file by typing `\.\&' after the initial `\.{**}' prompt. The buffer -contains the first line of input in |buffer[loc..(last-1)]|, where -|loc<last| and |buffer[loc]<>" "|. - -@<Declare the function called |open_fmt_file|@>= -function open_fmt_file:boolean; -label found,exit; -var j:0..buf_size; {the first space after the format file name} -begin j:=loc; -if buffer[loc]="&" then - begin incr(loc); j:=loc; buffer[last]:=" "; - while buffer[j]<>" " do incr(j); - pack_buffered_name(0,loc,j-1); {try first without the system file area} - if w_open_in(fmt_file) then goto found; - pack_buffered_name(format_area_length,loc,j-1); - {now try the system format file area} - if w_open_in(fmt_file) then goto found; - wake_up_terminal; - wterm_ln('Sorry, I can''t find that format;',' will try PLAIN.'); -@.Sorry, I can't find...@> - update_terminal; - end; - {now pull out all the stops: try for the system \.{plain} file} -pack_buffered_name(format_default_length-format_ext_length,1,0); -if not w_open_in(fmt_file) then - begin wake_up_terminal; - wterm_ln('I can''t find the PLAIN format file!'); -@.I can't find PLAIN...@> -@.plain@> - open_fmt_file:=false; return; - end; -found:loc:=j; open_fmt_file:=true; -exit:end; - -@ Operating systems often make it possible to determine the exact name (and -possible version number) of a file that has been opened. The following routine, -which simply makes a \TeX\ string from the value of |name_of_file|, should -ideally be changed to deduce the full name of file~|f|, which is the file -most recently opened, if it is possible to do this in a \PASCAL\ program. -@^system dependencies@> - -This routine might be called after string memory has overflowed, hence -we dare not use `|str_room|'. - -@p function make_name_string:str_number; -var k:1..file_name_size; {index into |name_of_file|} -begin if (pool_ptr+name_length>pool_size)or(str_ptr=max_strings)or - (cur_length>0) then - make_name_string:="?" -else begin for k:=1 to name_length do append_char(xord[name_of_file[k]]); - make_name_string:=make_string; - end; -end; -function a_make_name_string(var f:alpha_file):str_number; -begin a_make_name_string:=make_name_string; -end; -function b_make_name_string(var f:byte_file):str_number; -begin b_make_name_string:=make_name_string; -end; -function w_make_name_string(var f:word_file):str_number; -begin w_make_name_string:=make_name_string; -end; - -@ Now let's consider the ``driver'' -routines by which \TeX\ deals with file names -in a system-independent manner. First comes a procedure that looks for a -file name in the input by calling |get_x_token| for the information. - -@p procedure scan_file_name; -label done; -begin name_in_progress:=true; begin_name; -@<Get the next non-blank non-call...@>; -loop@+begin if (cur_cmd>other_char)or(cur_chr>255) then {not a character} - begin back_input; goto done; - end; - if not more_name(cur_chr) then goto done; - get_x_token; - end; -done: end_name; name_in_progress:=false; -end; - -@ The global variable |name_in_progress| is used to prevent recursive -use of |scan_file_name|, since the |begin_name| and other procedures -communicate via global variables. Recursion would arise only by -devious tricks like `\.{\\input\\input f}'; such attempts at sabotage -must be thwarted. Furthermore, |name_in_progress| prevents \.{\\input} -@^recursion@> -from being initiated when a font size specification is being scanned. - -Another global variable, |job_name|, contains the file name that was first -\.{\\input} by the user. This name is extended by `\.{.log}' and `\.{.dvi}' -and `\.{.fmt}' in the names of \TeX's output files. - -@<Glob...@>= -@!name_in_progress:boolean; {is a file name being scanned?} -@!job_name:str_number; {principal file name} -@!log_opened:boolean; {has the transcript file been opened?} - -@ Initially |job_name=0|; it becomes nonzero as soon as the true name is known. -We have |job_name=0| if and only if the `\.{log}' file has not been opened, -except of course for a short time just after |job_name| has become nonzero. - -@<Initialize the output...@>= -job_name:=0; name_in_progress:=false; log_opened:=false; - -@ Here is a routine that manufactures the output file names, assuming that -|job_name<>0|. It ignores and changes the current settings of |cur_area| -and |cur_ext|. - -@d pack_cur_name==pack_file_name(cur_name,cur_area,cur_ext) - -@p procedure pack_job_name(@!s:str_number); {|s = ".log"|, |".dvi"|, or - |format_extension|} -begin cur_area:=""; cur_ext:=s; -cur_name:=job_name; pack_cur_name; -end; - -@ If some trouble arises when \TeX\ tries to open a file, the following -routine calls upon the user to supply another file name. Parameter~|s| -is used in the error message to identify the type of file; parameter~|e| -is the default extension if none is given. Upon exit from the routine, -variables |cur_name|, |cur_area|, |cur_ext|, and |name_of_file| are -ready for another attempt at file opening. - -@p procedure prompt_file_name(@!s,@!e:str_number); -label done; -var k:0..buf_size; {index into |buffer|} -begin if interaction=scroll_mode then wake_up_terminal; -if s="input file name" then print_err("I can't find file `") -@.I can't find file x@> -else print_err("I can't write on file `"); -@.I can't write on file x@> -print_file_name(cur_name,cur_area,cur_ext); print("'."); -if e=".tex" then show_context; -print_nl("Please type another "); print(s); -@.Please type...@> -if interaction<scroll_mode then - fatal_error("*** (job aborted, file error in nonstop mode)"); -@.job aborted, file error...@> -clear_terminal; prompt_input(": "); @<Scan file name in the buffer@>; -if cur_ext="" then cur_ext:=e; -pack_cur_name; -end; - -@ @<Scan file name in the buffer@>= -begin begin_name; k:=first; -while (buffer[k]=" ")and(k<last) do incr(k); -loop@+ begin if k=last then goto done; - if not more_name(buffer[k]) then goto done; - incr(k); - end; -done:end_name; -end - -@ Here's an example of how these conventions are used. Whenever it is time to -ship out a box of stuff, we shall use the macro |ensure_dvi_open|. - -@d ensure_dvi_open==if output_file_name=0 then - begin if job_name=0 then open_log_file; - pack_job_name(".dvi"); - while not b_open_out(dvi_file) do - prompt_file_name("file name for output",".dvi"); - output_file_name:=b_make_name_string(dvi_file); - end - -@<Glob...@>= -@!dvi_file: byte_file; {the device-independent output goes here} -@!output_file_name: str_number; {full name of the output file} -@!log_name:str_number; {full name of the log file} - -@ @<Initialize the output...@>=output_file_name:=0; - -@ The |open_log_file| routine is used to open the transcript file and to help -it catch up to what has previously been printed on the terminal. - -@p procedure open_log_file; -var old_setting:0..max_selector; {previous |selector| setting} -@!k:0..buf_size; {index into |months| and |buffer|} -@!l:0..buf_size; {end of first input line} -@!months:packed array [1..36] of char; {abbreviations of month names} -begin old_setting:=selector; -if job_name=0 then job_name:="texput"; -@.texput@> -pack_job_name(".log"); -while not a_open_out(log_file) do @<Try to get a different log file name@>; -log_name:=a_make_name_string(log_file); -selector:=log_only; log_opened:=true; -@<Print the banner line, including the date and time@>; -input_stack[input_ptr]:=cur_input; {make sure bottom level is in memory} -print_nl("**"); -@.**@> -l:=input_stack[0].limit_field; {last position of first line} -if buffer[l]=end_line_char then decr(l); -for k:=1 to l do print(buffer[k]); -print_ln; {now the transcript file contains the first line of input} -selector:=old_setting+2; {|log_only| or |term_and_log|} -end; - -@ Sometimes |open_log_file| is called at awkward moments when \TeX\ is -unable to print error messages or even to |show_context|. -The |prompt_file_name| routine can result in a |fatal_error|, but the |error| -routine will not be invoked because |log_opened| will be false. - -The normal idea of |batch_mode| is that nothing at all should be written -on the terminal. However, in the unusual case that -no log file could be opened, we make an exception and allow -an explanatory message to be seen. - -Incidentally, the program always refers to the log file as a `\.{transcript -file}', because some systems cannot use the extension `\.{.log}' for -this file. - -@<Try to get a different log file name@>= -begin selector:=term_only; -prompt_file_name("transcript file name",".log"); -end - -@ @<Print the banner...@>= -begin wlog(banner); -slow_print(format_ident); print(" "); -print_int(sys_day); print_char(" "); -months:='JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC'; -for k:=3*sys_month-2 to 3*sys_month do wlog(months[k]); -print_char(" "); print_int(sys_year); print_char(" "); -print_two(sys_time div 60); print_char(":"); print_two(sys_time mod 60); -end - -@ Let's turn now to the procedure that is used to initiate file reading -when an `\.{\\input}' command is being processed. -Beware: For historic reasons, this code foolishly conserves a tiny bit -of string pool space; but that can confuse the interactive `\.E' option. -@^system dependencies@> - -@p procedure start_input; {\TeX\ will \.{\\input} something} -label done; -begin scan_file_name; {set |cur_name| to desired file name} -if cur_ext="" then cur_ext:=".tex"; -pack_cur_name; -loop@+ begin begin_file_reading; {set up |cur_file| and new level of input} - if a_open_in(cur_file) then goto done; - if cur_area="" then - begin pack_file_name(cur_name,TEX_area,cur_ext); - if a_open_in(cur_file) then goto done; - end; - end_file_reading; {remove the level that didn't work} - prompt_file_name("input file name",".tex"); - end; -done: name:=a_make_name_string(cur_file); -if job_name=0 then - begin job_name:=cur_name; open_log_file; - end; {|open_log_file| doesn't |show_context|, so |limit| - and |loc| needn't be set to meaningful values yet} -if term_offset+length(name)>max_print_line-2 then print_ln -else if (term_offset>0)or(file_offset>0) then print_char(" "); -print_char("("); incr(open_parens); slow_print(name); update_terminal; -state:=new_line; -if name=str_ptr-1 then {conserve string pool space (but see note above)} - begin flush_string; name:=cur_name; - end; -@<Read the first line of the new file@>; -end; - -@ Here we have to remember to tell the |input_ln| routine not to -start with a |get|. If the file is empty, it is considered to -contain a single blank line. -@^system dependencies@> -@^empty line at end of file@> - -@<Read the first line...@>= -begin line:=1; -if input_ln(cur_file,false) then do_nothing; -firm_up_the_line; -if end_line_char_inactive then decr(limit) -else buffer[limit]:=end_line_char; -first:=limit+1; loc:=start; -end - -@* \[30] Font metric data. -\TeX\ gets its knowledge about fonts from font metric files, also called -\.{TFM} files; the `\.T' in `\.{TFM}' stands for \TeX, -but other programs know about them too. -@:TFM files}{\.{TFM} files@> -@^font metric files@> - -The information in a \.{TFM} file appears in a sequence of 8-bit bytes. -Since the number of bytes is always a multiple of 4, we could -also regard the file as a sequence of 32-bit words, but \TeX\ uses the -byte interpretation. The format of \.{TFM} files was designed by -Lyle Ramshaw in 1980. The intent is to convey a lot of different kinds -@^Ramshaw, Lyle Harold@> -of information in a compact but useful form. - -@<Glob...@>= -@!tfm_file:byte_file; - -@ The first 24 bytes (6 words) of a \.{TFM} file contain twelve 16-bit -integers that give the lengths of the various subsequent portions -of the file. These twelve integers are, in order: -$$\vbox{\halign{\hfil#&$\null=\null$#\hfil\cr -|lf|&length of the entire file, in words;\cr -|lh|&length of the header data, in words;\cr -|bc|&smallest character code in the font;\cr -|ec|&largest character code in the font;\cr -|nw|&number of words in the width table;\cr -|nh|&number of words in the height table;\cr -|nd|&number of words in the depth table;\cr -|ni|&number of words in the italic correction table;\cr -|nl|&number of words in the lig/kern table;\cr -|nk|&number of words in the kern table;\cr -|ne|&number of words in the extensible character table;\cr -|np|&number of font parameter words.\cr}}$$ -They are all nonnegative and less than $2^{15}$. We must have |bc-1<=ec<=255|, -and -$$\hbox{|lf=6+lh+(ec-bc+1)+nw+nh+nd+ni+nl+nk+ne+np|.}$$ -Note that a font may contain as many as 256 characters (if |bc=0| and |ec=255|), -and as few as 0 characters (if |bc=ec+1|). - -Incidentally, when two or more 8-bit bytes are combined to form an integer of -16 or more bits, the most significant bytes appear first in the file. -This is called BigEndian order. -@!@^BigEndian order@> - -@ The rest of the \.{TFM} file may be regarded as a sequence of ten data -arrays having the informal specification -$$\def\arr$[#1]#2${\&{array} $[#1]$ \&{of} #2} -\vbox{\halign{\hfil\\{#}&$\,:\,$\arr#\hfil\cr -header&|[0..lh-1]@t\\{stuff}@>|\cr -char\_info&|[bc..ec]char_info_word|\cr -width&|[0..nw-1]fix_word|\cr -height&|[0..nh-1]fix_word|\cr -depth&|[0..nd-1]fix_word|\cr -italic&|[0..ni-1]fix_word|\cr -lig\_kern&|[0..nl-1]lig_kern_command|\cr -kern&|[0..nk-1]fix_word|\cr -exten&|[0..ne-1]extensible_recipe|\cr -param&|[1..np]fix_word|\cr}}$$ -The most important data type used here is a |@!fix_word|, which is -a 32-bit representation of a binary fraction. A |fix_word| is a signed -quantity, with the two's complement of the entire word used to represent -negation. Of the 32 bits in a |fix_word|, exactly 12 are to the left of the -binary point; thus, the largest |fix_word| value is $2048-2^{-20}$, and -the smallest is $-2048$. We will see below, however, that all but two of -the |fix_word| values must lie between $-16$ and $+16$. - -@ The first data array is a block of header information, which contains -general facts about the font. The header must contain at least two words, -|header[0]| and |header[1]|, whose meaning is explained below. -Additional header information of use to other software routines might -also be included, but \TeX82 does not need to know about such details. -For example, 16 more words of header information are in use at the Xerox -Palo Alto Research Center; the first ten specify the character coding -scheme used (e.g., `\.{XEROX text}' or `\.{TeX math symbols}'), the next five -give the font identifier (e.g., `\.{HELVETICA}' or `\.{CMSY}'), and the -last gives the ``face byte.'' The program that converts \.{DVI} files -to Xerox printing format gets this information by looking at the \.{TFM} -file, which it needs to read anyway because of other information that -is not explicitly repeated in \.{DVI}~format. - -\yskip\hang|header[0]| is a 32-bit check sum that \TeX\ will copy into -the \.{DVI} output file. Later on when the \.{DVI} file is printed, -possibly on another computer, the actual font that gets used is supposed -to have a check sum that agrees with the one in the \.{TFM} file used by -\TeX. In this way, users will be warned about potential incompatibilities. -(However, if the check sum is zero in either the font file or the \.{TFM} -file, no check is made.) The actual relation between this check sum and -the rest of the \.{TFM} file is not important; the check sum is simply an -identification number with the property that incompatible fonts almost -always have distinct check sums. -@^check sum@> - -\yskip\hang|header[1]| is a |fix_word| containing the design size of -the font, in units of \TeX\ points. This number must be at least 1.0; it is -fairly arbitrary, but usually the design size is 10.0 for a ``10 point'' -font, i.e., a font that was designed to look best at a 10-point size, -whatever that really means. When a \TeX\ user asks for a font -`\.{at} $\delta$ \.{pt}', the effect is to override the design size -and replace it by $\delta$, and to multiply the $x$ and~$y$ coordinates -of the points in the font image by a factor of $\delta$ divided by the -design size. {\sl All other dimensions in the\/ \.{TFM} file are -|fix_word|\kern-1pt\ numbers in design-size units}, with the exception of -|param[1]| (which denotes the slant ratio). Thus, for example, the value -of |param[6]|, which defines the \.{em} unit, is often the |fix_word| value -$2^{20}=1.0$, since many fonts have a design size equal to one em. -The other dimensions must be less than 16 design-size units in absolute -value; thus, |header[1]| and |param[1]| are the only |fix_word| -entries in the whole \.{TFM} file whose first byte might be something -besides 0 or 255. - -@ Next comes the |char_info| array, which contains one |@!char_info_word| -per character. Each word in this part of the file contains six fields -packed into four bytes as follows. - -\yskip\hang first byte: |@!width_index| (8 bits)\par -\hang second byte: |@!height_index| (4 bits) times 16, plus |@!depth_index| - (4~bits)\par -\hang third byte: |@!italic_index| (6 bits) times 4, plus |@!tag| - (2~bits)\par -\hang fourth byte: |@!remainder| (8 bits)\par -\yskip\noindent -The actual width of a character is \\{width}|[width_index]|, in design-size -units; this is a device for compressing information, since many characters -have the same width. Since it is quite common for many characters -to have the same height, depth, or italic correction, the \.{TFM} format -imposes a limit of 16 different heights, 16 different depths, and -64 different italic corrections. - -@!@^italic correction@> -The italic correction of a character has two different uses. -(a)~In ordinary text, the italic correction is added to the width only if -the \TeX\ user specifies `\.{\\/}' after the character. -(b)~In math formulas, the italic correction is always added to the width, -except with respect to the positioning of subscripts. - -Incidentally, the relation $\\{width}[0]=\\{height}[0]=\\{depth}[0]= -\\{italic}[0]=0$ should always hold, so that an index of zero implies a -value of zero. The |width_index| should never be zero unless the -character does not exist in the font, since a character is valid if and -only if it lies between |bc| and |ec| and has a nonzero |width_index|. - -@ The |tag| field in a |char_info_word| has four values that explain how to -interpret the |remainder| field. - -\yskip\hangg|tag=0| (|no_tag|) means that |remainder| is unused.\par -\hangg|tag=1| (|lig_tag|) means that this character has a ligature/kerning -program starting at position |remainder| in the |lig_kern| array.\par -\hangg|tag=2| (|list_tag|) means that this character is part of a chain of -characters of ascending sizes, and not the largest in the chain. The -|remainder| field gives the character code of the next larger character.\par -\hangg|tag=3| (|ext_tag|) means that this character code represents an -extensible character, i.e., a character that is built up of smaller pieces -so that it can be made arbitrarily large. The pieces are specified in -|@!exten[remainder]|.\par -\yskip\noindent -Characters with |tag=2| and |tag=3| are treated as characters with |tag=0| -unless they are used in special circumstances in math formulas. For example, -the \.{\\sum} operation looks for a |list_tag|, and the \.{\\left} -operation looks for both |list_tag| and |ext_tag|. - -@d no_tag=0 {vanilla character} -@d lig_tag=1 {character has a ligature/kerning program} -@d list_tag=2 {character has a successor in a charlist} -@d ext_tag=3 {character is extensible} - -@ The |lig_kern| array contains instructions in a simple programming language -that explains what to do for special letter pairs. Each word in this array is a -|@!lig_kern_command| of four bytes. - -\yskip\hang first byte: |skip_byte|, indicates that this is the final program - step if the byte is 128 or more, otherwise the next step is obtained by - skipping this number of intervening steps.\par -\hang second byte: |next_char|, ``if |next_char| follows the current character, - then perform the operation and stop, otherwise continue.''\par -\hang third byte: |op_byte|, indicates a ligature step if less than~128, - a kern step otherwise.\par -\hang fourth byte: |remainder|.\par -\yskip\noindent -In a kern step, an -additional space equal to |kern[256*(op_byte-128)+remainder]| is inserted -between the current character and |next_char|. This amount is -often negative, so that the characters are brought closer together -by kerning; but it might be positive. - -There are eight kinds of ligature steps, having |op_byte| codes $4a+2b+c$ where -$0\le a\le b+c$ and $0\le b,c\le1$. The character whose code is -|remainder| is inserted between the current character and |next_char|; -then the current character is deleted if $b=0$, and |next_char| is -deleted if $c=0$; then we pass over $a$~characters to reach the next -current character (which may have a ligature/kerning program of its own). - -If the very first instruction of the |lig_kern| array has |skip_byte=255|, -the |next_char| byte is the so-called boundary character of this font; -the value of |next_char| need not lie between |bc| and~|ec|. -If the very last instruction of the |lig_kern| array has |skip_byte=255|, -there is a special ligature/kerning program for a boundary character at the -left, beginning at location |256*op_byte+remainder|. -The interpretation is that \TeX\ puts implicit boundary characters -before and after each consecutive string of characters from the same font. -These implicit characters do not appear in the output, but they can affect -ligatures and kerning. - -If the very first instruction of a character's |lig_kern| program has -|skip_byte>128|, the program actually begins in location -|256*op_byte+remainder|. This feature allows access to large |lig_kern| -arrays, because the first instruction must otherwise -appear in a location |<=255|. - -Any instruction with |skip_byte>128| in the |lig_kern| array must satisfy -the condition -$$\hbox{|256*op_byte+remainder<nl|.}$$ -If such an instruction is encountered during -normal program execution, it denotes an unconditional halt; no ligature -or kerning command is performed. - -@d stop_flag==qi(128) {value indicating `\.{STOP}' in a lig/kern program} -@d kern_flag==qi(128) {op code for a kern step} -@d skip_byte(#)==#.b0 -@d next_char(#)==#.b1 -@d op_byte(#)==#.b2 -@d rem_byte(#)==#.b3 - -@ Extensible characters are specified by an |@!extensible_recipe|, which -consists of four bytes called |@!top|, |@!mid|, |@!bot|, and |@!rep| (in this -order). These bytes are the character codes of individual pieces used to -build up a large symbol. If |top|, |mid|, or |bot| are zero, they are not -present in the built-up result. For example, an extensible vertical line is -like an extensible bracket, except that the top and bottom pieces are missing. - -Let $T$, $M$, $B$, and $R$ denote the respective pieces, or an empty box -if the piece isn't present. Then the extensible characters have the form -$TR^kMR^kB$ from top to bottom, for some |k>=0|, unless $M$ is absent; -in the latter case we can have $TR^kB$ for both even and odd values of~|k|. -The width of the extensible character is the width of $R$; and the -height-plus-depth is the sum of the individual height-plus-depths of the -components used, since the pieces are butted together in a vertical list. - -@d ext_top(#)==#.b0 {|top| piece in a recipe} -@d ext_mid(#)==#.b1 {|mid| piece in a recipe} -@d ext_bot(#)==#.b2 {|bot| piece in a recipe} -@d ext_rep(#)==#.b3 {|rep| piece in a recipe} - -@ The final portion of a \.{TFM} file is the |param| array, which is another -sequence of |fix_word| values. - -\yskip\hang|param[1]=slant| is the amount of italic slant, which is used -to help position accents. For example, |slant=.25| means that when you go -up one unit, you also go .25 units to the right. The |slant| is a pure -number; it's the only |fix_word| other than the design size itself that is -not scaled by the design size. - -\hang|param[2]=space| is the normal spacing between words in text. -Note that character |" "| in the font need not have anything to do with -blank spaces. - -\hang|param[3]=space_stretch| is the amount of glue stretching between words. - -\hang|param[4]=space_shrink| is the amount of glue shrinking between words. - -\hang|param[5]=x_height| is the size of one ex in the font; it is also -the height of letters for which accents don't have to be raised or lowered. - -\hang|param[6]=quad| is the size of one em in the font. - -\hang|param[7]=extra_space| is the amount added to |param[2]| at the -ends of sentences. - -\yskip\noindent -If fewer than seven parameters are present, \TeX\ sets the missing parameters -to zero. Fonts used for math symbols are required to have -additional parameter information, which is explained later. - -@d slant_code=1 -@d space_code=2 -@d space_stretch_code=3 -@d space_shrink_code=4 -@d x_height_code=5 -@d quad_code=6 -@d extra_space_code=7 - -@ So that is what \.{TFM} files hold. Since \TeX\ has to absorb such information -about lots of fonts, it stores most of the data in a large array called -|font_info|. Each item of |font_info| is a |memory_word|; the |fix_word| -data gets converted into |scaled| entries, while everything else goes into -words of type |four_quarters|. - -When the user defines \.{\\font\\f}, say, \TeX\ assigns an internal number -to the user's font~\.{\\f}. Adding this number to |font_id_base| gives the -|eqtb| location of a ``frozen'' control sequence that will always select -the font. - -@<Types...@>= -@!internal_font_number=font_base..font_max; {|font| in a |char_node|} -@!font_index=0..font_mem_size; {index into |font_info|} - -@ Here now is the (rather formidable) array of font arrays. - -@d non_char==qi(256) {a |halfword| code that can't match a real character} -@d non_address=0 {a spurious |bchar_label|} - -@<Glob...@>= -@!font_info:array[font_index] of memory_word; - {the big collection of font data} -@!fmem_ptr:font_index; {first unused word of |font_info|} -@!font_ptr:internal_font_number; {largest internal font number in use} -@!font_check:array[internal_font_number] of four_quarters; {check sum} -@!font_size:array[internal_font_number] of scaled; {``at'' size} -@!font_dsize:array[internal_font_number] of scaled; {``design'' size} -@!font_params:array[internal_font_number] of font_index; {how many font - parameters are present} -@!font_name:array[internal_font_number] of str_number; {name of the font} -@!font_area:array[internal_font_number] of str_number; {area of the font} -@!font_bc:array[internal_font_number] of eight_bits; - {beginning (smallest) character code} -@!font_ec:array[internal_font_number] of eight_bits; - {ending (largest) character code} -@!font_glue:array[internal_font_number] of pointer; - {glue specification for interword space, |null| if not allocated} -@!font_used:array[internal_font_number] of boolean; - {has a character from this font actually appeared in the output?} -@!hyphen_char:array[internal_font_number] of integer; - {current \.{\\hyphenchar} values} -@!skew_char:array[internal_font_number] of integer; - {current \.{\\skewchar} values} -@!bchar_label:array[internal_font_number] of font_index; - {start of |lig_kern| program for left boundary character, - |non_address| if there is none} -@!font_bchar:array[internal_font_number] of min_quarterword..non_char; - {boundary character, |non_char| if there is none} -@!font_false_bchar:array[internal_font_number] of min_quarterword..non_char; - {|font_bchar| if it doesn't exist in the font, otherwise |non_char|} - -@ Besides the arrays just enumerated, we have directory arrays that make it -easy to get at the individual entries in |font_info|. For example, the -|char_info| data for character |c| in font |f| will be in -|font_info[char_base[f]+c].qqqq|; and if |w| is the |width_index| -part of this word (the |b0| field), the width of the character is -|font_info[width_base[f]+w].sc|. (These formulas assume that -|min_quarterword| has already been added to |c| and to |w|, since \TeX\ -stores its quarterwords that way.) - -@<Glob...@>= -@!char_base:array[internal_font_number] of integer; - {base addresses for |char_info|} -@!width_base:array[internal_font_number] of integer; - {base addresses for widths} -@!height_base:array[internal_font_number] of integer; - {base addresses for heights} -@!depth_base:array[internal_font_number] of integer; - {base addresses for depths} -@!italic_base:array[internal_font_number] of integer; - {base addresses for italic corrections} -@!lig_kern_base:array[internal_font_number] of integer; - {base addresses for ligature/kerning programs} -@!kern_base:array[internal_font_number] of integer; - {base addresses for kerns} -@!exten_base:array[internal_font_number] of integer; - {base addresses for extensible recipes} -@!param_base:array[internal_font_number] of integer; - {base addresses for font parameters} - -@ @<Set init...@>= -for k:=font_base to font_max do font_used[k]:=false; - -@ \TeX\ always knows at least one font, namely the null font. It has no -characters, and its seven parameters are all equal to zero. - -@<Initialize table...@>= -font_ptr:=null_font; fmem_ptr:=7; -font_name[null_font]:="nullfont"; font_area[null_font]:=""; -hyphen_char[null_font]:="-"; skew_char[null_font]:=-1; -bchar_label[null_font]:=non_address; -font_bchar[null_font]:=non_char; font_false_bchar[null_font]:=non_char; -font_bc[null_font]:=1; font_ec[null_font]:=0; -font_size[null_font]:=0; font_dsize[null_font]:=0; -char_base[null_font]:=0; width_base[null_font]:=0; -height_base[null_font]:=0; depth_base[null_font]:=0; -italic_base[null_font]:=0; lig_kern_base[null_font]:=0; -kern_base[null_font]:=0; exten_base[null_font]:=0; -font_glue[null_font]:=null; font_params[null_font]:=7; -param_base[null_font]:=-1; -for k:=0 to 6 do font_info[k].sc:=0; - -@ @<Put each...@>= -primitive("nullfont",set_font,null_font); -@!@:null_font_}{\.{\\nullfont} primitive@> -text(frozen_null_font):="nullfont"; eqtb[frozen_null_font]:=eqtb[cur_val]; - -@ Of course we want to define macros that suppress the detail of how font -information is actually packed, so that we don't have to write things like -$$\hbox{|font_info[width_base[f]+font_info[char_base[f]+c].qqqq.b0].sc|}$$ -too often. The \.{WEB} definitions here make |char_info(f)(c)| the -|four_quarters| word of font information corresponding to character -|c| of font |f|. If |q| is such a word, |char_width(f)(q)| will be -the character's width; hence the long formula above is at least -abbreviated to -$$\hbox{|char_width(f)(char_info(f)(c))|.}$$ -Usually, of course, we will fetch |q| first and look at several of its -fields at the same time. - -The italic correction of a character will be denoted by -|char_italic(f)(q)|, so it is analogous to |char_width|. But we will get -at the height and depth in a slightly different way, since we usually want -to compute both height and depth if we want either one. The value of -|height_depth(q)| will be the 8-bit quantity -$$b=|height_index|\times16+|depth_index|,$$ and if |b| is such a byte we -will write |char_height(f)(b)| and |char_depth(f)(b)| for the height and -depth of the character |c| for which |q=char_info(f)(c)|. Got that? - -The tag field will be called |char_tag(q)|; the remainder byte will be -called |rem_byte(q)|, using a macro that we have already defined above. - -Access to a character's |width|, |height|, |depth|, and |tag| fields is -part of \TeX's inner loop, so we want these macros to produce code that is -as fast as possible under the circumstances. -@^inner loop@> - -@d char_info_end(#)==#].qqqq -@d char_info(#)==font_info[char_base[#]+char_info_end -@d char_width_end(#)==#.b0].sc -@d char_width(#)==font_info[width_base[#]+char_width_end -@d char_exists(#)==(#.b0>min_quarterword) -@d char_italic_end(#)==(qo(#.b2)) div 4].sc -@d char_italic(#)==font_info[italic_base[#]+char_italic_end -@d height_depth(#)==qo(#.b1) -@d char_height_end(#)==(#) div 16].sc -@d char_height(#)==font_info[height_base[#]+char_height_end -@d char_depth_end(#)==(#) mod 16].sc -@d char_depth(#)==font_info[depth_base[#]+char_depth_end -@d char_tag(#)==((qo(#.b2)) mod 4) - -@ The global variable |null_character| is set up to be a word of -|char_info| for a character that doesn't exist. Such a word provides a -convenient way to deal with erroneous situations. - -@<Glob...@>= -@!null_character:four_quarters; {nonexistent character information} - -@ @<Set init...@>= -null_character.b0:=min_quarterword; null_character.b1:=min_quarterword; -null_character.b2:=min_quarterword; null_character.b3:=min_quarterword; - -@ Here are some macros that help process ligatures and kerns. -We write |char_kern(f)(j)| to find the amount of kerning specified by -kerning command~|j| in font~|f|. If |j| is the |char_info| for a character -with a ligature/kern program, the first instruction of that program is either -|i=font_info[lig_kern_start(f)(j)]| or |font_info[lig_kern_restart(f)(i)]|, -depending on whether or not |skip_byte(i)<=stop_flag|. - -The constant |kern_base_offset| should be simplified, for \PASCAL\ compilers -that do not do local optimization. -@^system dependencies@> - -@d char_kern_end(#)==256*op_byte(#)+rem_byte(#)].sc -@d char_kern(#)==font_info[kern_base[#]+char_kern_end -@d kern_base_offset==256*(128+min_quarterword) -@d lig_kern_start(#)==lig_kern_base[#]+rem_byte {beginning of lig/kern program} -@d lig_kern_restart_end(#)==256*op_byte(#)+rem_byte(#)+32768-kern_base_offset -@d lig_kern_restart(#)==lig_kern_base[#]+lig_kern_restart_end - -@ Font parameters are referred to as |slant(f)|, |space(f)|, etc. - -@d param_end(#)==param_base[#]].sc -@d param(#)==font_info[#+param_end -@d slant==param(slant_code) {slant to the right, per unit distance upward} -@d space==param(space_code) {normal space between words} -@d space_stretch==param(space_stretch_code) {stretch between words} -@d space_shrink==param(space_shrink_code) {shrink between words} -@d x_height==param(x_height_code) {one ex} -@d quad==param(quad_code) {one em} -@d extra_space==param(extra_space_code) {additional space at end of sentence} - -@<The em width for |cur_font|@>=quad(cur_font) - -@ @<The x-height for |cur_font|@>=x_height(cur_font) - -@ \TeX\ checks the information of a \.{TFM} file for validity as the -file is being read in, so that no further checks will be needed when -typesetting is going on. The somewhat tedious subroutine that does this -is called |read_font_info|. It has four parameters: the user font -identifier~|u|, the file name and area strings |nom| and |aire|, and the -``at'' size~|s|. If |s|~is negative, it's the negative of a scale factor -to be applied to the design size; |s=-1000| is the normal case. -Otherwise |s| will be substituted for the design size; in this -case, |s| must be positive and less than $2048\rm\,pt$ -(i.e., it must be less than $2^{27}$ when considered as an integer). - -The subroutine opens and closes a global file variable called |tfm_file|. -It returns the value of the internal font number that was just loaded. -If an error is detected, an error message is issued and no font -information is stored; |null_font| is returned in this case. - -@d bad_tfm=11 {label for |read_font_info|} -@d abort==goto bad_tfm {do this when the \.{TFM} data is wrong} - -@p function read_font_info(@!u:pointer;@!nom,@!aire:str_number; - @!s:scaled):internal_font_number; {input a \.{TFM} file} -label done,bad_tfm,not_found; -var k:font_index; {index into |font_info|} -@!file_opened:boolean; {was |tfm_file| successfully opened?} -@!lf,@!lh,@!bc,@!ec,@!nw,@!nh,@!nd,@!ni,@!nl,@!nk,@!ne,@!np:halfword; - {sizes of subfiles} -@!f:internal_font_number; {the new font's number} -@!g:internal_font_number; {the number to return} -@!a,@!b,@!c,@!d:eight_bits; {byte variables} -@!qw:four_quarters;@!sw:scaled; {accumulators} -@!bch_label:integer; {left boundary start location, or infinity} -@!bchar:0..256; {boundary character, or 256} -@!z:scaled; {the design size or the ``at'' size} -@!alpha:integer;@!beta:1..16; - {auxiliary quantities used in fixed-point multiplication} -begin g:=null_font;@/ -@<Read and check the font data; |abort| if the \.{TFM} file is - malformed; if there's no room for this font, say so and |goto - done|; otherwise |incr(font_ptr)| and |goto done|@>; -bad_tfm: @<Report that the font won't be loaded@>; -done: if file_opened then b_close(tfm_file); -read_font_info:=g; -end; - -@ There are programs called \.{TFtoPL} and \.{PLtoTF} that convert -between the \.{TFM} format and a symbolic property-list format -that can be easily edited. These programs contain extensive -diagnostic information, so \TeX\ does not have to bother giving -precise details about why it rejects a particular \.{TFM} file. -@.TFtoPL@> @.PLtoTF@> - -@d start_font_error_message==print_err("Font "); sprint_cs(u); - print_char("="); print_file_name(nom,aire,""); - if s>=0 then - begin print(" at "); print_scaled(s); print("pt"); - end - else if s<>-1000 then - begin print(" scaled "); print_int(-s); - end - -@<Report that the font won't be loaded@>= -start_font_error_message; -@.Font x=xx not loadable...@> -if file_opened then print(" not loadable: Bad metric (TFM) file") -else print(" not loadable: Metric (TFM) file not found"); -help5("I wasn't able to read the size data for this font,")@/ -("so I will ignore the font specification.")@/ -("[Wizards can fix TFM files using TFtoPL/PLtoTF.]")@/ -("You might try inserting a different font spec;")@/ -("e.g., type `I\font<same font id>=<substitute font name>'."); -error - -@ @<Read and check...@>= -@<Open |tfm_file| for input@>; -@<Read the {\.{TFM}} size fields@>; -@<Use size fields to allocate font information@>; -@<Read the {\.{TFM}} header@>; -@<Read character data@>; -@<Read box dimensions@>; -@<Read ligature/kern program@>; -@<Read extensible character recipes@>; -@<Read font parameters@>; -@<Make final adjustments and |goto done|@> - -@ @<Open |tfm_file| for input@>= -file_opened:=false; -if aire="" then pack_file_name(nom,TEX_font_area,".tfm") -else pack_file_name(nom,aire,".tfm"); -if not b_open_in(tfm_file) then abort; -file_opened:=true - -@ Note: A malformed \.{TFM} file might be shorter than it claims to be; -thus |eof(tfm_file)| might be true when |read_font_info| refers to -|tfm_file^| or when it says |get(tfm_file)|. If such circumstances -cause system error messages, you will have to defeat them somehow, -for example by defining |fget| to be `\ignorespaces|begin get(tfm_file);| -|if eof(tfm_file) then abort; end|\unskip'. -@^system dependencies@> - -@d fget==get(tfm_file) -@d fbyte==tfm_file^ -@d read_sixteen(#)==begin #:=fbyte; - if #>127 then abort; - fget; #:=#*@'400+fbyte; - end -@d store_four_quarters(#)==begin fget; a:=fbyte; qw.b0:=qi(a); - fget; b:=fbyte; qw.b1:=qi(b); - fget; c:=fbyte; qw.b2:=qi(c); - fget; d:=fbyte; qw.b3:=qi(d); - #:=qw; - end - -@ @<Read the {\.{TFM}} size fields@>= -begin read_sixteen(lf); -fget; read_sixteen(lh); -fget; read_sixteen(bc); -fget; read_sixteen(ec); -if (bc>ec+1)or(ec>255) then abort; -if bc>255 then {|bc=256| and |ec=255|} - begin bc:=1; ec:=0; - end; -fget; read_sixteen(nw); -fget; read_sixteen(nh); -fget; read_sixteen(nd); -fget; read_sixteen(ni); -fget; read_sixteen(nl); -fget; read_sixteen(nk); -fget; read_sixteen(ne); -fget; read_sixteen(np); -if lf<>6+lh+(ec-bc+1)+nw+nh+nd+ni+nl+nk+ne+np then abort; -if (nw=0)or(nh=0)or(nd=0)or(ni=0) then abort; -end - -@ The preliminary settings of the index-offset variables |char_base|, -|width_base|, |lig_kern_base|, |kern_base|, and |exten_base| will be -corrected later by subtracting |min_quarterword| from them; and we will -subtract 1 from |param_base| too. It's best to forget about such anomalies -until later. - -@<Use size fields to allocate font information@>= -lf:=lf-6-lh; {|lf| words should be loaded into |font_info|} -if np<7 then lf:=lf+7-np; {at least seven parameters will appear} -if (font_ptr=font_max)or(fmem_ptr+lf>font_mem_size) then - @<Apologize for not loading the font, |goto done|@>; -f:=font_ptr+1; -char_base[f]:=fmem_ptr-bc; -width_base[f]:=char_base[f]+ec+1; -height_base[f]:=width_base[f]+nw; -depth_base[f]:=height_base[f]+nh; -italic_base[f]:=depth_base[f]+nd; -lig_kern_base[f]:=italic_base[f]+ni; -kern_base[f]:=lig_kern_base[f]+nl-kern_base_offset; -exten_base[f]:=kern_base[f]+kern_base_offset+nk; -param_base[f]:=exten_base[f]+ne - -@ @<Apologize for not loading...@>= -begin start_font_error_message; -print(" not loaded: Not enough room left"); -@.Font x=xx not loaded...@> -help4("I'm afraid I won't be able to make use of this font,")@/ -("because my memory for character-size data is too small.")@/ -("If you're really stuck, ask a wizard to enlarge me.")@/ -("Or maybe try `I\font<same font id>=<name of loaded font>'."); -error; goto done; -end - -@ Only the first two words of the header are needed by \TeX82. - -@<Read the {\.{TFM}} header@>= -begin if lh<2 then abort; -store_four_quarters(font_check[f]); -fget; read_sixteen(z); {this rejects a negative design size} -fget; z:=z*@'400+fbyte; fget; z:=(z*@'20)+(fbyte div@'20); -if z<unity then abort; -while lh>2 do - begin fget;fget;fget;fget;decr(lh); {ignore the rest of the header} - end; -font_dsize[f]:=z; -if s<>-1000 then - if s>=0 then z:=s - else z:=xn_over_d(z,-s,1000); -font_size[f]:=z; -end - -@ @<Read character data@>= -for k:=fmem_ptr to width_base[f]-1 do - begin store_four_quarters(font_info[k].qqqq); - if (a>=nw)or(b div @'20>=nh)or(b mod @'20>=nd)or - (c div 4>=ni) then abort; - case c mod 4 of - lig_tag: if d>=nl then abort; - ext_tag: if d>=ne then abort; - list_tag: @<Check for charlist cycle@>; - othercases do_nothing {|no_tag|} - endcases; - end - -@ We want to make sure that there is no cycle of characters linked together -by |list_tag| entries, since such a cycle would get \TeX\ into an endless -loop. If such a cycle exists, the routine here detects it when processing -the largest character code in the cycle. - -@d check_byte_range(#)==begin if (#<bc)or(#>ec) then abort@+end -@d current_character_being_worked_on==k+bc-fmem_ptr - -@<Check for charlist cycle@>= -begin check_byte_range(d); -while d<current_character_being_worked_on do - begin qw:=char_info(f)(d); - {N.B.: not |qi(d)|, since |char_base[f]| hasn't been adjusted yet} - if char_tag(qw)<>list_tag then goto not_found; - d:=qo(rem_byte(qw)); {next character on the list} - end; -if d=current_character_being_worked_on then abort; {yes, there's a cycle} -not_found:end - -@ A |fix_word| whose four bytes are $(a,b,c,d)$ from left to right represents -the number -$$x=\left\{\vcenter{\halign{$#$,\hfil\qquad&if $#$\hfil\cr -b\cdot2^{-4}+c\cdot2^{-12}+d\cdot2^{-20}&a=0;\cr --16+b\cdot2^{-4}+c\cdot2^{-12}+d\cdot2^{-20}&a=255.\cr}}\right.$$ -(No other choices of |a| are allowed, since the magnitude of a number in -design-size units must be less than 16.) We want to multiply this -quantity by the integer~|z|, which is known to be less than $2^{27}$. -If $|z|<2^{23}$, the individual multiplications $b\cdot z$, -$c\cdot z$, $d\cdot z$ cannot overflow; otherwise we will divide |z| by 2, -4, 8, or 16, to obtain a multiplier less than $2^{23}$, and we can -compensate for this later. If |z| has thereby been replaced by -$|z|^\prime=|z|/2^e$, let $\beta=2^{4-e}$; we shall compute -$$\lfloor(b+c\cdot2^{-8}+d\cdot2^{-16})\,z^\prime/\beta\rfloor$$ -if $a=0$, or the same quantity minus $\alpha=2^{4+e}z^\prime$ if $a=255$. -This calculation must be done exactly, in order to guarantee portability -of \TeX\ between computers. - -@d store_scaled(#)==begin fget; a:=fbyte; fget; b:=fbyte; - fget; c:=fbyte; fget; d:=fbyte;@/ - sw:=(((((d*z)div@'400)+(c*z))div@'400)+(b*z))div beta; - if a=0 then #:=sw@+else if a=255 then #:=sw-alpha@+else abort; - end - -@<Read box dimensions@>= -begin @<Replace |z| by $|z|^\prime$ and compute $\alpha,\beta$@>; -for k:=width_base[f] to lig_kern_base[f]-1 do - store_scaled(font_info[k].sc); -if font_info[width_base[f]].sc<>0 then abort; {\\{width}[0] must be zero} -if font_info[height_base[f]].sc<>0 then abort; {\\{height}[0] must be zero} -if font_info[depth_base[f]].sc<>0 then abort; {\\{depth}[0] must be zero} -if font_info[italic_base[f]].sc<>0 then abort; {\\{italic}[0] must be zero} -end - -@ @<Replace |z|...@>= -begin alpha:=16; -while z>=@'40000000 do - begin z:=z div 2; alpha:=alpha+alpha; - end; -beta:=256 div alpha; alpha:=alpha*z; -end - -@ @d check_existence(#)==@t@>@;@/ - begin check_byte_range(#); - qw:=char_info(f)(#); {N.B.: not |qi(#)|} - if not char_exists(qw) then abort; - end - -@<Read ligature/kern program@>= -bch_label:=@'77777; bchar:=256; -if nl>0 then - begin for k:=lig_kern_base[f] to kern_base[f]+kern_base_offset-1 do - begin store_four_quarters(font_info[k].qqqq); - if a>128 then - begin if 256*c+d>=nl then abort; - if a=255 then if k=lig_kern_base[f] then bchar:=b; - end - else begin if b<>bchar then check_existence(b); - if c<128 then check_existence(d) {check ligature} - else if 256*(c-128)+d>=nk then abort; {check kern} - if a<128 then if k-lig_kern_base[f]+a+1>=nl then abort; - end; - end; - if a=255 then bch_label:=256*c+d; - end; -for k:=kern_base[f]+kern_base_offset to exten_base[f]-1 do - store_scaled(font_info[k].sc); - -@ @<Read extensible character recipes@>= -for k:=exten_base[f] to param_base[f]-1 do - begin store_four_quarters(font_info[k].qqqq); - if a<>0 then check_existence(a); - if b<>0 then check_existence(b); - if c<>0 then check_existence(c); - check_existence(d); - end - -@ We check to see that the \.{TFM} file doesn't end prematurely; but -no error message is given for files having more than |lf| words. - -@<Read font parameters@>= -begin for k:=1 to np do - if k=1 then {the |slant| parameter is a pure number} - begin fget; sw:=fbyte; if sw>127 then sw:=sw-256; - fget; sw:=sw*@'400+fbyte; fget; sw:=sw*@'400+fbyte; - fget; font_info[param_base[f]].sc:= - (sw*@'20)+(fbyte div@'20); - end - else store_scaled(font_info[param_base[f]+k-1].sc); -if eof(tfm_file) then abort; -for k:=np+1 to 7 do font_info[param_base[f]+k-1].sc:=0; -end - -@ Now to wrap it up, we have checked all the necessary things about the \.{TFM} -file, and all we need to do is put the finishing touches on the data for -the new font. - -@d adjust(#)==#[f]:=qo(#[f]) - {correct for the excess |min_quarterword| that was added} - -@<Make final adjustments...@>= -if np>=7 then font_params[f]:=np@+else font_params[f]:=7; -hyphen_char[f]:=default_hyphen_char; skew_char[f]:=default_skew_char; -if bch_label<nl then bchar_label[f]:=bch_label+lig_kern_base[f] -else bchar_label[f]:=non_address; -font_bchar[f]:=qi(bchar); -font_false_bchar[f]:=qi(bchar); -if bchar<=ec then if bchar>=bc then - begin qw:=char_info(f)(bchar); {N.B.: not |qi(bchar)|} - if char_exists(qw) then font_false_bchar[f]:=non_char; - end; -font_name[f]:=nom; -font_area[f]:=aire; -font_bc[f]:=bc; font_ec[f]:=ec; font_glue[f]:=null; -adjust(char_base); adjust(width_base); adjust(lig_kern_base); -adjust(kern_base); adjust(exten_base); -decr(param_base[f]); -fmem_ptr:=fmem_ptr+lf; font_ptr:=f; g:=f; goto done - -@ Before we forget about the format of these tables, let's deal with two -of \TeX's basic scanning routines related to font information. - -@<Declare procedures that scan font-related stuff@>= -procedure scan_font_ident; -var f:internal_font_number; -@!m:halfword; -begin @<Get the next non-blank non-call...@>; -if cur_cmd=def_font then f:=cur_font -else if cur_cmd=set_font then f:=cur_chr -else if cur_cmd=def_family then - begin m:=cur_chr; scan_four_bit_int; f:=equiv(m+cur_val); - end -else begin print_err("Missing font identifier"); -@.Missing font identifier@> - help2("I was looking for a control sequence whose")@/ - ("current meaning has been defined by \font."); - back_error; f:=null_font; - end; -cur_val:=f; -end; - -@ The following routine is used to implement `\.{\\fontdimen} |n| |f|'. -The boolean parameter |writing| is set |true| if the calling program -intends to change the parameter value. - -@<Declare procedures that scan font-related stuff@>= -procedure find_font_dimen(@!writing:boolean); - {sets |cur_val| to |font_info| location} -var f:internal_font_number; -@!n:integer; {the parameter number} -begin scan_int; n:=cur_val; scan_font_ident; f:=cur_val; -if n<=0 then cur_val:=fmem_ptr -else begin if writing and(n<=space_shrink_code)and@| - (n>=space_code)and(font_glue[f]<>null) then - begin delete_glue_ref(font_glue[f]); - font_glue[f]:=null; - end; - if n>font_params[f] then - if f<font_ptr then cur_val:=fmem_ptr - else @<Increase the number of parameters in the last font@> - else cur_val:=n+param_base[f]; - end; -@<Issue an error message if |cur_val=fmem_ptr|@>; -end; - -@ @<Issue an error message if |cur_val=fmem_ptr|@>= -if cur_val=fmem_ptr then - begin print_err("Font "); print_esc(font_id_text(f)); - print(" has only "); print_int(font_params[f]); - print(" fontdimen parameters"); -@.Font x has only...@> - help2("To increase the number of font parameters, you must")@/ - ("use \fontdimen immediately after the \font is loaded."); - error; - end - -@ @<Increase the number of parameters...@>= -begin repeat if fmem_ptr=font_mem_size then - overflow("font memory",font_mem_size); -@:TeX capacity exceeded font memory}{\quad font memory@> -font_info[fmem_ptr].sc:=0; incr(fmem_ptr); incr(font_params[f]); -until n=font_params[f]; -cur_val:=fmem_ptr-1; {this equals |param_base[f]+font_params[f]|} -end - -@ When \TeX\ wants to typeset a character that doesn't exist, the -character node is not created; thus the output routine can assume -that characters exist when it sees them. The following procedure -prints a warning message unless the user has suppressed it. - -@p procedure char_warning(@!f:internal_font_number;@!c:eight_bits); -begin if tracing_lost_chars>0 then - begin begin_diagnostic; - print_nl("Missing character: There is no "); -@.Missing character@> - print_ASCII(c); print(" in font "); - slow_print(font_name[f]); print_char("!"); end_diagnostic(false); - end; -end; - -@ Here is a function that returns a pointer to a character node for a -given character in a given font. If that character doesn't exist, -|null| is returned instead. - -@p function new_character(@!f:internal_font_number;@!c:eight_bits):pointer; -label exit; -var p:pointer; {newly allocated node} -begin if font_bc[f]<=c then if font_ec[f]>=c then - if char_exists(char_info(f)(qi(c))) then - begin p:=get_avail; font(p):=f; character(p):=qi(c); - new_character:=p; return; - end; -char_warning(f,c); -new_character:=null; -exit:end; - -@* \[31] Device-independent file format. -The most important output produced by a run of \TeX\ is the ``device -independent'' (\.{DVI}) file that specifies where characters and rules -are to appear on printed pages. The form of these files was designed by -David R. Fuchs in 1979. Almost any reasonable typesetting device can be -@^Fuchs, David Raymond@> -@:DVI_files}{\.{DVI} files@> -driven by a program that takes \.{DVI} files as input, and dozens of such -\.{DVI}-to-whatever programs have been written. Thus, it is possible to -print the output of \TeX\ on many different kinds of equipment, using \TeX\ -as a device-independent ``front end.'' - -A \.{DVI} file is a stream of 8-bit bytes, which may be regarded as a -series of commands in a machine-like language. The first byte of each command -is the operation code, and this code is followed by zero or more bytes -that provide parameters to the command. The parameters themselves may consist -of several consecutive bytes; for example, the `|set_rule|' command has two -parameters, each of which is four bytes long. Parameters are usually -regarded as nonnegative integers; but four-byte-long parameters, -and shorter parameters that denote distances, can be -either positive or negative. Such parameters are given in two's complement -notation. For example, a two-byte-long distance parameter has a value between -$-2^{15}$ and $2^{15}-1$. As in \.{TFM} files, numbers that occupy -more than one byte position appear in BigEndian order. - -A \.{DVI} file consists of a ``preamble,'' followed by a sequence of one -or more ``pages,'' followed by a ``postamble.'' The preamble is simply a -|pre| command, with its parameters that define the dimensions used in the -file; this must come first. Each ``page'' consists of a |bop| command, -followed by any number of other commands that tell where characters are to -be placed on a physical page, followed by an |eop| command. The pages -appear in the order that \TeX\ generated them. If we ignore |nop| commands -and \\{fnt\_def} commands (which are allowed between any two commands in -the file), each |eop| command is immediately followed by a |bop| command, -or by a |post| command; in the latter case, there are no more pages in the -file, and the remaining bytes form the postamble. Further details about -the postamble will be explained later. - -Some parameters in \.{DVI} commands are ``pointers.'' These are four-byte -quantities that give the location number of some other byte in the file; -the first byte is number~0, then comes number~1, and so on. For example, -one of the parameters of a |bop| command points to the previous |bop|; -this makes it feasible to read the pages in backwards order, in case the -results are being directed to a device that stacks its output face up. -Suppose the preamble of a \.{DVI} file occupies bytes 0 to 99. Now if the -first page occupies bytes 100 to 999, say, and if the second -page occupies bytes 1000 to 1999, then the |bop| that starts in byte 1000 -points to 100 and the |bop| that starts in byte 2000 points to 1000. (The -very first |bop|, i.e., the one starting in byte 100, has a pointer of~$-1$.) - -@ The \.{DVI} format is intended to be both compact and easily interpreted -by a machine. Compactness is achieved by making most of the information -implicit instead of explicit. When a \.{DVI}-reading program reads the -commands for a page, it keeps track of several quantities: (a)~The current -font |f| is an integer; this value is changed only -by \\{fnt} and \\{fnt\_num} commands. (b)~The current position on the page -is given by two numbers called the horizontal and vertical coordinates, -|h| and |v|. Both coordinates are zero at the upper left corner of the page; -moving to the right corresponds to increasing the horizontal coordinate, and -moving down corresponds to increasing the vertical coordinate. Thus, the -coordinates are essentially Cartesian, except that vertical directions are -flipped; the Cartesian version of |(h,v)| would be |(h,-v)|. (c)~The -current spacing amounts are given by four numbers |w|, |x|, |y|, and |z|, -where |w| and~|x| are used for horizontal spacing and where |y| and~|z| -are used for vertical spacing. (d)~There is a stack containing -|(h,v,w,x,y,z)| values; the \.{DVI} commands |push| and |pop| are used to -change the current level of operation. Note that the current font~|f| is -not pushed and popped; the stack contains only information about -positioning. - -The values of |h|, |v|, |w|, |x|, |y|, and |z| are signed integers having up -to 32 bits, including the sign. Since they represent physical distances, -there is a small unit of measurement such that increasing |h| by~1 means -moving a certain tiny distance to the right. The actual unit of -measurement is variable, as explained below; \TeX\ sets things up so that -its \.{DVI} output is in sp units, i.e., scaled points, in agreement with -all the |scaled| dimensions in \TeX's data structures. - -@ Here is a list of all the commands that may appear in a \.{DVI} file. Each -command is specified by its symbolic name (e.g., |bop|), its opcode byte -(e.g., 139), and its parameters (if any). The parameters are followed -by a bracketed number telling how many bytes they occupy; for example, -`|p[4]|' means that parameter |p| is four bytes long. - -\yskip\hang|set_char_0| 0. Typeset character number~0 from font~|f| -such that the reference point of the character is at |(h,v)|. Then -increase |h| by the width of that character. Note that a character may -have zero or negative width, so one cannot be sure that |h| will advance -after this command; but |h| usually does increase. - -\yskip\hang\\{set\_char\_1} through \\{set\_char\_127} (opcodes 1 to 127). -Do the operations of |set_char_0|; but use the character whose number -matches the opcode, instead of character~0. - -\yskip\hang|set1| 128 |c[1]|. Same as |set_char_0|, except that character -number~|c| is typeset. \TeX82 uses this command for characters in the -range |128<=c<256|. - -\yskip\hang|@!set2| 129 |c[2]|. Same as |set1|, except that |c|~is two -bytes long, so it is in the range |0<=c<65536|. \TeX82 never uses this -command, but it should come in handy for extensions of \TeX\ that deal -with oriental languages. -@^oriental characters@>@^Chinese characters@>@^Japanese characters@> - -\yskip\hang|@!set3| 130 |c[3]|. Same as |set1|, except that |c|~is three -bytes long, so it can be as large as $2^{24}-1$. Not even the Chinese -language has this many characters, but this command might prove useful -in some yet unforeseen extension. - -\yskip\hang|@!set4| 131 |c[4]|. Same as |set1|, except that |c|~is four -bytes long. Imagine that. - -\yskip\hang|set_rule| 132 |a[4]| |b[4]|. Typeset a solid black rectangle -of height~|a| and width~|b|, with its bottom left corner at |(h,v)|. Then -set |h:=h+b|. If either |a<=0| or |b<=0|, nothing should be typeset. Note -that if |b<0|, the value of |h| will decrease even though nothing else happens. -See below for details about how to typeset rules so that consistency with -\MF\ is guaranteed. - -\yskip\hang|@!put1| 133 |c[1]|. Typeset character number~|c| from font~|f| -such that the reference point of the character is at |(h,v)|. (The `put' -commands are exactly like the `set' commands, except that they simply put out a -character or a rule without moving the reference point afterwards.) - -\yskip\hang|@!put2| 134 |c[2]|. Same as |set2|, except that |h| is not changed. - -\yskip\hang|@!put3| 135 |c[3]|. Same as |set3|, except that |h| is not changed. - -\yskip\hang|@!put4| 136 |c[4]|. Same as |set4|, except that |h| is not changed. - -\yskip\hang|put_rule| 137 |a[4]| |b[4]|. Same as |set_rule|, except that -|h| is not changed. - -\yskip\hang|nop| 138. No operation, do nothing. Any number of |nop|'s -may occur between \.{DVI} commands, but a |nop| cannot be inserted between -a command and its parameters or between two parameters. - -\yskip\hang|bop| 139 $c_0[4]$ $c_1[4]$ $\ldots$ $c_9[4]$ $p[4]$. Beginning -of a page: Set |(h,v,w,x,y,z):=(0,0,0,0,0,0)| and set the stack empty. Set -the current font |f| to an undefined value. The ten $c_i$ parameters hold -the values of \.{\\count0} $\ldots$ \.{\\count9} in \TeX\ at the time -\.{\\shipout} was invoked for this page; they can be used to identify -pages, if a user wants to print only part of a \.{DVI} file. The parameter -|p| points to the previous |bop| in the file; the first -|bop| has $p=-1$. - -\yskip\hang|eop| 140. End of page: Print what you have read since the -previous |bop|. At this point the stack should be empty. (The \.{DVI}-reading -programs that drive most output devices will have kept a buffer of the -material that appears on the page that has just ended. This material is -largely, but not entirely, in order by |v| coordinate and (for fixed |v|) by -|h|~coordinate; so it usually needs to be sorted into some order that is -appropriate for the device in question.) - -\yskip\hang|push| 141. Push the current values of |(h,v,w,x,y,z)| onto the -top of the stack; do not change any of these values. Note that |f| is -not pushed. - -\yskip\hang|pop| 142. Pop the top six values off of the stack and assign -them respectively to |(h,v,w,x,y,z)|. The number of pops should never -exceed the number of pushes, since it would be highly embarrassing if the -stack were empty at the time of a |pop| command. - -\yskip\hang|right1| 143 |b[1]|. Set |h:=h+b|, i.e., move right |b| units. -The parameter is a signed number in two's complement notation, |-128<=b<128|; -if |b<0|, the reference point moves left. - -\yskip\hang|@!right2| 144 |b[2]|. Same as |right1|, except that |b| is a -two-byte quantity in the range |-32768<=b<32768|. - -\yskip\hang|@!right3| 145 |b[3]|. Same as |right1|, except that |b| is a -three-byte quantity in the range |@t$-2^{23}$@><=b<@t$2^{23}$@>|. - -\yskip\hang|@!right4| 146 |b[4]|. Same as |right1|, except that |b| is a -four-byte quantity in the range |@t$-2^{31}$@><=b<@t$2^{31}$@>|. - -\yskip\hang|w0| 147. Set |h:=h+w|; i.e., move right |w| units. With luck, -this parameterless command will usually suffice, because the same kind of motion -will occur several times in succession; the following commands explain how -|w| gets particular values. - -\yskip\hang|w1| 148 |b[1]|. Set |w:=b| and |h:=h+b|. The value of |b| is a -signed quantity in two's complement notation, |-128<=b<128|. This command -changes the current |w|~spacing and moves right by |b|. - -\yskip\hang|@!w2| 149 |b[2]|. Same as |w1|, but |b| is two bytes long, -|-32768<=b<32768|. - -\yskip\hang|@!w3| 150 |b[3]|. Same as |w1|, but |b| is three bytes long, -|@t$-2^{23}$@><=b<@t$2^{23}$@>|. - -\yskip\hang|@!w4| 151 |b[4]|. Same as |w1|, but |b| is four bytes long, -|@t$-2^{31}$@><=b<@t$2^{31}$@>|. - -\yskip\hang|x0| 152. Set |h:=h+x|; i.e., move right |x| units. The `|x|' -commands are like the `|w|' commands except that they involve |x| instead -of |w|. - -\yskip\hang|x1| 153 |b[1]|. Set |x:=b| and |h:=h+b|. The value of |b| is a -signed quantity in two's complement notation, |-128<=b<128|. This command -changes the current |x|~spacing and moves right by |b|. - -\yskip\hang|@!x2| 154 |b[2]|. Same as |x1|, but |b| is two bytes long, -|-32768<=b<32768|. - -\yskip\hang|@!x3| 155 |b[3]|. Same as |x1|, but |b| is three bytes long, -|@t$-2^{23}$@><=b<@t$2^{23}$@>|. - -\yskip\hang|@!x4| 156 |b[4]|. Same as |x1|, but |b| is four bytes long, -|@t$-2^{31}$@><=b<@t$2^{31}$@>|. - -\yskip\hang|down1| 157 |a[1]|. Set |v:=v+a|, i.e., move down |a| units. -The parameter is a signed number in two's complement notation, |-128<=a<128|; -if |a<0|, the reference point moves up. - -\yskip\hang|@!down2| 158 |a[2]|. Same as |down1|, except that |a| is a -two-byte quantity in the range |-32768<=a<32768|. - -\yskip\hang|@!down3| 159 |a[3]|. Same as |down1|, except that |a| is a -three-byte quantity in the range |@t$-2^{23}$@><=a<@t$2^{23}$@>|. - -\yskip\hang|@!down4| 160 |a[4]|. Same as |down1|, except that |a| is a -four-byte quantity in the range |@t$-2^{31}$@><=a<@t$2^{31}$@>|. - -\yskip\hang|y0| 161. Set |v:=v+y|; i.e., move down |y| units. With luck, -this parameterless command will usually suffice, because the same kind of motion -will occur several times in succession; the following commands explain how -|y| gets particular values. - -\yskip\hang|y1| 162 |a[1]|. Set |y:=a| and |v:=v+a|. The value of |a| is a -signed quantity in two's complement notation, |-128<=a<128|. This command -changes the current |y|~spacing and moves down by |a|. - -\yskip\hang|@!y2| 163 |a[2]|. Same as |y1|, but |a| is two bytes long, -|-32768<=a<32768|. - -\yskip\hang|@!y3| 164 |a[3]|. Same as |y1|, but |a| is three bytes long, -|@t$-2^{23}$@><=a<@t$2^{23}$@>|. - -\yskip\hang|@!y4| 165 |a[4]|. Same as |y1|, but |a| is four bytes long, -|@t$-2^{31}$@><=a<@t$2^{31}$@>|. - -\yskip\hang|z0| 166. Set |v:=v+z|; i.e., move down |z| units. The `|z|' commands -are like the `|y|' commands except that they involve |z| instead of |y|. - -\yskip\hang|z1| 167 |a[1]|. Set |z:=a| and |v:=v+a|. The value of |a| is a -signed quantity in two's complement notation, |-128<=a<128|. This command -changes the current |z|~spacing and moves down by |a|. - -\yskip\hang|@!z2| 168 |a[2]|. Same as |z1|, but |a| is two bytes long, -|-32768<=a<32768|. - -\yskip\hang|@!z3| 169 |a[3]|. Same as |z1|, but |a| is three bytes long, -|@t$-2^{23}$@><=a<@t$2^{23}$@>|. - -\yskip\hang|@!z4| 170 |a[4]|. Same as |z1|, but |a| is four bytes long, -|@t$-2^{31}$@><=a<@t$2^{31}$@>|. - -\yskip\hang|fnt_num_0| 171. Set |f:=0|. Font 0 must previously have been -defined by a \\{fnt\_def} instruction, as explained below. - -\yskip\hang\\{fnt\_num\_1} through \\{fnt\_num\_63} (opcodes 172 to 234). Set -|f:=1|, \dots, \hbox{|f:=63|}, respectively. - -\yskip\hang|fnt1| 235 |k[1]|. Set |f:=k|. \TeX82 uses this command for font -numbers in the range |64<=k<256|. - -\yskip\hang|@!fnt2| 236 |k[2]|. Same as |fnt1|, except that |k|~is two -bytes long, so it is in the range |0<=k<65536|. \TeX82 never generates this -command, but large font numbers may prove useful for specifications of -color or texture, or they may be used for special fonts that have fixed -numbers in some external coding scheme. - -\yskip\hang|@!fnt3| 237 |k[3]|. Same as |fnt1|, except that |k|~is three -bytes long, so it can be as large as $2^{24}-1$. - -\yskip\hang|@!fnt4| 238 |k[4]|. Same as |fnt1|, except that |k|~is four -bytes long; this is for the really big font numbers (and for the negative ones). - -\yskip\hang|xxx1| 239 |k[1]| |x[k]|. This command is undefined in -general; it functions as a $(k+2)$-byte |nop| unless special \.{DVI}-reading -programs are being used. \TeX82 generates |xxx1| when a short enough -\.{\\special} appears, setting |k| to the number of bytes being sent. It -is recommended that |x| be a string having the form of a keyword followed -by possible parameters relevant to that keyword. - -\yskip\hang|@!xxx2| 240 |k[2]| |x[k]|. Like |xxx1|, but |0<=k<65536|. - -\yskip\hang|@!xxx3| 241 |k[3]| |x[k]|. Like |xxx1|, but |0<=k<@t$2^{24}$@>|. - -\yskip\hang|xxx4| 242 |k[4]| |x[k]|. Like |xxx1|, but |k| can be ridiculously -large. \TeX82 uses |xxx4| when sending a string of length 256 or more. - -\yskip\hang|fnt_def1| 243 |k[1]| |c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|. -Define font |k|, where |0<=k<256|; font definitions will be explained shortly. - -\yskip\hang|@!fnt_def2| 244 |k[2]| |c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|. -Define font |k|, where |0<=k<65536|. - -\yskip\hang|@!fnt_def3| 245 |k[3]| |c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|. -Define font |k|, where |0<=k<@t$2^{24}$@>|. - -\yskip\hang|@!fnt_def4| 246 |k[4]| |c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|. -Define font |k|, where |@t$-2^{31}$@><=k<@t$2^{31}$@>|. - -\yskip\hang|pre| 247 |i[1]| |num[4]| |den[4]| |mag[4]| |k[1]| |x[k]|. -Beginning of the preamble; this must come at the very beginning of the -file. Parameters |i|, |num|, |den|, |mag|, |k|, and |x| are explained below. - -\yskip\hang|post| 248. Beginning of the postamble, see below. - -\yskip\hang|post_post| 249. Ending of the postamble, see below. - -\yskip\noindent Commands 250--255 are undefined at the present time. - -@ @d set_char_0=0 {typeset character 0 and move right} -@d set1=128 {typeset a character and move right} -@d set_rule=132 {typeset a rule and move right} -@d put_rule=137 {typeset a rule} -@d nop=138 {no operation} -@d bop=139 {beginning of page} -@d eop=140 {ending of page} -@d push=141 {save the current positions} -@d pop=142 {restore previous positions} -@d right1=143 {move right} -@d w0=147 {move right by |w|} -@d w1=148 {move right and set |w|} -@d x0=152 {move right by |x|} -@d x1=153 {move right and set |x|} -@d down1=157 {move down} -@d y0=161 {move down by |y|} -@d y1=162 {move down and set |y|} -@d z0=166 {move down by |z|} -@d z1=167 {move down and set |z|} -@d fnt_num_0=171 {set current font to 0} -@d fnt1=235 {set current font} -@d xxx1=239 {extension to \.{DVI} primitives} -@d xxx4=242 {potentially long extension to \.{DVI} primitives} -@d fnt_def1=243 {define the meaning of a font number} -@d pre=247 {preamble} -@d post=248 {postamble beginning} -@d post_post=249 {postamble ending} - -@ The preamble contains basic information about the file as a whole. As -stated above, there are six parameters: -$$\hbox{|@!i[1]| |@!num[4]| |@!den[4]| |@!mag[4]| |@!k[1]| |@!x[k]|.}$$ -The |i| byte identifies \.{DVI} format; currently this byte is always set -to~2. (The value |i=3| is currently used for an extended format that -allows a mixture of right-to-left and left-to-right typesetting. -Some day we will set |i=4|, when \.{DVI} format makes another -incompatible change---perhaps in the year 2048.) - -The next two parameters, |num| and |den|, are positive integers that define -the units of measurement; they are the numerator and denominator of a -fraction by which all dimensions in the \.{DVI} file could be multiplied -in order to get lengths in units of $10^{-7}$ meters. Since $\rm 7227{pt} = -254{cm}$, and since \TeX\ works with scaled points where there are $2^{16}$ -sp in a point, \TeX\ sets -$|num|/|den|=(254\cdot10^5)/(7227\cdot2^{16})=25400000/473628672$. -@^sp@> - -The |mag| parameter is what \TeX\ calls \.{\\mag}, i.e., 1000 times the -desired magnification. The actual fraction by which dimensions are -multiplied is therefore $|mag|\cdot|num|/1000|den|$. Note that if a \TeX\ -source document does not call for any `\.{true}' dimensions, and if you -change it only by specifying a different \.{\\mag} setting, the \.{DVI} -file that \TeX\ creates will be completely unchanged except for the value -of |mag| in the preamble and postamble. (Fancy \.{DVI}-reading programs allow -users to override the |mag|~setting when a \.{DVI} file is being printed.) - -Finally, |k| and |x| allow the \.{DVI} writer to include a comment, which is not -interpreted further. The length of comment |x| is |k|, where |0<=k<256|. - -@d id_byte=2 {identifies the kind of \.{DVI} files described here} - -@ Font definitions for a given font number |k| contain further parameters -$$\hbox{|c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|.}$$ -The four-byte value |c| is the check sum that \TeX\ found in the \.{TFM} -file for this font; |c| should match the check sum of the font found by -programs that read this \.{DVI} file. -@^check sum@> - -Parameter |s| contains a fixed-point scale factor that is applied to -the character widths in font |k|; font dimensions in \.{TFM} files and -other font files are relative to this quantity, which is called the -``at size'' elsewhere in this documentation. The value of |s| is -always positive and less than $2^{27}$. It is given in the same units -as the other \.{DVI} dimensions, i.e., in sp when \TeX82 has made the -file. Parameter |d| is similar to |s|; it is the ``design size,'' and -(like~|s|) it is given in \.{DVI} units. Thus, font |k| is to be used -at $|mag|\cdot s/1000d$ times its normal size. - -The remaining part of a font definition gives the external name of the font, -which is an ASCII string of length |a+l|. The number |a| is the length -of the ``area'' or directory, and |l| is the length of the font name itself; -the standard local system font area is supposed to be used when |a=0|. -The |n| field contains the area in its first |a| bytes. - -Font definitions must appear before the first use of a particular font number. -Once font |k| is defined, it must not be defined again; however, we -shall see below that font definitions appear in the postamble as well as -in the pages, so in this sense each font number is defined exactly twice, -if at all. Like |nop| commands, font definitions can -appear before the first |bop|, or between an |eop| and a |bop|. - -@ Sometimes it is desirable to make horizontal or vertical rules line up -precisely with certain features in characters of a font. It is possible to -guarantee the correct matching between \.{DVI} output and the characters -generated by \MF\ by adhering to the following principles: (1)~The \MF\ -characters should be positioned so that a bottom edge or left edge that is -supposed to line up with the bottom or left edge of a rule appears at the -reference point, i.e., in row~0 and column~0 of the \MF\ raster. This -ensures that the position of the rule will not be rounded differently when -the pixel size is not a perfect multiple of the units of measurement in -the \.{DVI} file. (2)~A typeset rule of height $a>0$ and width $b>0$ -should be equivalent to a \MF-generated character having black pixels in -precisely those raster positions whose \MF\ coordinates satisfy -|0<=x<@t$\alpha$@>b| and |0<=y<@t$\alpha$@>a|, where $\alpha$ is the number -of pixels per \.{DVI} unit. -@:METAFONT}{\MF@> -@^alignment of rules with characters@> -@^rules aligning with characters@> - -@ The last page in a \.{DVI} file is followed by `|post|'; this command -introduces the postamble, which summarizes important facts that \TeX\ has -accumulated about the file, making it possible to print subsets of the data -with reasonable efficiency. The postamble has the form -$$\vbox{\halign{\hbox{#\hfil}\cr - |post| |p[4]| |num[4]| |den[4]| |mag[4]| |l[4]| |u[4]| |s[2]| |t[2]|\cr - $\langle\,$font definitions$\,\rangle$\cr - |post_post| |q[4]| |i[1]| 223's$[{\G}4]$\cr}}$$ -Here |p| is a pointer to the final |bop| in the file. The next three -parameters, |num|, |den|, and |mag|, are duplicates of the quantities that -appeared in the preamble. - -Parameters |l| and |u| give respectively the height-plus-depth of the tallest -page and the width of the widest page, in the same units as other dimensions -of the file. These numbers might be used by a \.{DVI}-reading program to -position individual ``pages'' on large sheets of film or paper; however, -the standard convention for output on normal size paper is to position each -page so that the upper left-hand corner is exactly one inch from the left -and the top. Experience has shown that it is unwise to design \.{DVI}-to-printer -software that attempts cleverly to center the output; a fixed position of -the upper left corner is easiest for users to understand and to work with. -Therefore |l| and~|u| are often ignored. - -Parameter |s| is the maximum stack depth (i.e., the largest excess of -|push| commands over |pop| commands) needed to process this file. Then -comes |t|, the total number of pages (|bop| commands) present. - -The postamble continues with font definitions, which are any number of -\\{fnt\_def} commands as described above, possibly interspersed with |nop| -commands. Each font number that is used in the \.{DVI} file must be defined -exactly twice: Once before it is first selected by a \\{fnt} command, and once -in the postamble. - -@ The last part of the postamble, following the |post_post| byte that -signifies the end of the font definitions, contains |q|, a pointer to the -|post| command that started the postamble. An identification byte, |i|, -comes next; this currently equals~2, as in the preamble. - -The |i| byte is followed by four or more bytes that are all equal to -the decimal number 223 (i.e., @'337 in octal). \TeX\ puts out four to seven of -these trailing bytes, until the total length of the file is a multiple of -four bytes, since this works out best on machines that pack four bytes per -word; but any number of 223's is allowed, as long as there are at least four -of them. In effect, 223 is a sort of signature that is added at the very end. -@^Fuchs, David Raymond@> - -This curious way to finish off a \.{DVI} file makes it feasible for -\.{DVI}-reading programs to find the postamble first, on most computers, -even though \TeX\ wants to write the postamble last. Most operating -systems permit random access to individual words or bytes of a file, so -the \.{DVI} reader can start at the end and skip backwards over the 223's -until finding the identification byte. Then it can back up four bytes, read -|q|, and move to byte |q| of the file. This byte should, of course, -contain the value 248 (|post|); now the postamble can be read, so the -\.{DVI} reader can discover all the information needed for typesetting the -pages. Note that it is also possible to skip through the \.{DVI} file at -reasonably high speed to locate a particular page, if that proves -desirable. This saves a lot of time, since \.{DVI} files used in production -jobs tend to be large. - -Unfortunately, however, standard \PASCAL\ does not include the ability to -@^system dependencies@> -access a random position in a file, or even to determine the length of a file. -Almost all systems nowadays provide the necessary capabilities, so \.{DVI} -format has been designed to work most efficiently with modern operating systems. -But if \.{DVI} files have to be processed under the restrictions of standard -\PASCAL, one can simply read them from front to back, since the necessary -header information is present in the preamble and in the font definitions. -(The |l| and |u| and |s| and |t| parameters, which appear only in the -postamble, are ``frills'' that are handy but not absolutely necessary.) - -@* \[32] Shipping pages out. -After considering \TeX's eyes and stomach, we come now to the bowels. -@^bowels@> - -The |ship_out| procedure is given a pointer to a box; its mission is -to describe that box in \.{DVI} form, outputting a ``page'' to |dvi_file|. -The \.{DVI} coordinates $(h,v)=(0,0)$ should correspond to the upper left -corner of the box being shipped. - -Since boxes can be inside of boxes inside of boxes, the main work of -|ship_out| is done by two mutually recursive routines, |hlist_out| -and |vlist_out|, which traverse the hlists and vlists inside of horizontal -and vertical boxes. - -As individual pages are being processed, we need to accumulate -information about the entire set of pages, since such statistics must be -reported in the postamble. The global variables |total_pages|, |max_v|, -|max_h|, |max_push|, and |last_bop| are used to record this information. - -The variable |doing_leaders| is |true| while leaders are being output. -The variable |dead_cycles| contains the number of times an output routine -has been initiated since the last |ship_out|. - -A few additional global variables are also defined here for use in -|vlist_out| and |hlist_out|. They could have been local variables, but -that would waste stack space when boxes are deeply nested, since the -values of these variables are not needed during recursive calls. -@^recursion@> - -@<Glob...@>= -@!total_pages:integer; {the number of pages that have been shipped out} -@!max_v:scaled; {maximum height-plus-depth of pages shipped so far} -@!max_h:scaled; {maximum width of pages shipped so far} -@!max_push:integer; {deepest nesting of |push| commands encountered so far} -@!last_bop:integer; {location of previous |bop| in the \.{DVI} output} -@!dead_cycles:integer; {recent outputs that didn't ship anything out} -@!doing_leaders:boolean; {are we inside a leader box?} -@# -@!c,@!f:quarterword; {character and font in current |char_node|} -@!rule_ht,@!rule_dp,@!rule_wd:scaled; {size of current rule being output} -@!g:pointer; {current glue specification} -@!lq,@!lr:integer; {quantities used in calculations for leaders} - -@ @<Set init...@>= -total_pages:=0; max_v:=0; max_h:=0; max_push:=0; last_bop:=-1; -doing_leaders:=false; dead_cycles:=0; cur_s:=-1; - -@ The \.{DVI} bytes are output to a buffer instead of being written directly -to the output file. This makes it possible to reduce the overhead of -subroutine calls, thereby measurably speeding up the computation, since -output of \.{DVI} bytes is part of \TeX's inner loop. And it has another -advantage as well, since we can change instructions in the buffer in order to -make the output more compact. For example, a `|down2|' command can be -changed to a `|y2|', thereby making a subsequent `|y0|' command possible, -saving two bytes. - -The output buffer is divided into two parts of equal size; the bytes found -in |dvi_buf[0..half_buf-1]| constitute the first half, and those in -|dvi_buf[half_buf..dvi_buf_size-1]| constitute the second. The global -variable |dvi_ptr| points to the position that will receive the next -output byte. When |dvi_ptr| reaches |dvi_limit|, which is always equal -to one of the two values |half_buf| or |dvi_buf_size|, the half buffer that -is about to be invaded next is sent to the output and |dvi_limit| is -changed to its other value. Thus, there is always at least a half buffer's -worth of information present, except at the very beginning of the job. - -Bytes of the \.{DVI} file are numbered sequentially starting with 0; -the next byte to be generated will be number |dvi_offset+dvi_ptr|. -A byte is present in the buffer only if its number is |>=dvi_gone|. - -@<Types...@>= -@!dvi_index=0..dvi_buf_size; {an index into the output buffer} - -@ Some systems may find it more efficient to make |dvi_buf| a |packed| -array, since output of four bytes at once may be facilitated. -@^system dependencies@> - -@<Glob...@>= -@!dvi_buf:array[dvi_index] of eight_bits; {buffer for \.{DVI} output} -@!half_buf:dvi_index; {half of |dvi_buf_size|} -@!dvi_limit:dvi_index; {end of the current half buffer} -@!dvi_ptr:dvi_index; {the next available buffer address} -@!dvi_offset:integer; {|dvi_buf_size| times the number of times the - output buffer has been fully emptied} -@!dvi_gone:integer; {the number of bytes already output to |dvi_file|} - -@ Initially the buffer is all in one piece; we will output half of it only -after it first fills up. - -@<Set init...@>= -half_buf:=dvi_buf_size div 2; dvi_limit:=dvi_buf_size; dvi_ptr:=0; -dvi_offset:=0; dvi_gone:=0; - -@ The actual output of |dvi_buf[a..b]| to |dvi_file| is performed by calling -|write_dvi(a,b)|. For best results, this procedure should be optimized to -run as fast as possible on each particular system, since it is part of -\TeX's inner loop. It is safe to assume that |a| and |b+1| will both be -multiples of 4 when |write_dvi(a,b)| is called; therefore it is possible on -many machines to use efficient methods to pack four bytes per word and to -output an array of words with one system call. -@^system dependencies@> -@^inner loop@> -@^defecation@> - -@p procedure write_dvi(@!a,@!b:dvi_index); -var k:dvi_index; -begin for k:=a to b do write(dvi_file,dvi_buf[k]); -end; - -@ To put a byte in the buffer without paying the cost of invoking a procedure -each time, we use the macro |dvi_out|. - -@d dvi_out(#)==@+begin dvi_buf[dvi_ptr]:=#; incr(dvi_ptr); - if dvi_ptr=dvi_limit then dvi_swap; - end - -@p procedure dvi_swap; {outputs half of the buffer} -begin if dvi_limit=dvi_buf_size then - begin write_dvi(0,half_buf-1); dvi_limit:=half_buf; - dvi_offset:=dvi_offset+dvi_buf_size; dvi_ptr:=0; - end -else begin write_dvi(half_buf,dvi_buf_size-1); dvi_limit:=dvi_buf_size; - end; -dvi_gone:=dvi_gone+half_buf; -end; - -@ Here is how we clean out the buffer when \TeX\ is all through; |dvi_ptr| -will be a multiple of~4. - -@<Empty the last bytes out of |dvi_buf|@>= -if dvi_limit=half_buf then write_dvi(half_buf,dvi_buf_size-1); -if dvi_ptr>0 then write_dvi(0,dvi_ptr-1) - -@ The |dvi_four| procedure outputs four bytes in two's complement notation, -without risking arithmetic overflow. - -@p procedure dvi_four(@!x:integer); -begin if x>=0 then dvi_out(x div @'100000000) -else begin x:=x+@'10000000000; - x:=x+@'10000000000; - dvi_out((x div @'100000000) + 128); - end; -x:=x mod @'100000000; dvi_out(x div @'200000); -x:=x mod @'200000; dvi_out(x div @'400); -dvi_out(x mod @'400); -end; - -@ A mild optimization of the output is performed by the |dvi_pop| -routine, which issues a |pop| unless it is possible to cancel a -`|push| |pop|' pair. The parameter to |dvi_pop| is the byte address -following the old |push| that matches the new |pop|. - -@p procedure dvi_pop(@!l:integer); -begin if (l=dvi_offset+dvi_ptr)and(dvi_ptr>0) then decr(dvi_ptr) -else dvi_out(pop); -end; - -@ Here's a procedure that outputs a font definition. Since \TeX82 uses at -most 256 different fonts per job, |fnt_def1| is always used as the command code. - -@p procedure dvi_font_def(@!f:internal_font_number); -var k:pool_pointer; {index into |str_pool|} -begin dvi_out(fnt_def1); -dvi_out(f-font_base-1);@/ -dvi_out(qo(font_check[f].b0)); -dvi_out(qo(font_check[f].b1)); -dvi_out(qo(font_check[f].b2)); -dvi_out(qo(font_check[f].b3));@/ -dvi_four(font_size[f]); -dvi_four(font_dsize[f]);@/ -dvi_out(length(font_area[f])); -dvi_out(length(font_name[f])); -@<Output the font name whose internal number is |f|@>; -end; - -@ @<Output the font name whose internal number is |f|@>= -for k:=str_start[font_area[f]] to str_start[font_area[f]+1]-1 do - dvi_out(so(str_pool[k])); -for k:=str_start[font_name[f]] to str_start[font_name[f]+1]-1 do - dvi_out(so(str_pool[k])) - -@ Versions of \TeX\ intended for small computers might well choose to omit -the ideas in the next few parts of this program, since it is not really -necessary to optimize the \.{DVI} code by making use of the |w0|, |x0|, -|y0|, and |z0| commands. Furthermore, the algorithm that we are about to -describe does not pretend to give an optimum reduction in the length -of the \.{DVI} code; after all, speed is more important than compactness. -But the method is surprisingly effective, and it takes comparatively little -time. - -We can best understand the basic idea by first considering a simpler problem -that has the same essential characteristics. Given a sequence of digits, -say $3\,1\,4\,1\,5\,9\,2\,6\,5\,3\,5\,8\,9$, we want to assign subscripts -$d$, $y$, or $z$ to each digit so as to maximize the number of ``$y$-hits'' -and ``$z$-hits''; a $y$-hit is an instance of two appearances of the same -digit with the subscript $y$, where no $y$'s intervene between the two -appearances, and a $z$-hit is defined similarly. For example, the sequence -above could be decorated with subscripts as follows: -$$3_z\,1_y\,4_d\,1_y\,5_y\,9_d\,2_d\,6_d\,5_y\,3_z\,5_y\,8_d\,9_d.$$ -There are three $y$-hits ($1_y\ldots1_y$ and $5_y\ldots5_y\ldots5_y$) and -one $z$-hit ($3_z\ldots3_z$); there are no $d$-hits, since the two appearances -of $9_d$ have $d$'s between them, but we don't count $d$-hits so it doesn't -matter how many there are. These subscripts are analogous to the \.{DVI} -commands called \\{down}, $y$, and $z$, and the digits are analogous to -different amounts of vertical motion; a $y$-hit or $z$-hit corresponds to -the opportunity to use the one-byte commands |y0| or |z0| in a \.{DVI} file. - -\TeX's method of assigning subscripts works like this: Append a new digit, -say $\delta$, to the right of the sequence. Now look back through the -sequence until one of the following things happens: (a)~You see -$\delta_y$ or $\delta_z$, and this was the first time you encountered a -$y$ or $z$ subscript, respectively. Then assign $y$ or $z$ to the new -$\delta$; you have scored a hit. (b)~You see $\delta_d$, and no $y$ -subscripts have been encountered so far during this search. Then change -the previous $\delta_d$ to $\delta_y$ (this corresponds to changing a -command in the output buffer), and assign $y$ to the new $\delta$; it's -another hit. (c)~You see $\delta_d$, and a $y$ subscript has been seen -but not a $z$. Change the previous $\delta_d$ to $\delta_z$ and assign -$z$ to the new $\delta$. (d)~You encounter both $y$ and $z$ subscripts -before encountering a suitable $\delta$, or you scan all the way to the -front of the sequence. Assign $d$ to the new $\delta$; this assignment may -be changed later. - -The subscripts $3_z\,1_y\,4_d\ldots\,$ in the example above were, in fact, -produced by this procedure, as the reader can verify. (Go ahead and try it.) - -@ In order to implement such an idea, \TeX\ maintains a stack of pointers -to the \\{down}, $y$, and $z$ commands that have been generated for the -current page. And there is a similar stack for \\{right}, |w|, and |x| -commands. These stacks are called the down stack and right stack, and their -top elements are maintained in the variables |down_ptr| and |right_ptr|. - -Each entry in these stacks contains four fields: The |width| field is -the amount of motion down or to the right; the |location| field is the -byte number of the \.{DVI} command in question (including the appropriate -|dvi_offset|); the |link| field points to the next item below this one -on the stack; and the |info| field encodes the options for possible change -in the \.{DVI} command. - -@d movement_node_size=3 {number of words per entry in the down and right stacks} -@d location(#)==mem[#+2].int {\.{DVI} byte number for a movement command} - -@<Glob...@>= -@!down_ptr,@!right_ptr:pointer; {heads of the down and right stacks} - -@ @<Set init...@>= -down_ptr:=null; right_ptr:=null; - -@ Here is a subroutine that produces a \.{DVI} command for some specified -downward or rightward motion. It has two parameters: |w| is the amount -of motion, and |o| is either |down1| or |right1|. We use the fact that -the command codes have convenient arithmetic properties: |y1-down1=w1-right1| -and |z1-down1=x1-right1|. - -@p procedure movement(@!w:scaled;@!o:eight_bits); -label exit,found,not_found,2,1; -var mstate:small_number; {have we seen a |y| or |z|?} -@!p,@!q:pointer; {current and top nodes on the stack} -@!k:integer; {index into |dvi_buf|, modulo |dvi_buf_size|} -begin q:=get_node(movement_node_size); {new node for the top of the stack} -width(q):=w; location(q):=dvi_offset+dvi_ptr; -if o=down1 then - begin link(q):=down_ptr; down_ptr:=q; - end -else begin link(q):=right_ptr; right_ptr:=q; - end; -@<Look at the other stack entries until deciding what sort of \.{DVI} command - to generate; |goto found| if node |p| is a ``hit''@>; -@<Generate a |down| or |right| command for |w| and |return|@>; -found: @<Generate a |y0| or |z0| command in order to reuse a previous - appearance of~|w|@>; -exit:end; - -@ The |info| fields in the entries of the down stack or the right stack -have six possible settings: |y_here| or |z_here| mean that the \.{DVI} -command refers to |y| or |z|, respectively (or to |w| or |x|, in the -case of horizontal motion); |yz_OK| means that the \.{DVI} command is -\\{down} (or \\{right}) but can be changed to either |y| or |z| (or -to either |w| or |x|); |y_OK| means that it is \\{down} and can be changed -to |y| but not |z|; |z_OK| is similar; and |d_fixed| means it must stay -\\{down}. - -The four settings |yz_OK|, |y_OK|, |z_OK|, |d_fixed| would not need to -be distinguished from each other if we were simply solving the -digit-subscripting problem mentioned above. But in \TeX's case there is -a complication because of the nested structure of |push| and |pop| -commands. Suppose we add parentheses to the digit-subscripting problem, -redefining hits so that $\delta_y\ldots \delta_y$ is a hit if all $y$'s between -the $\delta$'s are enclosed in properly nested parentheses, and if the -parenthesis level of the right-hand $\delta_y$ is deeper than or equal to -that of the left-hand one. Thus, `(' and `)' correspond to `|push|' -and `|pop|'. Now if we want to assign a subscript to the final 1 in the -sequence -$$2_y\,7_d\,1_d\,(\,8_z\,2_y\,8_z\,)\,1$$ -we cannot change the previous $1_d$ to $1_y$, since that would invalidate -the $2_y\ldots2_y$ hit. But we can change it to $1_z$, scoring a hit -since the intervening $8_z$'s are enclosed in parentheses. - -The program below removes movement nodes that are introduced after a |push|, -before it outputs the corresponding |pop|. - -@d y_here=1 {|info| when the movement entry points to a |y| command} -@d z_here=2 {|info| when the movement entry points to a |z| command} -@d yz_OK=3 {|info| corresponding to an unconstrained \\{down} command} -@d y_OK=4 {|info| corresponding to a \\{down} that can't become a |z|} -@d z_OK=5 {|info| corresponding to a \\{down} that can't become a |y|} -@d d_fixed=6 {|info| corresponding to a \\{down} that can't change} - -@ When the |movement| procedure gets to the label |found|, the value of -|info(p)| will be either |y_here| or |z_here|. If it is, say, |y_here|, -the procedure generates a |y0| command (or a |w0| command), and marks -all |info| fields between |q| and |p| so that |y| is not OK in that range. - -@<Generate a |y0| or |z0| command...@>= -info(q):=info(p); -if info(q)=y_here then - begin dvi_out(o+y0-down1); {|y0| or |w0|} - while link(q)<>p do - begin q:=link(q); - case info(q) of - yz_OK: info(q):=z_OK; - y_OK: info(q):=d_fixed; - othercases do_nothing - endcases; - end; - end -else begin dvi_out(o+z0-down1); {|z0| or |x0|} - while link(q)<>p do - begin q:=link(q); - case info(q) of - yz_OK: info(q):=y_OK; - z_OK: info(q):=d_fixed; - othercases do_nothing - endcases; - end; - end - -@ @<Generate a |down| or |right|...@>= -info(q):=yz_OK; -if abs(w)>=@'40000000 then - begin dvi_out(o+3); {|down4| or |right4|} - dvi_four(w); return; - end; -if abs(w)>=@'100000 then - begin dvi_out(o+2); {|down3| or |right3|} - if w<0 then w:=w+@'100000000; - dvi_out(w div @'200000); w:=w mod @'200000; goto 2; - end; -if abs(w)>=@'200 then - begin dvi_out(o+1); {|down2| or |right2|} - if w<0 then w:=w+@'200000; - goto 2; - end; -dvi_out(o); {|down1| or |right1|} -if w<0 then w:=w+@'400; -goto 1; -2: dvi_out(w div @'400); -1: dvi_out(w mod @'400); return - -@ As we search through the stack, we are in one of three states, -|y_seen|, |z_seen|, or |none_seen|, depending on whether we have -encountered |y_here| or |z_here| nodes. These states are encoded as -multiples of 6, so that they can be added to the |info| fields for quick -decision-making. -@^inner loop@> - -@d none_seen=0 {no |y_here| or |z_here| nodes have been encountered yet} -@d y_seen=6 {we have seen |y_here| but not |z_here|} -@d z_seen=12 {we have seen |z_here| but not |y_here|} - -@<Look at the other stack entries until deciding...@>= -p:=link(q); mstate:=none_seen; -while p<>null do - begin if width(p)=w then @<Consider a node with matching width; - |goto found| if it's a hit@> - else case mstate+info(p) of - none_seen+y_here: mstate:=y_seen; - none_seen+z_here: mstate:=z_seen; - y_seen+z_here,z_seen+y_here: goto not_found; - othercases do_nothing - endcases; - p:=link(p); - end; -not_found: - -@ We might find a valid hit in a |y| or |z| byte that is already gone -from the buffer. But we can't change bytes that are gone forever; ``the -moving finger writes, $\ldots\,\,$.'' - -@<Consider a node with matching width...@>= -case mstate+info(p) of -none_seen+yz_OK,none_seen+y_OK,z_seen+yz_OK,z_seen+y_OK:@t@>@;@/ - if location(p)<dvi_gone then goto not_found - else @<Change buffered instruction to |y| or |w| and |goto found|@>; -none_seen+z_OK,y_seen+yz_OK,y_seen+z_OK:@t@>@;@/ - if location(p)<dvi_gone then goto not_found - else @<Change buffered instruction to |z| or |x| and |goto found|@>; -none_seen+y_here,none_seen+z_here,y_seen+z_here,z_seen+y_here: goto found; -othercases do_nothing -endcases - -@ @<Change buffered instruction to |y| or |w| and |goto found|@>= -begin k:=location(p)-dvi_offset; -if k<0 then k:=k+dvi_buf_size; -dvi_buf[k]:=dvi_buf[k]+y1-down1; -info(p):=y_here; goto found; -end - -@ @<Change buffered instruction to |z| or |x| and |goto found|@>= -begin k:=location(p)-dvi_offset; -if k<0 then k:=k+dvi_buf_size; -dvi_buf[k]:=dvi_buf[k]+z1-down1; -info(p):=z_here; goto found; -end - -@ In case you are wondering when all the movement nodes are removed from -\TeX's memory, the answer is that they are recycled just before -|hlist_out| and |vlist_out| finish outputting a box. This restores the -down and right stacks to the state they were in before the box was output, -except that some |info|'s may have become more restrictive. - -@p procedure prune_movements(@!l:integer); - {delete movement nodes with |location>=l|} -label done,exit; -var p:pointer; {node being deleted} -begin while down_ptr<>null do - begin if location(down_ptr)<l then goto done; - p:=down_ptr; down_ptr:=link(p); free_node(p,movement_node_size); - end; -done: while right_ptr<>null do - begin if location(right_ptr)<l then return; - p:=right_ptr; right_ptr:=link(p); free_node(p,movement_node_size); - end; -exit:end; - -@ The actual distances by which we want to move might be computed as the -sum of several separate movements. For example, there might be several -glue nodes in succession, or we might want to move right by the width of -some box plus some amount of glue. More importantly, the baselineskip -distances are computed in terms of glue together with the depth and -height of adjacent boxes, and we want the \.{DVI} file to lump these -three quantities together into a single motion. - -Therefore, \TeX\ maintains two pairs of global variables: |dvi_h| and |dvi_v| -are the |h| and |v| coordinates corresponding to the commands actually -output to the \.{DVI} file, while |cur_h| and |cur_v| are the coordinates -corresponding to the current state of the output routines. Coordinate -changes will accumulate in |cur_h| and |cur_v| without being reflected -in the output, until such a change becomes necessary or desirable; we -can call the |movement| procedure whenever we want to make |dvi_h=cur_h| -or |dvi_v=cur_v|. - -The current font reflected in the \.{DVI} output is called |dvi_f|; -there is no need for a `\\{cur\_f}' variable. - -The depth of nesting of |hlist_out| and |vlist_out| is called |cur_s|; -this is essentially the depth of |push| commands in the \.{DVI} output. - -@d synch_h==if cur_h<>dvi_h then - begin movement(cur_h-dvi_h,right1); dvi_h:=cur_h; - end -@d synch_v==if cur_v<>dvi_v then - begin movement(cur_v-dvi_v,down1); dvi_v:=cur_v; - end - -@<Glob...@>= -@!dvi_h,@!dvi_v:scaled; {a \.{DVI} reader program thinks we are here} -@!cur_h,@!cur_v:scaled; {\TeX\ thinks we are here} -@!dvi_f:internal_font_number; {the current font} -@!cur_s:integer; {current depth of output box nesting, initially $-1$} - -@ @<Initialize variables as |ship_out| begins@>= -dvi_h:=0; dvi_v:=0; cur_h:=h_offset; dvi_f:=null_font; -ensure_dvi_open; -if total_pages=0 then - begin dvi_out(pre); dvi_out(id_byte); {output the preamble} -@^preamble of \.{DVI} file@> - dvi_four(25400000); dvi_four(473628672); {conversion ratio for sp} - prepare_mag; dvi_four(mag); {magnification factor is frozen} - old_setting:=selector; selector:=new_string; - print(" TeX output "); print_int(year); print_char("."); - print_two(month); print_char("."); print_two(day); - print_char(":"); print_two(time div 60); - print_two(time mod 60); - selector:=old_setting; dvi_out(cur_length); - for s:=str_start[str_ptr] to pool_ptr-1 do dvi_out(so(str_pool[s])); - pool_ptr:=str_start[str_ptr]; {flush the current string} - end - -@ When |hlist_out| is called, its duty is to output the box represented -by the |hlist_node| pointed to by |temp_ptr|. The reference point of that -box has coordinates |(cur_h,cur_v)|. - -Similarly, when |vlist_out| is called, its duty is to output the box represented -by the |vlist_node| pointed to by |temp_ptr|. The reference point of that -box has coordinates |(cur_h,cur_v)|. -@^recursion@> - -@p procedure@?vlist_out; forward; {|hlist_out| and |vlist_out| are mutually - recursive} - -@ The recursive procedures |hlist_out| and |vlist_out| each have local variables -|save_h| and |save_v| to hold the values of |dvi_h| and |dvi_v| just before -entering a new level of recursion. In effect, the values of |save_h| and -|save_v| on \TeX's run-time stack correspond to the values of |h| and |v| -that a \.{DVI}-reading program will push onto its coordinate stack. - -@d move_past=13 {go to this label when advancing past glue or a rule} -@d fin_rule=14 {go to this label to finish processing a rule} -@d next_p=15 {go to this label when finished with node |p|} - -@p @t\4@>@<Declare procedures needed in |hlist_out|, |vlist_out|@>@t@>@/ -procedure hlist_out; {output an |hlist_node| box} -label reswitch, move_past, fin_rule, next_p; -var base_line: scaled; {the baseline coordinate for this box} -@!left_edge: scaled; {the left coordinate for this box} -@!save_h,@!save_v: scaled; {what |dvi_h| and |dvi_v| should pop to} -@!this_box: pointer; {pointer to containing box} -@!g_order: glue_ord; {applicable order of infinity for glue} -@!g_sign: normal..shrinking; {selects type of glue} -@!p:pointer; {current position in the hlist} -@!save_loc:integer; {\.{DVI} byte location upon entry} -@!leader_box:pointer; {the leader box being replicated} -@!leader_wd:scaled; {width of leader box being replicated} -@!lx:scaled; {extra space between leader boxes} -@!outer_doing_leaders:boolean; {were we doing leaders?} -@!edge:scaled; {left edge of sub-box, or right edge of leader space} -@!glue_temp:real; {glue value before rounding} -@!cur_glue:real; {glue seen so far} -@!cur_g:scaled; {rounded equivalent of |cur_glue| times the glue ratio} -begin cur_g:=0; cur_glue:=float_constant(0); -this_box:=temp_ptr; g_order:=glue_order(this_box); -g_sign:=glue_sign(this_box); p:=list_ptr(this_box); -incr(cur_s); -if cur_s>0 then dvi_out(push); -if cur_s>max_push then max_push:=cur_s; -save_loc:=dvi_offset+dvi_ptr; base_line:=cur_v; left_edge:=cur_h; -while p<>null do @<Output node |p| for |hlist_out| and move to the next node, - maintaining the condition |cur_v=base_line|@>; -prune_movements(save_loc); -if cur_s>0 then dvi_pop(save_loc); -decr(cur_s); -end; - -@ We ought to give special care to the efficiency of one part of |hlist_out|, -since it belongs to \TeX's inner loop. When a |char_node| is encountered, -we save a little time by processing several nodes in succession until -reaching a non-|char_node|. The program uses the fact that |set_char_0=0|. -@^inner loop@> - -@<Output node |p| for |hlist_out|...@>= -reswitch: if is_char_node(p) then - begin synch_h; synch_v; - repeat f:=font(p); c:=character(p); - if f<>dvi_f then @<Change font |dvi_f| to |f|@>; - if c>=qi(128) then dvi_out(set1); - dvi_out(qo(c));@/ - cur_h:=cur_h+char_width(f)(char_info(f)(c)); - p:=link(p); - until not is_char_node(p); - dvi_h:=cur_h; - end -else @<Output the non-|char_node| |p| for |hlist_out| - and move to the next node@> - -@ @<Change font |dvi_f| to |f|@>= -begin if not font_used[f] then - begin dvi_font_def(f); font_used[f]:=true; - end; -if f<=64+font_base then dvi_out(f-font_base-1+fnt_num_0) -else begin dvi_out(fnt1); dvi_out(f-font_base-1); - end; -dvi_f:=f; -end - -@ @<Output the non-|char_node| |p| for |hlist_out|...@>= -begin case type(p) of -hlist_node,vlist_node:@<Output a box in an hlist@>; -rule_node: begin rule_ht:=height(p); rule_dp:=depth(p); rule_wd:=width(p); - goto fin_rule; - end; -whatsit_node: @<Output the whatsit node |p| in an hlist@>; -glue_node: @<Move right or output leaders@>; -kern_node,math_node:cur_h:=cur_h+width(p); -ligature_node: @<Make node |p| look like a |char_node| and |goto reswitch|@>; -othercases do_nothing -endcases;@/ -goto next_p; -fin_rule: @<Output a rule in an hlist@>; -move_past: cur_h:=cur_h+rule_wd; -next_p:p:=link(p); -end - -@ @<Output a box in an hlist@>= -if list_ptr(p)=null then cur_h:=cur_h+width(p) -else begin save_h:=dvi_h; save_v:=dvi_v; - cur_v:=base_line+shift_amount(p); {shift the box down} - temp_ptr:=p; edge:=cur_h; - if type(p)=vlist_node then vlist_out@+else hlist_out; - dvi_h:=save_h; dvi_v:=save_v; - cur_h:=edge+width(p); cur_v:=base_line; - end - -@ @<Output a rule in an hlist@>= -if is_running(rule_ht) then rule_ht:=height(this_box); -if is_running(rule_dp) then rule_dp:=depth(this_box); -rule_ht:=rule_ht+rule_dp; {this is the rule thickness} -if (rule_ht>0)and(rule_wd>0) then {we don't output empty rules} - begin synch_h; cur_v:=base_line+rule_dp; synch_v; - dvi_out(set_rule); dvi_four(rule_ht); dvi_four(rule_wd); - cur_v:=base_line; dvi_h:=dvi_h+rule_wd; - end - -@ @d billion==float_constant(1000000000) -@d vet_glue(#)== glue_temp:=#; - if glue_temp>billion then - glue_temp:=billion - else if glue_temp<-billion then - glue_temp:=-billion - -@<Move right or output leaders@>= -begin g:=glue_ptr(p); rule_wd:=width(g)-cur_g; -if g_sign<>normal then - begin if g_sign=stretching then - begin if stretch_order(g)=g_order then - begin cur_glue:=cur_glue+stretch(g); - vet_glue(float(glue_set(this_box))*cur_glue); -@^real multiplication@> - cur_g:=round(glue_temp); - end; - end - else if shrink_order(g)=g_order then - begin cur_glue:=cur_glue-shrink(g); - vet_glue(float(glue_set(this_box))*cur_glue); - cur_g:=round(glue_temp); - end; - end; -rule_wd:=rule_wd+cur_g; -if subtype(p)>=a_leaders then - @<Output leaders in an hlist, |goto fin_rule| if a rule - or to |next_p| if done@>; -goto move_past; -end - -@ @<Output leaders in an hlist...@>= -begin leader_box:=leader_ptr(p); -if type(leader_box)=rule_node then - begin rule_ht:=height(leader_box); rule_dp:=depth(leader_box); - goto fin_rule; - end; -leader_wd:=width(leader_box); -if (leader_wd>0)and(rule_wd>0) then - begin rule_wd:=rule_wd+10; {compensate for floating-point rounding} - edge:=cur_h+rule_wd; lx:=0; - @<Let |cur_h| be the position of the first box, and set |leader_wd+lx| - to the spacing between corresponding parts of boxes@>; - while cur_h+leader_wd<=edge do - @<Output a leader box at |cur_h|, - then advance |cur_h| by |leader_wd+lx|@>; - cur_h:=edge-10; goto next_p; - end; -end - -@ The calculations related to leaders require a bit of care. First, in the -case of |a_leaders| (aligned leaders), we want to move |cur_h| to -|left_edge| plus the smallest multiple of |leader_wd| for which the result -is not less than the current value of |cur_h|; i.e., |cur_h| should become -$|left_edge|+|leader_wd|\times\lceil -(|cur_h|-|left_edge|)/|leader_wd|\rceil$. The program here should work in -all cases even though some implementations of \PASCAL\ give nonstandard -results for the |div| operation when |cur_h| is less than |left_edge|. - -In the case of |c_leaders| (centered leaders), we want to increase |cur_h| -by half of the excess space not occupied by the leaders; and in the -case of |x_leaders| (expanded leaders) we increase |cur_h| -by $1/(q+1)$ of this excess space, where $q$ is the number of times the -leader box will be replicated. Slight inaccuracies in the division might -accumulate; half of this rounding error is placed at each end of the leaders. - -@<Let |cur_h| be the position of the first box, ...@>= -if subtype(p)=a_leaders then - begin save_h:=cur_h; - cur_h:=left_edge+leader_wd*((cur_h-left_edge)@!div leader_wd); - if cur_h<save_h then cur_h:=cur_h+leader_wd; - end -else begin lq:=rule_wd div leader_wd; {the number of box copies} - lr:=rule_wd mod leader_wd; {the remaining space} - if subtype(p)=c_leaders then cur_h:=cur_h+(lr div 2) - else begin lx:=lr div (lq+1); - cur_h:=cur_h+((lr-(lq-1)*lx) div 2); - end; - end - -@ The `\\{synch}' operations here are intended to decrease the number of -bytes needed to specify horizontal and vertical motion in the \.{DVI} output. - -@<Output a leader box at |cur_h|, ...@>= -begin cur_v:=base_line+shift_amount(leader_box); synch_v; save_v:=dvi_v;@/ -synch_h; save_h:=dvi_h; temp_ptr:=leader_box; -outer_doing_leaders:=doing_leaders; doing_leaders:=true; -if type(leader_box)=vlist_node then vlist_out@+else hlist_out; -doing_leaders:=outer_doing_leaders; -dvi_v:=save_v; dvi_h:=save_h; cur_v:=base_line; -cur_h:=save_h+leader_wd+lx; -end - -@ The |vlist_out| routine is similar to |hlist_out|, but a bit simpler. - -@p procedure vlist_out; {output a |vlist_node| box} -label move_past, fin_rule, next_p; -var left_edge: scaled; {the left coordinate for this box} -@!top_edge: scaled; {the top coordinate for this box} -@!save_h,@!save_v: scaled; {what |dvi_h| and |dvi_v| should pop to} -@!this_box: pointer; {pointer to containing box} -@!g_order: glue_ord; {applicable order of infinity for glue} -@!g_sign: normal..shrinking; {selects type of glue} -@!p:pointer; {current position in the vlist} -@!save_loc:integer; {\.{DVI} byte location upon entry} -@!leader_box:pointer; {the leader box being replicated} -@!leader_ht:scaled; {height of leader box being replicated} -@!lx:scaled; {extra space between leader boxes} -@!outer_doing_leaders:boolean; {were we doing leaders?} -@!edge:scaled; {bottom boundary of leader space} -@!glue_temp:real; {glue value before rounding} -@!cur_glue:real; {glue seen so far} -@!cur_g:scaled; {rounded equivalent of |cur_glue| times the glue ratio} -begin cur_g:=0; cur_glue:=float_constant(0); -this_box:=temp_ptr; g_order:=glue_order(this_box); -g_sign:=glue_sign(this_box); p:=list_ptr(this_box); -incr(cur_s); -if cur_s>0 then dvi_out(push); -if cur_s>max_push then max_push:=cur_s; -save_loc:=dvi_offset+dvi_ptr; left_edge:=cur_h; cur_v:=cur_v-height(this_box); -top_edge:=cur_v; -while p<>null do @<Output node |p| for |vlist_out| and move to the next node, - maintaining the condition |cur_h=left_edge|@>; -prune_movements(save_loc); -if cur_s>0 then dvi_pop(save_loc); -decr(cur_s); -end; - -@ @<Output node |p| for |vlist_out|...@>= -begin if is_char_node(p) then confusion("vlistout") -@:this can't happen vlistout}{\quad vlistout@> -else @<Output the non-|char_node| |p| for |vlist_out|@>; -next_p:p:=link(p); -end - -@ @<Output the non-|char_node| |p| for |vlist_out|@>= -begin case type(p) of -hlist_node,vlist_node:@<Output a box in a vlist@>; -rule_node: begin rule_ht:=height(p); rule_dp:=depth(p); rule_wd:=width(p); - goto fin_rule; - end; -whatsit_node: @<Output the whatsit node |p| in a vlist@>; -glue_node: @<Move down or output leaders@>; -kern_node:cur_v:=cur_v+width(p); -othercases do_nothing -endcases;@/ -goto next_p; -fin_rule: @<Output a rule in a vlist, |goto next_p|@>; -move_past: cur_v:=cur_v+rule_ht; -end - -@ The |synch_v| here allows the \.{DVI} output to use one-byte commands -for adjusting |v| in most cases, since the baselineskip distance will -usually be constant. - -@<Output a box in a vlist@>= -if list_ptr(p)=null then cur_v:=cur_v+height(p)+depth(p) -else begin cur_v:=cur_v+height(p); synch_v; - save_h:=dvi_h; save_v:=dvi_v; - cur_h:=left_edge+shift_amount(p); {shift the box right} - temp_ptr:=p; - if type(p)=vlist_node then vlist_out@+else hlist_out; - dvi_h:=save_h; dvi_v:=save_v; - cur_v:=save_v+depth(p); cur_h:=left_edge; - end - -@ @<Output a rule in a vlist...@>= -if is_running(rule_wd) then rule_wd:=width(this_box); -rule_ht:=rule_ht+rule_dp; {this is the rule thickness} -cur_v:=cur_v+rule_ht; -if (rule_ht>0)and(rule_wd>0) then {we don't output empty rules} - begin synch_h; synch_v; - dvi_out(put_rule); dvi_four(rule_ht); dvi_four(rule_wd); - end; -goto next_p - -@ @<Move down or output leaders@>= -begin g:=glue_ptr(p); rule_ht:=width(g)-cur_g; -if g_sign<>normal then - begin if g_sign=stretching then - begin if stretch_order(g)=g_order then - begin cur_glue:=cur_glue+stretch(g); - vet_glue(float(glue_set(this_box))*cur_glue); -@^real multiplication@> - cur_g:=round(glue_temp); - end; - end - else if shrink_order(g)=g_order then - begin cur_glue:=cur_glue-shrink(g); - vet_glue(float(glue_set(this_box))*cur_glue); - cur_g:=round(glue_temp); - end; - end; -rule_ht:=rule_ht+cur_g; -if subtype(p)>=a_leaders then - @<Output leaders in a vlist, |goto fin_rule| if a rule - or to |next_p| if done@>; -goto move_past; -end - -@ @<Output leaders in a vlist...@>= -begin leader_box:=leader_ptr(p); -if type(leader_box)=rule_node then - begin rule_wd:=width(leader_box); rule_dp:=0; - goto fin_rule; - end; -leader_ht:=height(leader_box)+depth(leader_box); -if (leader_ht>0)and(rule_ht>0) then - begin rule_ht:=rule_ht+10; {compensate for floating-point rounding} - edge:=cur_v+rule_ht; lx:=0; - @<Let |cur_v| be the position of the first box, and set |leader_ht+lx| - to the spacing between corresponding parts of boxes@>; - while cur_v+leader_ht<=edge do - @<Output a leader box at |cur_v|, - then advance |cur_v| by |leader_ht+lx|@>; - cur_v:=edge-10; goto next_p; - end; -end - -@ @<Let |cur_v| be the position of the first box, ...@>= -if subtype(p)=a_leaders then - begin save_v:=cur_v; - cur_v:=top_edge+leader_ht*((cur_v-top_edge)@!div leader_ht); - if cur_v<save_v then cur_v:=cur_v+leader_ht; - end -else begin lq:=rule_ht div leader_ht; {the number of box copies} - lr:=rule_ht mod leader_ht; {the remaining space} - if subtype(p)=c_leaders then cur_v:=cur_v+(lr div 2) - else begin lx:=lr div (lq+1); - cur_v:=cur_v+((lr-(lq-1)*lx) div 2); - end; - end - -@ When we reach this part of the program, |cur_v| indicates the top of a -leader box, not its baseline. - -@<Output a leader box at |cur_v|, ...@>= -begin cur_h:=left_edge+shift_amount(leader_box); synch_h; save_h:=dvi_h;@/ -cur_v:=cur_v+height(leader_box); synch_v; save_v:=dvi_v; -temp_ptr:=leader_box; -outer_doing_leaders:=doing_leaders; doing_leaders:=true; -if type(leader_box)=vlist_node then vlist_out@+else hlist_out; -doing_leaders:=outer_doing_leaders; -dvi_v:=save_v; dvi_h:=save_h; cur_h:=left_edge; -cur_v:=save_v-height(leader_box)+leader_ht+lx; -end - -@ The |hlist_out| and |vlist_out| procedures are now complete, so we are -ready for the |ship_out| routine that gets them started in the first place. - -@p procedure ship_out(@!p:pointer); {output the box |p|} -label done; -var page_loc:integer; {location of the current |bop|} -@!j,@!k:0..9; {indices to first ten count registers} -@!s:pool_pointer; {index into |str_pool|} -@!old_setting:0..max_selector; {saved |selector| setting} -begin if tracing_output>0 then - begin print_nl(""); print_ln; - print("Completed box being shipped out"); -@.Completed box...@> - end; -if term_offset>max_print_line-9 then print_ln -else if (term_offset>0)or(file_offset>0) then print_char(" "); -print_char("["); j:=9; -while (count(j)=0)and(j>0) do decr(j); -for k:=0 to j do - begin print_int(count(k)); - if k<j then print_char("."); - end; -update_terminal; -if tracing_output>0 then - begin print_char("]"); - begin_diagnostic; show_box(p); end_diagnostic(true); - end; -@<Ship box |p| out@>; -if tracing_output<=0 then print_char("]"); -dead_cycles:=0; -update_terminal; {progress report} -@<Flush the box from memory, showing statistics if requested@>; -end; - -@ @<Flush the box from memory, showing statistics if requested@>= -@!stat if tracing_stats>1 then - begin print_nl("Memory usage before: "); -@.Memory usage...@> - print_int(var_used); print_char("&"); - print_int(dyn_used); print_char(";"); - end; -tats@/ -flush_node_list(p); -@!stat if tracing_stats>1 then - begin print(" after: "); - print_int(var_used); print_char("&"); - print_int(dyn_used); print("; still untouched: "); - print_int(hi_mem_min-lo_mem_max-1); print_ln; - end; -tats - -@ @<Ship box |p| out@>= -@<Update the values of |max_h| and |max_v|; but if the page is too large, - |goto done|@>; -@<Initialize variables as |ship_out| begins@>; -page_loc:=dvi_offset+dvi_ptr; -dvi_out(bop); -for k:=0 to 9 do dvi_four(count(k)); -dvi_four(last_bop); last_bop:=page_loc; -cur_v:=height(p)+v_offset; temp_ptr:=p; -if type(p)=vlist_node then vlist_out@+else hlist_out; -dvi_out(eop); incr(total_pages); cur_s:=-1; -done: - -@ Sometimes the user will generate a huge page because other error messages -are being ignored. Such pages are not output to the \.{dvi} file, since they -may confuse the printing software. - -@<Update the values of |max_h| and |max_v|; but if the page is too large...@>= -if (height(p)>max_dimen)or@|(depth(p)>max_dimen)or@| - (height(p)+depth(p)+v_offset>max_dimen)or@| - (width(p)+h_offset>max_dimen) then - begin print_err("Huge page cannot be shipped out"); -@.Huge page...@> - help2("The page just created is more than 18 feet tall or")@/ - ("more than 18 feet wide, so I suspect something went wrong."); - error; - if tracing_output<=0 then - begin begin_diagnostic; - print_nl("The following box has been deleted:"); -@.The following...deleted@> - show_box(p); - end_diagnostic(true); - end; - goto done; - end; -if height(p)+depth(p)+v_offset>max_v then max_v:=height(p)+depth(p)+v_offset; -if width(p)+h_offset>max_h then max_h:=width(p)+h_offset - -@ At the end of the program, we must finish things off by writing the -post\-amble. If |total_pages=0|, the \.{DVI} file was never opened. -If |total_pages>=65536|, the \.{DVI} file will lie. And if -|max_push>=65536|, the user deserves whatever chaos might ensue. - -An integer variable |k| will be declared for use by this routine. - -@<Finish the \.{DVI} file@>= -while cur_s>-1 do - begin if cur_s>0 then dvi_out(pop) - else begin dvi_out(eop); incr(total_pages); - end; - decr(cur_s); - end; -if total_pages=0 then print_nl("No pages of output.") -@.No pages of output@> -else begin dvi_out(post); {beginning of the postamble} - dvi_four(last_bop); last_bop:=dvi_offset+dvi_ptr-5; {|post| location} - dvi_four(25400000); dvi_four(473628672); {conversion ratio for sp} - prepare_mag; dvi_four(mag); {magnification factor} - dvi_four(max_v); dvi_four(max_h);@/ - dvi_out(max_push div 256); dvi_out(max_push mod 256);@/ - dvi_out((total_pages div 256) mod 256); dvi_out(total_pages mod 256);@/ - @<Output the font definitions for all fonts that were used@>; - dvi_out(post_post); dvi_four(last_bop); dvi_out(id_byte);@/ - k:=4+((dvi_buf_size-dvi_ptr) mod 4); {the number of 223's} - while k>0 do - begin dvi_out(223); decr(k); - end; - @<Empty the last bytes out of |dvi_buf|@>; - print_nl("Output written on "); slow_print(output_file_name); -@.Output written on x@> - print(" ("); print_int(total_pages); print(" page"); - if total_pages<>1 then print_char("s"); - print(", "); print_int(dvi_offset+dvi_ptr); print(" bytes)."); - b_close(dvi_file); - end - -@ @<Output the font definitions...@>= -while font_ptr>font_base do - begin if font_used[font_ptr] then dvi_font_def(font_ptr); - decr(font_ptr); - end - -@* \[33] Packaging. -We're essentially done with the parts of \TeX\ that are concerned with -the input (|get_next|) and the output (|ship_out|). So it's time to -get heavily into the remaining part, which does the real work of typesetting. - -After lists are constructed, \TeX\ wraps them up and puts them into boxes. -Two major subroutines are given the responsibility for this task: |hpack| -applies to horizontal lists (hlists) and |vpack| applies to vertical lists -(vlists). The main duty of |hpack| and |vpack| is to compute the dimensions -of the resulting boxes, and to adjust the glue if one of those dimensions -is pre-specified. The computed sizes normally enclose all of the material -inside the new box; but some items may stick out if negative glue is used, -if the box is overfull, or if a \.{\\vbox} includes other boxes that have -been shifted left. - -The subroutine call |hpack(p,w,m)| returns a pointer to an |hlist_node| -for a box containing the hlist that starts at |p|. Parameter |w| specifies -a width; and parameter |m| is either `|exactly|' or `|additional|'. Thus, -|hpack(p,w,exactly)| produces a box whose width is exactly |w|, while -|hpack(p,w,additional)| yields a box whose width is the natural width plus -|w|. It is convenient to define a macro called `|natural|' to cover the -most common case, so that we can say |hpack(p,natural)| to get a box that -has the natural width of list |p|. - -Similarly, |vpack(p,w,m)| returns a pointer to a |vlist_node| for a -box containing the vlist that starts at |p|. In this case |w| represents -a height instead of a width; the parameter |m| is interpreted as in |hpack|. - -@d exactly=0 {a box dimension is pre-specified} -@d additional=1 {a box dimension is increased from the natural one} -@d natural==0,additional {shorthand for parameters to |hpack| and |vpack|} - -@ The parameters to |hpack| and |vpack| correspond to \TeX's primitives -like `\.{\\hbox} \.{to} \.{300pt}', `\.{\\hbox} \.{spread} \.{10pt}'; note -that `\.{\\hbox}' with no dimension following it is equivalent to -`\.{\\hbox} \.{spread} \.{0pt}'. The |scan_spec| subroutine scans such -constructions in the user's input, including the mandatory left brace that -follows them, and it puts the specification onto |save_stack| so that the -desired box can later be obtained by executing the following code: -$$\vbox{\halign{#\hfil\cr -|save_ptr:=save_ptr-2;|\cr -|hpack(p,saved(1),saved(0)).|\cr}}$$ -Special care is necessary to ensure that the special |save_stack| codes -are placed just below the new group code, because scanning can change -|save_stack| when \.{\\csname} appears. - -@p procedure scan_spec(@!c:group_code;@!three_codes:boolean); - {scans a box specification and left brace} -label found; -var @!s:integer; {temporarily saved value} -@!spec_code:exactly..additional; -begin if three_codes then s:=saved(0); -if scan_keyword("to") then spec_code:=exactly -@.to@> -else if scan_keyword("spread") then spec_code:=additional -@.spread@> -else begin spec_code:=additional; cur_val:=0; - goto found; - end; -scan_normal_dimen; -found: if three_codes then - begin saved(0):=s; incr(save_ptr); - end; -saved(0):=spec_code; saved(1):=cur_val; save_ptr:=save_ptr+2; -new_save_level(c); scan_left_brace; -end; - -@ To figure out the glue setting, |hpack| and |vpack| determine how much -stretchability and shrinkability are present, considering all four orders -of infinity. The highest order of infinity that has a nonzero coefficient -is then used as if no other orders were present. - -For example, suppose that the given list contains six glue nodes with -the respective stretchabilities 3pt, 8fill, 5fil, 6pt, $-3$fil, $-8$fill. -Then the total is essentially 2fil; and if a total additional space of 6pt -is to be achieved by stretching, the actual amounts of stretch will be -0pt, 0pt, 15pt, 0pt, $-9$pt, and 0pt, since only `fil' glue will be -considered. (The `fill' glue is therefore not really stretching infinitely -with respect to `fil'; nobody would actually want that to happen.) - -The arrays |total_stretch| and |total_shrink| are used to determine how much -glue of each kind is present. A global variable |last_badness| is used -to implement \.{\\badness}. - -@<Glob...@>= -@!total_stretch, @!total_shrink: array[glue_ord] of scaled; - {glue found by |hpack| or |vpack|} -@!last_badness:integer; {badness of the most recently packaged box} - -@ If the global variable |adjust_tail| is non-null, the |hpack| routine -also removes all occurrences of |ins_node|, |mark_node|, and |adjust_node| -items and appends the resulting material onto the list that ends at -location |adjust_tail|. - -@<Glob...@>= -@!adjust_tail:pointer; {tail of adjustment list} - -@ @<Set init...@>=adjust_tail:=null; last_badness:=0; - -@ Here now is |hpack|, which contains few if any surprises. - -@p function hpack(@!p:pointer;@!w:scaled;@!m:small_number):pointer; -label reswitch, common_ending, exit; -var r:pointer; {the box node that will be returned} -@!q:pointer; {trails behind |p|} -@!h,@!d,@!x:scaled; {height, depth, and natural width} -@!s:scaled; {shift amount} -@!g:pointer; {points to a glue specification} -@!o:glue_ord; {order of infinity} -@!f:internal_font_number; {the font in a |char_node|} -@!i:four_quarters; {font information about a |char_node|} -@!hd:eight_bits; {height and depth indices for a character} -begin last_badness:=0; r:=get_node(box_node_size); type(r):=hlist_node; -subtype(r):=min_quarterword; shift_amount(r):=0; -q:=r+list_offset; link(q):=p;@/ -h:=0; @<Clear dimensions to zero@>; -while p<>null do @<Examine node |p| in the hlist, taking account of its effect - on the dimensions of the new box, or moving it to the adjustment list; - then advance |p| to the next node@>; -if adjust_tail<>null then link(adjust_tail):=null; -height(r):=h; depth(r):=d;@/ -@<Determine the value of |width(r)| and the appropriate glue setting; - then |return| or |goto common_ending|@>; -common_ending: @<Finish issuing a diagnostic message - for an overfull or underfull hbox@>; -exit: hpack:=r; -end; - -@ @<Clear dimensions to zero@>= -d:=0; x:=0; -total_stretch[normal]:=0; total_shrink[normal]:=0; -total_stretch[fil]:=0; total_shrink[fil]:=0; -total_stretch[fill]:=0; total_shrink[fill]:=0; -total_stretch[filll]:=0; total_shrink[filll]:=0 - -@ @<Examine node |p| in the hlist, taking account of its effect...@>= -@^inner loop@> -begin reswitch: while is_char_node(p) do - @<Incorporate character dimensions into the dimensions of - the hbox that will contain~it, then move to the next node@>; -if p<>null then - begin case type(p) of - hlist_node,vlist_node,rule_node,unset_node: - @<Incorporate box dimensions into the dimensions of - the hbox that will contain~it@>; - ins_node,mark_node,adjust_node: if adjust_tail<>null then - @<Transfer node |p| to the adjustment list@>; - whatsit_node:@<Incorporate a whatsit node into an hbox@>; - glue_node:@<Incorporate glue into the horizontal totals@>; - kern_node,math_node: x:=x+width(p); - ligature_node: @<Make node |p| look like a |char_node| - and |goto reswitch|@>; - othercases do_nothing - endcases;@/ - p:=link(p); - end; -end - - -@ @<Make node |p| look like a |char_node| and |goto reswitch|@>= -begin mem[lig_trick]:=mem[lig_char(p)]; link(lig_trick):=link(p); -p:=lig_trick; goto reswitch; -end - -@ The code here implicitly uses the fact that running dimensions are -indicated by |null_flag|, which will be ignored in the calculations -because it is a highly negative number. - -@<Incorporate box dimensions into the dimensions of the hbox...@>= -begin x:=x+width(p); -if type(p)>=rule_node then s:=0 @+else s:=shift_amount(p); -if height(p)-s>h then h:=height(p)-s; -if depth(p)+s>d then d:=depth(p)+s; -end - -@ The following code is part of \TeX's inner loop; i.e., adding another -character of text to the user's input will cause each of these instructions -to be exercised one more time. -@^inner loop@> - -@<Incorporate character dimensions into the dimensions of the hbox...@>= -begin f:=font(p); i:=char_info(f)(character(p)); hd:=height_depth(i); -x:=x+char_width(f)(i);@/ -s:=char_height(f)(hd);@+if s>h then h:=s; -s:=char_depth(f)(hd);@+if s>d then d:=s; -p:=link(p); -end - -@ Although node |q| is not necessarily the immediate predecessor of node |p|, -it always points to some node in the list preceding |p|. Thus, we can delete -nodes by moving |q| when necessary. The algorithm takes linear time, and the -extra computation does not intrude on the inner loop unless it is necessary -to make a deletion. -@^inner loop@> - -@<Transfer node |p| to the adjustment list@>= -begin while link(q)<>p do q:=link(q); -if type(p)=adjust_node then - begin link(adjust_tail):=adjust_ptr(p); - while link(adjust_tail)<>null do adjust_tail:=link(adjust_tail); - p:=link(p); free_node(link(q),small_node_size); - end -else begin link(adjust_tail):=p; adjust_tail:=p; p:=link(p); - end; -link(q):=p; p:=q; -end - -@ @<Incorporate glue into the horizontal totals@>= -begin g:=glue_ptr(p); x:=x+width(g);@/ -o:=stretch_order(g); total_stretch[o]:=total_stretch[o]+stretch(g); -o:=shrink_order(g); total_shrink[o]:=total_shrink[o]+shrink(g); -if subtype(p)>=a_leaders then - begin g:=leader_ptr(p); - if height(g)>h then h:=height(g); - if depth(g)>d then d:=depth(g); - end; -end - -@ When we get to the present part of the program, |x| is the natural width -of the box being packaged. - -@<Determine the value of |width(r)| and the appropriate glue setting...@>= -if m=additional then w:=x+w; -width(r):=w; x:=w-x; {now |x| is the excess to be made up} -if x=0 then - begin glue_sign(r):=normal; glue_order(r):=normal; - set_glue_ratio_zero(glue_set(r)); - return; - end -else if x>0 then @<Determine horizontal glue stretch setting, then |return| - or \hbox{|goto common_ending|}@> -else @<Determine horizontal glue shrink setting, then |return| - or \hbox{|goto common_ending|}@> - -@ @<Determine horizontal glue stretch setting...@>= -begin @<Determine the stretch order@>; -glue_order(r):=o; glue_sign(r):=stretching; -if total_stretch[o]<>0 then glue_set(r):=unfloat(x/total_stretch[o]) -@^real division@> -else begin glue_sign(r):=normal; - set_glue_ratio_zero(glue_set(r)); {there's nothing to stretch} - end; -if o=normal then if list_ptr(r)<>null then - @<Report an underfull hbox and |goto common_ending|, if this box - is sufficiently bad@>; -return; -end - -@ @<Determine the stretch order@>= -if total_stretch[filll]<>0 then o:=filll -else if total_stretch[fill]<>0 then o:=fill -else if total_stretch[fil]<>0 then o:=fil -else o:=normal - -@ @<Report an underfull hbox and |goto common_ending|, if...@>= -begin last_badness:=badness(x,total_stretch[normal]); -if last_badness>hbadness then - begin print_ln; - if last_badness>100 then print_nl("Underfull")@+else print_nl("Loose"); - print(" \hbox (badness "); print_int(last_badness); -@.Underfull \\hbox...@> -@.Loose \\hbox...@> - goto common_ending; - end; -end - -@ In order to provide a decent indication of where an overfull or underfull -box originated, we use a global variable |pack_begin_line| that is -set nonzero only when |hpack| is being called by the paragraph builder -or the alignment finishing routine. - -@<Glob...@>= -@!pack_begin_line:integer; {source file line where the current paragraph - or alignment began; a negative value denotes alignment} - -@ @<Set init...@>= -pack_begin_line:=0; - -@ @<Finish issuing a diagnostic message for an overfull or underfull hbox@>= -if output_active then print(") has occurred while \output is active") -else begin if pack_begin_line<>0 then - begin if pack_begin_line>0 then print(") in paragraph at lines ") - else print(") in alignment at lines "); - print_int(abs(pack_begin_line)); - print("--"); - end - else print(") detected at line "); - print_int(line); - end; -print_ln;@/ -font_in_short_display:=null_font; short_display(list_ptr(r)); print_ln;@/ -begin_diagnostic; show_box(r); end_diagnostic(true) - -@ @<Determine horizontal glue shrink setting...@>= -begin @<Determine the shrink order@>; -glue_order(r):=o; glue_sign(r):=shrinking; -if total_shrink[o]<>0 then glue_set(r):=unfloat((-x)/total_shrink[o]) -@^real division@> -else begin glue_sign(r):=normal; - set_glue_ratio_zero(glue_set(r)); {there's nothing to shrink} - end; -if (total_shrink[o]<-x)and(o=normal)and(list_ptr(r)<>null) then - begin last_badness:=1000000; - set_glue_ratio_one(glue_set(r)); {use the maximum shrinkage} - @<Report an overfull hbox and |goto common_ending|, if this box - is sufficiently bad@>; - end -else if o=normal then if list_ptr(r)<>null then - @<Report a tight hbox and |goto common_ending|, if this box - is sufficiently bad@>; -return; -end - -@ @<Determine the shrink order@>= -if total_shrink[filll]<>0 then o:=filll -else if total_shrink[fill]<>0 then o:=fill -else if total_shrink[fil]<>0 then o:=fil -else o:=normal - -@ @<Report an overfull hbox and |goto common_ending|, if...@>= -if (-x-total_shrink[normal]>hfuzz)or(hbadness<100) then - begin if (overfull_rule>0)and(-x-total_shrink[normal]>hfuzz) then - begin while link(q)<>null do q:=link(q); - link(q):=new_rule; - width(link(q)):=overfull_rule; - end; - print_ln; print_nl("Overfull \hbox ("); -@.Overfull \\hbox...@> - print_scaled(-x-total_shrink[normal]); print("pt too wide"); - goto common_ending; - end - -@ @<Report a tight hbox and |goto common_ending|, if...@>= -begin last_badness:=badness(-x,total_shrink[normal]); -if last_badness>hbadness then - begin print_ln; print_nl("Tight \hbox (badness "); print_int(last_badness); -@.Tight \\hbox...@> - goto common_ending; - end; -end - -@ The |vpack| subroutine is actually a special case of a slightly more -general routine called |vpackage|, which has four parameters. The fourth -parameter, which is |max_dimen| in the case of |vpack|, specifies the -maximum depth of the page box that is constructed. The depth is first -computed by the normal rules; if it exceeds this limit, the reference -point is simply moved down until the limiting depth is attained. - -@d vpack(#)==vpackage(#,max_dimen) {special case of unconstrained depth} - -@p function vpackage(@!p:pointer;@!h:scaled;@!m:small_number;@!l:scaled): - pointer; -label common_ending, exit; -var r:pointer; {the box node that will be returned} -@!w,@!d,@!x:scaled; {width, depth, and natural height} -@!s:scaled; {shift amount} -@!g:pointer; {points to a glue specification} -@!o:glue_ord; {order of infinity} -begin last_badness:=0; r:=get_node(box_node_size); type(r):=vlist_node; -subtype(r):=min_quarterword; shift_amount(r):=0; -list_ptr(r):=p;@/ -w:=0; @<Clear dimensions to zero@>; -while p<>null do @<Examine node |p| in the vlist, taking account of its effect - on the dimensions of the new box; then advance |p| to the next node@>; -width(r):=w; -if d>l then - begin x:=x+d-l; depth(r):=l; - end -else depth(r):=d; -@<Determine the value of |height(r)| and the appropriate glue setting; - then |return| or |goto common_ending|@>; -common_ending: @<Finish issuing a diagnostic message - for an overfull or underfull vbox@>; -exit: vpackage:=r; -end; - -@ @<Examine node |p| in the vlist, taking account of its effect...@>= -begin if is_char_node(p) then confusion("vpack") -@:this can't happen vpack}{\quad vpack@> -else case type(p) of - hlist_node,vlist_node,rule_node,unset_node: - @<Incorporate box dimensions into the dimensions of - the vbox that will contain~it@>; - whatsit_node:@<Incorporate a whatsit node into a vbox@>; - glue_node: @<Incorporate glue into the vertical totals@>; - kern_node: begin x:=x+d+width(p); d:=0; - end; - othercases do_nothing - endcases; -p:=link(p); -end - -@ @<Incorporate box dimensions into the dimensions of the vbox...@>= -begin x:=x+d+height(p); d:=depth(p); -if type(p)>=rule_node then s:=0 @+else s:=shift_amount(p); -if width(p)+s>w then w:=width(p)+s; -end - -@ @<Incorporate glue into the vertical totals@>= -begin x:=x+d; d:=0;@/ -g:=glue_ptr(p); x:=x+width(g);@/ -o:=stretch_order(g); total_stretch[o]:=total_stretch[o]+stretch(g); -o:=shrink_order(g); total_shrink[o]:=total_shrink[o]+shrink(g); -if subtype(p)>=a_leaders then - begin g:=leader_ptr(p); - if width(g)>w then w:=width(g); - end; -end - -@ When we get to the present part of the program, |x| is the natural height -of the box being packaged. - -@<Determine the value of |height(r)| and the appropriate glue setting...@>= -if m=additional then h:=x+h; -height(r):=h; x:=h-x; {now |x| is the excess to be made up} -if x=0 then - begin glue_sign(r):=normal; glue_order(r):=normal; - set_glue_ratio_zero(glue_set(r)); - return; - end -else if x>0 then @<Determine vertical glue stretch setting, then |return| - or \hbox{|goto common_ending|}@> -else @<Determine vertical glue shrink setting, then |return| - or \hbox{|goto common_ending|}@> - -@ @<Determine vertical glue stretch setting...@>= -begin @<Determine the stretch order@>; -glue_order(r):=o; glue_sign(r):=stretching; -if total_stretch[o]<>0 then glue_set(r):=unfloat(x/total_stretch[o]) -@^real division@> -else begin glue_sign(r):=normal; - set_glue_ratio_zero(glue_set(r)); {there's nothing to stretch} - end; -if o=normal then if list_ptr(r)<>null then - @<Report an underfull vbox and |goto common_ending|, if this box - is sufficiently bad@>; -return; -end - -@ @<Report an underfull vbox and |goto common_ending|, if...@>= -begin last_badness:=badness(x,total_stretch[normal]); -if last_badness>vbadness then - begin print_ln; - if last_badness>100 then print_nl("Underfull")@+else print_nl("Loose"); - print(" \vbox (badness "); print_int(last_badness); -@.Underfull \\vbox...@> -@.Loose \\vbox...@> - goto common_ending; - end; -end - -@ @<Finish issuing a diagnostic message for an overfull or underfull vbox@>= -if output_active then print(") has occurred while \output is active") -else begin if pack_begin_line<>0 then {it's actually negative} - begin print(") in alignment at lines "); - print_int(abs(pack_begin_line)); - print("--"); - end - else print(") detected at line "); - print_int(line); - print_ln;@/ - end; -begin_diagnostic; show_box(r); end_diagnostic(true) - -@ @<Determine vertical glue shrink setting...@>= -begin @<Determine the shrink order@>; -glue_order(r):=o; glue_sign(r):=shrinking; -if total_shrink[o]<>0 then glue_set(r):=unfloat((-x)/total_shrink[o]) -@^real division@> -else begin glue_sign(r):=normal; - set_glue_ratio_zero(glue_set(r)); {there's nothing to shrink} - end; -if (total_shrink[o]<-x)and(o=normal)and(list_ptr(r)<>null) then - begin last_badness:=1000000; - set_glue_ratio_one(glue_set(r)); {use the maximum shrinkage} - @<Report an overfull vbox and |goto common_ending|, if this box - is sufficiently bad@>; - end -else if o=normal then if list_ptr(r)<>null then - @<Report a tight vbox and |goto common_ending|, if this box - is sufficiently bad@>; -return; -end - -@ @<Report an overfull vbox and |goto common_ending|, if...@>= -if (-x-total_shrink[normal]>vfuzz)or(vbadness<100) then - begin print_ln; print_nl("Overfull \vbox ("); -@.Overfull \\vbox...@> - print_scaled(-x-total_shrink[normal]); print("pt too high"); - goto common_ending; - end - -@ @<Report a tight vbox and |goto common_ending|, if...@>= -begin last_badness:=badness(-x,total_shrink[normal]); -if last_badness>vbadness then - begin print_ln; print_nl("Tight \vbox (badness "); print_int(last_badness); -@.Tight \\vbox...@> - goto common_ending; - end; -end - -@ When a box is being appended to the current vertical list, the -baselineskip calculation is handled by the |append_to_vlist| routine. - -@p procedure append_to_vlist(@!b:pointer); -var d:scaled; {deficiency of space between baselines} -@!p:pointer; {a new glue node} -begin if prev_depth>ignore_depth then - begin d:=width(baseline_skip)-prev_depth-height(b); - if d<line_skip_limit then p:=new_param_glue(line_skip_code) - else begin p:=new_skip_param(baseline_skip_code); - width(temp_ptr):=d; {|temp_ptr=glue_ptr(p)|} - end; - link(tail):=p; tail:=p; - end; -link(tail):=b; tail:=b; prev_depth:=depth(b); -end; - -@* \[34] Data structures for math mode. -When \TeX\ reads a formula that is enclosed between \.\$'s, it constructs an -{\sl mlist}, which is essentially a tree structure representing that -formula. An mlist is a linear sequence of items, but we can regard it as -a tree structure because mlists can appear within mlists. For example, many -of the entries can be subscripted or superscripted, and such ``scripts'' -are mlists in their own right. - -An entire formula is parsed into such a tree before any of the actual -typesetting is done, because the current style of type is usually not -known until the formula has been fully scanned. For example, when the -formula `\.{\$a+b \\over c+d\$}' is being read, there is no way to tell -that `\.{a+b}' will be in script size until `\.{\\over}' has appeared. - -During the scanning process, each element of the mlist being built is -classified as a relation, a binary operator, an open parenthesis, etc., -or as a construct like `\.{\\sqrt}' that must be built up. This classification -appears in the mlist data structure. - -After a formula has been fully scanned, the mlist is converted to an hlist -so that it can be incorporated into the surrounding text. This conversion is -controlled by a recursive procedure that decides all of the appropriate -styles by a ``top-down'' process starting at the outermost level and working -in towards the subformulas. The formula is ultimately pasted together using -combinations of horizontal and vertical boxes, with glue and penalty nodes -inserted as necessary. - -An mlist is represented internally as a linked list consisting chiefly -of ``noads'' (pronounced ``no-adds''), to distinguish them from the somewhat -similar ``nodes'' in hlists and vlists. Certain kinds of ordinary nodes are -allowed to appear in mlists together with the noads; \TeX\ tells the difference -by means of the |type| field, since a noad's |type| is always greater than -that of a node. An mlist does not contain character nodes, hlist nodes, vlist -nodes, math nodes, ligature nodes, -or unset nodes; in particular, each mlist item appears in the -variable-size part of |mem|, so the |type| field is always present. - -@ Each noad is four or more words long. The first word contains the |type| -and |subtype| and |link| fields that are already so familiar to us; the -second, third, and fourth words are called the noad's |nucleus|, |subscr|, -and |supscr| fields. - -Consider, for example, the simple formula `\.{\$x\^2\$}', which would be -parsed into an mlist containing a single element called an |ord_noad|. -The |nucleus| of this noad is a representation of `\.x', the |subscr| is -empty, and the |supscr| is a representation of `\.2'. - -The |nucleus|, |subscr|, and |supscr| fields are further broken into -subfields. If |p| points to a noad, and if |q| is one of its principal -fields (e.g., |q=subscr(p)|), there are several possibilities for the -subfields, depending on the |math_type| of |q|. - -\yskip\hang|math_type(q)=math_char| means that |fam(q)| refers to one of -the sixteen font families, and |character(q)| is the number of a character -within a font of that family, as in a character node. - -\yskip\hang|math_type(q)=math_text_char| is similar, but the character is -unsubscripted and unsuperscripted and it is followed immediately by another -character from the same font. (This |math_type| setting appears only -briefly during the processing; it is used to suppress unwanted italic -corrections.) - -\yskip\hang|math_type(q)=empty| indicates a field with no value (the -corresponding attribute of noad |p| is not present). - -\yskip\hang|math_type(q)=sub_box| means that |info(q)| points to a box -node (either an |hlist_node| or a |vlist_node|) that should be used as the -value of the field. The |shift_amount| in the subsidiary box node is the -amount by which that box will be shifted downward. - -\yskip\hang|math_type(q)=sub_mlist| means that |info(q)| points to -an mlist; the mlist must be converted to an hlist in order to obtain -the value of this field. - -\yskip\noindent In the latter case, we might have |info(q)=null|. This -is not the same as |math_type(q)=empty|; for example, `\.{\$P\_\{\}\$}' -and `\.{\$P\$}' produce different results (the former will not have the -``italic correction'' added to the width of |P|, but the ``script skip'' -will be added). - -The definitions of subfields given here are evidently wasteful of space, -since a halfword is being used for the |math_type| although only three -bits would be needed. However, there are hardly ever many noads present at -once, since they are soon converted to nodes that take up even more space, -so we can afford to represent them in whatever way simplifies the -programming. - -@d noad_size=4 {number of words in a normal noad} -@d nucleus(#)==#+1 {the |nucleus| field of a noad} -@d supscr(#)==#+2 {the |supscr| field of a noad} -@d subscr(#)==#+3 {the |subscr| field of a noad} -@d math_type==link {a |halfword| in |mem|} -@d fam==font {a |quarterword| in |mem|} -@d math_char=1 {|math_type| when the attribute is simple} -@d sub_box=2 {|math_type| when the attribute is a box} -@d sub_mlist=3 {|math_type| when the attribute is a formula} -@d math_text_char=4 {|math_type| when italic correction is dubious} - -@ Each portion of a formula is classified as Ord, Op, Bin, Rel, Open, -Close, Punct, or Inner, for purposes of spacing and line breaking. An -|ord_noad|, |op_noad|, |bin_noad|, |rel_noad|, |open_noad|, |close_noad|, -|punct_noad|, or |inner_noad| is used to represent portions of the various -types. For example, an `\.=' sign in a formula leads to the creation of a -|rel_noad| whose |nucleus| field is a representation of an equals sign -(usually |fam=0|, |character=@'75|). A formula preceded by \.{\\mathrel} -also results in a |rel_noad|. When a |rel_noad| is followed by an -|op_noad|, say, and possibly separated by one or more ordinary nodes (not -noads), \TeX\ will insert a penalty node (with the current |rel_penalty|) -just after the formula that corresponds to the |rel_noad|, unless there -already was a penalty immediately following; and a ``thick space'' will be -inserted just before the formula that corresponds to the |op_noad|. - -A noad of type |ord_noad|, |op_noad|, \dots, |inner_noad| usually -has a |subtype=normal|. The only exception is that an |op_noad| might -have |subtype=limits| or |no_limits|, if the normal positioning of -limits has been overridden for this operator. - -@d ord_noad=unset_node+3 {|type| of a noad classified Ord} -@d op_noad=ord_noad+1 {|type| of a noad classified Op} -@d bin_noad=ord_noad+2 {|type| of a noad classified Bin} -@d rel_noad=ord_noad+3 {|type| of a noad classified Rel} -@d open_noad=ord_noad+4 {|type| of a noad classified Open} -@d close_noad=ord_noad+5 {|type| of a noad classified Close} -@d punct_noad=ord_noad+6 {|type| of a noad classified Punct} -@d inner_noad=ord_noad+7 {|type| of a noad classified Inner} -@d limits=1 {|subtype| of |op_noad| whose scripts are to be above, below} -@d no_limits=2 {|subtype| of |op_noad| whose scripts are to be normal} - -@ A |radical_noad| is five words long; the fifth word is the |left_delimiter| -field, which usually represents a square root sign. - -A |fraction_noad| is six words long; it has a |right_delimiter| field -as well as a |left_delimiter|. - -Delimiter fields are of type |four_quarters|, and they have four subfields -called |small_fam|, |small_char|, |large_fam|, |large_char|. These subfields -represent variable-size delimiters by giving the ``small'' and ``large'' -starting characters, as explained in Chapter~17 of {\sl The \TeX book}. -@:TeXbook}{\sl The \TeX book@> - -A |fraction_noad| is actually quite different from all other noads. Not -only does it have six words, it has |thickness|, |denominator|, and -|numerator| fields instead of |nucleus|, |subscr|, and |supscr|. The -|thickness| is a scaled value that tells how thick to make a fraction -rule; however, the special value |default_code| is used to stand for the -|default_rule_thickness| of the current size. The |numerator| and -|denominator| point to mlists that define a fraction; we always have -$$\hbox{|math_type(numerator)=math_type(denominator)=sub_mlist|}.$$ The -|left_delimiter| and |right_delimiter| fields specify delimiters that will -be placed at the left and right of the fraction. In this way, a -|fraction_noad| is able to represent all of \TeX's operators \.{\\over}, -\.{\\atop}, \.{\\above}, \.{\\overwithdelims}, \.{\\atopwithdelims}, and - \.{\\abovewithdelims}. - -@d left_delimiter(#)==#+4 {first delimiter field of a noad} -@d right_delimiter(#)==#+5 {second delimiter field of a fraction noad} -@d radical_noad=inner_noad+1 {|type| of a noad for square roots} -@d radical_noad_size=5 {number of |mem| words in a radical noad} -@d fraction_noad=radical_noad+1 {|type| of a noad for generalized fractions} -@d fraction_noad_size=6 {number of |mem| words in a fraction noad} -@d small_fam(#)==mem[#].qqqq.b0 {|fam| for ``small'' delimiter} -@d small_char(#)==mem[#].qqqq.b1 {|character| for ``small'' delimiter} -@d large_fam(#)==mem[#].qqqq.b2 {|fam| for ``large'' delimiter} -@d large_char(#)==mem[#].qqqq.b3 {|character| for ``large'' delimiter} -@d thickness==width {|thickness| field in a fraction noad} -@d default_code==@'10000000000 {denotes |default_rule_thickness|} -@d numerator==supscr {|numerator| field in a fraction noad} -@d denominator==subscr {|denominator| field in a fraction noad} - -@ The global variable |empty_field| is set up for initialization of empty -fields in new noads. Similarly, |null_delimiter| is for the initialization -of delimiter fields. - -@<Glob...@>= -@!empty_field:two_halves; -@!null_delimiter:four_quarters; - -@ @<Set init...@>= -empty_field.rh:=empty; empty_field.lh:=null;@/ -null_delimiter.b0:=0; null_delimiter.b1:=min_quarterword;@/ -null_delimiter.b2:=0; null_delimiter.b3:=min_quarterword; - -@ The |new_noad| function creates an |ord_noad| that is completely null. - -@p function new_noad:pointer; -var p:pointer; -begin p:=get_node(noad_size); -type(p):=ord_noad; subtype(p):=normal; -mem[nucleus(p)].hh:=empty_field; -mem[subscr(p)].hh:=empty_field; -mem[supscr(p)].hh:=empty_field; -new_noad:=p; -end; - -@ A few more kinds of noads will complete the set: An |under_noad| has its -nucleus underlined; an |over_noad| has it overlined. An |accent_noad| places -an accent over its nucleus; the accent character appears as -|fam(accent_chr(p))| and |character(accent_chr(p))|. A |vcenter_noad| -centers its nucleus vertically with respect to the axis of the formula; -in such noads we always have |math_type(nucleus(p))=sub_box|. - -And finally, we have |left_noad| and |right_noad| types, to implement -\TeX's \.{\\left} and \.{\\right}. The |nucleus| of such noads is -replaced by a |delimiter| field; thus, for example, `\.{\\left(}' produces -a |left_noad| such that |delimiter(p)| holds the family and character -codes for all left parentheses. A |left_noad| never appears in an mlist -except as the first element, and a |right_noad| never appears in an mlist -except as the last element; furthermore, we either have both a |left_noad| -and a |right_noad|, or neither one is present. The |subscr| and |supscr| -fields are always |empty| in a |left_noad| and a |right_noad|. - -@d under_noad=fraction_noad+1 {|type| of a noad for underlining} -@d over_noad=under_noad+1 {|type| of a noad for overlining} -@d accent_noad=over_noad+1 {|type| of a noad for accented subformulas} -@d accent_noad_size=5 {number of |mem| words in an accent noad} -@d accent_chr(#)==#+4 {the |accent_chr| field of an accent noad} -@d vcenter_noad=accent_noad+1 {|type| of a noad for \.{\\vcenter}} -@d left_noad=vcenter_noad+1 {|type| of a noad for \.{\\left}} -@d right_noad=left_noad+1 {|type| of a noad for \.{\\right}} -@d delimiter==nucleus {|delimiter| field in left and right noads} -@d scripts_allowed(#)==(type(#)>=ord_noad)and(type(#)<left_noad) - -@ Math formulas can also contain instructions like \.{\\textstyle} that -override \TeX's normal style rules. A |style_node| is inserted into the -data structure to record such instructions; it is three words long, so it -is considered a node instead of a noad. The |subtype| is either |display_style| -or |text_style| or |script_style| or |script_script_style|. The -second and third words of a |style_node| are not used, but they are -present because a |choice_node| is converted to a |style_node|. - -\TeX\ uses even numbers 0, 2, 4, 6 to encode the basic styles -|display_style|, \dots, |script_script_style|, and adds~1 to get the -``cramped'' versions of these styles. This gives a numerical order that -is backwards from the convention of Appendix~G in {\sl The \TeX book\/}; -i.e., a smaller style has a larger numerical value. -@:TeXbook}{\sl The \TeX book@> - -@d style_node=unset_node+1 {|type| of a style node} -@d style_node_size=3 {number of words in a style node} -@d display_style=0 {|subtype| for \.{\\displaystyle}} -@d text_style=2 {|subtype| for \.{\\textstyle}} -@d script_style=4 {|subtype| for \.{\\scriptstyle}} -@d script_script_style=6 {|subtype| for \.{\\scriptscriptstyle}} -@d cramped=1 {add this to an uncramped style if you want to cramp it} - -@p function new_style(@!s:small_number):pointer; {create a style node} -var p:pointer; {the new node} -begin p:=get_node(style_node_size); type(p):=style_node; -subtype(p):=s; width(p):=0; depth(p):=0; {the |width| and |depth| are not used} -new_style:=p; -end; - -@ Finally, the \.{\\mathchoice} primitive creates a |choice_node|, which -has special subfields |display_mlist|, |text_mlist|, |script_mlist|, -and |script_script_mlist| pointing to the mlists for each style. - -@d choice_node=unset_node+2 {|type| of a choice node} -@d display_mlist(#)==info(#+1) {mlist to be used in display style} -@d text_mlist(#)==link(#+1) {mlist to be used in text style} -@d script_mlist(#)==info(#+2) {mlist to be used in script style} -@d script_script_mlist(#)==link(#+2) {mlist to be used in scriptscript style} - -@p function new_choice:pointer; {create a choice node} -var p:pointer; {the new node} -begin p:=get_node(style_node_size); type(p):=choice_node; -subtype(p):=0; {the |subtype| is not used} -display_mlist(p):=null; text_mlist(p):=null; script_mlist(p):=null; -script_script_mlist(p):=null; -new_choice:=p; -end; - -@ Let's consider now the previously unwritten part of |show_node_list| -that displays the things that can only be present in mlists; this -program illustrates how to access the data structures just defined. - -In the context of the following program, |p| points to a node or noad that -should be displayed, and the current string contains the ``recursion history'' -that leads to this point. The recursion history consists of a dot for each -outer level in which |p| is subsidiary to some node, or in which |p| is -subsidiary to the |nucleus| field of some noad; the dot is replaced by -`\.\_' or `\.\^' or `\./' or `\.\\' if |p| is descended from the |subscr| -or |supscr| or |denominator| or |numerator| fields of noads. For example, -the current string would be `\.{.\^.\_/}' if |p| points to the |ord_noad| for -|x| in the (ridiculous) formula -`\.{\$\\sqrt\{a\^\{\\mathinner\{b\_\{c\\over x+y\}\}\}\}\$}'. - -@<Cases of |show_node_list| that arise...@>= -style_node:print_style(subtype(p)); -choice_node:@<Display choice node |p|@>; -ord_noad,op_noad,bin_noad,rel_noad,open_noad,close_noad,punct_noad,inner_noad, - radical_noad,over_noad,under_noad,vcenter_noad,accent_noad, - left_noad,right_noad:@<Display normal noad |p|@>; -fraction_noad:@<Display fraction noad |p|@>; - -@ Here are some simple routines used in the display of noads. - -@<Declare procedures needed for displaying the elements of mlists@>= -procedure print_fam_and_char(@!p:pointer); {prints family and character} -begin print_esc("fam"); print_int(fam(p)); print_char(" "); -print_ASCII(qo(character(p))); -end; -@# -procedure print_delimiter(@!p:pointer); {prints a delimiter as 24-bit hex value} -var a:integer; {accumulator} -begin a:=small_fam(p)*256+qo(small_char(p)); -a:=a*@"1000+large_fam(p)*256+qo(large_char(p)); -if a<0 then print_int(a) {this should never happen} -else print_hex(a); -end; - -@ The next subroutine will descend to another level of recursion when a -subsidiary mlist needs to be displayed. The parameter |c| indicates what -character is to become part of the recursion history. An empty mlist is -distinguished from a field with |math_type(p)=empty|, because these are -not equivalent (as explained above). -@^recursion@> - -@<Declare procedures needed for displaying...@>= -procedure@?show_info; forward;@t\2@>@?{|show_node_list(info(temp_ptr))|} -procedure print_subsidiary_data(@!p:pointer;@!c:ASCII_code); - {display a noad field} -begin if cur_length>=depth_threshold then - begin if math_type(p)<>empty then print(" []"); - end -else begin append_char(c); {include |c| in the recursion history} - temp_ptr:=p; {prepare for |show_info| if recursion is needed} - case math_type(p) of - math_char: begin print_ln; print_current_string; print_fam_and_char(p); - end; - sub_box: show_info; {recursive call} - sub_mlist: if info(p)=null then - begin print_ln; print_current_string; print("{}"); - end - else show_info; {recursive call} - othercases do_nothing {|empty|} - endcases;@/ - flush_char; {remove |c| from the recursion history} - end; -end; - -@ The inelegant introduction of |show_info| in the code above seems better -than the alternative of using \PASCAL's strange |forward| declaration for a -procedure with parameters. The \PASCAL\ convention about dropping parameters -from a post-|forward| procedure is, frankly, so intolerable to the author -of \TeX\ that he would rather stoop to communication via a global temporary -variable. (A similar stoopidity occurred with respect to |hlist_out| and -|vlist_out| above, and it will occur with respect to |mlist_to_hlist| below.) -@^Knuth, Donald Ervin@> -@:PASCAL}{\PASCAL@> - -@p procedure show_info; {the reader will kindly forgive this} -begin show_node_list(info(temp_ptr)); -end; - -@ @<Declare procedures needed for displaying...@>= -procedure print_style(@!c:integer); -begin case c div 2 of -0: print_esc("displaystyle"); {|display_style=0|} -1: print_esc("textstyle"); {|text_style=2|} -2: print_esc("scriptstyle"); {|script_style=4|} -3: print_esc("scriptscriptstyle"); {|script_script_style=6|} -othercases print("Unknown style!") -endcases; -end; - -@ @<Display choice node |p|@>= -begin print_esc("mathchoice"); -append_char("D"); show_node_list(display_mlist(p)); flush_char; -append_char("T"); show_node_list(text_mlist(p)); flush_char; -append_char("S"); show_node_list(script_mlist(p)); flush_char; -append_char("s"); show_node_list(script_script_mlist(p)); flush_char; -end - -@ @<Display normal noad |p|@>= -begin case type(p) of -ord_noad: print_esc("mathord"); -op_noad: print_esc("mathop"); -bin_noad: print_esc("mathbin"); -rel_noad: print_esc("mathrel"); -open_noad: print_esc("mathopen"); -close_noad: print_esc("mathclose"); -punct_noad: print_esc("mathpunct"); -inner_noad: print_esc("mathinner"); -over_noad: print_esc("overline"); -under_noad: print_esc("underline"); -vcenter_noad: print_esc("vcenter"); -radical_noad: begin print_esc("radical"); print_delimiter(left_delimiter(p)); - end; -accent_noad: begin print_esc("accent"); print_fam_and_char(accent_chr(p)); - end; -left_noad: begin print_esc("left"); print_delimiter(delimiter(p)); - end; -right_noad: begin print_esc("right"); print_delimiter(delimiter(p)); - end; -end; -if subtype(p)<>normal then - if subtype(p)=limits then print_esc("limits") - else print_esc("nolimits"); -if type(p)<left_noad then print_subsidiary_data(nucleus(p),"."); -print_subsidiary_data(supscr(p),"^"); -print_subsidiary_data(subscr(p),"_"); -end - -@ @<Display fraction noad |p|@>= -begin print_esc("fraction, thickness "); -if thickness(p)=default_code then print("= default") -else print_scaled(thickness(p)); -if (small_fam(left_delimiter(p))<>0)or@+ - (small_char(left_delimiter(p))<>min_quarterword)or@| - (large_fam(left_delimiter(p))<>0)or@| - (large_char(left_delimiter(p))<>min_quarterword) then - begin print(", left-delimiter "); print_delimiter(left_delimiter(p)); - end; -if (small_fam(right_delimiter(p))<>0)or@| - (small_char(right_delimiter(p))<>min_quarterword)or@| - (large_fam(right_delimiter(p))<>0)or@| - (large_char(right_delimiter(p))<>min_quarterword) then - begin print(", right-delimiter "); print_delimiter(right_delimiter(p)); - end; -print_subsidiary_data(numerator(p),"\"); -print_subsidiary_data(denominator(p),"/"); -end - -@ That which can be displayed can also be destroyed. - -@<Cases of |flush_node_list| that arise...@>= -style_node: begin free_node(p,style_node_size); goto done; - end; -choice_node:begin flush_node_list(display_mlist(p)); - flush_node_list(text_mlist(p)); - flush_node_list(script_mlist(p)); - flush_node_list(script_script_mlist(p)); - free_node(p,style_node_size); goto done; - end; -ord_noad,op_noad,bin_noad,rel_noad,open_noad,close_noad,punct_noad,inner_noad, - radical_noad,over_noad,under_noad,vcenter_noad,accent_noad:@t@>@;@/ - begin if math_type(nucleus(p))>=sub_box then - flush_node_list(info(nucleus(p))); - if math_type(supscr(p))>=sub_box then - flush_node_list(info(supscr(p))); - if math_type(subscr(p))>=sub_box then - flush_node_list(info(subscr(p))); - if type(p)=radical_noad then free_node(p,radical_noad_size) - else if type(p)=accent_noad then free_node(p,accent_noad_size) - else free_node(p,noad_size); - goto done; - end; -left_noad,right_noad: begin free_node(p,noad_size); goto done; - end; -fraction_noad: begin flush_node_list(info(numerator(p))); - flush_node_list(info(denominator(p))); - free_node(p,fraction_noad_size); goto done; - end; - -@* \[35] Subroutines for math mode. -In order to convert mlists to hlists, i.e., noads to nodes, we need several -subroutines that are conveniently dealt with now. - -Let us first introduce the macros that make it easy to get at the parameters and -other font information. A size code, which is a multiple of 16, is added to a -family number to get an index into the table of internal font numbers -for each combination of family and size. (Be alert: Size codes get -larger as the type gets smaller.) - -@d text_size=0 {size code for the largest size in a family} -@d script_size=16 {size code for the medium size in a family} -@d script_script_size=32 {size code for the smallest size in a family} - -@<Basic printing procedures@>= -procedure print_size(@!s:integer); -begin if s=text_size then print_esc("textfont") -else if s=script_size then print_esc("scriptfont") -else print_esc("scriptscriptfont"); -end; - -@ Before an mlist is converted to an hlist, \TeX\ makes sure that -the fonts in family~2 have enough parameters to be math-symbol -fonts, and that the fonts in family~3 have enough parameters to be -math-extension fonts. The math-symbol parameters are referred to by using the -following macros, which take a size code as their parameter; for example, -|num1(cur_size)| gives the value of the |num1| parameter for the current size. -@^parameters for symbols@> -@^font parameters@> - -@d mathsy_end(#)==fam_fnt(2+#)]].sc -@d mathsy(#)==font_info[#+param_base[mathsy_end -@d math_x_height==mathsy(5) {height of `\.x'} -@d math_quad==mathsy(6) {\.{18mu}} -@d num1==mathsy(8) {numerator shift-up in display styles} -@d num2==mathsy(9) {numerator shift-up in non-display, non-\.{\\atop}} -@d num3==mathsy(10) {numerator shift-up in non-display \.{\\atop}} -@d denom1==mathsy(11) {denominator shift-down in display styles} -@d denom2==mathsy(12) {denominator shift-down in non-display styles} -@d sup1==mathsy(13) {superscript shift-up in uncramped display style} -@d sup2==mathsy(14) {superscript shift-up in uncramped non-display} -@d sup3==mathsy(15) {superscript shift-up in cramped styles} -@d sub1==mathsy(16) {subscript shift-down if superscript is absent} -@d sub2==mathsy(17) {subscript shift-down if superscript is present} -@d sup_drop==mathsy(18) {superscript baseline below top of large box} -@d sub_drop==mathsy(19) {subscript baseline below bottom of large box} -@d delim1==mathsy(20) {size of \.{\\atopwithdelims} delimiters - in display styles} -@d delim2==mathsy(21) {size of \.{\\atopwithdelims} delimiters in non-displays} -@d axis_height==mathsy(22) {height of fraction lines above the baseline} -@d total_mathsy_params=22 - -@ The math-extension parameters have similar macros, but the size code is -omitted (since it is always |cur_size| when we refer to such parameters). -@^parameters for symbols@> -@^font parameters@> - -@d mathex(#)==font_info[#+param_base[fam_fnt(3+cur_size)]].sc -@d default_rule_thickness==mathex(8) {thickness of \.{\\over} bars} -@d big_op_spacing1==mathex(9) {minimum clearance above a displayed op} -@d big_op_spacing2==mathex(10) {minimum clearance below a displayed op} -@d big_op_spacing3==mathex(11) {minimum baselineskip above displayed op} -@d big_op_spacing4==mathex(12) {minimum baselineskip below displayed op} -@d big_op_spacing5==mathex(13) {padding above and below displayed limits} -@d total_mathex_params=13 - -@ We also need to compute the change in style between mlists and their -subsidiaries. The following macros define the subsidiary style for -an overlined nucleus (|cramped_style|), for a subscript or a superscript -(|sub_style| or |sup_style|), or for a numerator or denominator (|num_style| -or |denom_style|). - -@d cramped_style(#)==2*(# div 2)+cramped {cramp the style} -@d sub_style(#)==2*(# div 4)+script_style+cramped {smaller and cramped} -@d sup_style(#)==2*(# div 4)+script_style+(# mod 2) {smaller} -@d num_style(#)==#+2-2*(# div 6) {smaller unless already script-script} -@d denom_style(#)==2*(# div 2)+cramped+2-2*(# div 6) {smaller, cramped} - -@ When the style changes, the following piece of program computes associated -information: - -@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>= -begin if cur_style<script_style then cur_size:=text_size -else cur_size:=16*((cur_style-text_style) div 2); -cur_mu:=x_over_n(math_quad(cur_size),18); -end - -@ Here is a function that returns a pointer to a rule node having a given -thickness |t|. The rule will extend horizontally to the boundary of the vlist -that eventually contains it. - -@p function fraction_rule(@!t:scaled):pointer; - {construct the bar for a fraction} -var p:pointer; {the new node} -begin p:=new_rule; height(p):=t; depth(p):=0; fraction_rule:=p; -end; - -@ The |overbar| function returns a pointer to a vlist box that consists of -a given box |b|, above which has been placed a kern of height |k| under a -fraction rule of thickness |t| under additional space of height |t|. - -@p function overbar(@!b:pointer;@!k,@!t:scaled):pointer; -var p,@!q:pointer; {nodes being constructed} -begin p:=new_kern(k); link(p):=b; q:=fraction_rule(t); link(q):=p; -p:=new_kern(t); link(p):=q; overbar:=vpack(p,natural); -end; - -@ The |var_delimiter| function, which finds or constructs a sufficiently -large delimiter, is the most interesting of the auxiliary functions that -currently concern us. Given a pointer |d| to a delimiter field in some noad, -together with a size code |s| and a vertical distance |v|, this function -returns a pointer to a box that contains the smallest variant of |d| whose -height plus depth is |v| or more. (And if no variant is large enough, it -returns the largest available variant.) In particular, this routine will -construct arbitrarily large delimiters from extensible components, if -|d| leads to such characters. - -The value returned is a box whose |shift_amount| has been set so that -the box is vertically centered with respect to the axis in the given size. -If a built-up symbol is returned, the height of the box before shifting -will be the height of its topmost component. - -@p@t\4@>@<Declare subprocedures for |var_delimiter|@> -function var_delimiter(@!d:pointer;@!s:small_number;@!v:scaled):pointer; -label found,continue; -var b:pointer; {the box that will be constructed} -@!f,@!g: internal_font_number; {best-so-far and tentative font codes} -@!c,@!x,@!y: quarterword; {best-so-far and tentative character codes} -@!m,@!n: integer; {the number of extensible pieces} -@!u: scaled; {height-plus-depth of a tentative character} -@!w: scaled; {largest height-plus-depth so far} -@!q: four_quarters; {character info} -@!hd: eight_bits; {height-depth byte} -@!r: four_quarters; {extensible pieces} -@!z: small_number; {runs through font family members} -@!large_attempt: boolean; {are we trying the ``large'' variant?} -begin f:=null_font; w:=0; large_attempt:=false; -z:=small_fam(d); x:=small_char(d); -loop@+ begin @<Look at the variants of |(z,x)|; set |f| and |c| whenever - a better character is found; |goto found| as soon as a - large enough variant is encountered@>; - if large_attempt then goto found; {there were none large enough} - large_attempt:=true; z:=large_fam(d); x:=large_char(d); - end; -found: if f<>null_font then - @<Make variable |b| point to a box for |(f,c)|@> -else begin b:=new_null_box; - width(b):=null_delimiter_space; {use this width if no delimiter was found} - end; -shift_amount(b):=half(height(b)-depth(b)) - axis_height(s); -var_delimiter:=b; -end; - -@ The search process is complicated slightly by the facts that some of the -characters might not be present in some of the fonts, and they might not -be probed in increasing order of height. - -@<Look at the variants of |(z,x)|; set |f| and |c|...@>= -if (z<>0)or(x<>min_quarterword) then - begin z:=z+s+16; - repeat z:=z-16; g:=fam_fnt(z); - if g<>null_font then - @<Look at the list of characters starting with |x| in - font |g|; set |f| and |c| whenever - a better character is found; |goto found| as soon as a - large enough variant is encountered@>; - until z<16; - end - -@ @<Look at the list of characters starting with |x|...@>= -begin y:=x; -if (qo(y)>=font_bc[g])and(qo(y)<=font_ec[g]) then - begin continue: q:=char_info(g)(y); - if char_exists(q) then - begin if char_tag(q)=ext_tag then - begin f:=g; c:=y; goto found; - end; - hd:=height_depth(q); - u:=char_height(g)(hd)+char_depth(g)(hd); - if u>w then - begin f:=g; c:=y; w:=u; - if u>=v then goto found; - end; - if char_tag(q)=list_tag then - begin y:=rem_byte(q); goto continue; - end; - end; - end; -end - -@ Here is a subroutine that creates a new box, whose list contains a -single character, and whose width includes the italic correction for -that character. The height or depth of the box will be negative, if -the height or depth of the character is negative; thus, this routine -may deliver a slightly different result than |hpack| would produce. - -@<Declare subprocedures for |var_delimiter|@>= -function char_box(@!f:internal_font_number;@!c:quarterword):pointer; -var q:four_quarters; -@!hd:eight_bits; {|height_depth| byte} -@!b,@!p:pointer; {the new box and its character node} -begin q:=char_info(f)(c); hd:=height_depth(q); -b:=new_null_box; width(b):=char_width(f)(q)+char_italic(f)(q); -height(b):=char_height(f)(hd); depth(b):=char_depth(f)(hd); -p:=get_avail; character(p):=c; font(p):=f; list_ptr(b):=p; char_box:=b; -end; - -@ When the following code is executed, |char_tag(q)| will be equal to -|ext_tag| if and only if a built-up symbol is supposed to be returned. - -@<Make variable |b| point to a box for |(f,c)|@>= -if char_tag(q)=ext_tag then - @<Construct an extensible character in a new box |b|, - using recipe |rem_byte(q)| and font |f|@> -else b:=char_box(f,c) - -@ When we build an extensible character, it's handy to have the -following subroutine, which puts a given character on top -of the characters already in box |b|: - -@<Declare subprocedures for |var_delimiter|@>= -procedure stack_into_box(@!b:pointer;@!f:internal_font_number; - @!c:quarterword); -var p:pointer; {new node placed into |b|} -begin p:=char_box(f,c); link(p):=list_ptr(b); list_ptr(b):=p; -height(b):=height(p); -end; - -@ Another handy subroutine computes the height plus depth of -a given character: - -@<Declare subprocedures for |var_delimiter|@>= -function height_plus_depth(@!f:internal_font_number;@!c:quarterword):scaled; -var q:four_quarters; -@!hd:eight_bits; {|height_depth| byte} -begin q:=char_info(f)(c); hd:=height_depth(q); -height_plus_depth:=char_height(f)(hd)+char_depth(f)(hd); -end; - -@ @<Construct an extensible...@>= -begin b:=new_null_box; -type(b):=vlist_node; -r:=font_info[exten_base[f]+rem_byte(q)].qqqq;@/ -@<Compute the minimum suitable height, |w|, and the corresponding - number of extension steps, |n|; also set |width(b)|@>; -c:=ext_bot(r); -if c<>min_quarterword then stack_into_box(b,f,c); -c:=ext_rep(r); -for m:=1 to n do stack_into_box(b,f,c); -c:=ext_mid(r); -if c<>min_quarterword then - begin stack_into_box(b,f,c); c:=ext_rep(r); - for m:=1 to n do stack_into_box(b,f,c); - end; -c:=ext_top(r); -if c<>min_quarterword then stack_into_box(b,f,c); -depth(b):=w-height(b); -end - -@ The width of an extensible character is the width of the repeatable -module. If this module does not have positive height plus depth, -we don't use any copies of it, otherwise we use as few as possible -(in groups of two if there is a middle part). - -@<Compute the minimum suitable height, |w|, and...@>= -c:=ext_rep(r); u:=height_plus_depth(f,c); -w:=0; q:=char_info(f)(c); width(b):=char_width(f)(q)+char_italic(f)(q);@/ -c:=ext_bot(r);@+if c<>min_quarterword then w:=w+height_plus_depth(f,c); -c:=ext_mid(r);@+if c<>min_quarterword then w:=w+height_plus_depth(f,c); -c:=ext_top(r);@+if c<>min_quarterword then w:=w+height_plus_depth(f,c); -n:=0; -if u>0 then while w<v do - begin w:=w+u; incr(n); - if ext_mid(r)<>min_quarterword then w:=w+u; - end - -@ The next subroutine is much simpler; it is used for numerators and -denominators of fractions as well as for displayed operators and -their limits above and below. It takes a given box~|b| and -changes it so that the new box is centered in a box of width~|w|. -The centering is done by putting \.{\\hss} glue at the left and right -of the list inside |b|, then packaging the new box; thus, the -actual box might not really be centered, if it already contains -infinite glue. - -The given box might contain a single character whose italic correction -has been added to the width of the box; in this case a compensating -kern is inserted. - -@p function rebox(@!b:pointer;@!w:scaled):pointer; -var p:pointer; {temporary register for list manipulation} -@!f:internal_font_number; {font in a one-character box} -@!v:scaled; {width of a character without italic correction} -begin if (width(b)<>w)and(list_ptr(b)<>null) then - begin if type(b)=vlist_node then b:=hpack(b,natural); - p:=list_ptr(b); - if (is_char_node(p))and(link(p)=null) then - begin f:=font(p); v:=char_width(f)(char_info(f)(character(p))); - if v<>width(b) then link(p):=new_kern(width(b)-v); - end; - free_node(b,box_node_size); - b:=new_glue(ss_glue); link(b):=p; - while link(p)<>null do p:=link(p); - link(p):=new_glue(ss_glue); - rebox:=hpack(b,w,exactly); - end -else begin width(b):=w; rebox:=b; - end; -end; - -@ Here is a subroutine that creates a new glue specification from another -one that is expressed in `\.{mu}', given the value of the math unit. - -@d mu_mult(#)==nx_plus_y(n,#,xn_over_d(#,f,@'200000)) - -@p function math_glue(@!g:pointer;@!m:scaled):pointer; -var p:pointer; {the new glue specification} -@!n:integer; {integer part of |m|} -@!f:scaled; {fraction part of |m|} -begin n:=x_over_n(m,@'200000); f:=remainder;@/ -if f<0 then - begin decr(n); f:=f+@'200000; - end; -p:=get_node(glue_spec_size); -width(p):=mu_mult(width(g)); {convert \.{mu} to \.{pt}} -stretch_order(p):=stretch_order(g); -if stretch_order(p)=normal then stretch(p):=mu_mult(stretch(g)) -else stretch(p):=stretch(g); -shrink_order(p):=shrink_order(g); -if shrink_order(p)=normal then shrink(p):=mu_mult(shrink(g)) -else shrink(p):=shrink(g); -math_glue:=p; -end; - -@ The |math_kern| subroutine removes |mu_glue| from a kern node, given -the value of the math unit. - -@p procedure math_kern(@!p:pointer;@!m:scaled); -var @!n:integer; {integer part of |m|} -@!f:scaled; {fraction part of |m|} -begin if subtype(p)=mu_glue then - begin n:=x_over_n(m,@'200000); f:=remainder;@/ - if f<0 then - begin decr(n); f:=f+@'200000; - end; - width(p):=mu_mult(width(p)); subtype(p):=explicit; - end; -end; - -@ Sometimes it is necessary to destroy an mlist. The following -subroutine empties the current list, assuming that |abs(mode)=mmode|. - -@p procedure flush_math; -begin flush_node_list(link(head)); flush_node_list(incompleat_noad); -link(head):=null; tail:=head; incompleat_noad:=null; -end; - -@* \[36] Typesetting math formulas. -\TeX's most important routine for dealing with formulas is called -|mlist_to_hlist|. After a formula has been scanned and represented as an -mlist, this routine converts it to an hlist that can be placed into a box -or incorporated into the text of a paragraph. There are three implicit -parameters, passed in global variables: |cur_mlist| points to the first -node or noad in the given mlist (and it might be |null|); |cur_style| is a -style code; and |mlist_penalties| is |true| if penalty nodes for potential -line breaks are to be inserted into the resulting hlist. After -|mlist_to_hlist| has acted, |link(temp_head)| points to the translated hlist. - -Since mlists can be inside mlists, the procedure is recursive. And since this -is not part of \TeX's inner loop, the program has been written in a manner -that stresses compactness over efficiency. -@^recursion@> - -@<Glob...@>= -@!cur_mlist:pointer; {beginning of mlist to be translated} -@!cur_style:small_number; {style code at current place in the list} -@!cur_size:small_number; {size code corresponding to |cur_style|} -@!cur_mu:scaled; {the math unit width corresponding to |cur_size|} -@!mlist_penalties:boolean; {should |mlist_to_hlist| insert penalties?} - -@ The recursion in |mlist_to_hlist| is due primarily to a subroutine -called |clean_box| that puts a given noad field into a box using a given -math style; |mlist_to_hlist| can call |clean_box|, which can call -|mlist_to_hlist|. -@^recursion@> - -The box returned by |clean_box| is ``clean'' in the -sense that its |shift_amount| is zero. - -@p procedure@?mlist_to_hlist; forward;@t\2@>@/ -function clean_box(@!p:pointer;@!s:small_number):pointer; -label found; -var q:pointer; {beginning of a list to be boxed} -@!save_style:small_number; {|cur_style| to be restored} -@!x:pointer; {box to be returned} -@!r:pointer; {temporary pointer} -begin case math_type(p) of -math_char: begin cur_mlist:=new_noad; mem[nucleus(cur_mlist)]:=mem[p]; - end; -sub_box: begin q:=info(p); goto found; - end; -sub_mlist: cur_mlist:=info(p); -othercases begin q:=new_null_box; goto found; - end -endcases;@/ -save_style:=cur_style; cur_style:=s; mlist_penalties:=false;@/ -mlist_to_hlist; q:=link(temp_head); {recursive call} -cur_style:=save_style; {restore the style} -@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; -found: if is_char_node(q)or(q=null) then x:=hpack(q,natural) - else if (link(q)=null)and(type(q)<=vlist_node)and(shift_amount(q)=0) then - x:=q {it's already clean} - else x:=hpack(q,natural); -@<Simplify a trivial box@>; -clean_box:=x; -end; - -@ Here we save memory space in a common case. - -@<Simplify a trivial box@>= -q:=list_ptr(x); -if is_char_node(q) then - begin r:=link(q); - if r<>null then if link(r)=null then if not is_char_node(r) then - if type(r)=kern_node then {unneeded italic correction} - begin free_node(r,small_node_size); link(q):=null; - end; - end - -@ It is convenient to have a procedure that converts a |math_char| -field to an ``unpacked'' form. The |fetch| routine sets |cur_f|, |cur_c|, -and |cur_i| to the font code, character code, and character information bytes of -a given noad field. It also takes care of issuing error messages for -nonexistent characters; in such cases, |char_exists(cur_i)| will be |false| -after |fetch| has acted, and the field will also have been reset to |empty|. - -@p procedure fetch(@!a:pointer); {unpack the |math_char| field |a|} -begin cur_c:=character(a); cur_f:=fam_fnt(fam(a)+cur_size); -if cur_f=null_font then - @<Complain about an undefined family and set |cur_i| null@> -else begin if (qo(cur_c)>=font_bc[cur_f])and(qo(cur_c)<=font_ec[cur_f]) then - cur_i:=char_info(cur_f)(cur_c) - else cur_i:=null_character; - if not(char_exists(cur_i)) then - begin char_warning(cur_f,qo(cur_c)); - math_type(a):=empty; cur_i:=null_character; - end; - end; -end; - -@ @<Complain about an undefined family...@>= -begin print_err(""); print_size(cur_size); print_char(" "); -print_int(fam(a)); print(" is undefined (character "); -print_ASCII(qo(cur_c)); print_char(")"); -help4("Somewhere in the math formula just ended, you used the")@/ -("stated character from an undefined font family. For example,")@/ -("plain TeX doesn't allow \it or \sl in subscripts. Proceed,")@/ -("and I'll try to forget that I needed that character."); -error; cur_i:=null_character; math_type(a):=empty; -end - -@ The outputs of |fetch| are placed in global variables. - -@<Glob...@>= -@!cur_f:internal_font_number; {the |font| field of a |math_char|} -@!cur_c:quarterword; {the |character| field of a |math_char|} -@!cur_i:four_quarters; {the |char_info| of a |math_char|, - or a lig/kern instruction} - -@ We need to do a lot of different things, so |mlist_to_hlist| makes two -passes over the given mlist. - -The first pass does most of the processing: It removes ``mu'' spacing from -glue, it recursively evaluates all subsidiary mlists so that only the -top-level mlist remains to be handled, it puts fractions and square roots -and such things into boxes, it attaches subscripts and superscripts, and -it computes the overall height and depth of the top-level mlist so that -the size of delimiters for a |left_noad| and a |right_noad| will be known. -The hlist resulting from each noad is recorded in that noad's |new_hlist| -field, an integer field that replaces the |nucleus| or |thickness|. -@^recursion@> - -The second pass eliminates all noads and inserts the correct glue and -penalties between nodes. - -@d new_hlist(#)==mem[nucleus(#)].int {the translation of an mlist} - -@ Here is the overall plan of |mlist_to_hlist|, and the list of its -local variables. - -@d done_with_noad=80 {go here when a noad has been fully translated} -@d done_with_node=81 {go here when a node has been fully converted} -@d check_dimensions=82 {go here to update |max_h| and |max_d|} -@d delete_q=83 {go here to delete |q| and move to the next node} - -@p@t\4@>@<Declare math construction procedures@> -procedure mlist_to_hlist; -label reswitch, check_dimensions, done_with_noad, done_with_node, delete_q, - done; -var mlist:pointer; {beginning of the given list} -@!penalties:boolean; {should penalty nodes be inserted?} -@!style:small_number; {the given style} -@!save_style:small_number; {holds |cur_style| during recursion} -@!q:pointer; {runs through the mlist} -@!r:pointer; {the most recent noad preceding |q|} -@!r_type:small_number; {the |type| of noad |r|, or |op_noad| if |r=null|} -@!t:small_number; {the effective |type| of noad |q| during the second pass} -@!p,@!x,@!y,@!z: pointer; {temporary registers for list construction} -@!pen:integer; {a penalty to be inserted} -@!s:small_number; {the size of a noad to be deleted} -@!max_h,@!max_d:scaled; {maximum height and depth of the list translated so far} -@!delta:scaled; {offset between subscript and superscript} -begin mlist:=cur_mlist; penalties:=mlist_penalties; -style:=cur_style; {tuck global parameters away as local variables} -q:=mlist; r:=null; r_type:=op_noad; max_h:=0; max_d:=0; -@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; -while q<>null do @<Process node-or-noad |q| as much as possible in preparation - for the second pass of |mlist_to_hlist|, then move to the next - item in the mlist@>; -@<Convert \(a)a final |bin_noad| to an |ord_noad|@>; -@<Make a second pass over the mlist, removing all noads and inserting the - proper spacing and penalties@>; -end; - -@ We use the fact that no character nodes appear in an mlist, hence -the field |type(q)| is always present. - -@<Process node-or-noad...@>= -begin @<Do first-pass processing based on |type(q)|; |goto done_with_noad| - if a noad has been fully processed, |goto check_dimensions| if it - has been translated into |new_hlist(q)|, or |goto done_with_node| - if a node has been fully processed@>; -check_dimensions: z:=hpack(new_hlist(q),natural); -if height(z)>max_h then max_h:=height(z); -if depth(z)>max_d then max_d:=depth(z); -free_node(z,box_node_size); -done_with_noad: r:=q; r_type:=type(r); -done_with_node: q:=link(q); -end - -@ One of the things we must do on the first pass is change a |bin_noad| to -an |ord_noad| if the |bin_noad| is not in the context of a binary operator. -The values of |r| and |r_type| make this fairly easy. - -@<Do first-pass processing...@>= -reswitch: delta:=0; -case type(q) of -bin_noad: case r_type of - bin_noad,op_noad,rel_noad,open_noad,punct_noad,left_noad: - begin type(q):=ord_noad; goto reswitch; - end; - othercases do_nothing - endcases; -rel_noad,close_noad,punct_noad,right_noad: begin@t@>@;@/ - @<Convert \(a)a final |bin_noad| to an |ord_noad|@>; - if type(q)=right_noad then goto done_with_noad; - end; -@t\4@>@<Cases for noads that can follow a |bin_noad|@>@; -@t\4@>@<Cases for nodes that can appear in an mlist, after which we - |goto done_with_node|@>@; -othercases confusion("mlist1") -@:this can't happen mlist1}{\quad mlist1@> -endcases;@/ -@<Convert \(n)|nucleus(q)| to an hlist and attach the sub/superscripts@> - -@ @<Convert \(a)a final |bin_noad| to an |ord_noad|@>= -if r_type=bin_noad then type(r):=ord_noad - -@ @<Cases for nodes that can appear in an mlist...@>= -style_node: begin cur_style:=subtype(q); - @<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; - goto done_with_node; - end; -choice_node: @<Change this node to a style node followed by the correct choice, - then |goto done_with_node|@>; -ins_node,mark_node,adjust_node, - whatsit_node,penalty_node,disc_node: goto done_with_node; -rule_node: begin if height(q)>max_h then max_h:=height(q); - if depth(q)>max_d then max_d:=depth(q); goto done_with_node; - end; -glue_node: begin @<Convert \(m)math glue to ordinary glue@>; - goto done_with_node; - end; -kern_node: begin math_kern(q,cur_mu); goto done_with_node; - end; - -@ @d choose_mlist(#)==begin p:=#(q); #(q):=null;@+end - -@<Change this node to a style node...@>= -begin case cur_style div 2 of -0: choose_mlist(display_mlist); {|display_style=0|} -1: choose_mlist(text_mlist); {|text_style=2|} -2: choose_mlist(script_mlist); {|script_style=4|} -3: choose_mlist(script_script_mlist); {|script_script_style=6|} -end; {there are no other cases} -flush_node_list(display_mlist(q)); -flush_node_list(text_mlist(q)); -flush_node_list(script_mlist(q)); -flush_node_list(script_script_mlist(q));@/ -type(q):=style_node; subtype(q):=cur_style; width(q):=0; depth(q):=0; -if p<>null then - begin z:=link(q); link(q):=p; - while link(p)<>null do p:=link(p); - link(p):=z; - end; -goto done_with_node; -end - -@ Conditional math glue (`\.{\\nonscript}') results in a |glue_node| -pointing to |zero_glue|, with |subtype(q)=cond_math_glue|; in such a case -the node following will be eliminated if it is a glue or kern node and if the -current size is different from |text_size|. Unconditional math glue -(`\.{\\muskip}') is converted to normal glue by multiplying the dimensions -by |cur_mu|. -@!@:non_script_}{\.{\\nonscript} primitive@> - -@<Convert \(m)math glue to ordinary glue@>= -if subtype(q)=mu_glue then - begin x:=glue_ptr(q); - y:=math_glue(x,cur_mu); delete_glue_ref(x); glue_ptr(q):=y; - subtype(q):=normal; - end -else if (cur_size<>text_size)and(subtype(q)=cond_math_glue) then - begin p:=link(q); - if p<>null then if (type(p)=glue_node)or(type(p)=kern_node) then - begin link(q):=link(p); link(p):=null; flush_node_list(p); - end; - end - -@ @<Cases for noads that can follow a |bin_noad|@>= -left_noad: goto done_with_noad; -fraction_noad: begin make_fraction(q); goto check_dimensions; - end; -op_noad: begin delta:=make_op(q); - if subtype(q)=limits then goto check_dimensions; - end; -ord_noad: make_ord(q); -open_noad,inner_noad: do_nothing; -radical_noad: make_radical(q); -over_noad: make_over(q); -under_noad: make_under(q); -accent_noad: make_math_accent(q); -vcenter_noad: make_vcenter(q); - -@ Most of the actual construction work of |mlist_to_hlist| is done -by procedures with names -like |make_fraction|, |make_radical|, etc. To illustrate -the general setup of such procedures, let's begin with a couple of -simple ones. - -@<Declare math...@>= -procedure make_over(@!q:pointer); -begin info(nucleus(q)):=@| - overbar(clean_box(nucleus(q),cramped_style(cur_style)),@| - 3*default_rule_thickness,default_rule_thickness); -math_type(nucleus(q)):=sub_box; -end; - -@ @<Declare math...@>= -procedure make_under(@!q:pointer); -var p,@!x,@!y: pointer; {temporary registers for box construction} -@!delta:scaled; {overall height plus depth} -begin x:=clean_box(nucleus(q),cur_style); -p:=new_kern(3*default_rule_thickness); link(x):=p; -link(p):=fraction_rule(default_rule_thickness); -y:=vpack(x,natural); -delta:=height(y)+depth(y)+default_rule_thickness; -height(y):=height(x); depth(y):=delta-height(y); -info(nucleus(q)):=y; math_type(nucleus(q)):=sub_box; -end; - -@ @<Declare math...@>= -procedure make_vcenter(@!q:pointer); -var v:pointer; {the box that should be centered vertically} -@!delta:scaled; {its height plus depth} -begin v:=info(nucleus(q)); -if type(v)<>vlist_node then confusion("vcenter"); -@:this can't happen vcenter}{\quad vcenter@> -delta:=height(v)+depth(v); -height(v):=axis_height(cur_size)+half(delta); -depth(v):=delta-height(v); -end; - -@ According to the rules in the \.{DVI} file specifications, we ensure alignment -@^square roots@> -between a square root sign and the rule above its nucleus by assuming that the -baseline of the square-root symbol is the same as the bottom of the rule. The -height of the square-root symbol will be the thickness of the rule, and the -depth of the square-root symbol should exceed or equal the height-plus-depth -of the nucleus plus a certain minimum clearance~|clr|. The symbol will be -placed so that the actual clearance is |clr| plus half the excess. - -@<Declare math...@>= -procedure make_radical(@!q:pointer); -var x,@!y:pointer; {temporary registers for box construction} -@!delta,@!clr:scaled; {dimensions involved in the calculation} -begin x:=clean_box(nucleus(q),cramped_style(cur_style)); -if cur_style<text_style then {display style} - clr:=default_rule_thickness+(abs(math_x_height(cur_size)) div 4) -else begin clr:=default_rule_thickness; clr:=clr + (abs(clr) div 4); - end; -y:=var_delimiter(left_delimiter(q),cur_size,height(x)+depth(x)+clr+ - default_rule_thickness); -delta:=depth(y)-(height(x)+depth(x)+clr); -if delta>0 then clr:=clr+half(delta); {increase the actual clearance} -shift_amount(y):=-(height(x)+clr); -link(y):=overbar(x,clr,height(y)); -info(nucleus(q)):=hpack(y,natural); math_type(nucleus(q)):=sub_box; -end; - -@ Slants are not considered when placing accents in math mode. The accenter is -centered over the accentee, and the accent width is treated as zero with -respect to the size of the final box. - -@<Declare math...@>= -procedure make_math_accent(@!q:pointer); -label done,done1; -var p,@!x,@!y:pointer; {temporary registers for box construction} -@!a:integer; {address of lig/kern instruction} -@!c:quarterword; {accent character} -@!f:internal_font_number; {its font} -@!i:four_quarters; {its |char_info|} -@!s:scaled; {amount to skew the accent to the right} -@!h:scaled; {height of character being accented} -@!delta:scaled; {space to remove between accent and accentee} -@!w:scaled; {width of the accentee, not including sub/superscripts} -begin fetch(accent_chr(q)); -if char_exists(cur_i) then - begin i:=cur_i; c:=cur_c; f:=cur_f;@/ - @<Compute the amount of skew@>; - x:=clean_box(nucleus(q),cramped_style(cur_style)); w:=width(x); h:=height(x); - @<Switch to a larger accent if available and appropriate@>; - if h<x_height(f) then delta:=h@+else delta:=x_height(f); - if (math_type(supscr(q))<>empty)or(math_type(subscr(q))<>empty) then - if math_type(nucleus(q))=math_char then - @<Swap the subscript and superscript into box |x|@>; - y:=char_box(f,c); - shift_amount(y):=s+half(w-width(y)); - width(y):=0; p:=new_kern(-delta); link(p):=x; link(y):=p; - y:=vpack(y,natural); width(y):=width(x); - if height(y)<h then @<Make the height of box |y| equal to |h|@>; - info(nucleus(q)):=y; - math_type(nucleus(q)):=sub_box; - end; -end; - -@ @<Make the height of box |y|...@>= -begin p:=new_kern(h-height(y)); link(p):=list_ptr(y); list_ptr(y):=p; -height(y):=h; -end - -@ @<Switch to a larger accent if available and appropriate@>= -loop@+ begin if char_tag(i)<>list_tag then goto done; - y:=rem_byte(i); - i:=char_info(f)(y); - if not char_exists(i) then goto done; - if char_width(f)(i)>w then goto done; - c:=y; - end; -done: - -@ @<Compute the amount of skew@>= -s:=0; -if math_type(nucleus(q))=math_char then - begin fetch(nucleus(q)); - if char_tag(cur_i)=lig_tag then - begin a:=lig_kern_start(cur_f)(cur_i); - cur_i:=font_info[a].qqqq; - if skip_byte(cur_i)>stop_flag then - begin a:=lig_kern_restart(cur_f)(cur_i); - cur_i:=font_info[a].qqqq; - end; - loop@+ begin if qo(next_char(cur_i))=skew_char[cur_f] then - begin if op_byte(cur_i)>=kern_flag then - if skip_byte(cur_i)<=stop_flag then s:=char_kern(cur_f)(cur_i); - goto done1; - end; - if skip_byte(cur_i)>=stop_flag then goto done1; - a:=a+qo(skip_byte(cur_i))+1; - cur_i:=font_info[a].qqqq; - end; - end; - end; -done1: - -@ @<Swap the subscript and superscript into box |x|@>= -begin flush_node_list(x); x:=new_noad; -mem[nucleus(x)]:=mem[nucleus(q)]; -mem[supscr(x)]:=mem[supscr(q)]; -mem[subscr(x)]:=mem[subscr(q)];@/ -mem[supscr(q)].hh:=empty_field; -mem[subscr(q)].hh:=empty_field;@/ -math_type(nucleus(q)):=sub_mlist; info(nucleus(q)):=x; -x:=clean_box(nucleus(q),cur_style); delta:=delta+height(x)-h; h:=height(x); -end - -@ The |make_fraction| procedure is a bit different because it sets -|new_hlist(q)| directly rather than making a sub-box. - -@<Declare math...@>= -procedure make_fraction(@!q:pointer); -var p,@!v,@!x,@!y,@!z:pointer; {temporary registers for box construction} -@!delta,@!delta1,@!delta2,@!shift_up,@!shift_down,@!clr:scaled; - {dimensions for box calculations} -begin if thickness(q)=default_code then thickness(q):=default_rule_thickness; -@<Create equal-width boxes |x| and |z| for the numerator and denominator, - and compute the default amounts |shift_up| and |shift_down| by which they - are displaced from the baseline@>; -if thickness(q)=0 then @<Adjust \(s)|shift_up| and |shift_down| for the case - of no fraction line@> -else @<Adjust \(s)|shift_up| and |shift_down| for the case of a fraction line@>; -@<Construct a vlist box for the fraction, according to |shift_up| and - |shift_down|@>; -@<Put the \(f)fraction into a box with its delimiters, and make |new_hlist(q)| - point to it@>; -end; - -@ @<Create equal-width boxes |x| and |z| for the numerator and denom...@>= -x:=clean_box(numerator(q),num_style(cur_style)); -z:=clean_box(denominator(q),denom_style(cur_style)); -if width(x)<width(z) then x:=rebox(x,width(z)) -else z:=rebox(z,width(x)); -if cur_style<text_style then {display style} - begin shift_up:=num1(cur_size); shift_down:=denom1(cur_size); - end -else begin shift_down:=denom2(cur_size); - if thickness(q)<>0 then shift_up:=num2(cur_size) - else shift_up:=num3(cur_size); - end - -@ The numerator and denominator must be separated by a certain minimum -clearance, called |clr| in the following program. The difference between -|clr| and the actual clearance is twice |delta|. - -@<Adjust \(s)|shift_up| and |shift_down| for the case of no fraction line@>= -begin if cur_style<text_style then clr:=7*default_rule_thickness -else clr:=3*default_rule_thickness; -delta:=half(clr-((shift_up-depth(x))-(height(z)-shift_down))); -if delta>0 then - begin shift_up:=shift_up+delta; - shift_down:=shift_down+delta; - end; -end - -@ In the case of a fraction line, the minimum clearance depends on the actual -thickness of the line. - -@<Adjust \(s)|shift_up| and |shift_down| for the case of a fraction line@>= -begin if cur_style<text_style then clr:=3*thickness(q) -else clr:=thickness(q); -delta:=half(thickness(q)); -delta1:=clr-((shift_up-depth(x))-(axis_height(cur_size)+delta)); -delta2:=clr-((axis_height(cur_size)-delta)-(height(z)-shift_down)); -if delta1>0 then shift_up:=shift_up+delta1; -if delta2>0 then shift_down:=shift_down+delta2; -end - -@ @<Construct a vlist box for the fraction...@>= -v:=new_null_box; type(v):=vlist_node; -height(v):=shift_up+height(x); depth(v):=depth(z)+shift_down; -width(v):=width(x); {this also equals |width(z)|} -if thickness(q)=0 then - begin p:=new_kern((shift_up-depth(x))-(height(z)-shift_down)); - link(p):=z; - end -else begin y:=fraction_rule(thickness(q));@/ - p:=new_kern((axis_height(cur_size)-delta)-@|(height(z)-shift_down));@/ - link(y):=p; link(p):=z;@/ - p:=new_kern((shift_up-depth(x))-(axis_height(cur_size)+delta)); - link(p):=y; - end; -link(x):=p; list_ptr(v):=x - -@ @<Put the \(f)fraction into a box with its delimiters...@>= -if cur_style<text_style then delta:=delim1(cur_size) -else delta:=delim2(cur_size); -x:=var_delimiter(left_delimiter(q), cur_size, delta); link(x):=v;@/ -z:=var_delimiter(right_delimiter(q), cur_size, delta); link(v):=z;@/ -new_hlist(q):=hpack(x,natural) - -@ If the nucleus of an |op_noad| is a single character, it is to be -centered vertically with respect to the axis, after first being enlarged -(via a character list in the font) if we are in display style. The normal -convention for placing displayed limits is to put them above and below the -operator in display style. - -The italic correction is removed from the character if there is a subscript -and the limits are not being displayed. The |make_op| -routine returns the value that should be used as an offset between -subscript and superscript. - -After |make_op| has acted, |subtype(q)| will be |limits| if and only if -the limits have been set above and below the operator. In that case, -|new_hlist(q)| will already contain the desired final box. - -@<Declare math...@>= -function make_op(@!q:pointer):scaled; -var delta:scaled; {offset between subscript and superscript} -@!p,@!v,@!x,@!y,@!z:pointer; {temporary registers for box construction} -@!c:quarterword;@+@!i:four_quarters; {registers for character examination} -@!shift_up,@!shift_down:scaled; {dimensions for box calculation} -begin if (subtype(q)=normal)and(cur_style<text_style) then - subtype(q):=limits; -if math_type(nucleus(q))=math_char then - begin fetch(nucleus(q)); - if (cur_style<text_style)and(char_tag(cur_i)=list_tag) then {make it larger} - begin c:=rem_byte(cur_i); i:=char_info(cur_f)(c); - if char_exists(i) then - begin cur_c:=c; cur_i:=i; character(nucleus(q)):=c; - end; - end; - delta:=char_italic(cur_f)(cur_i); x:=clean_box(nucleus(q),cur_style); - if (math_type(subscr(q))<>empty)and(subtype(q)<>limits) then - width(x):=width(x)-delta; {remove italic correction} - shift_amount(x):=half(height(x)-depth(x)) - axis_height(cur_size); - {center vertically} - math_type(nucleus(q)):=sub_box; info(nucleus(q)):=x; - end -else delta:=0; -if subtype(q)=limits then - @<Construct a box with limits above and below it, skewed by |delta|@>; -make_op:=delta; -end; - -@ The following program builds a vlist box |v| for displayed limits. The -width of the box is not affected by the fact that the limits may be skewed. - -@<Construct a box with limits above and below it...@>= -begin x:=clean_box(supscr(q),sup_style(cur_style)); -y:=clean_box(nucleus(q),cur_style); -z:=clean_box(subscr(q),sub_style(cur_style)); -v:=new_null_box; type(v):=vlist_node; width(v):=width(y); -if width(x)>width(v) then width(v):=width(x); -if width(z)>width(v) then width(v):=width(z); -x:=rebox(x,width(v)); y:=rebox(y,width(v)); z:=rebox(z,width(v));@/ -shift_amount(x):=half(delta); shift_amount(z):=-shift_amount(x); -height(v):=height(y); depth(v):=depth(y); -@<Attach the limits to |y| and adjust |height(v)|, |depth(v)| to - account for their presence@>; -new_hlist(q):=v; -end - -@ We use |shift_up| and |shift_down| in the following program for the -amount of glue between the displayed operator |y| and its limits |x| and -|z|. The vlist inside box |v| will consist of |x| followed by |y| followed -by |z|, with kern nodes for the spaces between and around them. - -@<Attach the limits to |y| and adjust |height(v)|, |depth(v)|...@>= -if math_type(supscr(q))=empty then - begin free_node(x,box_node_size); list_ptr(v):=y; - end -else begin shift_up:=big_op_spacing3-depth(x); - if shift_up<big_op_spacing1 then shift_up:=big_op_spacing1; - p:=new_kern(shift_up); link(p):=y; link(x):=p;@/ - p:=new_kern(big_op_spacing5); link(p):=x; list_ptr(v):=p; - height(v):=height(v)+big_op_spacing5+height(x)+depth(x)+shift_up; - end; -if math_type(subscr(q))=empty then free_node(z,box_node_size) -else begin shift_down:=big_op_spacing4-height(z); - if shift_down<big_op_spacing2 then shift_down:=big_op_spacing2; - p:=new_kern(shift_down); link(y):=p; link(p):=z;@/ - p:=new_kern(big_op_spacing5); link(z):=p; - depth(v):=depth(v)+big_op_spacing5+height(z)+depth(z)+shift_down; - end - -@ A ligature found in a math formula does not create a |ligature_node|, because -there is no question of hyphenation afterwards; the ligature will simply be -stored in an ordinary |char_node|, after residing in an |ord_noad|. - -The |math_type| is converted to |math_text_char| here if we would not want to -apply an italic correction to the current character unless it belongs -to a math font (i.e., a font with |space=0|). - -No boundary characters enter into these ligatures. - -@<Declare math...@>= -procedure make_ord(@!q:pointer); -label restart,exit; -var a:integer; {address of lig/kern instruction} -@!p,@!r:pointer; {temporary registers for list manipulation} -begin restart:@t@>@;@/ -if math_type(subscr(q))=empty then if math_type(supscr(q))=empty then - if math_type(nucleus(q))=math_char then - begin p:=link(q); - if p<>null then if (type(p)>=ord_noad)and(type(p)<=punct_noad) then - if math_type(nucleus(p))=math_char then - if fam(nucleus(p))=fam(nucleus(q)) then - begin math_type(nucleus(q)):=math_text_char; - fetch(nucleus(q)); - if char_tag(cur_i)=lig_tag then - begin a:=lig_kern_start(cur_f)(cur_i); - cur_c:=character(nucleus(p)); - cur_i:=font_info[a].qqqq; - if skip_byte(cur_i)>stop_flag then - begin a:=lig_kern_restart(cur_f)(cur_i); - cur_i:=font_info[a].qqqq; - end; - loop@+ begin @<If instruction |cur_i| is a kern with |cur_c|, attach - the kern after~|q|; or if it is a ligature with |cur_c|, combine - noads |q| and~|p| appropriately; then |return| if the cursor has - moved past a noad, or |goto restart|@>; - if skip_byte(cur_i)>=stop_flag then return; - a:=a+qo(skip_byte(cur_i))+1; - cur_i:=font_info[a].qqqq; - end; - end; - end; - end; -exit:end; - -@ Note that a ligature between an |ord_noad| and another kind of noad -is replaced by an |ord_noad|, when the two noads collapse into one. -But we could make a parenthesis (say) change shape when it follows -certain letters. Presumably a font designer will define such -ligatures only when this convention makes sense. - -\chardef\?='174 % vertical line to indicate character retention - -@<If instruction |cur_i| is a kern with |cur_c|, ...@>= -if next_char(cur_i)=cur_c then if skip_byte(cur_i)<=stop_flag then - if op_byte(cur_i)>=kern_flag then - begin p:=new_kern(char_kern(cur_f)(cur_i)); - link(p):=link(q); link(q):=p; return; - end - else begin check_interrupt; {allow a way out of infinite ligature loop} - case op_byte(cur_i) of - qi(1),qi(5): character(nucleus(q)):=rem_byte(cur_i); {\.{=:\?}, \.{=:\?>}} - qi(2),qi(6): character(nucleus(p)):=rem_byte(cur_i); {\.{\?=:}, \.{\?=:>}} - qi(3),qi(7),qi(11):begin r:=new_noad; {\.{\?=:\?}, \.{\?=:\?>}, \.{\?=:\?>>}} - character(nucleus(r)):=rem_byte(cur_i); - fam(nucleus(r)):=fam(nucleus(q));@/ - link(q):=r; link(r):=p; - if op_byte(cur_i)<qi(11) then math_type(nucleus(r)):=math_char - else math_type(nucleus(r)):=math_text_char; {prevent combination} - end; - othercases begin link(q):=link(p); - character(nucleus(q)):=rem_byte(cur_i); {\.{=:}} - mem[subscr(q)]:=mem[subscr(p)]; mem[supscr(q)]:=mem[supscr(p)];@/ - free_node(p,noad_size); - end - endcases; - if op_byte(cur_i)>qi(3) then return; - math_type(nucleus(q)):=math_char; goto restart; - end - -@ When we get to the following part of the program, we have ``fallen through'' -from cases that did not lead to |check_dimensions| or |done_with_noad| or -|done_with_node|. Thus, |q|~points to a noad whose nucleus may need to be -converted to an hlist, and whose subscripts and superscripts need to be -appended if they are present. - -If |nucleus(q)| is not a |math_char|, the variable |delta| is the amount -by which a superscript should be moved right with respect to a subscript -when both are present. -@^subscripts@> -@^superscripts@> - -@<Convert \(n)|nucleus(q)| to an hlist and attach the sub/superscripts@>= -case math_type(nucleus(q)) of -math_char, math_text_char: - @<Create a character node |p| for |nucleus(q)|, possibly followed - by a kern node for the italic correction, and set |delta| to the - italic correction if a subscript is present@>; -empty: p:=null; -sub_box: p:=info(nucleus(q)); -sub_mlist: begin cur_mlist:=info(nucleus(q)); save_style:=cur_style; - mlist_penalties:=false; mlist_to_hlist; {recursive call} -@^recursion@> - cur_style:=save_style; @<Set up the values...@>; - p:=hpack(link(temp_head),natural); - end; -othercases confusion("mlist2") -@:this can't happen mlist2}{\quad mlist2@> -endcases;@/ -new_hlist(q):=p; -if (math_type(subscr(q))=empty)and(math_type(supscr(q))=empty) then - goto check_dimensions; -make_scripts(q,delta) - -@ @<Create a character node |p| for |nucleus(q)|...@>= -begin fetch(nucleus(q)); -if char_exists(cur_i) then - begin delta:=char_italic(cur_f)(cur_i); p:=new_character(cur_f,qo(cur_c)); - if (math_type(nucleus(q))=math_text_char)and(space(cur_f)<>0) then - delta:=0; {no italic correction in mid-word of text font} - if (math_type(subscr(q))=empty)and(delta<>0) then - begin link(p):=new_kern(delta); delta:=0; - end; - end -else p:=null; -end - -@ The purpose of |make_scripts(q,delta)| is to attach the subscript and/or -superscript of noad |q| to the list that starts at |new_hlist(q)|, -given that the subscript and superscript aren't both empty. The superscript -will appear to the right of the subscript by a given distance |delta|. - -We set |shift_down| and |shift_up| to the minimum amounts to shift the -baseline of subscripts and superscripts based on the given nucleus. - -@<Declare math...@>= -procedure make_scripts(@!q:pointer;@!delta:scaled); -var p,@!x,@!y,@!z:pointer; {temporary registers for box construction} -@!shift_up,@!shift_down,@!clr:scaled; {dimensions in the calculation} -@!t:small_number; {subsidiary size code} -begin p:=new_hlist(q); -if is_char_node(p) then - begin shift_up:=0; shift_down:=0; - end -else begin z:=hpack(p,natural); - if cur_style<script_style then t:=script_size@+else t:=script_script_size; - shift_up:=height(z)-sup_drop(t); - shift_down:=depth(z)+sub_drop(t); - free_node(z,box_node_size); - end; -if math_type(supscr(q))=empty then - @<Construct a subscript box |x| when there is no superscript@> -else begin @<Construct a superscript box |x|@>; - if math_type(subscr(q))=empty then shift_amount(x):=-shift_up - else @<Construct a sub/superscript combination box |x|, with the - superscript offset by |delta|@>; - end; -if new_hlist(q)=null then new_hlist(q):=x -else begin p:=new_hlist(q); - while link(p)<>null do p:=link(p); - link(p):=x; - end; -end; - -@ When there is a subscript without a superscript, the top of the subscript -should not exceed the baseline plus four-fifths of the x-height. - -@<Construct a subscript box |x| when there is no superscript@>= -begin x:=clean_box(subscr(q),sub_style(cur_style)); -width(x):=width(x)+script_space; -if shift_down<sub1(cur_size) then shift_down:=sub1(cur_size); -clr:=height(x)-(abs(math_x_height(cur_size)*4) div 5); -if shift_down<clr then shift_down:=clr; -shift_amount(x):=shift_down; -end - -@ The bottom of a superscript should never descend below the baseline plus -one-fourth of the x-height. - -@<Construct a superscript box |x|@>= -begin x:=clean_box(supscr(q),sup_style(cur_style)); -width(x):=width(x)+script_space; -if odd(cur_style) then clr:=sup3(cur_size) -else if cur_style<text_style then clr:=sup1(cur_size) -else clr:=sup2(cur_size); -if shift_up<clr then shift_up:=clr; -clr:=depth(x)+(abs(math_x_height(cur_size)) div 4); -if shift_up<clr then shift_up:=clr; -end - -@ When both subscript and superscript are present, the subscript must be -separated from the superscript by at least four times |default_rule_thickness|. -If this condition would be violated, the subscript moves down, after which -both subscript and superscript move up so that the bottom of the superscript -is at least as high as the baseline plus four-fifths of the x-height. - -@<Construct a sub/superscript combination box |x|...@>= -begin y:=clean_box(subscr(q),sub_style(cur_style)); -width(y):=width(y)+script_space; -if shift_down<sub2(cur_size) then shift_down:=sub2(cur_size); -clr:=4*default_rule_thickness- - ((shift_up-depth(x))-(height(y)-shift_down)); -if clr>0 then - begin shift_down:=shift_down+clr; - clr:=(abs(math_x_height(cur_size)*4) div 5)-(shift_up-depth(x)); - if clr>0 then - begin shift_up:=shift_up+clr; - shift_down:=shift_down-clr; - end; - end; -shift_amount(x):=delta; {superscript is |delta| to the right of the subscript} -p:=new_kern((shift_up-depth(x))-(height(y)-shift_down)); link(x):=p; link(p):=y; -x:=vpack(x,natural); shift_amount(x):=shift_down; -end - -@ We have now tied up all the loose ends of the first pass of |mlist_to_hlist|. -The second pass simply goes through and hooks everything together with the -proper glue and penalties. It also handles the |left_noad| and |right_noad| that -might be present, since |max_h| and |max_d| are now known. Variable |p| points -to a node at the current end of the final hlist. - -@<Make a second pass over the mlist, ...@>= -p:=temp_head; link(p):=null; q:=mlist; r_type:=0; cur_style:=style; -@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; -while q<>null do - begin @<If node |q| is a style node, change the style and |goto delete_q|; - otherwise if it is not a noad, put it into the hlist, - advance |q|, and |goto done|; otherwise set |s| to the size - of noad |q|, set |t| to the associated type (|ord_noad.. - inner_noad|), and set |pen| to the associated penalty@>; - @<Append inter-element spacing based on |r_type| and |t|@>; - @<Append any |new_hlist| entries for |q|, and any appropriate penalties@>; - r_type:=t; - delete_q: r:=q; q:=link(q); free_node(r,s); - done: end - -@ Just before doing the big |case| switch in the second pass, the program -sets up default values so that most of the branches are short. - -@<If node |q| is a style node, change the style...@>= -t:=ord_noad; s:=noad_size; pen:=inf_penalty; -case type(q) of -op_noad,open_noad,close_noad,punct_noad,inner_noad: t:=type(q); -bin_noad: begin t:=bin_noad; pen:=bin_op_penalty; - end; -rel_noad: begin t:=rel_noad; pen:=rel_penalty; - end; -ord_noad,vcenter_noad,over_noad,under_noad: do_nothing; -radical_noad: s:=radical_noad_size; -accent_noad: s:=accent_noad_size; -fraction_noad: s:=fraction_noad_size; -left_noad,right_noad: t:=make_left_right(q,style,max_d,max_h); -style_node: @<Change the current style and |goto delete_q|@>; -whatsit_node,penalty_node,rule_node,disc_node,adjust_node,ins_node,mark_node, - glue_node,kern_node:@t@>@;@/ - begin link(p):=q; p:=q; q:=link(q); link(p):=null; goto done; - end; -othercases confusion("mlist3") -@:this can't happen mlist3}{\quad mlist3@> -endcases - -@ The |make_left_right| function constructs a left or right delimiter of -the required size and returns the value |open_noad| or |close_noad|. The -|right_noad| and |left_noad| will both be based on the original |style|, -so they will have consistent sizes. - -We use the fact that |right_noad-left_noad=close_noad-open_noad|. - -@<Declare math...@>= -function make_left_right(@!q:pointer;@!style:small_number; - @!max_d,@!max_h:scaled):small_number; -var delta,@!delta1,@!delta2:scaled; {dimensions used in the calculation} -begin if style<script_style then cur_size:=text_size -else cur_size:=16*((style-text_style) div 2); -delta2:=max_d+axis_height(cur_size); -delta1:=max_h+max_d-delta2; -if delta2>delta1 then delta1:=delta2; {|delta1| is max distance from axis} -delta:=(delta1 div 500)*delimiter_factor; -delta2:=delta1+delta1-delimiter_shortfall; -if delta<delta2 then delta:=delta2; -new_hlist(q):=var_delimiter(delimiter(q),cur_size,delta); -make_left_right:=type(q)-(left_noad-open_noad); {|open_noad| or |close_noad|} -end; - -@ @<Change the current style and |goto delete_q|@>= -begin cur_style:=subtype(q); s:=style_node_size; -@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; -goto delete_q; -end - -@ The inter-element spacing in math formulas depends on an $8\times8$ table that -\TeX\ preloads as a 64-digit string. The elements of this string have the -following significance: -$$\vbox{\halign{#\hfil\cr -\.0 means no space;\cr -\.1 means a conditional thin space (\.{\\nonscript\\mskip\\thinmuskip});\cr -\.2 means a thin space (\.{\\mskip\\thinmuskip});\cr -\.3 means a conditional medium space - (\.{\\nonscript\\mskip\\medmuskip});\cr -\.4 means a conditional thick space - (\.{\\nonscript\\mskip\\thickmuskip});\cr -\.* means an impossible case.\cr}}$$ -This is all pretty cryptic, but {\sl The \TeX book\/} explains what is -supposed to happen, and the string makes it happen. -@:TeXbook}{\sl The \TeX book@> - -A global variable |magic_offset| is computed so that if |a| and |b| are -in the range |ord_noad..inner_noad|, then |str_pool[a*8+b+magic_offset]| -is the digit for spacing between noad types |a| and |b|. - -If \PASCAL\ had provided a good way to preload constant arrays, this part of -the program would not have been so strange. -@:PASCAL}{\PASCAL@> - -@d math_spacing=@;@/ -@t\hskip-35pt@> -"0234000122*4000133**3**344*0400400*000000234000111*1111112341011" -@t$ \hskip-35pt$@> - -@<Glob...@>= -@!magic_offset:integer; {used to find inter-element spacing} - -@ @<Compute the magic offset@>= -magic_offset:=str_start[math_spacing]-9*ord_noad - -@ @<Append inter-element spacing based on |r_type| and |t|@>= -if r_type>0 then {not the first noad} - begin case so(str_pool[r_type*8+t+magic_offset]) of - "0": x:=0; - "1": if cur_style<script_style then x:=thin_mu_skip_code@+else x:=0; - "2": x:=thin_mu_skip_code; - "3": if cur_style<script_style then x:=med_mu_skip_code@+else x:=0; - "4": if cur_style<script_style then x:=thick_mu_skip_code@+else x:=0; - othercases confusion("mlist4") -@:this can't happen mlist4}{\quad mlist4@> - endcases; - if x<>0 then - begin y:=math_glue(glue_par(x),cur_mu); - z:=new_glue(y); glue_ref_count(y):=null; link(p):=z; p:=z;@/ - subtype(z):=x+1; {store a symbolic subtype} - end; - end - -@ We insert a penalty node after the hlist entries of noad |q| if |pen| -is not an ``infinite'' penalty, and if the node immediately following |q| -is not a penalty node or a |rel_noad| or absent entirely. - -@<Append any |new_hlist| entries for |q|, and any appropriate penalties@>= -if new_hlist(q)<>null then - begin link(p):=new_hlist(q); - repeat p:=link(p); - until link(p)=null; - end; -if penalties then if link(q)<>null then if pen<inf_penalty then - begin r_type:=type(link(q)); - if r_type<>penalty_node then if r_type<>rel_noad then - begin z:=new_penalty(pen); link(p):=z; p:=z; - end; - end - -@* \[37] Alignment. -It's sort of a miracle whenever \.{\\halign} and \.{\\valign} work, because -they cut across so many of the control structures of \TeX. - -Therefore the -present page is probably not the best place for a beginner to start reading -this program; it is better to master everything else first. - -Let us focus our thoughts on an example of what the input might be, in order -to get some idea about how the alignment miracle happens. The example doesn't -do anything useful, but it is sufficiently general to indicate all of the -special cases that must be dealt with; please do not be disturbed by its -apparent complexity and meaninglessness. -$$\vbox{\halign{\.{#}\hfil\cr -{}\\tabskip 2pt plus 3pt\cr -{}\\halign to 300pt\{u1\#v1\&\cr -\hskip 50pt\\tabskip 1pt plus 1fil u2\#v2\&\cr -\hskip 50pt u3\#v3\\cr\cr -\hskip 25pt a1\&\\omit a2\&\\vrule\\cr\cr -\hskip 25pt \\noalign\{\\vskip 3pt\}\cr -\hskip 25pt b1\\span b2\\cr\cr -\hskip 25pt \\omit\&c2\\span\\omit\\cr\}\cr}}$$ -Here's what happens: - -\yskip -(0) When `\.{\\halign to 300pt\{}' is scanned, the |scan_spec| routine -places the 300pt dimension onto the |save_stack|, and an |align_group| -code is placed above it. This will make it possible to complete the alignment -when the matching `\.\}' is found. - -(1) The preamble is scanned next. Macros in the preamble are not expanded, -@^preamble@> -except as part of a tabskip specification. For example, if \.{u2} had been -a macro in the preamble above, it would have been expanded, since \TeX\ -must look for `\.{minus...}' as part of the tabskip glue. A ``preamble list'' -is constructed based on the user's preamble; in our case it contains the -following seven items: -$$\vbox{\halign{\.{#}\hfil\qquad&(#)\hfil\cr -{}\\glue 2pt plus 3pt&the tabskip preceding column 1\cr -{}\\alignrecord, width $-\infty$&preamble info for column 1\cr -{}\\glue 2pt plus 3pt&the tabskip between columns 1 and 2\cr -{}\\alignrecord, width $-\infty$&preamble info for column 2\cr -{}\\glue 1pt plus 1fil&the tabskip between columns 2 and 3\cr -{}\\alignrecord, width $-\infty$&preamble info for column 3\cr -{}\\glue 1pt plus 1fil&the tabskip following column 3\cr}}$$ -These ``alignrecord'' entries have the same size as an |unset_node|, -since they will later be converted into such nodes. However, at the -moment they have no |type| or |subtype| fields; they have |info| fields -instead, and these |info| fields are initially set to the value |end_span|, -for reasons explained below. Furthermore, the alignrecord nodes have no -|height| or |depth| fields; these are renamed |u_part| and |v_part|, -and they point to token lists for the templates of the alignment. -For example, the |u_part| field in the first alignrecord points to the -token list `\.{u1}', i.e., the template preceding the `\.\#' for column~1. - -(2) \TeX\ now looks at what follows the \.{\\cr} that ended the preamble. -It is not `\.{\\noalign}' or `\.{\\omit}', so this input is put back to -be read again, and the template `\.{u1}' is fed to the scanner. Just -before reading `\.{u1}', \TeX\ goes into restricted horizontal mode. -Just after reading `\.{u1}', \TeX\ will see `\.{a1}', and then (when the -{\.\&} is sensed) \TeX\ will see `\.{v1}'. Then \TeX\ scans an |endv| -token, indicating the end of a column. At this point an |unset_node| is -created, containing the contents of the current hlist (i.e., `\.{u1a1v1}'). -The natural width of this unset node replaces the |width| field of the -alignrecord for column~1; in general, the alignrecords will record the -maximum natural width that has occurred so far in a given column. - -(3) Since `\.{\\omit}' follows the `\.\&', the templates for column~2 -are now bypassed. Again \TeX\ goes into restricted horizontal mode and -makes an |unset_node| from the resulting hlist; but this time the -hlist contains simply `\.{a2}'. The natural width of the new unset box -is remembered in the |width| field of the alignrecord for column~2. - -(4) A third |unset_node| is created for column 3, using essentially the -mechanism that worked for column~1; this unset box contains `\.{u3\\vrule -v3}'. The vertical rule in this case has running dimensions that will later -extend to the height and depth of the whole first row, since each |unset_node| -in a row will eventually inherit the height and depth of its enclosing box. - -(5) The first row has now ended; it is made into a single unset box -comprising the following seven items: -$$\vbox{\halign{\hbox to 325pt{\qquad\.{#}\hfil}\cr -{}\\glue 2pt plus 3pt\cr -{}\\unsetbox for 1 column: u1a1v1\cr -{}\\glue 2pt plus 3pt\cr -{}\\unsetbox for 1 column: a2\cr -{}\\glue 1pt plus 1fil\cr -{}\\unsetbox for 1 column: u3\\vrule v3\cr -{}\\glue 1pt plus 1fil\cr}}$$ -The width of this unset row is unimportant, but it has the correct height -and depth, so the correct baselineskip glue will be computed as the row -is inserted into a vertical list. - -(6) Since `\.{\\noalign}' follows the current \.{\\cr}, \TeX\ appends -additional material (in this case \.{\\vskip 3pt}) to the vertical list. -While processing this material, \TeX\ will be in internal vertical -mode, and |no_align_group| will be on |save_stack|. - -(7) The next row produces an unset box that looks like this: -$$\vbox{\halign{\hbox to 325pt{\qquad\.{#}\hfil}\cr -{}\\glue 2pt plus 3pt\cr -{}\\unsetbox for 2 columns: u1b1v1u2b2v2\cr -{}\\glue 1pt plus 1fil\cr -{}\\unsetbox for 1 column: {\rm(empty)}\cr -{}\\glue 1pt plus 1fil\cr}}$$ -The natural width of the unset box that spans columns 1~and~2 is stored -in a ``span node,'' which we will explain later; the |info| field of the -alignrecord for column~1 now points to the new span node, and the |info| -of the span node points to |end_span|. - -(8) The final row produces the unset box -$$\vbox{\halign{\hbox to 325pt{\qquad\.{#}\hfil}\cr -{}\\glue 2pt plus 3pt\cr -{}\\unsetbox for 1 column: {\rm(empty)}\cr -{}\\glue 2pt plus 3pt\cr -{}\\unsetbox for 2 columns: u2c2v2\cr -{}\\glue 1pt plus 1fil\cr}}$$ -A new span node is attached to the alignrecord for column 2. - -(9) The last step is to compute the true column widths and to change all the -unset boxes to hboxes, appending the whole works to the vertical list that -encloses the \.{\\halign}. The rules for deciding on the final widths of -each unset column box will be explained below. - -\yskip\noindent -Note that as \.{\\halign} is being processed, we fearlessly give up control -to the rest of \TeX. At critical junctures, an alignment routine is -called upon to step in and do some little action, but most of the time -these routines just lurk in the background. It's something like -post-hypnotic suggestion. - -@ We have mentioned that alignrecords contain no |height| or |depth| fields. -Their |glue_sign| and |glue_order| are pre-empted as well, since it -is necessary to store information about what to do when a template ends. -This information is called the |extra_info| field. - -@d u_part(#)==mem[#+height_offset].int {pointer to \<u_j> token list} -@d v_part(#)==mem[#+depth_offset].int {pointer to \<v_j> token list} -@d extra_info(#)==info(#+list_offset) {info to remember during template} - -@ Alignments can occur within alignments, so a small stack is used to access -the alignrecord information. At each level we have a |preamble| pointer, -indicating the beginning of the preamble list; a |cur_align| pointer, -indicating the current position in the preamble list; a |cur_span| pointer, -indicating the value of |cur_align| at the beginning of a sequence of -spanned columns; a |cur_loop| pointer, indicating the tabskip glue before -an alignrecord that should be copied next if the current list is extended; -and the |align_state| variable, which indicates the nesting of braces so -that \.{\\cr} and \.{\\span} and tab marks are properly intercepted. -There also are pointers |cur_head| and |cur_tail| to the head and tail -of a list of adjustments being moved out from horizontal mode to -vertical~mode. - -The current values of these seven quantities appear in global variables; -when they have to be pushed down, they are stored in 5-word nodes, and -|align_ptr| points to the topmost such node. - -@d preamble==link(align_head) {the current preamble list} -@d align_stack_node_size=5 {number of |mem| words to save alignment states} - -@<Glob...@>= -@!cur_align:pointer; {current position in preamble list} -@!cur_span:pointer; {start of currently spanned columns in preamble list} -@!cur_loop:pointer; {place to copy when extending a periodic preamble} -@!align_ptr:pointer; {most recently pushed-down alignment stack node} -@!cur_head,@!cur_tail:pointer; {adjustment list pointers} - -@ The |align_state| and |preamble| variables are initialized elsewhere. - -@<Set init...@>= -align_ptr:=null; cur_align:=null; cur_span:=null; cur_loop:=null; -cur_head:=null; cur_tail:=null; - -@ Alignment stack maintenance is handled by a pair of trivial routines -called |push_alignment| and |pop_alignment|. - -@p procedure push_alignment; -var p:pointer; {the new alignment stack node} -begin p:=get_node(align_stack_node_size); -link(p):=align_ptr; info(p):=cur_align; -llink(p):=preamble; rlink(p):=cur_span; -mem[p+2].int:=cur_loop; mem[p+3].int:=align_state; -info(p+4):=cur_head; link(p+4):=cur_tail; -align_ptr:=p; -cur_head:=get_avail; -end; -@# -procedure pop_alignment; -var p:pointer; {the top alignment stack node} -begin free_avail(cur_head); -p:=align_ptr; -cur_tail:=link(p+4); cur_head:=info(p+4); -align_state:=mem[p+3].int; cur_loop:=mem[p+2].int; -cur_span:=rlink(p); preamble:=llink(p); -cur_align:=info(p); align_ptr:=link(p); -free_node(p,align_stack_node_size); -end; - -@ \TeX\ has eight procedures that govern alignments: |init_align| and -|fin_align| are used at the very beginning and the very end; |init_row| and -|fin_row| are used at the beginning and end of individual rows; |init_span| -is used at the beginning of a sequence of spanned columns (possibly involving -only one column); |init_col| and |fin_col| are used at the beginning and -end of individual columns; and |align_peek| is used after \.{\\cr} to see -whether the next item is \.{\\noalign}. - -We shall consider these routines in the order they are first used during -the course of a complete \.{\\halign}, namely |init_align|, |align_peek|, -|init_row|, |init_span|, |init_col|, |fin_col|, |fin_row|, |fin_align|. - -@ When \.{\\halign} or \.{\\valign} has been scanned in an appropriate -mode, \TeX\ calls |init_align|, whose task is to get everything off to a -good start. This mostly involves scanning the preamble and putting its -information into the preamble list. -@^preamble@> - -@p @t\4@>@<Declare the procedure called |get_preamble_token|@>@t@>@/ -procedure@?align_peek; forward;@t\2@>@/ -procedure@?normal_paragraph; forward;@t\2@>@/ -procedure init_align; -label done, done1, done2, continue; -var save_cs_ptr:pointer; {|warning_index| value for error messages} -@!p:pointer; {for short-term temporary use} -begin save_cs_ptr:=cur_cs; {\.{\\halign} or \.{\\valign}, usually} -push_alignment; align_state:=-1000000; {enter a new alignment level} -@<Check for improper alignment in displayed math@>; -push_nest; {enter a new semantic level} -@<Change current mode to |-vmode| for \.{\\halign}, |-hmode| for \.{\\valign}@>; -scan_spec(align_group,false);@/ -@<Scan the preamble and record it in the |preamble| list@>; -new_save_level(align_group); -if every_cr<>null then begin_token_list(every_cr,every_cr_text); -align_peek; {look for \.{\\noalign} or \.{\\omit}} -end; - -@ In vertical modes, |prev_depth| already has the correct value. But -if we are in |mmode| (displayed formula mode), we reach out to the -enclosing vertical mode for the |prev_depth| value that produces the -correct baseline calculations. - -@<Change current mode...@>= -if mode=mmode then - begin mode:=-vmode; prev_depth:=nest[nest_ptr-2].aux_field.sc; - end -else if mode>0 then negate(mode) - -@ When \.{\\halign} is used as a displayed formula, there should be -no other pieces of mlists present. - -@<Check for improper alignment in displayed math@>= -if (mode=mmode)and((tail<>head)or(incompleat_noad<>null)) then - begin print_err("Improper "); print_esc("halign"); print(" inside $$'s"); -@.Improper \\halign...@> - help3("Displays can use special alignments (like \eqalignno)")@/ - ("only if nothing but the alignment itself is between $$'s.")@/ - ("So I've deleted the formulas that preceded this alignment."); - error; flush_math; - end - -@ @<Scan the preamble and record it in the |preamble| list@>= -preamble:=null; cur_align:=align_head; cur_loop:=null; scanner_status:=aligning; -warning_index:=save_cs_ptr; align_state:=-1000000; - {at this point, |cur_cmd=left_brace|} -loop@+ begin @<Append the current tabskip glue to the preamble list@>; - if cur_cmd=car_ret then goto done; {\.{\\cr} ends the preamble} - @<Scan preamble text until |cur_cmd| is |tab_mark| or |car_ret|, - looking for changes in the tabskip glue; append an - alignrecord to the preamble list@>; - end; -done: scanner_status:=normal - -@ @<Append the current tabskip glue to the preamble list@>= -link(cur_align):=new_param_glue(tab_skip_code); -cur_align:=link(cur_align) - -@ @<Scan preamble text until |cur_cmd| is |tab_mark| or |car_ret|...@>= -@<Scan the template \<u_j>, putting the resulting token list in |hold_head|@>; -link(cur_align):=new_null_box; cur_align:=link(cur_align); {a new alignrecord} -info(cur_align):=end_span; width(cur_align):=null_flag; -u_part(cur_align):=link(hold_head); -@<Scan the template \<v_j>, putting the resulting token list in |hold_head|@>; -v_part(cur_align):=link(hold_head) - -@ We enter `\.{\\span}' into |eqtb| with |tab_mark| as its command code, -and with |span_code| as the command modifier. This makes \TeX\ interpret it -essentially the same as an alignment delimiter like `\.\&', yet it is -recognizably different when we need to distinguish it from a normal delimiter. -It also turns out to be useful to give a special |cr_code| to `\.{\\cr}', -and an even larger |cr_cr_code| to `\.{\\crcr}'. - -The end of a template is represented by two ``frozen'' control sequences -called \.{\\endtemplate}. The first has the command code |end_template|, which -is |>outer_call|, so it will not easily disappear in the presence of errors. -The |get_x_token| routine converts the first into the second, which has |endv| -as its command code. - -@d span_code=256 {distinct from any character} -@d cr_code=257 {distinct from |span_code| and from any character} -@d cr_cr_code=cr_code+1 {this distinguishes \.{\\crcr} from \.{\\cr}} -@d end_template_token==cs_token_flag+frozen_end_template - -@<Put each of \TeX's primitives into the hash table@>= -primitive("span",tab_mark,span_code);@/ -@!@:span_}{\.{\\span} primitive@> -primitive("cr",car_ret,cr_code); -@!@:cr_}{\.{\\cr} primitive@> -text(frozen_cr):="cr"; eqtb[frozen_cr]:=eqtb[cur_val];@/ -primitive("crcr",car_ret,cr_cr_code); -@!@:cr_cr_}{\.{\\crcr} primitive@> -text(frozen_end_template):="endtemplate"; text(frozen_endv):="endtemplate"; -@.endtemplate@> -eq_type(frozen_endv):=endv; equiv(frozen_endv):=null_list; -eq_level(frozen_endv):=level_one;@/ -eqtb[frozen_end_template]:=eqtb[frozen_endv]; -eq_type(frozen_end_template):=end_template; - -@ @<Cases of |print_cmd_chr|...@>= -tab_mark: if chr_code=span_code then print_esc("span") - else chr_cmd("alignment tab character "); -car_ret: if chr_code=cr_code then print_esc("cr") - else print_esc("crcr"); - -@ The preamble is copied directly, except that \.{\\tabskip} causes a change -to the tabskip glue, thereby possibly expanding macros that immediately -follow it. An appearance of \.{\\span} also causes such an expansion. - -Note that if the preamble contains `\.{\\global\\tabskip}', the `\.{\\global}' -token survives in the preamble and the `\.{\\tabskip}' defines new -tabskip glue (locally). - -@<Declare the procedure called |get_preamble_token|@>= -procedure get_preamble_token; -label restart; -begin restart: get_token; -while (cur_chr=span_code)and(cur_cmd=tab_mark) do - begin get_token; {this token will be expanded once} - if cur_cmd>max_command then - begin expand; get_token; - end; - end; -if cur_cmd=endv then - fatal_error("(interwoven alignment preambles are not allowed)"); -@.interwoven alignment preambles...@> -if (cur_cmd=assign_glue)and(cur_chr=glue_base+tab_skip_code) then - begin scan_optional_equals; scan_glue(glue_val); - if global_defs>0 then geq_define(glue_base+tab_skip_code,glue_ref,cur_val) - else eq_define(glue_base+tab_skip_code,glue_ref,cur_val); - goto restart; - end; -end; - -@ Spaces are eliminated from the beginning of a template. - -@<Scan the template \<u_j>...@>= -p:=hold_head; link(p):=null; -loop@+ begin get_preamble_token; - if cur_cmd=mac_param then goto done1; - if (cur_cmd<=car_ret)and(cur_cmd>=tab_mark)and(align_state=-1000000) then - if (p=hold_head)and(cur_loop=null)and(cur_cmd=tab_mark) - then cur_loop:=cur_align - else begin print_err("Missing # inserted in alignment preamble"); -@.Missing \# inserted...@> - help3("There should be exactly one # between &'s, when an")@/ - ("\halign or \valign is being set up. In this case you had")@/ - ("none, so I've put one in; maybe that will work."); - back_error; goto done1; - end - else if (cur_cmd<>spacer)or(p<>hold_head) then - begin link(p):=get_avail; p:=link(p); info(p):=cur_tok; - end; - end; -done1: - -@ @<Scan the template \<v_j>...@>= -p:=hold_head; link(p):=null; -loop@+ begin continue: get_preamble_token; - if (cur_cmd<=car_ret)and(cur_cmd>=tab_mark)and(align_state=-1000000) then - goto done2; - if cur_cmd=mac_param then - begin print_err("Only one # is allowed per tab"); -@.Only one \# is allowed...@> - help3("There should be exactly one # between &'s, when an")@/ - ("\halign or \valign is being set up. In this case you had")@/ - ("more than one, so I'm ignoring all but the first."); - error; goto continue; - end; - link(p):=get_avail; p:=link(p); info(p):=cur_tok; - end; -done2: link(p):=get_avail; p:=link(p); -info(p):=end_template_token {put \.{\\endtemplate} at the end} - -@ The tricky part about alignments is getting the templates into the -scanner at the right time, and recovering control when a row or column -is finished. - -We usually begin a row after each \.{\\cr} has been sensed, unless that -\.{\\cr} is followed by \.{\\noalign} or by the right brace that terminates -the alignment. The |align_peek| routine is used to look ahead and do -the right thing; it either gets a new row started, or gets a \.{\\noalign} -started, or finishes off the alignment. - -@<Declare the procedure called |align_peek|@>= -procedure align_peek; -label restart; -begin restart: align_state:=1000000; @<Get the next non-blank non-call token@>; -if cur_cmd=no_align then - begin scan_left_brace; new_save_level(no_align_group); - if mode=-vmode then normal_paragraph; - end -else if cur_cmd=right_brace then fin_align -else if (cur_cmd=car_ret)and(cur_chr=cr_cr_code) then - goto restart {ignore \.{\\crcr}} -else begin init_row; {start a new row} - init_col; {start a new column and replace what we peeked at} - end; -end; - -@ To start a row (i.e., a `row' that rhymes with `dough' but not with `bough'), -we enter a new semantic level, copy the first tabskip glue, and change -from internal vertical mode to restricted horizontal mode or vice versa. -The |space_factor| and |prev_depth| are not used on this semantic level, -but we clear them to zero just to be tidy. - -@p @t\4@>@<Declare the procedure called |init_span|@>@t@>@/ -procedure init_row; -begin push_nest; mode:=(-hmode-vmode)-mode; -if mode=-hmode then space_factor:=0 @+else prev_depth:=0; -tail_append(new_glue(glue_ptr(preamble))); -subtype(tail):=tab_skip_code+1;@/ -cur_align:=link(preamble); cur_tail:=cur_head; init_span(cur_align); -end; - -@ The parameter to |init_span| is a pointer to the alignrecord where the -next column or group of columns will begin. A new semantic level is -entered, so that the columns will generate a list for subsequent packaging. - -@<Declare the procedure called |init_span|@>= -procedure init_span(@!p:pointer); -begin push_nest; -if mode=-hmode then space_factor:=1000 -else begin prev_depth:=ignore_depth; normal_paragraph; - end; -cur_span:=p; -end; - -@ When a column begins, we assume that |cur_cmd| is either |omit| or else -the current token should be put back into the input until the \<u_j> -template has been scanned. (Note that |cur_cmd| might be |tab_mark| or -|car_ret|.) We also assume that |align_state| is approximately 1000000 at -this time. We remain in the same mode, and start the template if it is -called for. - -@p procedure init_col; -begin extra_info(cur_align):=cur_cmd; -if cur_cmd=omit then align_state:=0 -else begin back_input; begin_token_list(u_part(cur_align),u_template); - end; {now |align_state=1000000|} -end; - -@ The scanner sets |align_state| to zero when the \<u_j> template ends. When -a subsequent \.{\\cr} or \.{\\span} or tab mark occurs with |align_state=0|, -the scanner activates the following code, which fires up the \<v_j> template. -We need to remember the |cur_chr|, which is either |cr_cr_code|, |cr_code|, -|span_code|, or a character code, depending on how the column text has ended. - -This part of the program had better not be activated when the preamble -to another alignment is being scanned, or when no alignment preamble is active. - -@<Insert the \(v)\<v_j>...@>= -begin if (scanner_status=aligning) or (cur_align=null) then - fatal_error("(interwoven alignment preambles are not allowed)"); -@.interwoven alignment preambles...@> -cur_cmd:=extra_info(cur_align); extra_info(cur_align):=cur_chr; -if cur_cmd=omit then begin_token_list(omit_template,v_template) -else begin_token_list(v_part(cur_align),v_template); -align_state:=1000000; goto restart; -end - -@ The token list |omit_template| just referred to is a constant token -list that contains the special control sequence \.{\\endtemplate} only. - -@<Initialize the special...@>= -info(omit_template):=end_template_token; {|link(omit_template)=null|} - -@ When the |endv| command at the end of a \<v_j> template comes through the -scanner, things really start to happen; and it is the |fin_col| routine -that makes them happen. This routine returns |true| if a row as well as a -column has been finished. - -@p function fin_col:boolean; -label exit; -var p:pointer; {the alignrecord after the current one} -@!q,@!r:pointer; {temporary pointers for list manipulation} -@!s:pointer; {a new span node} -@!u:pointer; {a new unset box} -@!w:scaled; {natural width} -@!o:glue_ord; {order of infinity} -@!n:halfword; {span counter} -begin if cur_align=null then confusion("endv"); -q:=link(cur_align);@+if q=null then confusion("endv"); -@:this can't happen endv}{\quad endv@> -if align_state<500000 then - fatal_error("(interwoven alignment preambles are not allowed)"); -@.interwoven alignment preambles...@> -p:=link(q); -@<If the preamble list has been traversed, check that the row has ended@>; -if extra_info(cur_align)<>span_code then - begin unsave; new_save_level(align_group);@/ - @<Package an unset box for the current column and record its width@>; - @<Copy the tabskip glue between columns@>; - if extra_info(cur_align)>=cr_code then - begin fin_col:=true; return; - end; - init_span(p); - end; -align_state:=1000000; @<Get the next non-blank non-call token@>; -cur_align:=p; -init_col; fin_col:=false; -exit: end; - -@ @<If the preamble list has been traversed, check that the row has ended@>= -if (p=null)and(extra_info(cur_align)<cr_code) then - if cur_loop<>null then @<Lengthen the preamble periodically@> - else begin print_err("Extra alignment tab has been changed to "); -@.Extra alignment tab...@> - print_esc("cr"); - help3("You have given more \span or & marks than there were")@/ - ("in the preamble to the \halign or \valign now in progress.")@/ - ("So I'll assume that you meant to type \cr instead."); - extra_info(cur_align):=cr_code; error; - end - -@ @<Lengthen the preamble...@>= -begin link(q):=new_null_box; p:=link(q); {a new alignrecord} -info(p):=end_span; width(p):=null_flag; cur_loop:=link(cur_loop); -@<Copy the templates from node |cur_loop| into node |p|@>; -cur_loop:=link(cur_loop); -link(p):=new_glue(glue_ptr(cur_loop)); -subtype(link(p)):=tab_skip_code+1; -end - -@ @<Copy the templates from node |cur_loop| into node |p|@>= -q:=hold_head; r:=u_part(cur_loop); -while r<>null do - begin link(q):=get_avail; q:=link(q); info(q):=info(r); r:=link(r); - end; -link(q):=null; u_part(p):=link(hold_head); -q:=hold_head; r:=v_part(cur_loop); -while r<>null do - begin link(q):=get_avail; q:=link(q); info(q):=info(r); r:=link(r); - end; -link(q):=null; v_part(p):=link(hold_head) - -@ @<Copy the tabskip glue...@>= -tail_append(new_glue(glue_ptr(link(cur_align)))); -subtype(tail):=tab_skip_code+1 - -@ @<Package an unset...@>= -begin if mode=-hmode then - begin adjust_tail:=cur_tail; u:=hpack(link(head),natural); w:=width(u); - cur_tail:=adjust_tail; adjust_tail:=null; - end -else begin u:=vpackage(link(head),natural,0); w:=height(u); - end; -n:=min_quarterword; {this represents a span count of 1} -if cur_span<>cur_align then @<Update width entry for spanned columns@> -else if w>width(cur_align) then width(cur_align):=w; -type(u):=unset_node; span_count(u):=n;@/ -@<Determine the stretch order@>; -glue_order(u):=o; glue_stretch(u):=total_stretch[o];@/ -@<Determine the shrink order@>; -glue_sign(u):=o; glue_shrink(u):=total_shrink[o];@/ -pop_nest; link(tail):=u; tail:=u; -end - -@ A span node is a 2-word record containing |width|, |info|, and |link| -fields. The |link| field is not really a link, it indicates the number of -spanned columns; the |info| field points to a span node for the same -starting column, having a greater extent of spanning, or to |end_span|, -which has the largest possible |link| field; the |width| field holds the -largest natural width corresponding to a particular set of spanned columns. - -A list of the maximum widths so far, for spanned columns starting at a -given column, begins with the |info| field of the alignrecord for that -column. - -@d span_node_size=2 {number of |mem| words for a span node} - -@<Initialize the special list heads...@>= -link(end_span):=max_quarterword+1; info(end_span):=null; - -@ @<Update width entry for spanned columns@>= -begin q:=cur_span; -repeat incr(n); q:=link(link(q)); -until q=cur_align; -if n>max_quarterword then confusion("256 spans"); {this can happen, but won't} -@^system dependencies@> -@:this can't happen 256 spans}{\quad 256 spans@> -q:=cur_span; while link(info(q))<n do q:=info(q); -if link(info(q))>n then - begin s:=get_node(span_node_size); info(s):=info(q); link(s):=n; - info(q):=s; width(s):=w; - end -else if width(info(q))<w then width(info(q)):=w; -end - -@ At the end of a row, we append an unset box to the current vlist (for -\.{\\halign}) or the current hlist (for \.{\\valign}). This unset box -contains the unset boxes for the columns, separated by the tabskip glue. -Everything will be set later. - -@p procedure fin_row; -var p:pointer; {the new unset box} -begin if mode=-hmode then - begin p:=hpack(link(head),natural); - pop_nest; append_to_vlist(p); - if cur_head<>cur_tail then - begin link(tail):=link(cur_head); tail:=cur_tail; - end; - end -else begin p:=vpack(link(head),natural); pop_nest; - link(tail):=p; tail:=p; space_factor:=1000; - end; -type(p):=unset_node; glue_stretch(p):=0; -if every_cr<>null then begin_token_list(every_cr,every_cr_text); -align_peek; -end; {note that |glue_shrink(p)=0| since |glue_shrink==shift_amount|} - -@ Finally, we will reach the end of the alignment, and we can breathe a -sigh of relief that memory hasn't overflowed. All the unset boxes will now be -set so that the columns line up, taking due account of spanned columns. - -@p procedure@?do_assignments; forward;@t\2@>@/ -procedure@?resume_after_display; forward;@t\2@>@/ -procedure@?build_page; forward;@t\2@>@/ -procedure fin_align; -var @!p,@!q,@!r,@!s,@!u,@!v: pointer; {registers for the list operations} -@!t,@!w:scaled; {width of column} -@!o:scaled; {shift offset for unset boxes} -@!n:halfword; {matching span amount} -@!rule_save:scaled; {temporary storage for |overfull_rule|} -@!aux_save:memory_word; {temporary storage for |aux|} -begin if cur_group<>align_group then confusion("align1"); -@:this can't happen align}{\quad align@> -unsave; {that |align_group| was for individual entries} -if cur_group<>align_group then confusion("align0"); -unsave; {that |align_group| was for the whole alignment} -if nest[nest_ptr-1].mode_field=mmode then o:=display_indent - else o:=0; -@<Go through the preamble list, determining the column widths and - changing the alignrecords to dummy unset boxes@>; -@<Package the preamble list, to determine the actual tabskip glue amounts, - and let |p| point to this prototype box@>; -@<Set the glue in all the unset boxes of the current list@>; -flush_node_list(p); pop_alignment; -@<Insert the \(c)current list into its environment@>; -end;@/ -@t\4@>@<Declare the procedure called |align_peek|@> - -@ It's time now to dismantle the preamble list and to compute the column -widths. Let $w_{ij}$ be the maximum of the natural widths of all entries -that span columns $i$ through $j$, inclusive. The alignrecord for column~$i$ -contains $w_{ii}$ in its |width| field, and there is also a linked list of -the nonzero $w_{ij}$ for increasing $j$, accessible via the |info| field; -these span nodes contain the value $j-i+|min_quarterword|$ in their -|link| fields. The values of $w_{ii}$ were initialized to |null_flag|, which -we regard as $-\infty$. - -The final column widths are defined by the formula -$$w_j=\max_{1\L i\L j}\biggl( w_{ij}-\sum_{i\L k<j}(t_k+w_k)\biggr),$$ -where $t_k$ is the natural width of the tabskip glue between columns -$k$ and~$k+1$. However, if $w_{ij}=-\infty$ for all |i| in the range -|1<=i<=j| (i.e., if every entry that involved column~|j| also involved -column~|j+1|), we let $w_j=0$, and we zero out the tabskip glue after -column~|j|. - -\TeX\ computes these values by using the following scheme: First $w_1=w_{11}$. -Then replace $w_{2j}$ by $\max(w_{2j},w_{1j}-t_1-w_1)$, for all $j>1$. -Then $w_2=w_{22}$. Then replace $w_{3j}$ by $\max(w_{3j},w_{2j}-t_2-w_2)$ -for all $j>2$; and so on. If any $w_j$ turns out to be $-\infty$, its -value is changed to zero and so is the next tabskip. - -@<Go through the preamble list,...@>= -q:=link(preamble); -repeat flush_list(u_part(q)); flush_list(v_part(q)); -p:=link(link(q)); -if width(q)=null_flag then - @<Nullify |width(q)| and the tabskip glue following this column@>; -if info(q)<>end_span then - @<Merge the widths in the span nodes of |q| with those of |p|, - destroying the span nodes of |q|@>; -type(q):=unset_node; span_count(q):=min_quarterword; height(q):=0; -depth(q):=0; glue_order(q):=normal; glue_sign(q):=normal; -glue_stretch(q):=0; glue_shrink(q):=0; q:=p; -until q=null - -@ @<Nullify |width(q)| and the tabskip glue following this column@>= -begin width(q):=0; r:=link(q); s:=glue_ptr(r); -if s<>zero_glue then - begin add_glue_ref(zero_glue); delete_glue_ref(s); - glue_ptr(r):=zero_glue; - end; -end - -@ Merging of two span-node lists is a typical exercise in the manipulation of -linearly linked data structures. The essential invariant in the following -|repeat| loop is that we want to dispense with node |r|, in |q|'s list, -and |u| is its successor; all nodes of |p|'s list up to and including |s| -have been processed, and the successor of |s| matches |r| or precedes |r| -or follows |r|, according as |link(r)=n| or |link(r)>n| or |link(r)<n|. - -@<Merge the widths...@>= -begin t:=width(q)+width(glue_ptr(link(q))); -r:=info(q); s:=end_span; info(s):=p; n:=min_quarterword+1; -repeat width(r):=width(r)-t; u:=info(r); -while link(r)>n do - begin s:=info(s); n:=link(info(s))+1; - end; -if link(r)<n then - begin info(r):=info(s); info(s):=r; decr(link(r)); s:=r; - end -else begin if width(r)>width(info(s)) then width(info(s)):=width(r); - free_node(r,span_node_size); - end; -r:=u; -until r=end_span; -end - -@ Now the preamble list has been converted to a list of alternating unset -boxes and tabskip glue, where the box widths are equal to the final -column sizes. In case of \.{\\valign}, we change the widths to heights, -so that a correct error message will be produced if the alignment is -overfull or underfull. - -@<Package the preamble list...@>= -save_ptr:=save_ptr-2; pack_begin_line:=-mode_line; -if mode=-vmode then - begin rule_save:=overfull_rule; - overfull_rule:=0; {prevent rule from being packaged} - p:=hpack(preamble,saved(1),saved(0)); overfull_rule:=rule_save; - end -else begin q:=link(preamble); - repeat height(q):=width(q); width(q):=0; q:=link(link(q)); - until q=null; - p:=vpack(preamble,saved(1),saved(0)); - q:=link(preamble); - repeat width(q):=height(q); height(q):=0; q:=link(link(q)); - until q=null; - end; -pack_begin_line:=0 - -@ @<Set the glue in all the unset...@>= -q:=link(head); s:=head; -while q<>null do - begin if not is_char_node(q) then - if type(q)=unset_node then - @<Set the unset box |q| and the unset boxes in it@> - else if type(q)=rule_node then - @<Make the running dimensions in rule |q| extend to the - boundaries of the alignment@>; - s:=q; q:=link(q); - end - -@ @<Make the running dimensions in rule |q| extend...@>= -begin if is_running(width(q)) then width(q):=width(p); -if is_running(height(q)) then height(q):=height(p); -if is_running(depth(q)) then depth(q):=depth(p); -if o<>0 then - begin r:=link(q); link(q):=null; q:=hpack(q,natural); - shift_amount(q):=o; link(q):=r; link(s):=q; - end; -end - -@ The unset box |q| represents a row that contains one or more unset boxes, -depending on how soon \.{\\cr} occurred in that row. - -@<Set the unset box |q| and the unset boxes in it@>= -begin if mode=-vmode then - begin type(q):=hlist_node; width(q):=width(p); - end -else begin type(q):=vlist_node; height(q):=height(p); - end; -glue_order(q):=glue_order(p); glue_sign(q):=glue_sign(p); -glue_set(q):=glue_set(p); shift_amount(q):=o; -r:=link(list_ptr(q)); s:=link(list_ptr(p)); -repeat @<Set the glue in node |r| and change it from an unset node@>; -r:=link(link(r)); s:=link(link(s)); -until r=null; -end - -@ A box made from spanned columns will be followed by tabskip glue nodes and -by empty boxes as if there were no spanning. This permits perfect alignment -of subsequent entries, and it prevents values that depend on floating point -arithmetic from entering into the dimensions of any boxes. - -@<Set the glue in node |r|...@>= -n:=span_count(r); t:=width(s); w:=t; u:=hold_head; -while n>min_quarterword do - begin decr(n); - @<Append tabskip glue and an empty box to list |u|, - and update |s| and |t| as the prototype nodes are passed@>; - end; -if mode=-vmode then - @<Make the unset node |r| into an |hlist_node| of width |w|, - setting the glue as if the width were |t|@> -else @<Make the unset node |r| into a |vlist_node| of height |w|, - setting the glue as if the height were |t|@>; -shift_amount(r):=0; -if u<>hold_head then {append blank boxes to account for spanned nodes} - begin link(u):=link(r); link(r):=link(hold_head); r:=u; - end - -@ @<Append tabskip glue and an empty box to list |u|...@>= -s:=link(s); v:=glue_ptr(s); link(u):=new_glue(v); u:=link(u); -subtype(u):=tab_skip_code+1; t:=t+width(v); -if glue_sign(p)=stretching then - begin if stretch_order(v)=glue_order(p) then - t:=t+round(float(glue_set(p))*stretch(v)); -@^real multiplication@> - end -else if glue_sign(p)=shrinking then - begin if shrink_order(v)=glue_order(p) then - t:=t-round(float(glue_set(p))*shrink(v)); - end; -s:=link(s); link(u):=new_null_box; u:=link(u); t:=t+width(s); -if mode=-vmode then width(u):=width(s)@+else - begin type(u):=vlist_node; height(u):=width(s); - end - -@ @<Make the unset node |r| into an |hlist_node| of width |w|...@>= -begin height(r):=height(q); depth(r):=depth(q); -if t=width(r) then - begin glue_sign(r):=normal; glue_order(r):=normal; - set_glue_ratio_zero(glue_set(r)); - end -else if t>width(r) then - begin glue_sign(r):=stretching; - if glue_stretch(r)=0 then set_glue_ratio_zero(glue_set(r)) - else glue_set(r):=unfloat((t-width(r))/glue_stretch(r)); -@^real division@> - end -else begin glue_order(r):=glue_sign(r); glue_sign(r):=shrinking; - if glue_shrink(r)=0 then set_glue_ratio_zero(glue_set(r)) - else if (glue_order(r)=normal)and(width(r)-t>glue_shrink(r)) then - set_glue_ratio_one(glue_set(r)) - else glue_set(r):=unfloat((width(r)-t)/glue_shrink(r)); - end; -width(r):=w; type(r):=hlist_node; -end - -@ @<Make the unset node |r| into a |vlist_node| of height |w|...@>= -begin width(r):=width(q); -if t=height(r) then - begin glue_sign(r):=normal; glue_order(r):=normal; - set_glue_ratio_zero(glue_set(r)); - end -else if t>height(r) then - begin glue_sign(r):=stretching; - if glue_stretch(r)=0 then set_glue_ratio_zero(glue_set(r)) - else glue_set(r):=unfloat((t-height(r))/glue_stretch(r)); -@^real division@> - end -else begin glue_order(r):=glue_sign(r); glue_sign(r):=shrinking; - if glue_shrink(r)=0 then set_glue_ratio_zero(glue_set(r)) - else if (glue_order(r)=normal)and(height(r)-t>glue_shrink(r)) then - set_glue_ratio_one(glue_set(r)) - else glue_set(r):=unfloat((height(r)-t)/glue_shrink(r)); - end; -height(r):=w; type(r):=vlist_node; -end - -@ We now have a completed alignment, in the list that starts at |head| -and ends at |tail|. This list will be merged with the one that encloses -it. (In case the enclosing mode is |mmode|, for displayed formulas, -we will need to insert glue before and after the display; that part of the -program will be deferred until we're more familiar with such operations.) - -In restricted horizontal mode, the |clang| part of |aux| is undefined; -an over-cautious \PASCAL\ runtime system may complain about this. -@^dirty \PASCAL@> - -@<Insert the \(c)current list into its environment@>= -aux_save:=aux; p:=link(head); q:=tail; pop_nest; -if mode=mmode then @<Finish an alignment in a display@> -else begin aux:=aux_save; link(tail):=p; - if p<>null then tail:=q; - if mode=vmode then build_page; - end - -@* \[38] Breaking paragraphs into lines. -We come now to what is probably the most interesting algorithm of \TeX: -the mechanism for choosing the ``best possible'' breakpoints that yield -the individual lines of a paragraph. \TeX's line-breaking algorithm takes -a given horizontal list and converts it to a sequence of boxes that are -appended to the current vertical list. In the course of doing this, it -creates a special data structure containing three kinds of records that are -not used elsewhere in \TeX. Such nodes are created while a paragraph is -being processed, and they are destroyed afterwards; thus, the other parts -of \TeX\ do not need to know anything about how line-breaking is done. - -The method used here is based on an approach devised by Michael F. Plass and -@^Plass, Michael Frederick@> -@^Knuth, Donald Ervin@> -the author in 1977, subsequently generalized and improved by the same two -people in 1980. A detailed discussion appears in {\sl Software---Practice -and Experience \bf11} (1981), 1119--1184, where it is shown that the -line-breaking problem can be regarded as a special case of the problem of -computing the shortest path in an acyclic network. The cited paper includes -numerous examples and describes the history of line breaking as it has been -practiced by printers through the ages. The present implementation adds two -new ideas to the algorithm of 1980: Memory space requirements are considerably -reduced by using smaller records for inactive nodes than for active ones, -and arithmetic overflow is avoided by using ``delta distances'' instead of -keeping track of the total distance from the beginning of the paragraph to the -current point. - -@ The |line_break| procedure should be invoked only in horizontal mode; it -leaves that mode and places its output into the current vlist of the -enclosing vertical mode (or internal vertical mode). -There is one explicit parameter: |final_widow_penalty| is the amount of -additional penalty to be inserted before the final line of the paragraph. - -There are also a number of implicit parameters: The hlist to be broken -starts at |link(head)|, and it is nonempty. The value of |prev_graf| in the -enclosing semantic level tells where the paragraph should begin in the -sequence of line numbers, in case hanging indentation or \.{\\parshape} -is in use; |prev_graf| is zero unless this paragraph is being continued -after a displayed formula. Other implicit parameters, such as the -|par_shape_ptr| and various penalties to use for hyphenation, etc., appear -in |eqtb|. - -After |line_break| has acted, it will have updated the current vlist and the -value of |prev_graf|. Furthermore, the global variable |just_box| will -point to the final box created by |line_break|, so that the width of this -line can be ascertained when it is necessary to decide whether to use -|above_display_skip| or |above_display_short_skip| before a displayed formula. - -@<Glob...@>= -@!just_box:pointer; {the |hlist_node| for the last line of the new paragraph} - -@ Since |line_break| is a rather lengthy procedure---sort of a small world unto -itself---we must build it up little by little, somewhat more cautiously -than we have done with the simpler procedures of \TeX. Here is the -general outline. - -@p@t\4@>@<Declare subprocedures for |line_break|@> -procedure line_break(@!final_widow_penalty:integer); -label done,done1,done2,done3,done4,done5,continue; -var @<Local variables for line breaking@>@; -begin pack_begin_line:=mode_line; {this is for over/underfull box messages} -@<Get ready to start line breaking@>; -@<Find optimal breakpoints@>; -@<Break the paragraph at the chosen breakpoints, justify the resulting lines -to the correct widths, and append them to the current vertical list@>; -@<Clean up the memory by removing the break nodes@>; -pack_begin_line:=0; -end; - -@ The first task is to move the list from |head| to |temp_head| and go -into the enclosing semantic level. We also append the \.{\\parfillskip} -glue to the end of the paragraph, removing a space (or other glue node) if -it was there, since spaces usually precede blank lines and instances of -`\.{\$\$}'. The |par_fill_skip| is preceded by an infinite penalty, so -it will never be considered as a potential breakpoint. - -This code assumes that a |glue_node| and a |penalty_node| occupy the -same number of |mem|~words. -@^data structure assumptions@> - -@<Get ready to start...@>= -link(temp_head):=link(head); -if is_char_node(tail) then tail_append(new_penalty(inf_penalty)) -else if type(tail)<>glue_node then tail_append(new_penalty(inf_penalty)) -else begin type(tail):=penalty_node; delete_glue_ref(glue_ptr(tail)); - flush_node_list(leader_ptr(tail)); penalty(tail):=inf_penalty; - end; -link(tail):=new_param_glue(par_fill_skip_code); -init_cur_lang:=prev_graf mod @'200000; -init_l_hyf:=prev_graf div @'20000000; -init_r_hyf:=(prev_graf div @'200000) mod @'100; -pop_nest; - -@ When looking for optimal line breaks, \TeX\ creates a ``break node'' for -each break that is {\sl feasible}, in the sense that there is a way to end -a line at the given place without requiring any line to stretch more than -a given tolerance. A break node is characterized by three things: the position -of the break (which is a pointer to a |glue_node|, |math_node|, |penalty_node|, -or |disc_node|); the ordinal number of the line that will follow this -breakpoint; and the fitness classification of the line that has just -ended, i.e., |tight_fit|, |decent_fit|, |loose_fit|, or |very_loose_fit|. - -@d tight_fit=3 {fitness classification for lines shrinking 0.5 to 1.0 of their - shrinkability} -@d loose_fit=1 {fitness classification for lines stretching 0.5 to 1.0 of their - stretchability} -@d very_loose_fit=0 {fitness classification for lines stretching more than - their stretchability} -@d decent_fit=2 {fitness classification for all other lines} - -@ The algorithm essentially determines the best possible way to achieve -each feasible combination of position, line, and fitness. Thus, it answers -questions like, ``What is the best way to break the opening part of the -paragraph so that the fourth line is a tight line ending at such-and-such -a place?'' However, the fact that all lines are to be the same length -after a certain point makes it possible to regard all sufficiently large -line numbers as equivalent, when the looseness parameter is zero, and this -makes it possible for the algorithm to save space and time. - -An ``active node'' and a ``passive node'' are created in |mem| for each -feasible breakpoint that needs to be considered. Active nodes are three -words long and passive nodes are two words long. We need active nodes only -for breakpoints near the place in the paragraph that is currently being -examined, so they are recycled within a comparatively short time after -they are created. - -@ An active node for a given breakpoint contains six fields: - -\yskip\hang|link| points to the next node in the list of active nodes; the -last active node has |link=last_active|. - -\yskip\hang|break_node| points to the passive node associated with this -breakpoint. - -\yskip\hang|line_number| is the number of the line that follows this -breakpoint. - -\yskip\hang|fitness| is the fitness classification of the line ending at this -breakpoint. - -\yskip\hang|type| is either |hyphenated| or |unhyphenated|, depending on -whether this breakpoint is a |disc_node|. - -\yskip\hang|total_demerits| is the minimum possible sum of demerits over all -lines leading from the beginning of the paragraph to this breakpoint. - -\yskip\noindent -The value of |link(active)| points to the first active node on a linked list -of all currently active nodes. This list is in order by |line_number|, -except that nodes with |line_number>easy_line| may be in any order relative -to each other. - -@d active_node_size=3 {number of words in active nodes} -@d fitness==subtype {|very_loose_fit..tight_fit| on final line for this break} -@d break_node==rlink {pointer to the corresponding passive node} -@d line_number==llink {line that begins at this breakpoint} -@d total_demerits(#)==mem[#+2].int {the quantity that \TeX\ minimizes} -@d unhyphenated=0 {the |type| of a normal active break node} -@d hyphenated=1 {the |type| of an active node that breaks at a |disc_node|} -@d last_active==active {the active list ends where it begins} - -@ @<Initialize the special list heads...@>= -type(last_active):=hyphenated; line_number(last_active):=max_halfword; -subtype(last_active):=0; {the |subtype| is never examined by the algorithm} - -@ The passive node for a given breakpoint contains only four fields: - -\yskip\hang|link| points to the passive node created just before this one, -if any, otherwise it is |null|. - -\yskip\hang|cur_break| points to the position of this breakpoint in the -horizontal list for the paragraph being broken. - -\yskip\hang|prev_break| points to the passive node that should precede this -one in an optimal path to this breakpoint. - -\yskip\hang|serial| is equal to |n| if this passive node is the |n|th -one created during the current pass. (This field is used only when -printing out detailed statistics about the line-breaking calculations.) - -\yskip\noindent -There is a global variable called |passive| that points to the most -recently created passive node. Another global variable, |printed_node|, -is used to help print out the paragraph when detailed information about -the line-breaking computation is being displayed. - -@d passive_node_size=2 {number of words in passive nodes} -@d cur_break==rlink {in passive node, points to position of this breakpoint} -@d prev_break==llink {points to passive node that should precede this one} -@d serial==info {serial number for symbolic identification} - -@<Glob...@>= -@!passive:pointer; {most recent node on passive list} -@!printed_node:pointer; {most recent node that has been printed} -@!pass_number:halfword; {the number of passive nodes allocated on this pass} - -@ The active list also contains ``delta'' nodes that help the algorithm -compute the badness of individual lines. Such nodes appear only between two -active nodes, and they have |type=delta_node|. If |p| and |r| are active nodes -and if |q| is a delta node between them, so that |link(p)=q| and |link(q)=r|, -then |q| tells the space difference between lines in the horizontal list that -start after breakpoint |p| and lines that start after breakpoint |r|. In -other words, if we know the length of the line that starts after |p| and -ends at our current position, then the corresponding length of the line that -starts after |r| is obtained by adding the amounts in node~|q|. A delta node -contains six scaled numbers, since it must record the net change in glue -stretchability with respect to all orders of infinity. The natural width -difference appears in |mem[q+1].sc|; the stretch differences in units of -pt, fil, fill, and filll appear in |mem[q+2..q+5].sc|; and the shrink difference -appears in |mem[q+6].sc|. The |subtype| field of a delta node is not used. - -@d delta_node_size=7 {number of words in a delta node} -@d delta_node=2 {|type| field in a delta node} - -@ As the algorithm runs, it maintains a set of six delta-like registers -for the length of the line following the first active breakpoint to the -current position in the given hlist. When it makes a pass through the -active list, it also maintains a similar set of six registers for the -length following the active breakpoint of current interest. A third set -holds the length of an empty line (namely, the sum of \.{\\leftskip} and -\.{\\rightskip}); and a fourth set is used to create new delta nodes. - -When we pass a delta node we want to do operations like -$$\hbox{\ignorespaces|for -k:=1 to 6 do cur_active_width[k]:=cur_active_width[k]+mem[q+k].sc|};$$ and we -want to do this without the overhead of |for| loops. The |do_all_six| -macro makes such six-tuples convenient. - -@d do_all_six(#)==#(1);#(2);#(3);#(4);#(5);#(6) - -@<Glob...@>= -@!active_width:array[1..6] of scaled; - {distance from first active node to~|cur_p|} -@!cur_active_width:array[1..6] of scaled; {distance from current active node} -@!background:array[1..6] of scaled; {length of an ``empty'' line} -@!break_width:array[1..6] of scaled; {length being computed after current break} - -@ Let's state the principles of the delta nodes more precisely and concisely, -so that the following programs will be less obscure. For each legal -breakpoint~|p| in the paragraph, we define two quantities $\alpha(p)$ and -$\beta(p)$ such that the length of material in a line from breakpoint~|p| -to breakpoint~|q| is $\gamma+\beta(q)-\alpha(p)$, for some fixed $\gamma$. -Intuitively, $\alpha(p)$ and $\beta(q)$ are the total length of material from -the beginning of the paragraph to a point ``after'' a break at |p| and to a -point ``before'' a break at |q|; and $\gamma$ is the width of an empty line, -namely the length contributed by \.{\\leftskip} and \.{\\rightskip}. - -Suppose, for example, that the paragraph consists entirely of alternating -boxes and glue skips; let the boxes have widths $x_1\ldots x_n$ and -let the skips have widths $y_1\ldots y_n$, so that the paragraph can be -represented by $x_1y_1\ldots x_ny_n$. Let $p_i$ be the legal breakpoint -at $y_i$; then $\alpha(p_i)=x_1+y_1+\cdots+x_i+y_i$, and $\beta(p_i)= -x_1+y_1+\cdots+x_i$. To check this, note that the length of material from -$p_2$ to $p_5$, say, is $\gamma+x_3+y_3+x_4+y_4+x_5=\gamma+\beta(p_5) --\alpha(p_2)$. - -The quantities $\alpha$, $\beta$, $\gamma$ involve glue stretchability and -shrinkability as well as a natural width. If we were to compute $\alpha(p)$ -and $\beta(p)$ for each |p|, we would need multiple precision arithmetic, and -the multiprecise numbers would have to be kept in the active nodes. -\TeX\ avoids this problem by working entirely with relative differences -or ``deltas.'' Suppose, for example, that the active list contains -$a_1\,\delta_1\,a_2\,\delta_2\,a_3$, where the |a|'s are active breakpoints -and the $\delta$'s are delta nodes. Then $\delta_1=\alpha(a_1)-\alpha(a_2)$ -and $\delta_2=\alpha(a_2)-\alpha(a_3)$. If the line breaking algorithm is -currently positioned at some other breakpoint |p|, the |active_width| array -contains the value $\gamma+\beta(p)-\alpha(a_1)$. If we are scanning through -the list of active nodes and considering a tentative line that runs from -$a_2$ to~|p|, say, the |cur_active_width| array will contain the value -$\gamma+\beta(p)-\alpha(a_2)$. Thus, when we move from $a_2$ to $a_3$, -we want to add $\alpha(a_2)-\alpha(a_3)$ to |cur_active_width|; and this -is just $\delta_2$, which appears in the active list between $a_2$ and -$a_3$. The |background| array contains $\gamma$. The |break_width| array -will be used to calculate values of new delta nodes when the active -list is being updated. - -@ Glue nodes in a horizontal list that is being paragraphed are not supposed to -include ``infinite'' shrinkability; that is why the algorithm maintains -four registers for stretching but only one for shrinking. If the user tries to -introduce infinite shrinkability, the shrinkability will be reset to finite -and an error message will be issued. A boolean variable |no_shrink_error_yet| -prevents this error message from appearing more than once per paragraph. - -@d check_shrinkage(#)==if (shrink_order(#)<>normal)and(shrink(#)<>0) then - begin #:=finite_shrink(#); - end - -@<Glob...@>= -@!no_shrink_error_yet:boolean; {have we complained about infinite shrinkage?} - -@ @<Declare subprocedures for |line_break|@>= -function finite_shrink(@!p:pointer):pointer; {recovers from infinite shrinkage} -var q:pointer; {new glue specification} -begin if no_shrink_error_yet then - begin no_shrink_error_yet:=false; - @!stat if tracing_paragraphs>0 then end_diagnostic(true);@+tats@; - print_err("Infinite glue shrinkage found in a paragraph"); -@.Infinite glue shrinkage...@> - help5("The paragraph just ended includes some glue that has")@/ - ("infinite shrinkability, e.g., `\hskip 0pt minus 1fil'.")@/ - ("Such glue doesn't belong there---it allows a paragraph")@/ - ("of any length to fit on one line. But it's safe to proceed,")@/ - ("since the offensive shrinkability has been made finite."); - error; - @!stat if tracing_paragraphs>0 then begin_diagnostic;@+tats@; - end; -q:=new_spec(p); shrink_order(q):=normal; -delete_glue_ref(p); finite_shrink:=q; -end; - -@ @<Get ready to start...@>= -no_shrink_error_yet:=true;@/ -check_shrinkage(left_skip); check_shrinkage(right_skip);@/ -q:=left_skip; r:=right_skip; background[1]:=width(q)+width(r);@/ -background[2]:=0; background[3]:=0; background[4]:=0; background[5]:=0;@/ -background[2+stretch_order(q)]:=stretch(q);@/ -background[2+stretch_order(r)]:=@|background[2+stretch_order(r)]+stretch(r);@/ -background[6]:=shrink(q)+shrink(r); - -@ A pointer variable |cur_p| runs through the given horizontal list as we look -for breakpoints. This variable is global, since it is used both by |line_break| -and by its subprocedure |try_break|. - -Another global variable called |threshold| is used to determine the feasibility -of individual lines: Breakpoints are feasible if there is a way to reach -them without creating lines whose badness exceeds |threshold|. (The -badness is compared to |threshold| before penalties are added, so that -penalty values do not affect the feasibility of breakpoints, except that -no break is allowed when the penalty is 10000 or more.) If |threshold| -is 10000 or more, all legal breaks are considered feasible, since the -|badness| function specified above never returns a value greater than~10000. - -Up to three passes might be made through the paragraph in an attempt to find at -least one set of feasible breakpoints. On the first pass, we have -|threshold=pretolerance| and |second_pass=final_pass=false|. -If this pass fails to find a -feasible solution, |threshold| is set to |tolerance|, |second_pass| is set -|true|, and an attempt is made to hyphenate as many words as possible. -If that fails too, we add |emergency_stretch| to the background -stretchability and set |final_pass=true|. - -@<Glob...@>= -@!cur_p:pointer; {the current breakpoint under consideration} -@!second_pass:boolean; {is this our second attempt to break this paragraph?} -@!final_pass:boolean; {is this our final attempt to break this paragraph?} -@!threshold:integer; {maximum badness on feasible lines} - -@ The heart of the line-breaking procedure is `|try_break|', a subroutine -that tests if the current breakpoint |cur_p| is feasible, by running -through the active list to see what lines of text can be made from active -nodes to~|cur_p|. If feasible breaks are possible, new break nodes are -created. If |cur_p| is too far from an active node, that node is -deactivated. - -The parameter |pi| to |try_break| is the penalty associated -with a break at |cur_p|; we have |pi=eject_penalty| if the break is forced, -and |pi=inf_penalty| if the break is illegal. - -The other parameter, |break_type|, is set to |hyphenated| or |unhyphenated|, -depending on whether or not the current break is at a |disc_node|. The -end of a paragraph is also regarded as `|hyphenated|'; this case is -distinguishable by the condition |cur_p=null|. - -@d copy_to_cur_active(#)==cur_active_width[#]:=active_width[#] -@d deactivate=60 {go here when node |r| should be deactivated} - -@<Declare subprocedures for |line_break|@>= -procedure try_break(@!pi:integer;@!break_type:small_number); -label exit,done,done1,continue,deactivate; -var r:pointer; {runs through the active list} -@!prev_r:pointer; {stays a step behind |r|} -@!old_l:halfword; {maximum line number in current equivalence class of lines} -@!no_break_yet:boolean; {have we found a feasible break at |cur_p|?} -@<Other local variables for |try_break|@>@; -begin @<Make sure that |pi| is in the proper range@>; -no_break_yet:=true; prev_r:=active; old_l:=0; -do_all_six(copy_to_cur_active); -loop@+ begin continue: r:=link(prev_r); - @<If node |r| is of type |delta_node|, update |cur_active_width|, - set |prev_r| and |prev_prev_r|, then |goto continue|@>; - @<If a line number class has ended, create new active nodes for - the best feasible breaks in that class; then |return| - if |r=last_active|, otherwise compute the new |line_width|@>; - @<Consider the demerits for a line from |r| to |cur_p|; - deactivate node |r| if it should no longer be active; - then |goto continue| if a line from |r| to |cur_p| is infeasible, - otherwise record a new feasible break@>; - end; -exit: @!stat @<Update the value of |printed_node| for - symbolic displays@>@+tats@; -end; - -@ @<Other local variables for |try_break|@>= -@!prev_prev_r:pointer; {a step behind |prev_r|, if |type(prev_r)=delta_node|} -@!s:pointer; {runs through nodes ahead of |cur_p|} -@!q:pointer; {points to a new node being created} -@!v:pointer; {points to a glue specification or a node ahead of |cur_p|} -@!t:integer; {node count, if |cur_p| is a discretionary node} -@!f:internal_font_number; {used in character width calculation} -@!l:halfword; {line number of current active node} -@!node_r_stays_active:boolean; {should node |r| remain in the active list?} -@!line_width:scaled; {the current line will be justified to this width} -@!fit_class:very_loose_fit..tight_fit; {possible fitness class of test line} -@!b:halfword; {badness of test line} -@!d:integer; {demerits of test line} -@!artificial_demerits:boolean; {has |d| been forced to zero?} -@!save_link:pointer; {temporarily holds value of |link(cur_p)|} -@!shortfall:scaled; {used in badness calculations} - -@ @<Make sure that |pi| is in the proper range@>= -if abs(pi)>=inf_penalty then - if pi>0 then return {this breakpoint is inhibited by infinite penalty} - else pi:=eject_penalty {this breakpoint will be forced} - -@ The following code uses the fact that |type(last_active)<>delta_node|. - -@d update_width(#)==@| - cur_active_width[#]:=cur_active_width[#]+mem[r+#].sc - -@<If node |r|...@>= -@^inner loop@> -if type(r)=delta_node then - begin do_all_six(update_width); - prev_prev_r:=prev_r; prev_r:=r; goto continue; - end - -@ As we consider various ways to end a line at |cur_p|, in a given line number -class, we keep track of the best total demerits known, in an array with -one entry for each of the fitness classifications. For example, -|minimal_demerits[tight_fit]| contains the fewest total demerits of feasible -line breaks ending at |cur_p| with a |tight_fit| line; |best_place[tight_fit]| -points to the passive node for the break before~|cur_p| that achieves such -an optimum; and |best_pl_line[tight_fit]| is the |line_number| field in the -active node corresponding to |best_place[tight_fit]|. When no feasible break -sequence is known, the |minimal_demerits| entries will be equal to -|awful_bad|, which is $2^{30}-1$. Another variable, |minimum_demerits|, -keeps track of the smallest value in the |minimal_demerits| array. - -@d awful_bad==@'7777777777 {more than a billion demerits} - -@<Global...@>= -@!minimal_demerits:array[very_loose_fit..tight_fit] of integer; {best total - demerits known for current line class and position, given the fitness} -@!minimum_demerits:integer; {best total demerits known for current line class - and position} -@!best_place:array[very_loose_fit..tight_fit] of pointer; {how to achieve - |minimal_demerits|} -@!best_pl_line:array[very_loose_fit..tight_fit] of halfword; {corresponding - line number} - -@ @<Get ready to start...@>= -minimum_demerits:=awful_bad; -minimal_demerits[tight_fit]:=awful_bad; -minimal_demerits[decent_fit]:=awful_bad; -minimal_demerits[loose_fit]:=awful_bad; -minimal_demerits[very_loose_fit]:=awful_bad; - -@ The first part of the following code is part of \TeX's inner loop, so -we don't want to waste any time. The current active node, namely node |r|, -contains the line number that will be considered next. At the end of the -list we have arranged the data structure so that |r=last_active| and -|line_number(last_active)>old_l|. -@^inner loop@> - -@<If a line number class...@>= -begin l:=line_number(r); -if l>old_l then - begin {now we are no longer in the inner loop} - if (minimum_demerits<awful_bad)and@| - ((old_l<>easy_line)or(r=last_active)) then - @<Create new active nodes for the best feasible breaks - just found@>; - if r=last_active then return; - @<Compute the new line width@>; - end; -end - -@ It is not necessary to create new active nodes having |minimal_demerits| -greater than -|minimum_demerits+abs(adj_demerits)|, since such active nodes will never -be chosen in the final paragraph breaks. This observation allows us to -omit a substantial number of feasible breakpoints from further consideration. - -@<Create new active nodes...@>= -begin if no_break_yet then @<Compute the values of |break_width|@>; -@<Insert a delta node to prepare for breaks at |cur_p|@>; -if abs(adj_demerits)>=awful_bad-minimum_demerits then - minimum_demerits:=awful_bad-1 -else minimum_demerits:=minimum_demerits+abs(adj_demerits); -for fit_class:=very_loose_fit to tight_fit do - begin if minimal_demerits[fit_class]<=minimum_demerits then - @<Insert a new active node - from |best_place[fit_class]| to |cur_p|@>; - minimal_demerits[fit_class]:=awful_bad; - end; -minimum_demerits:=awful_bad; -@<Insert a delta node to prepare for the next active node@>; -end - -@ When we insert a new active node for a break at |cur_p|, suppose this -new node is to be placed just before active node |a|; then we essentially -want to insert `$\delta\,|cur_p|\,\delta^\prime$' before |a|, where -$\delta=\alpha(a)-\alpha(|cur_p|)$ and $\delta^\prime=\alpha(|cur_p|)-\alpha(a)$ -in the notation explained above. The |cur_active_width| array now holds -$\gamma+\beta(|cur_p|)-\alpha(a)$; so $\delta$ can be obtained by -subtracting |cur_active_width| from the quantity $\gamma+\beta(|cur_p|)- -\alpha(|cur_p|)$. The latter quantity can be regarded as the length of a -line ``from |cur_p| to |cur_p|''; we call it the |break_width| at |cur_p|. - -The |break_width| is usually negative, since it consists of the background -(which is normally zero) minus the width of nodes following~|cur_p| that are -eliminated after a break. If, for example, node |cur_p| is a glue node, the -width of this glue is subtracted from the background; and we also look -ahead to eliminate all subsequent glue and penalty and kern and math -nodes, subtracting their widths as well. - -Kern nodes do not disappear at a line break unless they are |explicit|. - -@d set_break_width_to_background(#)==break_width[#]:=background[#] - -@<Compute the values of |break...@>= -begin no_break_yet:=false; do_all_six(set_break_width_to_background); -s:=cur_p; -if break_type>unhyphenated then if cur_p<>null then - @<Compute the discretionary |break_width| values@>; -while s<>null do - begin if is_char_node(s) then goto done; - case type(s) of - glue_node:@<Subtract glue from |break_width|@>; - penalty_node: do_nothing; - math_node: break_width[1]:=break_width[1]-width(s); - kern_node: if subtype(s)<>explicit then goto done - else break_width[1]:=break_width[1]-width(s); - othercases goto done - endcases;@/ - s:=link(s); - end; -done: end - -@ @<Subtract glue from |break...@>= -begin v:=glue_ptr(s); break_width[1]:=break_width[1]-width(v); -break_width[2+stretch_order(v)]:=break_width[2+stretch_order(v)]-stretch(v); -break_width[6]:=break_width[6]-shrink(v); -end - -@ When |cur_p| is a discretionary break, the length of a line ``from |cur_p| to -|cur_p|'' has to be defined properly so that the other calculations work out. -Suppose that the pre-break text at |cur_p| has length $l_0$, the post-break -text has length $l_1$, and the replacement text has length |l|. Suppose -also that |q| is the node following the replacement text. Then length of a -line from |cur_p| to |q| will be computed as $\gamma+\beta(q)-\alpha(|cur_p|)$, -where $\beta(q)=\beta(|cur_p|)-l_0+l$. The actual length will be the background -plus $l_1$, so the length from |cur_p| to |cur_p| should be $\gamma+l_0+l_1-l$. -If the post-break text of the discretionary is empty, a break may also -discard~|q|; in that unusual case we subtract the length of~|q| and any -other nodes that will be discarded after the discretionary break. - -The value of $l_0$ need not be computed, since |line_break| will put -it into the global variable |disc_width| before calling |try_break|. - -@<Glob...@>= -@!disc_width:scaled; {the length of discretionary material preceding a break} - -@ @<Compute the discretionary |break...@>= -begin t:=replace_count(cur_p); v:=cur_p; s:=post_break(cur_p); -while t>0 do - begin decr(t); v:=link(v); - @<Subtract the width of node |v| from |break_width|@>; - end; -while s<>null do - begin @<Add the width of node |s| to |break_width|@>; - s:=link(s); - end; -break_width[1]:=break_width[1]+disc_width; -if post_break(cur_p)=null then s:=link(v); - {nodes may be discardable after the break} -end - -@ Replacement texts and discretionary texts are supposed to contain -only character nodes, kern nodes, ligature nodes, and box or rule nodes. - -@<Subtract the width of node |v|...@>= -if is_char_node(v) then - begin f:=font(v); - break_width[1]:=break_width[1]-char_width(f)(char_info(f)(character(v))); - end -else case type(v) of - ligature_node: begin f:=font(lig_char(v));@/ - break_width[1]:=@|break_width[1]- - char_width(f)(char_info(f)(character(lig_char(v)))); - end; - hlist_node,vlist_node,rule_node,kern_node: - break_width[1]:=break_width[1]-width(v); - othercases confusion("disc1") -@:this can't happen disc1}{\quad disc1@> - endcases - -@ @<Add the width of node |s| to |b...@>= -if is_char_node(s) then - begin f:=font(s); - break_width[1]:=@|break_width[1]+char_width(f)(char_info(f)(character(s))); - end -else case type(s) of - ligature_node: begin f:=font(lig_char(s)); - break_width[1]:=break_width[1]+ - char_width(f)(char_info(f)(character(lig_char(s)))); - end; - hlist_node,vlist_node,rule_node,kern_node: - break_width[1]:=break_width[1]+width(s); - othercases confusion("disc2") -@:this can't happen disc2}{\quad disc2@> - endcases - -@ We use the fact that |type(active)<>delta_node|. - -@d convert_to_break_width(#)==@| - mem[prev_r+#].sc:=@|@t\hskip10pt@>mem[prev_r+#].sc - -cur_active_width[#]+break_width[#] -@d store_break_width(#)==active_width[#]:=break_width[#] -@d new_delta_to_break_width(#)==@| - mem[q+#].sc:=break_width[#]-cur_active_width[#] - -@<Insert a delta node to prepare for breaks at |cur_p|@>= -if type(prev_r)=delta_node then {modify an existing delta node} - begin do_all_six(convert_to_break_width); - end -else if prev_r=active then {no delta node needed at the beginning} - begin do_all_six(store_break_width); - end -else begin q:=get_node(delta_node_size); link(q):=r; type(q):=delta_node;@/ - subtype(q):=0; {the |subtype| is not used} - do_all_six(new_delta_to_break_width); - link(prev_r):=q; prev_prev_r:=prev_r; prev_r:=q; - end - -@ When the following code is performed, we will have just inserted at -least one active node before |r|, so |type(prev_r)<>delta_node|. - -@d new_delta_from_break_width(#)==@|mem[q+#].sc:= - cur_active_width[#]-break_width[#] - -@<Insert a delta node to prepare for the next active node@>= -if r<>last_active then - begin q:=get_node(delta_node_size); link(q):=r; type(q):=delta_node;@/ - subtype(q):=0; {the |subtype| is not used} - do_all_six(new_delta_from_break_width); - link(prev_r):=q; prev_prev_r:=prev_r; prev_r:=q; - end - -@ When we create an active node, we also create the corresponding -passive node. - -@<Insert a new active node from |best_place[fit_class]| to |cur_p|@>= -begin q:=get_node(passive_node_size); -link(q):=passive; passive:=q; cur_break(q):=cur_p; -@!stat incr(pass_number); serial(q):=pass_number;@+tats@;@/ -prev_break(q):=best_place[fit_class];@/ -q:=get_node(active_node_size); break_node(q):=passive; -line_number(q):=best_pl_line[fit_class]+1; -fitness(q):=fit_class; type(q):=break_type; -total_demerits(q):=minimal_demerits[fit_class]; -link(q):=r; link(prev_r):=q; prev_r:=q; -@!stat if tracing_paragraphs>0 then - @<Print a symbolic description of the new break node@>; -tats@;@/ -end - -@ @<Print a symbolic description of the new break node@>= -begin print_nl("@@@@"); print_int(serial(passive)); -@.\AT!\AT!@> -print(": line "); print_int(line_number(q)-1); -print_char("."); print_int(fit_class); -if break_type=hyphenated then print_char("-"); -print(" t="); print_int(total_demerits(q)); -print(" -> @@@@"); -if prev_break(passive)=null then print_char("0") -else print_int(serial(prev_break(passive))); -end - -@ The length of lines depends on whether the user has specified -\.{\\parshape} or \.{\\hangindent}. If |par_shape_ptr| is not null, it -points to a $(2n+1)$-word record in |mem|, where the |info| in the first -word contains the value of |n|, and the other $2n$ words contain the left -margins and line lengths for the first |n| lines of the paragraph; the -specifications for line |n| apply to all subsequent lines. If -|par_shape_ptr=null|, the shape of the paragraph depends on the value of -|n=hang_after|; if |n>=0|, hanging indentation takes place on lines |n+1|, -|n+2|, \dots, otherwise it takes place on lines 1, \dots, $\vert -n\vert$. When hanging indentation is active, the left margin is -|hang_indent|, if |hang_indent>=0|, else it is 0; the line length is -$|hsize|-\vert|hang_indent|\vert$. The normal setting is -|par_shape_ptr=null|, |hang_after=1|, and |hang_indent=0|. -Note that if |hang_indent=0|, the value of |hang_after| is irrelevant. -@^length of lines@> @^hanging indentation@> - -@<Glob...@>= -@!easy_line:halfword; {line numbers |>easy_line| are equivalent in break nodes} -@!last_special_line:halfword; {line numbers |>last_special_line| all have - the same width} -@!first_width:scaled; {the width of all lines |<=last_special_line|, if - no \.{\\parshape} has been specified} -@!second_width:scaled; {the width of all lines |>last_special_line|} -@!first_indent:scaled; {left margin to go with |first_width|} -@!second_indent:scaled; {left margin to go with |second_width|} - -@ We compute the values of |easy_line| and the other local variables relating -to line length when the |line_break| procedure is initializing itself. - -@<Get ready to start...@>= -if par_shape_ptr=null then - if hang_indent=0 then - begin last_special_line:=0; second_width:=hsize; - second_indent:=0; - end - else @<Set line length parameters in preparation for hanging indentation@> -else begin last_special_line:=info(par_shape_ptr)-1; - second_width:=mem[par_shape_ptr+2*(last_special_line+1)].sc; - second_indent:=mem[par_shape_ptr+2*last_special_line+1].sc; - end; -if looseness=0 then easy_line:=last_special_line -else easy_line:=max_halfword - -@ @<Set line length parameters in preparation for hanging indentation@>= -begin last_special_line:=abs(hang_after); -if hang_after<0 then - begin first_width:=hsize-abs(hang_indent); - if hang_indent>=0 then first_indent:=hang_indent - else first_indent:=0; - second_width:=hsize; second_indent:=0; - end -else begin first_width:=hsize; first_indent:=0; - second_width:=hsize-abs(hang_indent); - if hang_indent>=0 then second_indent:=hang_indent - else second_indent:=0; - end; -end - -@ When we come to the following code, we have just encountered the first -active node~|r| whose |line_number| field contains |l|. Thus we want to -compute the length of the $l\mskip1mu$th line of the current paragraph. Furthermore, -we want to set |old_l| to the last number in the class of line numbers -equivalent to~|l|. - -@<Compute the new line width@>= -if l>easy_line then - begin line_width:=second_width; old_l:=max_halfword-1; - end -else begin old_l:=l; - if l>last_special_line then line_width:=second_width - else if par_shape_ptr=null then line_width:=first_width - else line_width:=mem[par_shape_ptr+2*l@,].sc; - end - -@ The remaining part of |try_break| deals with the calculation of -demerits for a break from |r| to |cur_p|. - -The first thing to do is calculate the badness, |b|. This value will always -be between zero and |inf_bad+1|; the latter value occurs only in the -case of lines from |r| to |cur_p| that cannot shrink enough to fit the necessary -width. In such cases, node |r| will be deactivated. -We also deactivate node~|r| when a break at~|cur_p| is forced, since future -breaks must go through a forced break. - -@<Consider the demerits for a line from |r| to |cur_p|...@>= -begin artificial_demerits:=false;@/ -@^inner loop@> -shortfall:=line_width-cur_active_width[1]; {we're this much too short} -if shortfall>0 then - @<Set the value of |b| to the badness for stretching the line, - and compute the corresponding |fit_class|@> -else @<Set the value of |b| to the badness for shrinking the line, - and compute the corresponding |fit_class|@>; -if (b>inf_bad)or(pi=eject_penalty) then - @<Prepare to deactivate node~|r|, and |goto deactivate| unless - there is a reason to consider lines of text from |r| to |cur_p|@> -else begin prev_r:=r; - if b>threshold then goto continue; - node_r_stays_active:=true; - end; -@<Record a new feasible break@>; -if node_r_stays_active then goto continue; {|prev_r| has been set to |r|} -deactivate: @<Deactivate node |r|@>; -end - -@ When a line must stretch, the available stretchability can be found in the -subarray |cur_active_width[2..5]|, in units of points, fil, fill, and filll. - -The present section is part of \TeX's inner loop, and it is most often performed -when the badness is infinite; therefore it is worth while to make a quick -test for large width excess and small stretchability, before calling the -|badness| subroutine. -@^inner loop@> - -@<Set the value of |b| to the badness for stretching...@>= -if (cur_active_width[3]<>0)or(cur_active_width[4]<>0)or@| - (cur_active_width[5]<>0) then - begin b:=0; fit_class:=decent_fit; {infinite stretch} - end -else begin if shortfall>7230584 then if cur_active_width[2]<1663497 then - begin b:=inf_bad; fit_class:=very_loose_fit; goto done1; - end; - b:=badness(shortfall,cur_active_width[2]); - if b>12 then - if b>99 then fit_class:=very_loose_fit - else fit_class:=loose_fit - else fit_class:=decent_fit; - done1: - end - -@ Shrinkability is never infinite in a paragraph; -we can shrink the line from |r| to |cur_p| by at most |cur_active_width[6]|. - -@<Set the value of |b| to the badness for shrinking...@>= -begin if -shortfall>cur_active_width[6] then b:=inf_bad+1 -else b:=badness(-shortfall,cur_active_width[6]); -if b>12 then fit_class:=tight_fit@+else fit_class:=decent_fit; -end - -@ During the final pass, we dare not lose all active nodes, lest we lose -touch with the line breaks already found. The code shown here makes sure -that such a catastrophe does not happen, by permitting overfull boxes as -a last resort. This particular part of \TeX\ was a source of several subtle -bugs before the correct program logic was finally discovered; readers -who seek to ``improve'' \TeX\ should therefore think thrice before daring -to make any changes here. -@^overfull boxes@> - -@<Prepare to deactivate node~|r|, and |goto deactivate| unless...@>= -begin if final_pass and (minimum_demerits=awful_bad) and@| - (link(r)=last_active) and - (prev_r=active) then - artificial_demerits:=true {set demerits zero, this break is forced} -else if b>threshold then goto deactivate; -node_r_stays_active:=false; -end - -@ When we get to this part of the code, the line from |r| to |cur_p| is -feasible, its badness is~|b|, and its fitness classification is |fit_class|. -We don't want to make an active node for this break yet, but we will -compute the total demerits and record them in the |minimal_demerits| array, -if such a break is the current champion among all ways to get to |cur_p| -in a given line-number class and fitness class. - -@<Record a new feasible break@>= -if artificial_demerits then d:=0 -else @<Compute the demerits, |d|, from |r| to |cur_p|@>; -@!stat if tracing_paragraphs>0 then - @<Print a symbolic description of this feasible break@>; -tats@;@/ -d:=d+total_demerits(r); {this is the minimum total demerits - from the beginning to |cur_p| via |r|} -if d<=minimal_demerits[fit_class] then - begin minimal_demerits[fit_class]:=d; - best_place[fit_class]:=break_node(r); best_pl_line[fit_class]:=l; - if d<minimum_demerits then minimum_demerits:=d; - end - -@ @<Print a symbolic description of this feasible break@>= -begin if printed_node<>cur_p then - @<Print the list between |printed_node| and |cur_p|, - then set |printed_node:=cur_p|@>; -print_nl("@@"); -@.\AT!@> -if cur_p=null then print_esc("par") -else if type(cur_p)<>glue_node then - begin if type(cur_p)=penalty_node then print_esc("penalty") - else if type(cur_p)=disc_node then print_esc("discretionary") - else if type(cur_p)=kern_node then print_esc("kern") - else print_esc("math"); - end; -print(" via @@@@"); -if break_node(r)=null then print_char("0") -else print_int(serial(break_node(r))); -print(" b="); -if b>inf_bad then print_char("*")@+else print_int(b); -@.*\relax@> -print(" p="); print_int(pi); print(" d="); -if artificial_demerits then print_char("*")@+else print_int(d); -end - -@ @<Print the list between |printed_node| and |cur_p|...@>= -begin print_nl(""); -if cur_p=null then short_display(link(printed_node)) -else begin save_link:=link(cur_p); - link(cur_p):=null; print_nl(""); short_display(link(printed_node)); - link(cur_p):=save_link; - end; -printed_node:=cur_p; -end - -@ When the data for a discretionary break is being displayed, we will have -printed the |pre_break| and |post_break| lists; we want to skip over the -third list, so that the discretionary data will not appear twice. The -following code is performed at the very end of |try_break|. - -@<Update the value of |printed_node|...@>= -if cur_p=printed_node then if cur_p<>null then if type(cur_p)=disc_node then - begin t:=replace_count(cur_p); - while t>0 do - begin decr(t); printed_node:=link(printed_node); - end; - end - -@ @<Compute the demerits, |d|, from |r| to |cur_p|@>= -begin d:=line_penalty+b; -if abs(d)>=10000 then d:=100000000@+else d:=d*d; -if pi<>0 then - if pi>0 then d:=d+pi*pi - else if pi>eject_penalty then d:=d-pi*pi; -if (break_type=hyphenated)and(type(r)=hyphenated) then - if cur_p<>null then d:=d+double_hyphen_demerits - else d:=d+final_hyphen_demerits; -if abs(fit_class-fitness(r))>1 then d:=d+adj_demerits; -end - -@ When an active node disappears, we must delete an adjacent delta node if the -active node was at the beginning or the end of the active list, or if it -was surrounded by delta nodes. We also must preserve the property that -|cur_active_width| represents the length of material from |link(prev_r)| -to~|cur_p|. - -@d combine_two_deltas(#)==@|mem[prev_r+#].sc:=mem[prev_r+#].sc+mem[r+#].sc -@d downdate_width(#)==@|cur_active_width[#]:=cur_active_width[#]- - mem[prev_r+#].sc - -@<Deactivate node |r|@>= -link(prev_r):=link(r); free_node(r,active_node_size); -if prev_r=active then @<Update the active widths, since the first active - node has been deleted@> -else if type(prev_r)=delta_node then - begin r:=link(prev_r); - if r=last_active then - begin do_all_six(downdate_width); - link(prev_prev_r):=last_active; - free_node(prev_r,delta_node_size); prev_r:=prev_prev_r; - end - else if type(r)=delta_node then - begin do_all_six(update_width); - do_all_six(combine_two_deltas); - link(prev_r):=link(r); free_node(r,delta_node_size); - end; - end - -@ The following code uses the fact that |type(last_active)<>delta_node|. If the -active list has just become empty, we do not need to update the -|active_width| array, since it will be initialized when an active -node is next inserted. - -@d update_active(#)==active_width[#]:=active_width[#]+mem[r+#].sc - -@<Update the active widths,...@>= -begin r:=link(active); -if type(r)=delta_node then - begin do_all_six(update_active); - do_all_six(copy_to_cur_active); - link(active):=link(r); free_node(r,delta_node_size); - end; -end - -@* \[39] Breaking paragraphs into lines, continued. -So far we have gotten a little way into the |line_break| routine, having -covered its important |try_break| subroutine. Now let's consider the -rest of the process. - -The main loop of |line_break| traverses the given hlist, -starting at |link(temp_head)|, and calls |try_break| at each legal -breakpoint. A variable called |auto_breaking| is set to true except -within math formulas, since glue nodes are not legal breakpoints when -they appear in formulas. - -The current node of interest in the hlist is pointed to by |cur_p|. Another -variable, |prev_p|, is usually one step behind |cur_p|, but the real -meaning of |prev_p| is this: If |type(cur_p)=glue_node| then |cur_p| is a legal -breakpoint if and only if |auto_breaking| is true and |prev_p| does not -point to a glue node, penalty node, explicit kern node, or math node. - -The following declarations provide for a few other local variables that are -used in special calculations. - -@<Local variables for line breaking@>= -@!auto_breaking:boolean; {is node |cur_p| outside a formula?} -@!prev_p:pointer; {helps to determine when glue nodes are breakpoints} -@!q,@!r,@!s,@!prev_s:pointer; {miscellaneous nodes of temporary interest} -@!f:internal_font_number; {used when calculating character widths} - -@ The `\ignorespaces|loop|\unskip' in the following code is performed at most -thrice per call of |line_break|, since it is actually a pass over the -entire paragraph. - -@<Find optimal breakpoints@>= -threshold:=pretolerance; -if threshold>=0 then - begin @!stat if tracing_paragraphs>0 then - begin begin_diagnostic; print_nl("@@firstpass");@+end;@;@+tats@;@/ - second_pass:=false; final_pass:=false; - end -else begin threshold:=tolerance; second_pass:=true; - final_pass:=(emergency_stretch<=0); - @!stat if tracing_paragraphs>0 then begin_diagnostic;@+tats@; - end; -loop@+ begin if threshold>inf_bad then threshold:=inf_bad; - if second_pass then @<Initialize for hyphenating a paragraph@>; - @<Create an active breakpoint representing the beginning of the paragraph@>; - cur_p:=link(temp_head); auto_breaking:=true;@/ - prev_p:=cur_p; {glue at beginning is not a legal breakpoint} - while (cur_p<>null)and(link(active)<>last_active) do - @<Call |try_break| if |cur_p| is a legal breakpoint; - on the second pass, also try to hyphenate the next - word, if |cur_p| is a glue node; - then advance |cur_p| to the next node of the paragraph - that could possibly be a legal breakpoint@>; - if cur_p=null then - @<Try the final line break at the end of the paragraph, - and |goto done| if the desired breakpoints have been found@>; - @<Clean up the memory by removing the break nodes@>; - if not second_pass then - begin@!stat if tracing_paragraphs>0 then print_nl("@@secondpass");@;@+tats@/ - threshold:=tolerance; second_pass:=true; final_pass:=(emergency_stretch<=0); - end {if at first you don't succeed, \dots} - else begin @!stat if tracing_paragraphs>0 then - print_nl("@@emergencypass");@;@+tats@/ - background[2]:=background[2]+emergency_stretch; final_pass:=true; - end; - end; -done: @!stat if tracing_paragraphs>0 then - begin end_diagnostic(true); normalize_selector; - end;@+tats@/ - -@ The active node that represents the starting point does not need a -corresponding passive node. - -@d store_background(#)==active_width[#]:=background[#] - -@<Create an active breakpoint representing the beginning of the paragraph@>= -q:=get_node(active_node_size); -type(q):=unhyphenated; fitness(q):=decent_fit; -link(q):=last_active; break_node(q):=null; -line_number(q):=prev_graf+1; total_demerits(q):=0; link(active):=q; -do_all_six(store_background);@/ -passive:=null; printed_node:=temp_head; pass_number:=0; -font_in_short_display:=null_font - -@ @<Clean...@>= -q:=link(active); -while q<>last_active do - begin cur_p:=link(q); - if type(q)=delta_node then free_node(q,delta_node_size) - else free_node(q,active_node_size); - q:=cur_p; - end; -q:=passive; -while q<>null do - begin cur_p:=link(q); - free_node(q,passive_node_size); - q:=cur_p; - end - -@ Here is the main switch in the |line_break| routine, where legal breaks -are determined. As we move through the hlist, we need to keep the |active_width| -array up to date, so that the badness of individual lines is readily calculated -by |try_break|. It is convenient to use the short name |act_width| for -the component of active width that represents real width as opposed to glue. - -@d act_width==active_width[1] {length from first active node to current node} -@d kern_break==begin if not is_char_node(link(cur_p)) and auto_breaking then - if type(link(cur_p))=glue_node then try_break(0,unhyphenated); - act_width:=act_width+width(cur_p); - end - -@<Call |try_break| if |cur_p| is a legal breakpoint...@>= -begin if is_char_node(cur_p) then - @<Advance \(c)|cur_p| to the node following the present - string of characters@>; -case type(cur_p) of -hlist_node,vlist_node,rule_node: act_width:=act_width+width(cur_p); -whatsit_node: @<Advance \(p)past a whatsit node in the \(l)|line_break| loop@>; -glue_node: begin @<If node |cur_p| is a legal breakpoint, call |try_break|; - then update the active widths by including the glue in |glue_ptr(cur_p)|@>; - if second_pass and auto_breaking then - @<Try to hyphenate the following word@>; - end; -kern_node: if subtype(cur_p)=explicit then kern_break - else act_width:=act_width+width(cur_p); -ligature_node: begin f:=font(lig_char(cur_p)); - act_width:=act_width+char_width(f)(char_info(f)(character(lig_char(cur_p)))); - end; -disc_node: @<Try to break after a discretionary fragment, then |goto done5|@>; -math_node: begin auto_breaking:=(subtype(cur_p)=after); kern_break; - end; -penalty_node: try_break(penalty(cur_p),unhyphenated); -mark_node,ins_node,adjust_node: do_nothing; -othercases confusion("paragraph") -@:this can't happen paragraph}{\quad paragraph@> -endcases;@/ -prev_p:=cur_p; cur_p:=link(cur_p); -done5:end - -@ The code that passes over the characters of words in a paragraph is -part of \TeX's inner loop, so it has been streamlined for speed. We use -the fact that `\.{\\parfillskip}' glue appears at the end of each paragraph; -it is therefore unnecessary to check if |link(cur_p)=null| when |cur_p| is a -character node. -@^inner loop@> - -@<Advance \(c)|cur_p| to the node following the present string...@>= -begin prev_p:=cur_p; -repeat f:=font(cur_p); -act_width:=act_width+char_width(f)(char_info(f)(character(cur_p))); -cur_p:=link(cur_p); -until not is_char_node(cur_p); -end - -@ When node |cur_p| is a glue node, we look at |prev_p| to see whether or not -a breakpoint is legal at |cur_p|, as explained above. - -@<If node |cur_p| is a legal breakpoint, call...@>= -if auto_breaking then - begin if is_char_node(prev_p) then try_break(0,unhyphenated) - else if precedes_break(prev_p) then try_break(0,unhyphenated) - else if (type(prev_p)=kern_node)and(subtype(prev_p)<>explicit) then - try_break(0,unhyphenated); - end; -check_shrinkage(glue_ptr(cur_p)); q:=glue_ptr(cur_p); -act_width:=act_width+width(q);@| -active_width[2+stretch_order(q)]:=@| - active_width[2+stretch_order(q)]+stretch(q);@/ -active_width[6]:=active_width[6]+shrink(q) - -@ The following code knows that discretionary texts contain -only character nodes, kern nodes, box nodes, rule nodes, and ligature nodes. - -@<Try to break after a discretionary fragment...@>= -begin s:=pre_break(cur_p); disc_width:=0; -if s=null then try_break(ex_hyphen_penalty,hyphenated) -else begin repeat @<Add the width of node |s| to |disc_width|@>; - s:=link(s); - until s=null; - act_width:=act_width+disc_width; - try_break(hyphen_penalty,hyphenated); - act_width:=act_width-disc_width; - end; -r:=replace_count(cur_p); s:=link(cur_p); -while r>0 do - begin @<Add the width of node |s| to |act_width|@>; - decr(r); s:=link(s); - end; -prev_p:=cur_p; cur_p:=s; goto done5; -end - -@ @<Add the width of node |s| to |disc_width|@>= -if is_char_node(s) then - begin f:=font(s); - disc_width:=disc_width+char_width(f)(char_info(f)(character(s))); - end -else case type(s) of - ligature_node: begin f:=font(lig_char(s)); - disc_width:=disc_width+ - char_width(f)(char_info(f)(character(lig_char(s)))); - end; - hlist_node,vlist_node,rule_node,kern_node: - disc_width:=disc_width+width(s); - othercases confusion("disc3") -@:this can't happen disc3}{\quad disc3@> - endcases - -@ @<Add the width of node |s| to |act_width|@>= -if is_char_node(s) then - begin f:=font(s); - act_width:=act_width+char_width(f)(char_info(f)(character(s))); - end -else case type(s) of - ligature_node: begin f:=font(lig_char(s)); - act_width:=act_width+ - char_width(f)(char_info(f)(character(lig_char(s)))); - end; - hlist_node,vlist_node,rule_node,kern_node: - act_width:=act_width+width(s); - othercases confusion("disc4") -@:this can't happen disc4}{\quad disc4@> - endcases - -@ The forced line break at the paragraph's end will reduce the list of -breakpoints so that all active nodes represent breaks at |cur_p=null|. -On the first pass, we insist on finding an active node that has the -correct ``looseness.'' On the final pass, there will be at least one active -node, and we will match the desired looseness as well as we can. - -The global variable |best_bet| will be set to the active node for the best -way to break the paragraph, and a few other variables are used to -help determine what is best. - -@<Glob...@>= -@!best_bet:pointer; {use this passive node and its predecessors} -@!fewest_demerits:integer; {the demerits associated with |best_bet|} -@!best_line:halfword; {line number following the last line of the new paragraph} -@!actual_looseness:integer; {the difference between |line_number(best_bet)| - and the optimum |best_line|} -@!line_diff:integer; {the difference between the current line number and - the optimum |best_line|} - -@ @<Try the final line break at the end of the paragraph...@>= -begin try_break(eject_penalty,hyphenated); -if link(active)<>last_active then - begin @<Find an active node with fewest demerits@>; - if looseness=0 then goto done; - @<Find the best active node for the desired looseness@>; - if (actual_looseness=looseness)or final_pass then goto done; - end; -end - -@ @<Find an active node...@>= -r:=link(active); fewest_demerits:=awful_bad; -repeat if type(r)<>delta_node then if total_demerits(r)<fewest_demerits then - begin fewest_demerits:=total_demerits(r); best_bet:=r; - end; -r:=link(r); -until r=last_active; -best_line:=line_number(best_bet) - -@ The adjustment for a desired looseness is a slightly more complicated -version of the loop just considered. Note that if a paragraph is broken -into segments by displayed equations, each segment will be subject to the -looseness calculation, independently of the other segments. - -@<Find the best active node...@>= -begin r:=link(active); actual_looseness:=0; -repeat if type(r)<>delta_node then - begin line_diff:=line_number(r)-best_line; - if ((line_diff<actual_looseness)and(looseness<=line_diff))or@| - ((line_diff>actual_looseness)and(looseness>=line_diff)) then - begin best_bet:=r; actual_looseness:=line_diff; - fewest_demerits:=total_demerits(r); - end - else if (line_diff=actual_looseness)and@| - (total_demerits(r)<fewest_demerits) then - begin best_bet:=r; fewest_demerits:=total_demerits(r); - end; - end; -r:=link(r); -until r=last_active; -best_line:=line_number(best_bet); -end - -@ Once the best sequence of breakpoints has been found (hurray), we call on the -procedure |post_line_break| to finish the remainder of the work. -(By introducing this subprocedure, we are able to keep |line_break| -from getting extremely long.) - -@<Break the paragraph at the chosen...@>= -post_line_break(final_widow_penalty) - -@ The total number of lines that will be set by |post_line_break| -is |best_line-prev_graf-1|. The last breakpoint is specified by -|break_node(best_bet)|, and this passive node points to the other breakpoints -via the |prev_break| links. The finishing-up phase starts by linking the -relevant passive nodes in forward order, changing |prev_break| to -|next_break|. (The |next_break| fields actually reside in the same memory -space as the |prev_break| fields did, but we give them a new name because -of their new significance.) Then the lines are justified, one by one. - -@d next_break==prev_break {new name for |prev_break| after links are reversed} - -@<Declare subprocedures for |line_break|@>= -procedure post_line_break(@!final_widow_penalty:integer); -label done,done1; -var q,@!r,@!s:pointer; {temporary registers for list manipulation} -@!disc_break:boolean; {was the current break at a discretionary node?} -@!post_disc_break:boolean; {and did it have a nonempty post-break part?} -@!cur_width:scaled; {width of line number |cur_line|} -@!cur_indent:scaled; {left margin of line number |cur_line|} -@!t:quarterword; {used for replacement counts in discretionary nodes} -@!pen:integer; {use when calculating penalties between lines} -@!cur_line: halfword; {the current line number being justified} -begin @<Reverse the links of the relevant passive nodes, setting |cur_p| to the - first breakpoint@>; -cur_line:=prev_graf+1; -repeat @<Justify the line ending at breakpoint |cur_p|, and append it to the - current vertical list, together with associated penalties and other - insertions@>; -incr(cur_line); cur_p:=next_break(cur_p); -if cur_p<>null then if not post_disc_break then - @<Prune unwanted nodes at the beginning of the next line@>; -until cur_p=null; -if (cur_line<>best_line)or(link(temp_head)<>null) then - confusion("line breaking"); -@:this can't happen line breaking}{\quad line breaking@> -prev_graf:=best_line-1; -end; - -@ The job of reversing links in a list is conveniently regarded as the job -of taking items off one stack and putting them on another. In this case we -take them off a stack pointed to by |q| and having |prev_break| fields; -we put them on a stack pointed to by |cur_p| and having |next_break| fields. -Node |r| is the passive node being moved from stack to stack. - -@<Reverse the links of the relevant passive nodes...@>= -q:=break_node(best_bet); cur_p:=null; -repeat r:=q; q:=prev_break(q); next_break(r):=cur_p; cur_p:=r; -until q=null - -@ Glue and penalty and kern and math nodes are deleted at the beginning of -a line, except in the anomalous case that the node to be deleted is actually -one of the chosen breakpoints. Otherwise -the pruning done here is designed to match -the lookahead computation in |try_break|, where the |break_width| values -are computed for non-discretionary breakpoints. - -@<Prune unwanted nodes at the beginning of the next line@>= -begin r:=temp_head; -loop@+ begin q:=link(r); - if q=cur_break(cur_p) then goto done1; - {|cur_break(cur_p)| is the next breakpoint} - {now |q| cannot be |null|} - if is_char_node(q) then goto done1; - if non_discardable(q) then goto done1; - if type(q)=kern_node then if subtype(q)<>explicit then goto done1; - r:=q; {now |type(q)=glue_node|, |kern_node|, |math_node|, or |penalty_node|} - end; -done1: if r<>temp_head then - begin link(r):=null; flush_node_list(link(temp_head)); - link(temp_head):=q; - end; -end - -@ The current line to be justified appears in a horizontal list starting -at |link(temp_head)| and ending at |cur_break(cur_p)|. If |cur_break(cur_p)| is -a glue node, we reset the glue to equal the |right_skip| glue; otherwise -we append the |right_skip| glue at the right. If |cur_break(cur_p)| is a -discretionary node, we modify the list so that the discretionary break -is compulsory, and we set |disc_break| to |true|. We also append -the |left_skip| glue at the left of the line, unless it is zero. - -@<Justify the line ending at breakpoint |cur_p|, and append it...@>= -@<Modify the end of the line to reflect the nature of the break and to include - \.{\\rightskip}; also set the proper value of |disc_break|@>; -@<Put the \(l)\.{\\leftskip} glue at the left and detach this line@>; -@<Call the packaging subroutine, setting |just_box| to the justified box@>; -@<Append the new box to the current vertical list, followed by the list of - special nodes taken out of the box by the packager@>; -@<Append a penalty node, if a nonzero penalty is appropriate@> - -@ At the end of the following code, |q| will point to the final node on the -list about to be justified. - -@<Modify the end of the line...@>= -q:=cur_break(cur_p); disc_break:=false; post_disc_break:=false; -if q<>null then {|q| cannot be a |char_node|} - if type(q)=glue_node then - begin delete_glue_ref(glue_ptr(q)); - glue_ptr(q):=right_skip; - subtype(q):=right_skip_code+1; add_glue_ref(right_skip); - goto done; - end - else begin if type(q)=disc_node then - @<Change discretionary to compulsory and set - |disc_break:=true|@> - else if (type(q)=math_node)or(type(q)=kern_node) then width(q):=0; - end -else begin q:=temp_head; - while link(q)<>null do q:=link(q); - end; -@<Put the \(r)\.{\\rightskip} glue after node |q|@>; -done: - -@ @<Change discretionary to compulsory...@>= -begin t:=replace_count(q); -@<Destroy the |t| nodes following |q|, and - make |r| point to the following node@>; -if post_break(q)<>null then @<Transplant the post-break list@>; -if pre_break(q)<>null then @<Transplant the pre-break list@>; -link(q):=r; disc_break:=true; -end - -@ @<Destroy the |t| nodes following |q|...@>= -if t=0 then r:=link(q) -else begin r:=q; - while t>1 do - begin r:=link(r); decr(t); - end; - s:=link(r); - r:=link(s); link(s):=null; - flush_node_list(link(q)); replace_count(q):=0; - end - -@ We move the post-break list from inside node |q| to the main list by -re\-attaching it just before the present node |r|, then resetting |r|. - -@<Transplant the post-break list@>= -begin s:=post_break(q); -while link(s)<>null do s:=link(s); -link(s):=r; r:=post_break(q); post_break(q):=null; post_disc_break:=true; -end - -@ We move the pre-break list from inside node |q| to the main list by -re\-attaching it just after the present node |q|, then resetting |q|. - -@<Transplant the pre-break list@>= -begin s:=pre_break(q); link(q):=s; -while link(s)<>null do s:=link(s); -pre_break(q):=null; q:=s; -end - -@ @<Put the \(r)\.{\\rightskip} glue after node |q|@>= -r:=new_param_glue(right_skip_code); link(r):=link(q); link(q):=r; q:=r - -@ The following code begins with |q| at the end of the list to be -justified. It ends with |q| at the beginning of that list, and with -|link(temp_head)| pointing to the remainder of the paragraph, if any. - -@<Put the \(l)\.{\\leftskip} glue at the left...@>= -r:=link(q); link(q):=null; q:=link(temp_head); link(temp_head):=r; -if left_skip<>zero_glue then - begin r:=new_param_glue(left_skip_code); - link(r):=q; q:=r; - end - -@ @<Append the new box to the current vertical list...@>= -append_to_vlist(just_box); -if adjust_head<>adjust_tail then - begin link(tail):=link(adjust_head); tail:=adjust_tail; - end; -adjust_tail:=null - -@ Now |q| points to the hlist that represents the current line of the -paragraph. We need to compute the appropriate line width, pack the -line into a box of this size, and shift the box by the appropriate -amount of indentation. - -@<Call the packaging subroutine...@>= -if cur_line>last_special_line then - begin cur_width:=second_width; cur_indent:=second_indent; - end -else if par_shape_ptr=null then - begin cur_width:=first_width; cur_indent:=first_indent; - end -else begin cur_width:=mem[par_shape_ptr+2*cur_line].sc; - cur_indent:=mem[par_shape_ptr+2*cur_line-1].sc; - end; -adjust_tail:=adjust_head; just_box:=hpack(q,cur_width,exactly); -shift_amount(just_box):=cur_indent - -@ Penalties between the lines of a paragraph come from club and widow lines, -from the |inter_line_penalty| parameter, and from lines that end at -discretionary breaks. Breaking between lines of a two-line paragraph gets -both club-line and widow-line penalties. The local variable |pen| will -be set to the sum of all relevant penalties for the current line, except -that the final line is never penalized. - -@<Append a penalty node, if a nonzero penalty is appropriate@>= -if cur_line+1<>best_line then - begin pen:=inter_line_penalty; - if cur_line=prev_graf+1 then pen:=pen+club_penalty; - if cur_line+2=best_line then pen:=pen+final_widow_penalty; - if disc_break then pen:=pen+broken_penalty; - if pen<>0 then - begin r:=new_penalty(pen); - link(tail):=r; tail:=r; - end; - end - -@* \[40] Pre-hyphenation. -When the line-breaking routine is unable to find a feasible sequence of -breakpoints, it makes a second pass over the paragraph, attempting to -hyphenate the hyphenatable words. The goal of hyphenation is to insert -discretionary material into the paragraph so that there are more -potential places to break. - -The general rules for hyphenation are somewhat complex and technical, -because we want to be able to hyphenate words that are preceded or -followed by punctuation marks, and because we want the rules to work -for languages other than English. We also must contend with the fact -that hyphens might radically alter the ligature and kerning structure -of a word. - -A sequence of characters will be considered for hyphenation only if it -belongs to a ``potentially hyphenatable part'' of the current paragraph. -This is a sequence of nodes $p_0p_1\ldots p_m$ where $p_0$ is a glue node, -$p_1\ldots p_{m-1}$ are either character or ligature or whatsit or -implicit kern nodes, and $p_m$ is a glue or penalty or insertion or adjust -or mark or whatsit or explicit kern node. (Therefore hyphenation is -disabled by boxes, math formulas, and discretionary nodes already inserted -by the user.) The ligature nodes among $p_1\ldots p_{m-1}$ are effectively -expanded into the original non-ligature characters; the kern nodes and -whatsits are ignored. Each character |c| is now classified as either a -nonletter (if |lc_code(c)=0|), a lowercase letter (if -|lc_code(c)=c|), or an uppercase letter (otherwise); an uppercase letter -is treated as if it were |lc_code(c)| for purposes of hyphenation. The -characters generated by $p_1\ldots p_{m-1}$ may begin with nonletters; let -$c_1$ be the first letter that is not in the middle of a ligature. Whatsit -nodes preceding $c_1$ are ignored; a whatsit found after $c_1$ will be the -terminating node $p_m$. All characters that do not have the same font as -$c_1$ will be treated as nonletters. The |hyphen_char| for that font -must be between 0 and 255, otherwise hyphenation will not be attempted. -\TeX\ looks ahead for as many consecutive letters $c_1\ldots c_n$ as -possible; however, |n| must be less than 64, so a character that would -otherwise be $c_{64}$ is effectively not a letter. Furthermore $c_n$ must -not be in the middle of a ligature. In this way we obtain a string of -letters $c_1\ldots c_n$ that are generated by nodes $p_a\ldots p_b$, where -|1<=a<=b+1<=m|. If |n>=l_hyf+r_hyf|, this string qualifies for hyphenation; -however, |uc_hyph| must be positive, if $c_1$ is uppercase. - -The hyphenation process takes place in three stages. First, the candidate -sequence $c_1\ldots c_n$ is found; then potential positions for hyphens -are determined by referring to hyphenation tables; and finally, the nodes -$p_a\ldots p_b$ are replaced by a new sequence of nodes that includes the -discretionary breaks found. - -Fortunately, we do not have to do all this calculation very often, because -of the way it has been taken out of \TeX's inner loop. For example, when -the second edition of the author's 700-page book {\sl Seminumerical -Algorithms} was typeset by \TeX, only about 1.2 hyphenations needed to be -@^Knuth, Donald Ervin@> -tried per paragraph, since the line breaking algorithm needed to use two -passes on only about 5 per cent of the paragraphs. - -@<Initialize for hyphenating...@>= -begin @!init if trie_not_ready then init_trie;@+tini@;@/ -cur_lang:=init_cur_lang; l_hyf:=init_l_hyf; r_hyf:=init_r_hyf; -end - -@ The letters $c_1\ldots c_n$ that are candidates for hyphenation are placed -into an array called |hc|; the number |n| is placed into |hn|; pointers to -nodes $p_{a-1}$ and~$p_b$ in the description above are placed into variables -|ha| and |hb|; and the font number is placed into |hf|. - -@<Glob...@>= -@!hc:array[0..65] of 0..256; {word to be hyphenated} -@!hn:0..64; {the number of positions occupied in |hc|; - not always a |small_number|} -@!ha,@!hb:pointer; {nodes |ha..hb| should be replaced by the hyphenated result} -@!hf:internal_font_number; {font number of the letters in |hc|} -@!hu:array[0..63] of 0..256; {like |hc|, before conversion to lowercase} -@!hyf_char:integer; {hyphen character of the relevant font} -@!cur_lang,@!init_cur_lang:ASCII_code; {current hyphenation table of interest} -@!l_hyf,@!r_hyf,@!init_l_hyf,@!init_r_hyf:integer; {limits on fragment sizes} -@!hyf_bchar:halfword; {boundary character after $c_n$} - -@ Hyphenation routines need a few more local variables. - -@<Local variables for line...@>= -@!j:small_number; {an index into |hc| or |hu|} -@!c:0..255; {character being considered for hyphenation} - -@ When the following code is activated, the |line_break| procedure is in its -second pass, and |cur_p| points to a glue node. - -@<Try to hyphenate...@>= -begin prev_s:=cur_p; s:=link(prev_s); -if s<>null then - begin @<Skip to node |ha|, or |goto done1| if no hyphenation - should be attempted@>; - if l_hyf+r_hyf>63 then goto done1; - @<Skip to node |hb|, putting letters into |hu| and |hc|@>; - @<Check that the nodes following |hb| permit hyphenation and that at least - |l_hyf+r_hyf| letters have been found, otherwise |goto done1|@>; - hyphenate; - end; -done1: end - -@ @<Declare subprocedures for |line_break|@>= -@t\4@>@<Declare the function called |reconstitute|@> -procedure hyphenate; -label common_ending,done,found,found1,found2,not_found,exit; -var @<Local variables for hyphenation@>@; -begin @<Find hyphen locations for the word in |hc|, or |return|@>; -@<If no hyphens were found, |return|@>; -@<Replace nodes |ha..hb| by a sequence of nodes that includes - the discretionary hyphens@>; -exit:end; - -@ The first thing we need to do is find the node |ha| just before the -first letter. - -@<Skip to node |ha|, or |goto done1|...@>= -loop@+ begin if is_char_node(s) then - begin c:=qo(character(s)); hf:=font(s); - end - else if type(s)=ligature_node then - if lig_ptr(s)=null then goto continue - else begin q:=lig_ptr(s); c:=qo(character(q)); hf:=font(q); - end - else if (type(s)=kern_node)and(subtype(s)=normal) then goto continue - else if type(s)=whatsit_node then - begin @<Advance \(p)past a whatsit node in the \(p)pre-hyphenation loop@>; - goto continue; - end - else goto done1; - if lc_code(c)<>0 then - if (lc_code(c)=c)or(uc_hyph>0) then goto done2 - else goto done1; -continue: prev_s:=s; s:=link(prev_s); - end; -done2: hyf_char:=hyphen_char[hf]; -if hyf_char<0 then goto done1; -if hyf_char>255 then goto done1; -ha:=prev_s - -@ The word to be hyphenated is now moved to the |hu| and |hc| arrays. - -@<Skip to node |hb|, putting letters...@>= -hn:=0; -loop@+ begin if is_char_node(s) then - begin if font(s)<>hf then goto done3; - hyf_bchar:=character(s); c:=qo(hyf_bchar); - if lc_code(c)=0 then goto done3; - if hn=63 then goto done3; - hb:=s; incr(hn); hu[hn]:=c; hc[hn]:=lc_code(c); hyf_bchar:=non_char; - end - else if type(s)=ligature_node then - @<Move the characters of a ligature node to |hu| and |hc|; - but |goto done3| if they are not all letters@> - else if (type(s)=kern_node)and(subtype(s)=normal) then - begin hb:=s; - hyf_bchar:=font_bchar[hf]; - end - else goto done3; - s:=link(s); - end; -done3: - -@ We let |j| be the index of the character being stored when a ligature node -is being expanded, since we do not want to advance |hn| until we are sure -that the entire ligature consists of letters. Note that it is possible -to get to |done3| with |hn=0| and |hb| not set to any value. - -@<Move the characters of a ligature node to |hu| and |hc|...@>= -begin if font(lig_char(s))<>hf then goto done3; -j:=hn; q:=lig_ptr(s);@+if q>null then hyf_bchar:=character(q); -while q>null do - begin c:=qo(character(q)); - if lc_code(c)=0 then goto done3; - if j=63 then goto done3; - incr(j); hu[j]:=c; hc[j]:=lc_code(c);@/ - q:=link(q); - end; -hb:=s; hn:=j; -if odd(subtype(s)) then hyf_bchar:=font_bchar[hf]@+else hyf_bchar:=non_char; -end - -@ @<Check that the nodes following |hb| permit hyphenation...@>= -if hn<l_hyf+r_hyf then goto done1; {|l_hyf| and |r_hyf| are |>=1|} -loop@+ begin if not(is_char_node(s)) then - case type(s) of - ligature_node: do_nothing; - kern_node: if subtype(s)<>normal then goto done4; - whatsit_node,glue_node,penalty_node,ins_node,adjust_node,mark_node: - goto done4; - othercases goto done1 - endcases; - s:=link(s); - end; -done4: - -@* \[41] Post-hyphenation. -If a hyphen may be inserted between |hc[j]| and |hc[j+1]|, the hyphenation -procedure will set |hyf[j]| to some small odd number. But before we look -at \TeX's hyphenation procedure, which is independent of the rest of the -line-breaking algorithm, let us consider what we will do with the hyphens -it finds, since it is better to work on this part of the program before -forgetting what |ha| and |hb|, etc., are all about. - -@<Glob...@>= -@!hyf:array [0..64] of 0..9; {odd values indicate discretionary hyphens} -@!init_list:pointer; {list of punctuation characters preceding the word} -@!init_lig:boolean; {does |init_list| represent a ligature?} -@!init_lft:boolean; {if so, did the ligature involve a left boundary?} - -@ @<Local variables for hyphenation@>= -@!i,@!j,@!l:0..65; {indices into |hc| or |hu|} -@!q,@!r,@!s:pointer; {temporary registers for list manipulation} -@!bchar:halfword; {boundary character of hyphenated word, or |non_char|} - -@ \TeX\ will never insert a hyphen that has fewer than -\.{\\lefthyphenmin} letters before it or fewer than -\.{\\righthyphenmin} after it; hence, a short word has -comparatively little chance of being hyphenated. If no hyphens have -been found, we can save time by not having to make any changes to the -paragraph. - -@<If no hyphens were found, |return|@>= -for j:=l_hyf to hn-r_hyf do if odd(hyf[j]) then goto found1; -return; -found1: - -@ If hyphens are in fact going to be inserted, \TeX\ first deletes the -subsequence of nodes between |ha| and~|hb|. An attempt is made to -preserve the effect that implicit boundary characters and punctuation marks -had on ligatures inside the hyphenated word, by storing a left boundary or -preceding character in |hu[0]| and by storing a possible right boundary -in |bchar|. We set |j:=0| if |hu[0]| is to be part of the reconstruction; -otherwise |j:=1|. -The variable |s| will point to the tail of the current hlist, and -|q| will point to the node following |hb|, so that -things can be hooked up after we reconstitute the hyphenated word. - -@<Replace nodes |ha..hb| by a sequence of nodes...@>= -q:=link(hb); link(hb):=null; r:=link(ha); link(ha):=null; bchar:=hyf_bchar; -if is_char_node(ha) then - if font(ha)<>hf then goto found2 - else begin init_list:=ha; init_lig:=false; hu[0]:=qo(character(ha)); - end -else if type(ha)=ligature_node then - if font(lig_char(ha))<>hf then goto found2 - else begin init_list:=lig_ptr(ha); init_lig:=true; init_lft:=(subtype(ha)>1); - hu[0]:=qo(character(lig_char(ha))); - if init_list=null then if init_lft then - begin hu[0]:=256; init_lig:=false; - end; {in this case a ligature will be reconstructed from scratch} - free_node(ha,small_node_size); - end -else begin {no punctuation found; look for left boundary} - if not is_char_node(r) then if type(r)=ligature_node then - if subtype(r)>1 then goto found2; - j:=1; s:=ha; init_list:=null; goto common_ending; - end; -s:=cur_p; {we have |cur_p<>ha| because |type(cur_p)=glue_node|} -while link(s)<>ha do s:=link(s); -j:=0; goto common_ending; -found2: s:=ha; j:=0; hu[0]:=256; init_lig:=false; init_list:=null; -common_ending: flush_node_list(r); -@<Reconstitute nodes for the hyphenated word, inserting discretionary hyphens@>; -flush_list(init_list) - -@ We must now face the fact that the battle is not over, even though the -{\def\!{\kern-1pt}% -hyphens have been found: The process of reconstituting a word can be nontrivial -because ligatures might change when a hyphen is present. {\sl The \TeX book\/} -discusses the difficulties of the word ``difficult'', and -the discretionary material surrounding a -hyphen can be considerably more complex than that. Suppose -\.{abcdef} is a word in a font for which the only ligatures are \.{b\!c}, -\.{c\!d}, \.{d\!e}, and \.{e\!f}. If this word permits hyphenation -between \.b and \.c, the two patterns with and without hyphenation are -$\.a\,\.b\,\.-\,\.{c\!d}\,\.{e\!f}$ and $\.a\,\.{b\!c}\,\.{d\!e}\,\.f$. -Thus the insertion of a hyphen might cause effects to ripple arbitrarily -far into the rest of the word. A further complication arises if additional -hyphens appear together with such rippling, e.g., if the word in the -example just given could also be hyphenated between \.c and \.d; \TeX\ -avoids this by simply ignoring the additional hyphens in such weird cases.} - -Still further complications arise in the presence of ligatures that do not -delete the original characters. When punctuation precedes the word being -hyphenated, \TeX's method is not perfect under all possible scenarios, -because punctuation marks and letters can propagate information back and forth. -For example, suppose the original pre-hyphenation pair -\.{*a} changes to \.{*y} via a \.{\?=:} ligature, which changes to \.{xy} -via a \.{=:\?} ligature; if $p_{a-1}=\.x$ and $p_a=\.y$, the reconstitution -procedure isn't smart enough to obtain \.{xy} again. In such cases the -font designer should include a ligature that goes from \.{xa} to \.{xy}. - -@ The processing is facilitated by a subroutine called |reconstitute|. Given -a string of characters $x_j\ldots x_n$, there is a smallest index $m\ge j$ -such that the ``translation'' of $x_j\ldots x_n$ by ligatures and kerning -has the form $y_1\ldots y_t$ followed by the translation of $x_{m+1}\ldots x_n$, -where $y_1\ldots y_t$ is some nonempty sequence of character, ligature, and -kern nodes. We call $x_j\ldots x_m$ a ``cut prefix'' of $x_j\ldots x_n$. -For example, if $x_1x_2x_3=\.{fly}$, and if the font contains `fl' as a -ligature and a kern between `fl' and `y', then $m=2$, $t=2$, and $y_1$ will -be a ligature node for `fl' followed by an appropriate kern node~$y_2$. -In the most common case, $x_j$~forms no ligature with $x_{j+1}$ and we -simply have $m=j$, $y_1=x_j$. If $m<n$ we can repeat the procedure on -$x_{m+1}\ldots x_n$ until the entire translation has been found. - -The |reconstitute| function returns the integer $m$ and puts the nodes -$y_1\ldots y_t$ into a linked list starting at |link(hold_head)|, -getting the input $x_j\ldots x_n$ from the |hu| array. If $x_j=256$, -we consider $x_j$ to be an implicit left boundary character; in this -case |j| must be strictly less than~|n|. There is a -parameter |bchar|, which is either 256 or an implicit right boundary character -assumed to be present just following~$x_n$. (The value |hu[n+1]| is never -explicitly examined, but the algorithm imagines that |bchar| is there.) - -If there exists an index |k| in the range $j\le k\le m$ such that |hyf[k]| -is odd and such that the result of |reconstitute| would have been different -if $x_{k+1}$ had been |hchar|, then |reconstitute| sets |hyphen_passed| -to the smallest such~|k|. Otherwise it sets |hyphen_passed| to zero. - -A special convention is used in the case |j=0|: Then we assume that the -translation of |hu[0]| appears in a special list of charnodes starting at -|init_list|; moreover, if |init_lig| is |true|, then |hu[0]| will be -a ligature character, involving a left boundary if |init_lft| is |true|. -This facility is provided for cases when a hyphenated -word is preceded by punctuation (like single or double quotes) that might -affect the translation of the beginning of the word. - -@<Glob...@>= -@!hyphen_passed:small_number; {first hyphen in a ligature, if any} - -@ @<Declare the function called |reconstitute|@>= -function reconstitute(@!j,@!n:small_number;@!bchar,@!hchar:halfword): - small_number; -label continue,done; -var @!p:pointer; {temporary register for list manipulation} -@!t:pointer; {a node being appended to} -@!q:four_quarters; {character information or a lig/kern instruction} -@!cur_rh:halfword; {hyphen character for ligature testing} -@!test_char:halfword; {hyphen or other character for ligature testing} -@!w:scaled; {amount of kerning} -@!k:font_index; {position of current lig/kern instruction} -begin hyphen_passed:=0; t:=hold_head; w:=0; link(hold_head):=null; - {at this point |ligature_present=lft_hit=rt_hit=false|} -@<Set up data structures with the cursor following position |j|@>; -continue:@<If there's a ligature or kern at the cursor position, update the data - structures, possibly advancing~|j|; continue until the cursor moves@>; -@<Append a ligature and/or kern to the translation; - |goto continue| if the stack of inserted ligatures is nonempty@>; -reconstitute:=j; -end; - -@ The reconstitution procedure shares many of the global data structures -by which \TeX\ has processed the words before they were hyphenated. -There is an implied ``cursor'' between characters |cur_l| and |cur_r|; -these characters will be tested for possible ligature activity. If -|ligature_present| then |cur_l| is a ligature character formed from the -original characters following |cur_q| in the current translation list. -There is a ``ligature stack'' between the cursor and character |j+1|, -consisting of pseudo-ligature nodes linked together by their |link| fields. -This stack is normally empty unless a ligature command has created a new -character that will need to be processed later. A pseudo-ligature is -a special node having a |character| field that represents a potential -ligature and a |lig_ptr| field that points to a |char_node| or is |null|. -We have -$$|cur_r|=\cases{|character(lig_stack)|,&if |lig_stack>null|;\cr - |qi(hu[j+1])|,&if |lig_stack=null| and |j<n|;\cr - bchar,&if |lig_stack=null| and |j=n|.\cr}$$ - -@<Glob...@>= -@!cur_l,@!cur_r:halfword; {characters before and after the cursor} -@!cur_q:pointer; {where a ligature should be detached} -@!lig_stack:pointer; {unfinished business to the right of the cursor} -@!ligature_present:boolean; {should a ligature node be made for |cur_l|?} -@!lft_hit,@!rt_hit:boolean; {did we hit a ligature with a boundary character?} - -@ @d append_charnode_to_t(#)== begin link(t):=get_avail; t:=link(t); - font(t):=hf; character(t):=#; - end -@d set_cur_r==begin if j<n then cur_r:=qi(hu[j+1])@+else cur_r:=bchar; - if odd(hyf[j]) then cur_rh:=hchar@+else cur_rh:=non_char; - end - -@<Set up data structures with the cursor following position |j|@>= -cur_l:=qi(hu[j]); cur_q:=t; -if j=0 then - begin ligature_present:=init_lig; p:=init_list; - if ligature_present then lft_hit:=init_lft; - while p>null do - begin append_charnode_to_t(character(p)); p:=link(p); - end; - end -else if cur_l<non_char then append_charnode_to_t(cur_l); -lig_stack:=null; set_cur_r - -@ We may want to look at the lig/kern program twice, once for a hyphen -and once for a normal letter. (The hyphen might appear after the letter -in the program, so we'd better not try to look for both at once.) - -@<If there's a ligature or kern at the cursor position, update...@>= -if cur_l=non_char then - begin k:=bchar_label[hf]; - if k=non_address then goto done@+else q:=font_info[k].qqqq; - end -else begin q:=char_info(hf)(cur_l); - if char_tag(q)<>lig_tag then goto done; - k:=lig_kern_start(hf)(q); q:=font_info[k].qqqq; - if skip_byte(q)>stop_flag then - begin k:=lig_kern_restart(hf)(q); q:=font_info[k].qqqq; - end; - end; {now |k| is the starting address of the lig/kern program} -if cur_rh<non_char then test_char:=cur_rh@+else test_char:=cur_r; -loop@+begin if next_char(q)=test_char then if skip_byte(q)<=stop_flag then - if cur_rh<non_char then - begin hyphen_passed:=j; hchar:=non_char; cur_rh:=non_char; - goto continue; - end - else begin if hchar<non_char then if odd(hyf[j]) then - begin hyphen_passed:=j; hchar:=non_char; - end; - if op_byte(q)<kern_flag then - @<Carry out a ligature replacement, updating the cursor structure - and possibly advancing~|j|; |goto continue| if the cursor doesn't - advance, otherwise |goto done|@>; - w:=char_kern(hf)(q); goto done; {this kern will be inserted below} - end; - if skip_byte(q)>=stop_flag then - if cur_rh=non_char then goto done - else begin cur_rh:=non_char; goto continue; - end; - k:=k+qo(skip_byte(q))+1; q:=font_info[k].qqqq; - end; -done: - -@ @d wrap_lig(#)==if ligature_present then - begin p:=new_ligature(hf,cur_l,link(cur_q)); - if lft_hit then - begin subtype(p):=2; lft_hit:=false; - end; - if # then if lig_stack=null then - begin incr(subtype(p)); rt_hit:=false; - end; - link(cur_q):=p; t:=p; ligature_present:=false; - end -@d pop_lig_stack==begin if lig_ptr(lig_stack)>null then - begin link(t):=lig_ptr(lig_stack); {this is a charnode for |hu[j+1]|} - t:=link(t); incr(j); - end; - p:=lig_stack; lig_stack:=link(p); free_node(p,small_node_size); - if lig_stack=null then set_cur_r@+else cur_r:=character(lig_stack); - end {if |lig_stack| isn't |null| we have |cur_rh=non_char|} - -@<Append a ligature and/or kern to the translation...@>= -wrap_lig(rt_hit); -if w<>0 then - begin link(t):=new_kern(w); t:=link(t); w:=0; - end; -if lig_stack>null then - begin cur_q:=t; cur_l:=character(lig_stack); ligature_present:=true; - pop_lig_stack; goto continue; - end - -@ @<Carry out a ligature replacement, updating the cursor structure...@>= -begin if cur_l=non_char then lft_hit:=true; -if j=n then if lig_stack=null then rt_hit:=true; -check_interrupt; {allow a way out in case there's an infinite ligature loop} -case op_byte(q) of -qi(1),qi(5):begin cur_l:=rem_byte(q); {\.{=:\?}, \.{=:\?>}} - ligature_present:=true; - end; -qi(2),qi(6):begin cur_r:=rem_byte(q); {\.{\?=:}, \.{\?=:>}} - if lig_stack>null then character(lig_stack):=cur_r - else begin lig_stack:=new_lig_item(cur_r); - if j=n then bchar:=non_char - else begin p:=get_avail; lig_ptr(lig_stack):=p; - character(p):=qi(hu[j+1]); font(p):=hf; - end; - end; - end; -qi(3):begin cur_r:=rem_byte(q); {\.{\?=:\?}} - p:=lig_stack; lig_stack:=new_lig_item(cur_r); link(lig_stack):=p; - end; -qi(7),qi(11):begin wrap_lig(false); {\.{\?=:\?>}, \.{\?=:\?>>}} - cur_q:=t; cur_l:=rem_byte(q); ligature_present:=true; - end; -othercases begin cur_l:=rem_byte(q); ligature_present:=true; {\.{=:}} - if lig_stack>null then pop_lig_stack - else if j=n then goto done - else begin append_charnode_to_t(cur_r); incr(j); set_cur_r; - end; - end -endcases; -if op_byte(q)>qi(4) then if op_byte(q)<>qi(7) then goto done; -goto continue; -end - -@ Okay, we're ready to insert the potential hyphenations that were found. -When the following program is executed, we want to append the word -|hu[1..hn]| after node |ha|, and node |q| should be appended to the result. -During this process, the variable |i| will be a temporary -index into |hu|; the variable |j| will be an index to our current position -in |hu|; the variable |l| will be the counterpart of |j|, in a discretionary -branch; the variable |r| will point to new nodes being created; and -we need a few new local variables: - -@<Local variables for hyph...@>= -@!major_tail,@!minor_tail:pointer; {the end of lists in the main and - discretionary branches being reconstructed} -@!c:ASCII_code; {character temporarily replaced by a hyphen} -@!c_loc:0..63; {where that character came from} -@!r_count:integer; {replacement count for discretionary} -@!hyf_node:pointer; {the hyphen, if it exists} - -@ When the following code is performed, |hyf[0]| and |hyf[hn]| will be zero. - -@<Reconstitute nodes for the hyphenated word...@>= -repeat l:=j; j:=reconstitute(j,hn,bchar,qi(hyf_char))+1; -if hyphen_passed=0 then - begin link(s):=link(hold_head); - while link(s)>null do s:=link(s); - if odd(hyf[j-1]) then - begin l:=j; hyphen_passed:=j-1; link(hold_head):=null; - end; - end; -if hyphen_passed>0 then - @<Create and append a discretionary node as an alternative to the - unhyphenated word, and continue to develop both branches until they - become equivalent@>; -until j>hn; -link(s):=q - -@ In this repeat loop we will insert another discretionary if |hyf[j-1]| is -odd, when both branches of the previous discretionary end at position |j-1|. -Strictly speaking, we aren't justified in doing this, because we don't know -that a hyphen after |j-1| is truly independent of those branches. But in almost -all applications we would rather not lose a potentially valuable hyphenation -point. (Consider the word `difficult', where the letter `c' is in position |j|.) - -@d advance_major_tail==begin major_tail:=link(major_tail); incr(r_count); - end - -@<Create and append a discretionary node as an alternative...@>= -repeat r:=get_node(small_node_size); -link(r):=link(hold_head); type(r):=disc_node; -major_tail:=r; r_count:=0; -while link(major_tail)>null do advance_major_tail; -i:=hyphen_passed; hyf[i]:=0; -@<Put the \(c)characters |hu[l..i]| and a hyphen into |pre_break(r)|@>; -@<Put the \(c)characters |hu[i+1..@,]| into |post_break(r)|, appending to this - list and to |major_tail| until synchronization has been achieved@>; -@<Move pointer |s| to the end of the current list, and set |replace_count(r)| - appropriately@>; -hyphen_passed:=j-1; link(hold_head):=null; -until not odd(hyf[j-1]) - -@ The new hyphen might combine with the previous character via ligature -or kern. At this point we have |l-1<=i<j| and |i<hn|. - -@<Put the \(c)characters |hu[l..i]| and a hyphen into |pre_break(r)|@>= -minor_tail:=null; pre_break(r):=null; hyf_node:=new_character(hf,hyf_char); -if hyf_node<>null then - begin incr(i); c:=hu[i]; hu[i]:=hyf_char; free_avail(hyf_node); - end; -while l<=i do - begin l:=reconstitute(l,i,font_bchar[hf],non_char)+1; - if link(hold_head)>null then - begin if minor_tail=null then pre_break(r):=link(hold_head) - else link(minor_tail):=link(hold_head); - minor_tail:=link(hold_head); - while link(minor_tail)>null do minor_tail:=link(minor_tail); - end; - end; -if hyf_node<>null then - begin hu[i]:=c; {restore the character in the hyphen position} - l:=i; decr(i); - end - -@ The synchronization algorithm begins with |l=i+1<=j|. - -@<Put the \(c)characters |hu[i+1..@,]| into |post_break(r)|...@>= -minor_tail:=null; post_break(r):=null; c_loc:=0; -if bchar_label[hf]<>non_address then {put left boundary at beginning of new line} - begin decr(l); c:=hu[l]; c_loc:=l; hu[l]:=256; - end; -while l<j do - begin repeat l:=reconstitute(l,hn,bchar,non_char)+1; - if c_loc>0 then - begin hu[c_loc]:=c; c_loc:=0; - end; - if link(hold_head)>null then - begin if minor_tail=null then post_break(r):=link(hold_head) - else link(minor_tail):=link(hold_head); - minor_tail:=link(hold_head); - while link(minor_tail)>null do minor_tail:=link(minor_tail); - end; - until l>=j; - while l>j do - @<Append characters of |hu[j..@,]| to |major_tail|, advancing~|j|@>; - end - -@ @<Append characters of |hu[j..@,]|...@>= -begin j:=reconstitute(j,hn,bchar,non_char)+1; -link(major_tail):=link(hold_head); -while link(major_tail)>null do advance_major_tail; -end - -@ Ligature insertion can cause a word to grow exponentially in size. Therefore -we must test the size of |r_count| here, even though the hyphenated text -was at most 63 characters long. - -@<Move pointer |s| to the end of the current list...@>= -if r_count>127 then {we have to forget the discretionary hyphen} - begin link(s):=link(r); link(r):=null; flush_node_list(r); - end -else begin link(s):=r; replace_count(r):=r_count; - end; -s:=major_tail - -@* \[42] Hyphenation. -When a word |hc[1..hn]| has been set up to contain a candidate for hyphenation, -\TeX\ first looks to see if it is in the user's exception dictionary. If not, -hyphens are inserted based on patterns that appear within the given word, -using an algorithm due to Frank~M. Liang. -@^Liang, Franklin Mark@> - -Let's consider Liang's method first, since it is much more interesting than the -exception-lookup routine. The algorithm begins by setting |hyf[j]| to zero -for all |j|, and invalid characters are inserted into |hc[0]| -and |hc[hn+1]| to serve as delimiters. Then a reasonably fast method is -used to see which of a given set of patterns occurs in the word -|hc[0..(hn+1)]|. Each pattern $p_1\ldots p_k$ of length |k| has an associated -sequence of |k+1| numbers $n_0\ldots n_k$; and if the pattern occurs in -|hc[(j+1)..(j+k)]|, \TeX\ will set |hyf[j+i]:=@tmax@>(hyf[j+i],@t$n_i$@>)| for -|0<=i<=k|. After this has been done for each pattern that occurs, a -discretionary hyphen will be inserted between |hc[j]| and |hc[j+1]| when -|hyf[j]| is odd, as we have already seen. - -The set of patterns $p_1\ldots p_k$ and associated numbers $n_0\ldots n_k$ -depends, of course, on the language whose words are being hyphenated, and -on the degree of hyphenation that is desired. A method for finding -appropriate |p|'s and |n|'s, from a given dictionary of words and acceptable -hyphenations, is discussed in Liang's Ph.D. thesis (Stanford University, -1983); \TeX\ simply starts with the patterns and works from there. - -@ The patterns are stored in a compact table that is also efficient for -retrieval, using a variant of ``trie memory'' [cf.\ {\sl The Art of -Computer Programming \bf3} (1973), 481--505]. We can find each pattern -$p_1\ldots p_k$ by letting $z_0$ be one greater than the relevant language -index and then, for |1<=i<=k|, -setting |@t$z_i$@>:=trie_link@t$(z_{i-1})+p_i$@>|; the pattern will be -identified by the number $z_k$. Since all the pattern information is -packed together into a single |trie_link| array, it is necessary to -prevent confusion between the data from inequivalent patterns, so another -table is provided such that |trie_char@t$(z_i)=p_i$@>| for all |i|. There -is also a table |trie_op|$(z_k)$ to identify the numbers $n_0\ldots n_k$ -associated with $p_1\ldots p_k$. - -Comparatively few different number sequences $n_0\ldots n_k$ actually occur, -since most of the |n|'s are generally zero. Therefore the number sequences -are encoded in such a way that |trie_op|$(z_k)$ is only one byte long. -If |trie_op(@t$z_k$@>)<>min_quarterword|, when $p_1\ldots p_k$ has matched -the letters in |hc[(l-k+1)..l@,]| of language |t|, -we perform all of the required operations -for this pattern by carrying out the following little program: Set -|v:=trie_op(@t$z_k$@>)|. Then set |v:=v+op_start[t]|, -|hyf[l-hyf_distance[v]]:=@tmax@>(hyf[l-hyf_distance[v]], hyf_num[v])|, -and |v:=hyf_next[v]|; repeat, if necessary, until |v=min_quarterword|. - -@<Types...@>= -@!trie_pointer=0..trie_size; {an index into |trie|} - -@ @d trie_link(#)==trie[#].rh {``downward'' link in a trie} -@d trie_char(#)==trie[#].b1 {character matched at this trie location} -@d trie_op(#)==trie[#].b0 {program for hyphenation at this trie location} - -@<Glob...@>= -@!trie:array[trie_pointer] of two_halves; {|trie_link|, |trie_char|, |trie_op|} -@!hyf_distance:array[1..trie_op_size] of small_number; {position |k-j| of $n_j$} -@!hyf_num:array[1..trie_op_size] of small_number; {value of $n_j$} -@!hyf_next:array[1..trie_op_size] of quarterword; {continuation code} -@!op_start:array[ASCII_code] of 0..trie_op_size; {offset for current language} - -@ @<Local variables for hyph...@>= -@!z:trie_pointer; {an index into |trie|} -@!v:integer; {an index into |hyf_distance|, etc.} - -@ Assuming that these auxiliary tables have been set up properly, the -hyphenation algorithm is quite short. In the following code we set |hc[hn+2]| -to the impossible value 256, in order to guarantee that |hc[hn+3]| will -never be fetched. - -@<Find hyphen locations for the word in |hc|...@>= -for j:=0 to hn do hyf[j]:=0; -@<Look for the word |hc[1..hn]| in the exception table, and |goto found| (with - |hyf| containing the hyphens) if an entry is found@>; -if trie_char(cur_lang+1)<>qi(cur_lang) then return; {no patterns for |cur_lang|} -hc[0]:=0; hc[hn+1]:=0; hc[hn+2]:=256; {insert delimiters} -for j:=0 to hn-r_hyf+1 do - begin z:=trie_link(cur_lang+1)+hc[j]; l:=j; - while hc[l]=qo(trie_char(z)) do - begin if trie_op(z)<>min_quarterword then - @<Store \(m)maximum values in the |hyf| table@>; - incr(l); z:=trie_link(z)+hc[l]; - end; - end; -found: for j:=0 to l_hyf-1 do hyf[j]:=0; -for j:=0 to r_hyf-1 do hyf[hn-j]:=0 - -@ @<Store \(m)maximum values in the |hyf| table@>= -begin v:=trie_op(z); -repeat v:=v+op_start[cur_lang]; i:=l-hyf_distance[v]; -if hyf_num[v]>hyf[i] then hyf[i]:=hyf_num[v]; -v:=hyf_next[v]; -until v=min_quarterword; -end - -@ The exception table that is built by \TeX's \.{\\hyphenation} primitive is -organized as an ordered hash table [cf.\ Amble and Knuth, {\sl The Computer -@^Amble, Ole@> @^Knuth, Donald Ervin@> -Journal\/ \bf17} (1974), 135--142] using linear probing. If $\alpha$ and -$\beta$ are words, we will say that $\alpha<\beta$ if $\vert\alpha\vert< -\vert\beta\vert$ or if $\vert\alpha\vert=\vert\beta\vert$ and -$\alpha$ is lexicographically smaller than $\beta$. (The notation $\vert -\alpha\vert$ stands for the length of $\alpha$.) The idea of ordered hashing -is to arrange the table so that a given word $\alpha$ can be sought by computing -a hash address $h=h(\alpha)$ and then looking in table positions |h|, |h-1|, -\dots, until encountering the first word $\L\alpha$. If this word is -different from $\alpha$, we can conclude that $\alpha$ is not in the table. - -The words in the table point to lists in |mem| that specify hyphen positions -in their |info| fields. The list for $c_1\ldots c_n$ contains the number |k| if -the word $c_1\ldots c_n$ has a discretionary hyphen between $c_k$ and -$c_{k+1}$. - -@<Types...@>= -@!hyph_pointer=0..hyph_size; {an index into the ordered hash table} - -@ @<Glob...@>= -@!hyph_word:array[hyph_pointer] of str_number; {exception words} -@!hyph_list:array[hyph_pointer] of pointer; {lists of hyphen positions} -@!hyph_count:hyph_pointer; {the number of words in the exception dictionary} - -@ @<Local variables for init...@>= -@!z:hyph_pointer; {runs through the exception dictionary} - -@ @<Set init...@>= -for z:=0 to hyph_size do - begin hyph_word[z]:=0; hyph_list[z]:=null; - end; -hyph_count:=0; - -@ The algorithm for exception lookup is quite simple, as soon as we have -a few more local variables to work with. - -@<Local variables for hyph...@>= -@!h:hyph_pointer; {an index into |hyph_word| and |hyph_list|} -@!k:str_number; {an index into |str_start|} -@!u:pool_pointer; {an index into |str_pool|} - -@ First we compute the hash code |h|, then we search until we either -find the word or we don't. Words from different languages are kept -separate by appending the language code to the string. - -@<Look for the word |hc[1...@>= -h:=hc[1]; incr(hn); hc[hn]:=cur_lang; -for j:=2 to hn do h:=(h+h+hc[j]) mod hyph_size; -loop@+ begin @<If the string |hyph_word[h]| is less than \(hc)|hc[1..hn]|, - |goto not_found|; but if the two strings are equal, - set |hyf| to the hyphen positions and |goto found|@>; - if h>0 then decr(h)@+else h:=hyph_size; - end; -not_found: decr(hn) - -@ @<If the string |hyph_word[h]| is less than \(hc)...@>= -k:=hyph_word[h]; if k=0 then goto not_found; -if length(k)<hn then goto not_found; -if length(k)=hn then - begin j:=1; u:=str_start[k]; - repeat if so(str_pool[u])<hc[j] then goto not_found; - if so(str_pool[u])>hc[j] then goto done; - incr(j); incr(u); - until j>hn; - @<Insert hyphens as specified in |hyph_list[h]|@>; - decr(hn); goto found; - end; -done: - -@ @<Insert hyphens as specified...@>= -s:=hyph_list[h]; -while s<>null do - begin hyf[info(s)]:=1; s:=link(s); - end - -@ @<Search |hyph_list| for pointers to |p|@>= -for q:=0 to hyph_size do - begin if hyph_list[q]=p then - begin print_nl("HYPH("); print_int(q); print_char(")"); - end; - end - -@ We have now completed the hyphenation routine, so the |line_break| procedure -is finished at last. Since the hyphenation exception table is fresh in our -minds, it's a good time to deal with the routine that adds new entries to it. - -When \TeX\ has scanned `\.{\\hyphenation}', it calls on a procedure named -|new_hyph_exceptions| to do the right thing. - -@d set_cur_lang==if language<=0 then cur_lang:=0 - else if language>255 then cur_lang:=0 - else cur_lang:=language - -@p procedure new_hyph_exceptions; {enters new exceptions} -label reswitch, exit, found, not_found; -var n:0..64; {length of current word; not always a |small_number|} -@!j:0..64; {an index into |hc|} -@!h:hyph_pointer; {an index into |hyph_word| and |hyph_list|} -@!k:str_number; {an index into |str_start|} -@!p:pointer; {head of a list of hyphen positions} -@!q:pointer; {used when creating a new node for list |p|} -@!s,@!t:str_number; {strings being compared or stored} -@!u,@!v:pool_pointer; {indices into |str_pool|} -begin scan_left_brace; {a left brace must follow \.{\\hyphenation}} -set_cur_lang; -@<Enter as many hyphenation exceptions as are listed, -until coming to a right brace; then |return|@>; -exit:end; - -@ @<Enter as many...@>= -n:=0; p:=null; -loop@+ begin get_x_token; - reswitch: case cur_cmd of - letter,other_char,char_given:@<Append a new letter or hyphen@>; - char_num: begin scan_char_num; cur_chr:=cur_val; cur_cmd:=char_given; - goto reswitch; - end; - spacer,right_brace: begin if n>1 then @<Enter a hyphenation exception@>; - if cur_cmd=right_brace then return; - n:=0; p:=null; - end; - othercases @<Give improper \.{\\hyphenation} error@> - endcases; - end - -@ @<Give improper \.{\\hyph...@>= -begin print_err("Improper "); print_esc("hyphenation"); -@.Improper \\hyphenation...@> - print(" will be flushed"); -help2("Hyphenation exceptions must contain only letters")@/ - ("and hyphens. But continue; I'll forgive and forget."); -error; -end - -@ @<Append a new letter or hyphen@>= -if cur_chr="-" then @<Append the value |n| to list |p|@> -else begin if lc_code(cur_chr)=0 then - begin print_err("Not a letter"); -@.Not a letter@> - help2("Letters in \hyphenation words must have \lccode>0.")@/ - ("Proceed; I'll ignore the character I just read."); - error; - end - else if n<63 then - begin incr(n); hc[n]:=lc_code(cur_chr); - end; - end - -@ @<Append the value |n| to list |p|@>= -begin if n<63 then - begin q:=get_avail; link(q):=p; info(q):=n; p:=q; - end; -end - -@ @<Enter a hyphenation exception@>= -begin incr(n); hc[n]:=cur_lang; str_room(n); h:=0; -for j:=1 to n do - begin h:=(h+h+hc[j]) mod hyph_size; - append_char(hc[j]); - end; -s:=make_string; -@<Insert the \(p)pair |(s,p)| into the exception table@>; -end - -@ @<Insert the \(p)pair |(s,p)|...@>= -if hyph_count=hyph_size then overflow("exception dictionary",hyph_size); -@:TeX capacity exceeded exception dictionary}{\quad exception dictionary@> -incr(hyph_count); -while hyph_word[h]<>0 do - begin @<If the string |hyph_word[h]| is less than \(or)or equal to - |s|, interchange |(hyph_word[h],hyph_list[h])| with |(s,p)|@>; - if h>0 then decr(h)@+else h:=hyph_size; - end; -hyph_word[h]:=s; hyph_list[h]:=p - -@ @<If the string |hyph_word[h]| is less than \(or)...@>= -k:=hyph_word[h]; -if length(k)<length(s) then goto found; -if length(k)>length(s) then goto not_found; -u:=str_start[k]; v:=str_start[s]; -repeat if str_pool[u]<str_pool[v] then goto found; -if str_pool[u]>str_pool[v] then goto not_found; -incr(u); incr(v); -until u=str_start[k+1]; -found:q:=hyph_list[h]; hyph_list[h]:=p; p:=q;@/ -t:=hyph_word[h]; hyph_word[h]:=s; s:=t; -not_found: - -@* \[43] Initializing the hyphenation tables. -The trie for \TeX's hyphenation algorithm is built from a sequence of -patterns following a \.{\\patterns} specification. Such a specification -is allowed only in \.{INITEX}, since the extra memory for auxiliary tables -and for the initialization program itself would only clutter up the -production version of \TeX\ with a lot of deadwood. - -The first step is to build a trie that is linked, instead of packed -into sequential storage, so that insertions are readily made. -After all patterns have been processed, \.{INITEX} -compresses the linked trie by identifying common subtries. Finally the -trie is packed into the efficient sequential form that the hyphenation -algorithm actually uses. - -@<Declare subprocedures for |line_break|@>= -@!init @<Declare procedures for preprocessing hyphenation patterns@>@; -tini - -@ Before we discuss trie building in detail, let's consider the simpler -problem of creating the |hyf_distance|, |hyf_num|, and |hyf_next| arrays. - -Suppose, for example, that \TeX\ reads the pattern `\.{ab2cde1}'. This is -a pattern of length 5, with $n_0\ldots n_5=0\,0\,2\,0\,0\,1$ in the -notation above. We want the corresponding |trie_op| code |v| to have -|hyf_distance[v]=3|, |hyf_num[v]=2|, and |hyf_next[v]=@t$v^\prime$@>|, -where the auxiliary |trie_op| code $v^\prime$ has -|hyf_distance[@t$v^\prime$@>]=0|, |hyf_num[@t$v^\prime$@>]=1|, and -|hyf_next[@t$v^\prime$@>]=min_quarterword|. - -\TeX\ computes an appropriate value |v| with the |new_trie_op| subroutine -below, by setting -$$\hbox{|@t$v^\prime$@>:=new_trie_op(0,1,min_quarterword)|,\qquad -|v:=new_trie_op(3,2,@t$v^\prime$@>)|.}$$ -This subroutine looks up its three -parameters in a special hash table, assigning a new value only if these -three have not appeared before for the current language. - -The hash table is called |trie_op_hash|, and the number of entries it contains -is |trie_op_ptr|. - -@<Glob...@>= -@!init @!trie_op_hash:array[-trie_op_size..trie_op_size] of 0..trie_op_size; - {trie op codes for quadruples} -@!trie_used:array[ASCII_code] of quarterword; - {largest opcode used so far for this language} -@!trie_op_lang:array[1..trie_op_size] of ASCII_code; - {language part of a hashed quadruple} -@!trie_op_val:array[1..trie_op_size] of quarterword; - {opcode corresponding to a hashed quadruple} -@!trie_op_ptr:0..trie_op_size; {number of stored ops so far} -tini - -@ It's tempting to remove the |overflow| stops in the following procedure; -|new_trie_op| could return |min_quarterword| (thereby simply ignoring -part of a hyphenation pattern) instead of aborting the job. However, that would -lead to different hyphenation results on different installations of \TeX\ -using the same patterns. The |overflow| stops are necessary for portability -of patterns. - -@<Declare procedures for preprocessing hyph...@>= -function new_trie_op(@!d,@!n:small_number;@!v:quarterword):quarterword; -label exit; -var h:-trie_op_size..trie_op_size; {trial hash location} -@!u:quarterword; {trial op code} -@!l:0..trie_op_size; {pointer to stored data} -begin h:=abs(n+313*d+361*v+1009*cur_lang) mod (trie_op_size+trie_op_size) - - trie_op_size; -loop@+ begin l:=trie_op_hash[h]; - if l=0 then {empty position found for a new op} - begin if trie_op_ptr=trie_op_size then - overflow("pattern memory ops",trie_op_size); - u:=trie_used[cur_lang]; - if u=max_quarterword then - overflow("pattern memory ops per language", - max_quarterword-min_quarterword); - incr(trie_op_ptr); incr(u); trie_used[cur_lang]:=u; - hyf_distance[trie_op_ptr]:=d; - hyf_num[trie_op_ptr]:=n; hyf_next[trie_op_ptr]:=v; - trie_op_lang[trie_op_ptr]:=cur_lang; trie_op_hash[h]:=trie_op_ptr; - trie_op_val[trie_op_ptr]:=u; new_trie_op:=u; return; - end; - if (hyf_distance[l]=d)and(hyf_num[l]=n)and(hyf_next[l]=v) - and(trie_op_lang[l]=cur_lang) then - begin new_trie_op:=trie_op_val[l]; return; - end; - if h>-trie_op_size then decr(h)@+else h:=trie_op_size; - end; -exit:end; - -@ After |new_trie_op| has compressed the necessary opcode information, -plenty of information is available to unscramble the data into the -final form needed by our hyphenation algorithm. - -@<Sort \(t)the hyphenation op tables into proper order@>= -op_start[0]:=-min_quarterword; -for j:=1 to 255 do op_start[j]:=op_start[j-1]+qo(trie_used[j-1]); -for j:=1 to trie_op_ptr do - trie_op_hash[j]:=op_start[trie_op_lang[j]]+trie_op_val[j]; {destination} -for j:=1 to trie_op_ptr do while trie_op_hash[j]>j do - begin k:=trie_op_hash[j];@/ - t:=hyf_distance[k]; hyf_distance[k]:=hyf_distance[j]; hyf_distance[j]:=t;@/ - t:=hyf_num[k]; hyf_num[k]:=hyf_num[j]; hyf_num[j]:=t;@/ - t:=hyf_next[k]; hyf_next[k]:=hyf_next[j]; hyf_next[j]:=t;@/ - trie_op_hash[j]:=trie_op_hash[k]; trie_op_hash[k]:=k; - end - -@ Before we forget how to initialize the data structures that have been -mentioned so far, let's write down the code that gets them started. - -@<Initialize table entries...@>= -for k:=-trie_op_size to trie_op_size do trie_op_hash[k]:=0; -for k:=0 to 255 do trie_used[k]:=min_quarterword; -trie_op_ptr:=0; - -@ The linked trie that is used to preprocess hyphenation patterns appears -in several global arrays. Each node represents an instruction of the form -``if you see character |c|, then perform operation |o|, move to the -next character, and go to node |l|; otherwise go to node |r|.'' -The four quantities |c|, |o|, |l|, and |r| are stored in four arrays -|trie_c|, |trie_o|, |trie_l|, and |trie_r|. The root of the trie -is |trie_l[0]|, and the number of nodes is |trie_ptr|. Null trie -pointers are represented by zero. To initialize the trie, we simply -set |trie_l[0]| and |trie_ptr| to zero. We also set |trie_c[0]| to some -arbitrary value, since the algorithm may access it. - -The algorithms maintain the condition -$$\hbox{|trie_c[trie_r[z]]>trie_c[z]|\qquad -whenever |z<>0| and |trie_r[z]<>0|};$$ in other words, sibling nodes are -ordered by their |c| fields. - -@d trie_root==trie_l[0] {root of the linked trie} - -@<Glob...@>= -@!init @!trie_c:packed array[trie_pointer] of packed_ASCII_code; - {characters to match} -@t\hskip10pt@>@!trie_o:packed array[trie_pointer] of quarterword; - {operations to perform} -@t\hskip10pt@>@!trie_l:packed array[trie_pointer] of trie_pointer; - {left subtrie links} -@t\hskip10pt@>@!trie_r:packed array[trie_pointer] of trie_pointer; - {right subtrie links} -@t\hskip10pt@>@!trie_ptr:trie_pointer; {the number of nodes in the trie} -@t\hskip10pt@>@!trie_hash:packed array[trie_pointer] of trie_pointer; - {used to identify equivalent subtries} -tini - -@ Let us suppose that a linked trie has already been constructed. -Experience shows that we can often reduce its size by recognizing common -subtries; therefore another hash table is introduced for this purpose, -somewhat similar to |trie_op_hash|. The new hash table will be -initialized to zero. - -The function |trie_node(p)| returns |p| if |p| is distinct from other nodes -that it has seen, otherwise it returns the number of the first equivalent -node that it has seen. - -Notice that we might make subtries equivalent even if they correspond to -patterns for different languages, in which the trie ops might mean quite -different things. That's perfectly all right. - -@<Declare procedures for preprocessing hyph...@>= -function trie_node(@!p:trie_pointer):trie_pointer; {converts - to a canonical form} -label exit; -var h:trie_pointer; {trial hash location} -@!q:trie_pointer; {trial trie node} -begin h:=abs(trie_c[p]+1009*trie_o[p]+@| - 2718*trie_l[p]+3142*trie_r[p]) mod trie_size; -loop@+ begin q:=trie_hash[h]; - if q=0 then - begin trie_hash[h]:=p; trie_node:=p; return; - end; - if (trie_c[q]=trie_c[p])and(trie_o[q]=trie_o[p])and@| - (trie_l[q]=trie_l[p])and(trie_r[q]=trie_r[p]) then - begin trie_node:=q; return; - end; - if h>0 then decr(h)@+else h:=trie_size; - end; -exit:end; - -@ A neat recursive procedure is now able to compress a trie by -traversing it and applying |trie_node| to its nodes in ``bottom up'' -fashion. We will compress the entire trie by clearing |trie_hash| to -zero and then saying `|trie_root:=compress_trie(trie_root)|'. -@^recursion@> - -@<Declare procedures for preprocessing hyph...@>= -function compress_trie(@!p:trie_pointer):trie_pointer; -begin if p=0 then compress_trie:=0 -else begin trie_l[p]:=compress_trie(trie_l[p]); - trie_r[p]:=compress_trie(trie_r[p]); - compress_trie:=trie_node(p); - end; -end; - -@ The compressed trie will be packed into the |trie| array using a -``top-down first-fit'' procedure. This is a little tricky, so the reader -should pay close attention: The |trie_hash| array is cleared to zero -again and renamed |trie_ref| for this phase of the operation; later on, -|trie_ref[p]| will be nonzero only if the linked trie node |p| is the -smallest character -in a family and if the characters |c| of that family have been allocated to -locations |trie_ref[p]+c| in the |trie| array. Locations of |trie| that -are in use will have |trie_link=0|, while the unused holes in |trie| -will be doubly linked with |trie_link| pointing to the next larger vacant -location and |trie_back| pointing to the next smaller one. This double -linking will have been carried out only as far as |trie_max|, where -|trie_max| is the largest index of |trie| that will be needed. -To save time at the low end of the trie, we maintain array entries -|trie_min[c]| pointing to the smallest hole that is greater than~|c|. -Another array |trie_taken| tells whether or not a given location is -equal to |trie_ref[p]| for some |p|; this array is used to ensure that -distinct nodes in the compressed trie will have distinct |trie_ref| -entries. - -@d trie_ref==trie_hash {where linked trie families go into |trie|} -@d trie_back(#)==trie[#].lh {backward links in |trie| holes} - -@<Glob...@>= -@!init @!trie_taken:packed array[1..trie_size] of boolean; - {does a family start here?} -@t\hskip10pt@>@!trie_min:array[ASCII_code] of trie_pointer; - {the first possible slot for each character} -@t\hskip10pt@>@!trie_max:trie_pointer; {largest location used in |trie|} -@t\hskip10pt@>@!trie_not_ready:boolean; {is the trie still in linked form?} -tini - -@ Each time \.{\\patterns} appears, it contributes further patterns to -the future trie, which will be built only when hyphenation is attempted or -when a format file is dumped. The boolean variable |trie_not_ready| -will change to |false| when the trie is compressed; this will disable -further patterns. - -@<Initialize table entries...@>= -trie_not_ready:=true; trie_root:=0; trie_c[0]:=si(0); trie_ptr:=0; - -@ Here is how the trie-compression data structures are initialized. -If storage is tight, it would be possible to overlap |trie_op_hash|, -|trie_op_lang|, and |trie_op_val| with |trie|, |trie_hash|, and |trie_taken|, -because we finish with the former just before we need the latter. - -@<Get ready to compress the trie@>= -@<Sort \(t)the hyphenation...@>; -for p:=0 to trie_size do trie_hash[p]:=0; -trie_root:=compress_trie(trie_root); {identify equivalent subtries} -for p:=0 to trie_ptr do trie_ref[p]:=0; -for p:=0 to 255 do trie_min[p]:=p+1; -trie_link(0):=1; trie_max:=0 - -@ The |first_fit| procedure finds the smallest hole |z| in |trie| such that -a trie family starting at a given node |p| will fit into vacant positions -starting at |z|. If |c=trie_c[p]|, this means that location |z-c| must -not already be taken by some other family, and that |z-c+@t$c^\prime$@>| -must be vacant for all characters $c^\prime$ in the family. The procedure -sets |trie_ref[p]| to |z-c| when the first fit has been found. - -@<Declare procedures for preprocessing hyph...@>= -procedure first_fit(@!p:trie_pointer); {packs a family into |trie|} -label not_found,found; -var h:trie_pointer; {candidate for |trie_ref[p]|} -@!z:trie_pointer; {runs through holes} -@!q:trie_pointer; {runs through the family starting at |p|} -@!c:ASCII_code; {smallest character in the family} -@!l,@!r:trie_pointer; {left and right neighbors} -@!ll:1..256; {upper limit of |trie_min| updating} -begin c:=so(trie_c[p]); -z:=trie_min[c]; {get the first conceivably good hole} -loop@+ begin h:=z-c;@/ - @<Ensure that |trie_max>=h+256|@>; - if trie_taken[h] then goto not_found; - @<If all characters of the family fit relative to |h|, then - |goto found|,\30\ otherwise |goto not_found|@>; - not_found: z:=trie_link(z); {move to the next hole} - end; -found: @<Pack the family into |trie| relative to |h|@>; -end; - -@ By making sure that |trie_max| is at least |h+256|, we can be sure that -|trie_max>z|, since |h=z-c|. It follows that location |trie_max| will -never be occupied in |trie|, and we will have |trie_max>=trie_link(z)|. - -@<Ensure that |trie_max>=h+256|@>= -if trie_max<h+256 then - begin if trie_size<=h+256 then overflow("pattern memory",trie_size); -@:TeX capacity exceeded pattern memory}{\quad pattern memory@> - repeat incr(trie_max); trie_taken[trie_max]:=false; - trie_link(trie_max):=trie_max+1; trie_back(trie_max):=trie_max-1; - until trie_max=h+256; - end - -@ @<If all characters of the family fit relative to |h|...@>= -q:=trie_r[p]; -while q>0 do - begin if trie_link(h+so(trie_c[q]))=0 then goto not_found; - q:=trie_r[q]; - end; -goto found - -@ @<Pack the family into |trie| relative to |h|@>= -trie_taken[h]:=true; trie_ref[p]:=h; q:=p; -repeat z:=h+so(trie_c[q]); l:=trie_back(z); r:=trie_link(z); -trie_back(r):=l; trie_link(l):=r; trie_link(z):=0; -if l<256 then - begin if z<256 then ll:=z @+else ll:=256; - repeat trie_min[l]:=r; incr(l); - until l=ll; - end; -q:=trie_r[q]; -until q=0 - -@ To pack the entire linked trie, we use the following recursive procedure. -@^recursion@> - -@<Declare procedures for preprocessing hyph...@>= -procedure trie_pack(@!p:trie_pointer); {pack subtries of a family} -var q:trie_pointer; {a local variable that need not be saved on recursive calls} -begin repeat q:=trie_l[p]; -if (q>0)and(trie_ref[q]=0) then - begin first_fit(q); trie_pack(q); - end; -p:=trie_r[p]; -until p=0; -end; - -@ When the whole trie has been allocated into the sequential table, we -must go through it once again so that |trie| contains the correct -information. Null pointers in the linked trie will be represented by the -value~0, which properly implements an ``empty'' family. - -@<Move the data into |trie|@>= -h.rh:=0; h.b0:=min_quarterword; h.b1:=min_quarterword; {|trie_link:=0|, - |trie_op:=min_quarterword|, |trie_char:=qi(0)|} -if trie_root=0 then {no patterns were given} - begin for r:=0 to 256 do trie[r]:=h; - trie_max:=256; - end -else begin trie_fix(trie_root); {this fixes the non-holes in |trie|} - r:=0; {now we will zero out all the holes} - repeat s:=trie_link(r); trie[r]:=h; r:=s; - until r>trie_max; - end; -trie_char(0):=qi("?"); {make |trie_char(c)<>c| for all |c|} - -@ The fixing-up procedure is, of course, recursive. Since the linked trie -usually has overlapping subtries, the same data may be moved several -times; but that causes no harm, and at most as much work is done as it -took to build the uncompressed trie. -@^recursion@> - -@<Declare procedures for preprocessing hyph...@>= -procedure trie_fix(@!p:trie_pointer); {moves |p| and its siblings into |trie|} -var q:trie_pointer; {a local variable that need not be saved on recursive calls} -@!c:ASCII_code; {another one that need not be saved} -@!z:trie_pointer; {|trie| reference; this local variable must be saved} -begin z:=trie_ref[p]; -repeat q:=trie_l[p]; c:=so(trie_c[p]); -trie_link(z+c):=trie_ref[q]; trie_char(z+c):=qi(c); trie_op(z+c):=trie_o[p]; -if q>0 then trie_fix(q); -p:=trie_r[p]; -until p=0; -end; - -@ Now let's go back to the easier problem, of building the linked -trie. When \.{INITEX} has scanned the `\.{\\patterns}' control -sequence, it calls on |new_patterns| to do the right thing. - -@<Declare procedures for preprocessing hyph...@>= -procedure new_patterns; {initializes the hyphenation pattern data} -label done, done1; -var k,@!l:0..64; {indices into |hc| and |hyf|; - not always in |small_number| range} -@!digit_sensed:boolean; {should the next digit be treated as a letter?} -@!v:quarterword; {trie op code} -@!p,@!q:trie_pointer; {nodes of trie traversed during insertion} -@!first_child:boolean; {is |p=trie_l[q]|?} -@!c:ASCII_code; {character being inserted} -begin if trie_not_ready then - begin set_cur_lang; scan_left_brace; {a left brace must follow \.{\\patterns}} - @<Enter all of the patterns into a linked trie, until coming to a right - brace@>; - end -else begin print_err("Too late for "); print_esc("patterns"); - help1("All patterns must be given before typesetting begins."); - error; link(garbage):=scan_toks(false,false); flush_list(def_ref); - end; -end; - -@ Novices are not supposed to be using \.{\\patterns}, so the error -messages are terse. (Note that all error messages appear in \TeX's string -pool, even if they are used only by \.{INITEX}.) - -@<Enter all of the patterns into a linked trie...@>= -k:=0; hyf[0]:=0; digit_sensed:=false; -loop@+ begin get_x_token; - case cur_cmd of - letter,other_char:@<Append a new letter or a hyphen level@>; - spacer,right_brace: begin if k>0 then - @<Insert a new pattern into the linked trie@>; - if cur_cmd=right_brace then goto done; - k:=0; hyf[0]:=0; digit_sensed:=false; - end; - othercases begin print_err("Bad "); print_esc("patterns"); -@.Bad \\patterns@> - help1("(See Appendix H.)"); error; - end - endcases; - end; -done: - -@ @<Append a new letter or a hyphen level@>= -if digit_sensed or(cur_chr<"0")or(cur_chr>"9") then - begin if cur_chr="." then cur_chr:=0 {edge-of-word delimiter} - else begin cur_chr:=lc_code(cur_chr); - if cur_chr=0 then - begin print_err("Nonletter"); -@.Nonletter@> - help1("(See Appendix H.)"); error; - end; - end; - if k<63 then - begin incr(k); hc[k]:=cur_chr; hyf[k]:=0; digit_sensed:=false; - end; - end -else if k<63 then - begin hyf[k]:=cur_chr-"0"; digit_sensed:=true; - end - -@ When the following code comes into play, the pattern $p_1\ldots p_k$ -appears in |hc[1..k]|, and the corresponding sequence of numbers $n_0\ldots -n_k$ appears in |hyf[0..k]|. - -@<Insert a new pattern into the linked trie@>= -begin @<Compute the trie op code, |v|, and set |l:=0|@>; -q:=0; hc[0]:=cur_lang; -while l<=k do - begin c:=hc[l]; incr(l); p:=trie_l[q]; first_child:=true; - while (p>0)and(c>so(trie_c[p])) do - begin q:=p; p:=trie_r[q]; first_child:=false; - end; - if (p=0)or(c<so(trie_c[p])) then - @<Insert a new trie node between |q| and |p|, and - make |p| point to it@>; - q:=p; {now node |q| represents $p_1\ldots p_{l-1}$} - end; -if trie_o[q]<>min_quarterword then - begin print_err("Duplicate pattern"); -@.Duplicate pattern@> - help1("(See Appendix H.)"); error; - end; -trie_o[q]:=v; -end - -@ @<Insert a new trie node between |q| and |p|...@>= -begin if trie_ptr=trie_size then overflow("pattern memory",trie_size); -@:TeX capacity exceeded pattern memory}{\quad pattern memory@> -incr(trie_ptr); trie_r[trie_ptr]:=p; p:=trie_ptr; trie_l[p]:=0; -if first_child then trie_l[q]:=p@+else trie_r[q]:=p; -trie_c[p]:=si(c); trie_o[p]:=min_quarterword; -end - -@ @<Compute the trie op code, |v|...@>= -if hc[1]=0 then hyf[0]:=0; -if hc[k]=0 then hyf[k]:=0; -l:=k; v:=min_quarterword; -loop@+ begin if hyf[l]<>0 then v:=new_trie_op(k-l,hyf[l],v); - if l>0 then decr(l)@+else goto done1; - end; -done1: - -@ Finally we put everything together: Here is how the trie gets to its -final, efficient form. -The following packing routine is rigged so that the root of the linked -tree gets mapped into location 1 of |trie|, as required by the hyphenation -algorithm. This happens because the first call of |first_fit| will -``take'' location~1. - -@<Declare procedures for preprocessing hyphenation patterns@>= -procedure init_trie; -var @!p:trie_pointer; {pointer for initialization} -@!j,@!k,@!t:integer; {all-purpose registers for initialization} -@!r,@!s:trie_pointer; {used to clean up the packed |trie|} -@!h:two_halves; {template used to zero out |trie|'s holes} -begin @<Get ready to compress the trie@>; -if trie_root<>0 then - begin first_fit(trie_root); trie_pack(trie_root); - end; -@<Move the data into |trie|@>; -trie_not_ready:=false; -end; - -@* \[44] Breaking vertical lists into pages. -The |vsplit| procedure, which implements \TeX's \.{\\vsplit} operation, -is considerably simpler than |line_break| because it doesn't have to -worry about hyphenation, and because its mission is to discover a single -break instead of an optimum sequence of breakpoints. But before we get -into the details of |vsplit|, we need to consider a few more basic things. - -@ A subroutine called |prune_page_top| takes a pointer to a vlist and -returns a pointer to a modified vlist in which all glue, kern, and penalty nodes -have been deleted before the first box or rule node. However, the first -box or rule is actually preceded by a newly created glue node designed so that -the topmost baseline will be at distance |split_top_skip| from the top, -whenever this is possible without backspacing. - -In this routine and those that follow, we make use of the fact that a -vertical list contains no character nodes, hence the |type| field exists -for each node in the list. -@^data structure assumptions@> - -@p function prune_page_top(@!p:pointer):pointer; {adjust top after page break} -var prev_p:pointer; {lags one step behind |p|} -@!q:pointer; {temporary variable for list manipulation} -begin prev_p:=temp_head; link(temp_head):=p; -while p<>null do - case type(p) of - hlist_node,vlist_node,rule_node:@<Insert glue for |split_top_skip| - and set~|p:=null|@>; - whatsit_node,mark_node,ins_node: begin prev_p:=p; p:=link(prev_p); - end; - glue_node,kern_node,penalty_node: begin q:=p; p:=link(q); link(q):=null; - link(prev_p):=p; flush_node_list(q); - end; - othercases confusion("pruning") -@:this can't happen pruning}{\quad pruning@> - endcases; -prune_page_top:=link(temp_head); -end; - -@ @<Insert glue for |split_top_skip|...@>= -begin q:=new_skip_param(split_top_skip_code); link(prev_p):=q; link(q):=p; - {now |temp_ptr=glue_ptr(q)|} -if width(temp_ptr)>height(p) then width(temp_ptr):=width(temp_ptr)-height(p) -else width(temp_ptr):=0; -p:=null; -end - -@ The next subroutine finds the best place to break a given vertical list -so as to obtain a box of height~|h|, with maximum depth~|d|. -A pointer to the beginning of the vertical list is given, -and a pointer to the optimum breakpoint is returned. The list is effectively -followed by a forced break, i.e., a penalty node with the |eject_penalty|; -if the best break occurs at this artificial node, the value |null| is returned. - -An array of six |scaled| distances is used to keep track of the height -from the beginning of the list to the current place, just as in |line_break|. -In fact, we use one of the same arrays, only changing its name to reflect -its new significance. - -@d active_height==active_width {new name for the six distance variables} -@d cur_height==active_height[1] {the natural height} -@d set_height_zero(#)==active_height[#]:=0 {initialize the height to zero} -@# -@d update_heights=90 {go here to record glue in the |active_height| table} - -@p function vert_break(@!p:pointer; @!h,@!d:scaled):pointer; - {finds optimum page break} -label done,not_found,update_heights; -var prev_p:pointer; {if |p| is a glue node, |type(prev_p)| determines - whether |p| is a legal breakpoint} -@!q,@!r:pointer; {glue specifications} -@!pi:integer; {penalty value} -@!b:integer; {badness at a trial breakpoint} -@!least_cost:integer; {the smallest badness plus penalties found so far} -@!best_place:pointer; {the most recent break that leads to |least_cost|} -@!prev_dp:scaled; {depth of previous box in the list} -@!t:small_number; {|type| of the node following a kern} -begin prev_p:=p; {an initial glue node is not a legal breakpoint} -least_cost:=awful_bad; do_all_six(set_height_zero); prev_dp:=0; -loop@+ begin @<If node |p| is a legal breakpoint, check if this break is - the best known, and |goto done| if |p| is null or - if the page-so-far is already too full to accept more stuff@>; - prev_p:=p; p:=link(prev_p); - end; -done: vert_break:=best_place; -end; - -@ A global variable |best_height_plus_depth| will be set to the natural size -of the box that corresponds to the optimum breakpoint found by |vert_break|. -(This value is used by the insertion-splitting algorithm of the page builder.) - -@<Glob...@>= -@!best_height_plus_depth:scaled; {height of the best box, without stretching or - shrinking} - -@ A subtle point to be noted here is that the maximum depth~|d| might be -negative, so |cur_height| and |prev_dp| might need to be corrected even -after a glue or kern node. - -@<If node |p| is a legal breakpoint, check...@>= -if p=null then pi:=eject_penalty -else @<Use node |p| to update the current height and depth measurements; - if this node is not a legal breakpoint, |goto not_found| - or |update_heights|, - otherwise set |pi| to the associated penalty at the break@>; -@<Check if node |p| is a new champion breakpoint; then \(go)|goto done| - if |p| is a forced break or if the page-so-far is already too full@>; -if (type(p)<glue_node)or(type(p)>kern_node) then goto not_found; -update_heights: @<Update the current height and depth measurements with - respect to a glue or kern node~|p|@>; -not_found: if prev_dp>d then - begin cur_height:=cur_height+prev_dp-d; - prev_dp:=d; - end; - -@ @<Use node |p| to update the current height and depth measurements...@>= -case type(p) of -hlist_node,vlist_node,rule_node: begin@t@>@;@/ - cur_height:=cur_height+prev_dp+height(p); prev_dp:=depth(p); - goto not_found; - end; -whatsit_node:@<Process whatsit |p| in |vert_break| loop, |goto not_found|@>; -glue_node: if precedes_break(prev_p) then pi:=0 - else goto update_heights; -kern_node: begin if link(p)=null then t:=penalty_node - else t:=type(link(p)); - if t=glue_node then pi:=0@+else goto update_heights; - end; -penalty_node: pi:=penalty(p); -mark_node,ins_node: goto not_found; -othercases confusion("vertbreak") -@:this can't happen vertbreak}{\quad vertbreak@> -endcases - -@ @d deplorable==100000 {more than |inf_bad|, but less than |awful_bad|} - -@<Check if node |p| is a new champion breakpoint; then \(go)...@>= -if pi<inf_penalty then - begin @<Compute the badness, |b|, using |awful_bad| - if the box is too full@>; - if b<awful_bad then - if pi<=eject_penalty then b:=pi - else if b<inf_bad then b:=b+pi - else b:=deplorable; - if b<=least_cost then - begin best_place:=p; least_cost:=b; - best_height_plus_depth:=cur_height+prev_dp; - end; - if (b=awful_bad)or(pi<=eject_penalty) then goto done; - end - -@ @<Compute the badness, |b|, using |awful_bad| if the box is too full@>= -if cur_height<h then - if (active_height[3]<>0) or (active_height[4]<>0) or - (active_height[5]<>0) then b:=0 - else b:=badness(h-cur_height,active_height[2]) -else if cur_height-h>active_height[6] then b:=awful_bad -else b:=badness(cur_height-h,active_height[6]) - -@ Vertical lists that are subject to the |vert_break| procedure should not -contain infinite shrinkability, since that would permit any amount of -information to ``fit'' on one page. - -@<Update the current height and depth measurements with...@>= -if type(p)=kern_node then q:=p -else begin q:=glue_ptr(p); - active_height[2+stretch_order(q)]:=@| - active_height[2+stretch_order(q)]+stretch(q);@/ - active_height[6]:=active_height[6]+shrink(q); - if (shrink_order(q)<>normal)and(shrink(q)<>0) then - begin@t@>@;@/ - print_err("Infinite glue shrinkage found in box being split");@/ -@.Infinite glue shrinkage...@> - help4("The box you are \vsplitting contains some infinitely")@/ - ("shrinkable glue, e.g., `\vss' or `\vskip 0pt minus 1fil'.")@/ - ("Such glue doesn't belong there; but you can safely proceed,")@/ - ("since the offensive shrinkability has been made finite."); - error; r:=new_spec(q); shrink_order(r):=normal; delete_glue_ref(q); - glue_ptr(p):=r; q:=r; - end; - end; -cur_height:=cur_height+prev_dp+width(q); prev_dp:=0 - -@ Now we are ready to consider |vsplit| itself. Most of -its work is accomplished by the two subroutines that we have just considered. - -Given the number of a vlist box |n|, and given a desired page height |h|, -the |vsplit| function finds the best initial segment of the vlist and -returns a box for a page of height~|h|. The remainder of the vlist, if -any, replaces the original box, after removing glue and penalties and -adjusting for |split_top_skip|. Mark nodes in the split-off box are used to -set the values of |split_first_mark| and |split_bot_mark|; we use the -fact that |split_first_mark=null| if and only if |split_bot_mark=null|. - -The original box becomes ``void'' if and only if it has been entirely -extracted. The extracted box is ``void'' if and only if the original -box was void (or if it was, erroneously, an hlist box). - -@p function vsplit(@!n:eight_bits; @!h:scaled):pointer; - {extracts a page of height |h| from box |n|} -label exit,done; -var v:pointer; {the box to be split} -p:pointer; {runs through the vlist} -q:pointer; {points to where the break occurs} -begin v:=box(n); -if split_first_mark<>null then - begin delete_token_ref(split_first_mark); split_first_mark:=null; - delete_token_ref(split_bot_mark); split_bot_mark:=null; - end; -@<Dispense with trivial cases of void or bad boxes@>; -q:=vert_break(list_ptr(v),h,split_max_depth); -@<Look at all the marks in nodes before the break, and set the final - link to |null| at the break@>; -q:=prune_page_top(q); p:=list_ptr(v); free_node(v,box_node_size); -if q=null then box(n):=null {the |eq_level| of the box stays the same} -else box(n):=vpack(q,natural); -vsplit:=vpackage(p,h,exactly,split_max_depth); -exit: end; - -@ @<Dispense with trivial cases of void or bad boxes@>= -if v=null then - begin vsplit:=null; return; - end; -if type(v)<>vlist_node then - begin print_err(""); print_esc("vsplit"); print(" needs a "); - print_esc("vbox"); -@:vsplit_}{\.{\\vsplit needs a \\vbox}@> - help2("The box you are trying to split is an \hbox.")@/ - ("I can't split such a box, so I'll leave it alone."); - error; vsplit:=null; return; - end - -@ It's possible that the box begins with a penalty node that is the -``best'' break, so we must be careful to handle this special case correctly. - -@<Look at all the marks...@>= -p:=list_ptr(v); -if p=q then list_ptr(v):=null -else loop@+begin if type(p)=mark_node then - if split_first_mark=null then - begin split_first_mark:=mark_ptr(p); - split_bot_mark:=split_first_mark; - token_ref_count(split_first_mark):=@| - token_ref_count(split_first_mark)+2; - end - else begin delete_token_ref(split_bot_mark); - split_bot_mark:=mark_ptr(p); - add_token_ref(split_bot_mark); - end; - if link(p)=q then - begin link(p):=null; goto done; - end; - p:=link(p); - end; -done: - -@* \[45] The page builder. -When \TeX\ appends new material to its main vlist in vertical mode, it uses -a method something like |vsplit| to decide where a page ends, except that -the calculations are done ``on line'' as new items come in. -The main complication in this process is that insertions must be put -into their boxes and removed from the vlist, in a more-or-less optimum manner. - -We shall use the term ``current page'' for that part of the main vlist that -is being considered as a candidate for being broken off and sent to the -user's output routine. The current page starts at |link(page_head)|, and -it ends at |page_tail|. We have |page_head=page_tail| if this list is empty. -@^current page@> - -Utter chaos would reign if the user kept changing page specifications -while a page is being constructed, so the page builder keeps the pertinent -specifications frozen as soon as the page receives its first box or -insertion. The global variable |page_contents| is |empty| when the -current page contains only mark nodes and content-less whatsit nodes; it -is |inserts_only| if the page contains only insertion nodes in addition to -marks and whatsits. Glue nodes, kern nodes, and penalty nodes are -discarded until a box or rule node appears, at which time |page_contents| -changes to |box_there|. As soon as |page_contents| becomes non-|empty|, -the current |vsize| and |max_depth| are squirreled away into |page_goal| -and |page_max_depth|; the latter values will be used until the page has -been forwarded to the user's output routine. The \.{\\topskip} adjustment -is made when |page_contents| changes to |box_there|. - -Although |page_goal| starts out equal to |vsize|, it is decreased by the -scaled natural height-plus-depth of the insertions considered so far, and by -the \.{\\skip} corrections for those insertions. Therefore it represents -the size into which the non-inserted material should fit, assuming that -all insertions in the current page have been made. - -The global variables |best_page_break| and |least_page_cost| correspond -respectively to the local variables |best_place| and |least_cost| in the -|vert_break| routine that we have already studied; i.e., they record the -location and value of the best place currently known for breaking the -current page. The value of |page_goal| at the time of the best break is -stored in |best_size|. - -@d inserts_only=1 - {|page_contents| when an insert node has been contributed, but no boxes} -@d box_there=2 {|page_contents| when a box or rule has been contributed} - -@<Glob...@>= -@!page_tail:pointer; {the final node on the current page} -@!page_contents:empty..box_there; {what is on the current page so far?} -@!page_max_depth:scaled; {maximum box depth on page being built} -@!best_page_break:pointer; {break here to get the best page known so far} -@!least_page_cost:integer; {the score for this currently best page} -@!best_size:scaled; {its |page_goal|} - -@ The page builder has another data structure to keep track of insertions. -This is a list of four-word nodes, starting and ending at |page_ins_head|. -That is, the first element of the list is node |r@t$_1$@>=link(page_ins_head)|; -node $r_j$ is followed by |r@t$_{j+1}$@>=link(r@t$_j$@>)|; and if there are -|n| items we have |r@t$_{n+1}$@>=page_ins_head|. The |subtype| field of -each node in this list refers to an insertion number; for example, `\.{\\insert -250}' would correspond to a node whose |subtype| is |qi(250)| -(the same as the |subtype| field of the relevant |ins_node|). These |subtype| -fields are in increasing order, and |subtype(page_ins_head)= -qi(255)|, so |page_ins_head| serves as a convenient sentinel -at the end of the list. A record is present for each insertion number that -appears in the current page. - -The |type| field in these nodes distinguishes two possibilities that -might occur as we look ahead before deciding on the optimum page break. -If |type(r)=inserting|, then |height(r)| contains the total of the -height-plus-depth dimensions of the box and all its inserts seen so far. -If |type(r)=split_up|, then no more insertions will be made into this box, -because at least one previous insertion was too big to fit on the current -page; |broken_ptr(r)| points to the node where that insertion will be -split, if \TeX\ decides to split it, |broken_ins(r)| points to the -insertion node that was tentatively split, and |height(r)| includes also the -natural height plus depth of the part that would be split off. - -In both cases, |last_ins_ptr(r)| points to the last |ins_node| -encountered for box |qo(subtype(r))| that would be at least partially -inserted on the next page; and |best_ins_ptr(r)| points to the last -such |ins_node| that should actually be inserted, to get the page with -minimum badness among all page breaks considered so far. We have -|best_ins_ptr(r)=null| if and only if no insertion for this box should -be made to produce this optimum page. - -The data structure definitions here use the fact that the |@!height| field -appears in the fourth word of a box node. -@^data structure assumptions@> - -@d page_ins_node_size=4 {number of words for a page insertion node} -@d inserting=0 {an insertion class that has not yet overflowed} -@d split_up=1 {an overflowed insertion class} -@d broken_ptr(#)==link(#+1) - {an insertion for this class will break here if anywhere} -@d broken_ins(#)==info(#+1) {this insertion might break at |broken_ptr|} -@d last_ins_ptr(#)==link(#+2) {the most recent insertion for this |subtype|} -@d best_ins_ptr(#)==info(#+2) {the optimum most recent insertion} - -@<Initialize the special list heads...@>= -subtype(page_ins_head):=qi(255); -type(page_ins_head):=split_up; link(page_ins_head):=page_ins_head; - -@ An array |page_so_far| records the heights and depths of everything -on the current page. This array contains six |scaled| numbers, like the -similar arrays already considered in |line_break| and |vert_break|; and it -also contains |page_goal| and |page_depth|, since these values are -all accessible to the user via |set_page_dimen| commands. The -value of |page_so_far[1]| is also called |page_total|. The stretch -and shrink components of the \.{\\skip} corrections for each insertion are -included in |page_so_far|, but the natural space components of these -corrections are not, since they have been subtracted from |page_goal|. - -The variable |page_depth| records the depth of the current page; it has been -adjusted so that it is at most |page_max_depth|. The variable -|last_glue| points to the glue specification of the most recent node -contributed from the contribution list, if this was a glue node; otherwise -|last_glue=max_halfword|. (If the contribution list is nonempty, -however, the value of |last_glue| is not necessarily accurate.) -The variables |last_penalty| and |last_kern| are similar. And -finally, |insert_penalties| holds the sum of the penalties associated with -all split and floating insertions. - -@d page_goal==page_so_far[0] {desired height of information on page being built} -@d page_total==page_so_far[1] {height of the current page} -@d page_shrink==page_so_far[6] {shrinkability of the current page} -@d page_depth==page_so_far[7] {depth of the current page} - -@<Glob...@>= -@!page_so_far:array [0..7] of scaled; {height and glue of the current page} -@!last_glue:pointer; {used to implement \.{\\lastskip}} -@!last_penalty:integer; {used to implement \.{\\lastpenalty}} -@!last_kern:scaled; {used to implement \.{\\lastkern}} -@!insert_penalties:integer; {sum of the penalties for insertions - that were held over} - -@ @<Put each...@>= -primitive("pagegoal",set_page_dimen,0); -@!@:page_goal_}{\.{\\pagegoal} primitive@> -primitive("pagetotal",set_page_dimen,1); -@!@:page_total_}{\.{\\pagetotal} primitive@> -primitive("pagestretch",set_page_dimen,2); -@!@:page_stretch_}{\.{\\pagestretch} primitive@> -primitive("pagefilstretch",set_page_dimen,3); -@!@:page_fil_stretch_}{\.{\\pagefilstretch} primitive@> -primitive("pagefillstretch",set_page_dimen,4); -@!@:page_fill_stretch_}{\.{\\pagefillstretch} primitive@> -primitive("pagefilllstretch",set_page_dimen,5); -@!@:page_filll_stretch_}{\.{\\pagefilllstretch} primitive@> -primitive("pageshrink",set_page_dimen,6); -@!@:page_shrink_}{\.{\\pageshrink} primitive@> -primitive("pagedepth",set_page_dimen,7); -@!@:page_depth_}{\.{\\pagedepth} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -set_page_dimen: case chr_code of -0: print_esc("pagegoal"); -1: print_esc("pagetotal"); -2: print_esc("pagestretch"); -3: print_esc("pagefilstretch"); -4: print_esc("pagefillstretch"); -5: print_esc("pagefilllstretch"); -6: print_esc("pageshrink"); -othercases print_esc("pagedepth") -endcases; - -@ @d print_plus_end(#)==print(#);@+end -@d print_plus(#)==if page_so_far[#]<>0 then - begin print(" plus "); print_scaled(page_so_far[#]); print_plus_end - -@p procedure print_totals; -begin print_scaled(page_total); -print_plus(2)(""); -print_plus(3)("fil"); -print_plus(4)("fill"); -print_plus(5)("filll"); -if page_shrink<>0 then - begin print(" minus "); print_scaled(page_shrink); - end; -end; - -@ @<Show the status of the current page@>= -if page_head<>page_tail then - begin print_nl("### current page:"); - if output_active then print(" (held over for next output)"); -@.held over for next output@> - show_box(link(page_head)); - if page_contents>empty then - begin print_nl("total height "); print_totals; -@:total_height}{\.{total height}@> - print_nl(" goal height "); print_scaled(page_goal); -@.goal height@> - r:=link(page_ins_head); - while r<>page_ins_head do - begin print_ln; print_esc("insert"); t:=qo(subtype(r)); - print_int(t); print(" adds "); - if count(t)=1000 then t:=height(r) - else t:=x_over_n(height(r),1000)*count(t); - print_scaled(t); - if type(r)=split_up then - begin q:=page_head; t:=0; - repeat q:=link(q); - if (type(q)=ins_node)and(subtype(q)=subtype(r)) then incr(t); - until q=broken_ins(r); - print(", #"); print_int(t); print(" might split"); - end; - r:=link(r); - end; - end; - end - -@ Here is a procedure that is called when the |page_contents| is changing -from |empty| to |inserts_only| or |box_there|. - -@d set_page_so_far_zero(#)==page_so_far[#]:=0 - -@p procedure freeze_page_specs(@!s:small_number); -begin page_contents:=s; -page_goal:=vsize; page_max_depth:=max_depth; -page_depth:=0; do_all_six(set_page_so_far_zero); -least_page_cost:=awful_bad; -@!stat if tracing_pages>0 then - begin begin_diagnostic; - print_nl("%% goal height="); print_scaled(page_goal); -@.goal height@> - print(", max depth="); print_scaled(page_max_depth); - end_diagnostic(false); - end;@;@+tats@;@/ -end; - -@ Pages are built by appending nodes to the current list in \TeX's -vertical mode, which is at the outermost level of the semantic nest. This -vlist is split into two parts; the ``current page'' that we have been -talking so much about already, and the ``contribution list'' that receives -new nodes as they are created. The current page contains everything that -the page builder has accounted for in its data structures, as described -above, while the contribution list contains other things that have been -generated by other parts of \TeX\ but have not yet been -seen by the page builder. -The contribution list starts at |link(contrib_head)|, and it ends at the -current node in \TeX's vertical mode. - -When \TeX\ has appended new material in vertical mode, it calls the procedure -|build_page|, which tries to catch up by moving nodes from the contribution -list to the current page. This procedure will succeed in its goal of -emptying the contribution list, unless a page break is discovered, i.e., -unless the current page has grown to the point where the optimum next -page break has been determined. In the latter case, the nodes after the -optimum break will go back onto the contribution list, and control will -effectively pass to the user's output routine. - -We make |type(page_head)=glue_node|, so that an initial glue node on -the current page will not be considered a valid breakpoint. - -@<Initialize the special list...@>= -type(page_head):=glue_node; subtype(page_head):=normal; - -@ The global variable |output_active| is true during the time the -user's output routine is driving \TeX. - -@<Glob...@>= -@!output_active:boolean; {are we in the midst of an output routine?} - -@ @<Set init...@>= -output_active:=false; insert_penalties:=0; - -@ The page builder is ready to start a fresh page if we initialize -the following state variables. (However, the page insertion list is initialized -elsewhere.) - -@<Start a new current page@>= -page_contents:=empty; page_tail:=page_head; link(page_head):=null;@/ -last_glue:=max_halfword; last_penalty:=0; last_kern:=0; -page_depth:=0; page_max_depth:=0 - -@ At certain times box 255 is supposed to be void (i.e., |null|), -or an insertion box is supposed to be ready to accept a vertical list. -If not, an error message is printed, and the following subroutine -flushes the unwanted contents, reporting them to the user. - -@p procedure box_error(@!n:eight_bits); -begin error; begin_diagnostic; -print_nl("The following box has been deleted:"); -@.The following...deleted@> -show_box(box(n)); end_diagnostic(true); -flush_node_list(box(n)); box(n):=null; -end; - -@ The following procedure guarantees that a given box register -does not contain an \.{\\hbox}. - -@p procedure ensure_vbox(@!n:eight_bits); -var p:pointer; {the box register contents} -begin p:=box(n); -if p<>null then if type(p)=hlist_node then - begin print_err("Insertions can only be added to a vbox"); -@.Insertions can only...@> - help3("Tut tut: You're trying to \insert into a")@/ - ("\box register that now contains an \hbox.")@/ - ("Proceed, and I'll discard its present contents."); - box_error(n); - end; -end; - -@ \TeX\ is not always in vertical mode at the time |build_page| -is called; the current mode reflects what \TeX\ should return to, after -the contribution list has been emptied. A call on |build_page| should -be immediately followed by `|goto big_switch|', which is \TeX's central -control point. - -@d contribute=80 {go here to link a node into the current page} - -@p @t\4@>@<Declare the procedure called |fire_up|@>@;@/ -procedure build_page; {append contributions to the current page} -label exit,done,done1,continue,contribute,update_heights; -var p:pointer; {the node being appended} -@!q,@!r:pointer; {nodes being examined} -@!b,@!c:integer; {badness and cost of current page} -@!pi:integer; {penalty to be added to the badness} -@!n:min_quarterword..255; {insertion box number} -@!delta,@!h,@!w:scaled; {sizes used for insertion calculations} -begin if (link(contrib_head)=null)or output_active then return; -repeat continue: p:=link(contrib_head);@/ -@<Update the values of |last_glue|, |last_penalty|, and |last_kern|@>; -@<Move node |p| to the current page; if it is time for a page break, - put the nodes following the break back onto the contribution list, - and |return| to the user's output routine if there is one@>; -until link(contrib_head)=null; -@<Make the contribution list empty by setting its tail to |contrib_head|@>; -exit:end; - -@ @d contrib_tail==nest[0].tail_field {tail of the contribution list} - -@<Make the contribution list empty...@>= -if nest_ptr=0 then tail:=contrib_head {vertical mode} -else contrib_tail:=contrib_head {other modes} - -@ @<Update the values of |last_glue|...@>= -if last_glue<>max_halfword then delete_glue_ref(last_glue); -last_penalty:=0; last_kern:=0; -if type(p)=glue_node then - begin last_glue:=glue_ptr(p); add_glue_ref(last_glue); - end -else begin last_glue:=max_halfword; - if type(p)=penalty_node then last_penalty:=penalty(p) - else if type(p)=kern_node then last_kern:=width(p); - end - -@ The code here is an example of a many-way switch into routines that -merge together in different places. Some people call this unstructured -programming, but the author doesn't see much wrong with it, as long as -@^Knuth, Donald Ervin@> -the various labels have a well-understood meaning. - -@<Move node |p| to the current page; ...@>= -@<If the current page is empty and node |p| is to be deleted, |goto done1|; - otherwise use node |p| to update the state of the current page; - if this node is an insertion, |goto contribute|; otherwise if this node - is not a legal breakpoint, |goto contribute| or |update_heights|; - otherwise set |pi| to the penalty associated with this breakpoint@>; -@<Check if node |p| is a new champion breakpoint; then \(if)if it is time for - a page break, prepare for output, and either fire up the user's - output routine and |return| or ship out the page and |goto done|@>; -if (type(p)<glue_node)or(type(p)>kern_node) then goto contribute; -update_heights:@<Update the current page measurements with respect to the - glue or kern specified by node~|p|@>; -contribute: @<Make sure that |page_max_depth| is not exceeded@>; -@<Link node |p| into the current page and |goto done|@>; -done1:@<Recycle node |p|@>; -done: - -@ @<Link node |p| into the current page and |goto done|@>= -link(page_tail):=p; page_tail:=p; -link(contrib_head):=link(p); link(p):=null; goto done - -@ @<Recycle node |p|@>= -link(contrib_head):=link(p); link(p):=null; flush_node_list(p) - -@ The title of this section is already so long, it seems best to avoid -making it more accurate but still longer, by mentioning the fact that a -kern node at the end of the contribution list will not be contributed until -we know its successor. - -@<If the current page is empty...@>= -case type(p) of -hlist_node,vlist_node,rule_node: if page_contents<box_there then - @<Initialize the current page, insert the \.{\\topskip} glue - ahead of |p|, and |goto continue|@> - else @<Prepare to move a box or rule node to the current page, - then |goto contribute|@>; -whatsit_node: @<Prepare to move whatsit |p| to the current page, - then |goto contribute|@>; -glue_node: if page_contents<box_there then goto done1 - else if precedes_break(page_tail) then pi:=0 - else goto update_heights; -kern_node: if page_contents<box_there then goto done1 - else if link(p)=null then return - else if type(link(p))=glue_node then pi:=0 - else goto update_heights; -penalty_node: if page_contents<box_there then goto done1@+else pi:=penalty(p); -mark_node: goto contribute; -ins_node: @<Append an insertion to the current page and |goto contribute|@>; -othercases confusion("page") -@:this can't happen page}{\quad page@> -endcases - -@ @<Initialize the current page, insert the \.{\\topskip} glue...@>= -begin if page_contents=empty then freeze_page_specs(box_there) -else page_contents:=box_there; -q:=new_skip_param(top_skip_code); {now |temp_ptr=glue_ptr(q)|} -if width(temp_ptr)>height(p) then width(temp_ptr):=width(temp_ptr)-height(p) -else width(temp_ptr):=0; -link(q):=p; link(contrib_head):=q; goto continue; -end - -@ @<Prepare to move a box or rule node to the current page...@>= -begin page_total:=page_total+page_depth+height(p); -page_depth:=depth(p); -goto contribute; -end - -@ @<Make sure that |page_max_depth| is not exceeded@>= -if page_depth>page_max_depth then - begin page_total:=@| - page_total+page_depth-page_max_depth;@/ - page_depth:=page_max_depth; - end; - -@ @<Update the current page measurements with respect to the glue...@>= -if type(p)=kern_node then q:=p -else begin q:=glue_ptr(p); - page_so_far[2+stretch_order(q)]:=@| - page_so_far[2+stretch_order(q)]+stretch(q);@/ - page_shrink:=page_shrink+shrink(q); - if (shrink_order(q)<>normal)and(shrink(q)<>0) then - begin@t@>@;@/ - print_err("Infinite glue shrinkage found on current page");@/ -@.Infinite glue shrinkage...@> - help4("The page about to be output contains some infinitely")@/ - ("shrinkable glue, e.g., `\vss' or `\vskip 0pt minus 1fil'.")@/ - ("Such glue doesn't belong there; but you can safely proceed,")@/ - ("since the offensive shrinkability has been made finite."); - error; - r:=new_spec(q); shrink_order(r):=normal; delete_glue_ref(q); - glue_ptr(p):=r; q:=r; - end; - end; -page_total:=page_total+page_depth+width(q); page_depth:=0 - -@ @<Check if node |p| is a new champion breakpoint; then \(if)...@>= -if pi<inf_penalty then - begin @<Compute the badness, |b|, of the current page, - using |awful_bad| if the box is too full@>; - if b<awful_bad then - if pi<=eject_penalty then c:=pi - else if b<inf_bad then c:=b+pi+insert_penalties - else c:=deplorable - else c:=b; - if insert_penalties>=10000 then c:=awful_bad; - @!stat if tracing_pages>0 then @<Display the page break cost@>;@+tats@;@/ - if c<=least_page_cost then - begin best_page_break:=p; best_size:=page_goal; - least_page_cost:=c; - r:=link(page_ins_head); - while r<>page_ins_head do - begin best_ins_ptr(r):=last_ins_ptr(r); - r:=link(r); - end; - end; - if (c=awful_bad)or(pi<=eject_penalty) then - begin fire_up(p); {output the current page at the best place} - if output_active then return; {user's output routine will act} - goto done; {the page has been shipped out by default output routine} - end; - end - -@ @<Display the page break cost@>= -begin begin_diagnostic; print_nl("%"); -print(" t="); print_totals;@/ -print(" g="); print_scaled(page_goal);@/ -print(" b="); -if b=awful_bad then print_char("*")@+else print_int(b); -@.*\relax@> -print(" p="); print_int(pi); -print(" c="); -if c=awful_bad then print_char("*")@+else print_int(c); -if c<=least_page_cost then print_char("#"); -end_diagnostic(false); -end - -@ @<Compute the badness, |b|, of the current page...@>= -if page_total<page_goal then - if (page_so_far[3]<>0) or (page_so_far[4]<>0) or@| - (page_so_far[5]<>0) then b:=0 - else b:=badness(page_goal-page_total,page_so_far[2]) -else if page_total-page_goal>page_shrink then b:=awful_bad -else b:=badness(page_total-page_goal,page_shrink) - -@ @<Append an insertion to the current page and |goto contribute|@>= -begin if page_contents=empty then freeze_page_specs(inserts_only); -n:=subtype(p); r:=page_ins_head; -while n>=subtype(link(r)) do r:=link(r); -n:=qo(n); -if subtype(r)<>qi(n) then - @<Create a page insertion node with |subtype(r)=qi(n)|, and - include the glue correction for box |n| in the - current page state@>; -if type(r)=split_up then insert_penalties:=insert_penalties+float_cost(p) -else begin last_ins_ptr(r):=p; - delta:=page_goal-page_total-page_depth+page_shrink; - {this much room is left if we shrink the maximum} - if count(n)=1000 then h:=height(p) - else h:=x_over_n(height(p),1000)*count(n); {this much room is needed} - if ((h<=0)or(h<=delta))and(height(p)+height(r)<=dimen(n)) then - begin page_goal:=page_goal-h; height(r):=height(r)+height(p); - end - else @<Find the best way to split the insertion, and change - |type(r)| to |split_up|@>; - end; -goto contribute; -end - -@ We take note of the value of \.{\\skip} |n| and the height plus depth -of \.{\\box}~|n| only when the first \.{\\insert}~|n| node is -encountered for a new page. A user who changes the contents of \.{\\box}~|n| -after that first \.{\\insert}~|n| had better be either extremely careful -or extremely lucky, or both. - -@<Create a page insertion node...@>= -begin q:=get_node(page_ins_node_size); link(q):=link(r); link(r):=q; r:=q; -subtype(r):=qi(n); type(r):=inserting; ensure_vbox(n); -if box(n)=null then height(r):=0 -else height(r):=height(box(n))+depth(box(n)); -best_ins_ptr(r):=null;@/ -q:=skip(n); -if count(n)=1000 then h:=height(r) -else h:=x_over_n(height(r),1000)*count(n); -page_goal:=page_goal-h-width(q);@/ -page_so_far[2+stretch_order(q)]:=@|page_so_far[2+stretch_order(q)]+stretch(q);@/ -page_shrink:=page_shrink+shrink(q); -if (shrink_order(q)<>normal)and(shrink(q)<>0) then - begin print_err("Infinite glue shrinkage inserted from "); print_esc("skip"); -@.Infinite glue shrinkage...@> - print_int(n); - help3("The correction glue for page breaking with insertions")@/ - ("must have finite shrinkability. But you may proceed,")@/ - ("since the offensive shrinkability has been made finite."); - error; - end; -end - -@ Here is the code that will split a long footnote between pages, in an -emergency. The current situation deserves to be recapitulated: Node |p| -is an insertion into box |n|; the insertion will not fit, in its entirety, -either because it would make the total contents of box |n| greater than -\.{\\dimen} |n|, or because it would make the incremental amount of growth -|h| greater than the available space |delta|, or both. (This amount |h| has -been weighted by the insertion scaling factor, i.e., by \.{\\count} |n| -over 1000.) Now we will choose the best way to break the vlist of the -insertion, using the same criteria as in the \.{\\vsplit} operation. - -@<Find the best way to split the insertion...@>= -begin if count(n)<=0 then w:=max_dimen -else begin w:=page_goal-page_total-page_depth; - if count(n)<>1000 then w:=x_over_n(w,count(n))*1000; - end; -if w>dimen(n)-height(r) then w:=dimen(n)-height(r); -q:=vert_break(ins_ptr(p),w,depth(p)); -height(r):=height(r)+best_height_plus_depth; -@!stat if tracing_pages>0 then @<Display the insertion split cost@>;@+tats@;@/ -if count(n)<>1000 then - best_height_plus_depth:=x_over_n(best_height_plus_depth,1000)*count(n); -page_goal:=page_goal-best_height_plus_depth; -type(r):=split_up; broken_ptr(r):=q; broken_ins(r):=p; -if q=null then insert_penalties:=insert_penalties+eject_penalty -else if type(q)=penalty_node then insert_penalties:=insert_penalties+penalty(q); -end - -@ @<Display the insertion split cost@>= -begin begin_diagnostic; print_nl("% split"); print_int(n); -@.split@> -print(" to "); print_scaled(w); -print_char(","); print_scaled(best_height_plus_depth);@/ -print(" p="); -if q=null then print_int(eject_penalty) -else if type(q)=penalty_node then print_int(penalty(q)) -else print_char("0"); -end_diagnostic(false); -end - -@ When the page builder has looked at as much material as could appear before -the next page break, it makes its decision. The break that gave minimum -badness will be used to put a completed ``page'' into box 255, with insertions -appended to their other boxes. - -We also set the values of |top_mark|, |first_mark|, and |bot_mark|. The -program uses the fact that |bot_mark<>null| implies |first_mark<>null|; -it also knows that |bot_mark=null| implies |top_mark=first_mark=null|. - -The |fire_up| subroutine prepares to output the current page at the best -place; then it fires up the user's output routine, if there is one, -or it simply ships out the page. There is one parameter, |c|, which represents -the node that was being contributed to the page when the decision to -force an output was made. - -@<Declare the procedure called |fire_up|@>= -procedure fire_up(@!c:pointer); -label exit; -var p,@!q,@!r,@!s:pointer; {nodes being examined and/or changed} -@!prev_p:pointer; {predecessor of |p|} -@!n:min_quarterword..255; {insertion box number} -@!wait:boolean; {should the present insertion be held over?} -@!save_vbadness:integer; {saved value of |vbadness|} -@!save_vfuzz: scaled; {saved value of |vfuzz|} -@!save_split_top_skip: pointer; {saved value of |split_top_skip|} -begin @<Set the value of |output_penalty|@>; -if bot_mark<>null then - begin if top_mark<>null then delete_token_ref(top_mark); - top_mark:=bot_mark; add_token_ref(top_mark); - delete_token_ref(first_mark); first_mark:=null; - end; -@<Put the \(o)optimal current page into box 255, update |first_mark| and - |bot_mark|, append insertions to their boxes, and put the - remaining nodes back on the contribution list@>; -if (top_mark<>null)and(first_mark=null) then - begin first_mark:=top_mark; add_token_ref(top_mark); - end; -if output_routine<>null then - if dead_cycles>=max_dead_cycles then - @<Explain that too many dead cycles have occurred in a row@> - else @<Fire up the user's output routine and |return|@>; -@<Perform the default output routine@>; -exit:end; - -@ @<Set the value of |output_penalty|@>= -if type(best_page_break)=penalty_node then - begin geq_word_define(int_base+output_penalty_code,penalty(best_page_break)); - penalty(best_page_break):=inf_penalty; - end -else geq_word_define(int_base+output_penalty_code,inf_penalty) - -@ As the page is finally being prepared for output, -pointer |p| runs through the vlist, with |prev_p| trailing behind; -pointer |q| is the tail of a list of insertions that -are being held over for a subsequent page. - -@<Put the \(o)optimal current page into box 255...@>= -if c=best_page_break then best_page_break:=null; {|c| not yet linked in} -@<Ensure that box 255 is empty before output@>; -insert_penalties:=0; {this will count the number of insertions held over} -save_split_top_skip:=split_top_skip; -if holding_inserts<=0 then - @<Prepare all the boxes involved in insertions to act as queues@>; -q:=hold_head; link(q):=null; prev_p:=page_head; p:=link(prev_p); -while p<>best_page_break do - begin if type(p)=ins_node then - begin if holding_inserts<=0 then - @<Either insert the material specified by node |p| into the - appropriate box, or hold it for the next page; - also delete node |p| from the current page@>; - end - else if type(p)=mark_node then @<Update the values of - |first_mark| and |bot_mark|@>; - prev_p:=p; p:=link(prev_p); - end; -split_top_skip:=save_split_top_skip; -@<Break the current page at node |p|, put it in box~255, - and put the remaining nodes on the contribution list@>; -@<Delete \(t)the page-insertion nodes@> - -@ @<Ensure that box 255 is empty before output@>= -if box(255)<>null then - begin print_err(""); print_esc("box"); print("255 is not void"); -@:box255}{\.{\\box255 is not void}@> - help2("You shouldn't use \box255 except in \output routines.")@/ - ("Proceed, and I'll discard its present contents."); - box_error(255); - end - -@ @<Update the values of |first_mark| and |bot_mark|@>= -begin if first_mark=null then - begin first_mark:=mark_ptr(p); - add_token_ref(first_mark); - end; -if bot_mark<>null then delete_token_ref(bot_mark); -bot_mark:=mark_ptr(p); add_token_ref(bot_mark); -end - -@ When the following code is executed, the current page runs from node -|link(page_head)| to node |prev_p|, and the nodes from |p| to |page_tail| -are to be placed back at the front of the contribution list. Furthermore -the heldover insertions appear in a list from |link(hold_head)| to |q|; we -will put them into the current page list for safekeeping while the user's -output routine is active. We might have |q=hold_head|; and |p=null| if -and only if |prev_p=page_tail|. Error messages are suppressed within -|vpackage|, since the box might appear to be overfull or underfull simply -because the stretch and shrink from the \.{\\skip} registers for inserts -are not actually present in the box. - -@<Break the current page at node |p|, put it...@>= -if p<>null then - begin if link(contrib_head)=null then - if nest_ptr=0 then tail:=page_tail - else contrib_tail:=page_tail; - link(page_tail):=link(contrib_head); - link(contrib_head):=p; - link(prev_p):=null; - end; -save_vbadness:=vbadness; vbadness:=inf_bad; -save_vfuzz:=vfuzz; vfuzz:=max_dimen; {inhibit error messages} -box(255):=vpackage(link(page_head),best_size,exactly,page_max_depth); -vbadness:=save_vbadness; vfuzz:=save_vfuzz; -if last_glue<>max_halfword then delete_glue_ref(last_glue); -@<Start a new current page@>; {this sets |last_glue:=max_halfword|} -if q<>hold_head then - begin link(page_head):=link(hold_head); page_tail:=q; - end - -@ If many insertions are supposed to go into the same box, we want to know -the position of the last node in that box, so that we don't need to waste time -when linking further information into it. The |last_ins_ptr| fields of the -page insertion nodes are therefore used for this purpose during the -packaging phase. - -@<Prepare all the boxes involved in insertions to act as queues@>= -begin r:=link(page_ins_head); -while r<>page_ins_head do - begin if best_ins_ptr(r)<>null then - begin n:=qo(subtype(r)); ensure_vbox(n); - if box(n)=null then box(n):=new_null_box; - p:=box(n)+list_offset; - while link(p)<>null do p:=link(p); - last_ins_ptr(r):=p; - end; - r:=link(r); - end; -end - -@ @<Delete \(t)the page-insertion nodes@>= -r:=link(page_ins_head); -while r<>page_ins_head do - begin q:=link(r); free_node(r,page_ins_node_size); r:=q; - end; -link(page_ins_head):=page_ins_head - -@ We will set |best_ins_ptr:=null| and package the box corresponding to -insertion node~|r|, just after making the final insertion into that box. -If this final insertion is `|split_up|', the remainder after splitting -and pruning (if any) will be carried over to the next page. - -@<Either insert the material specified by node |p| into...@>= -begin r:=link(page_ins_head); -while subtype(r)<>subtype(p) do r:=link(r); -if best_ins_ptr(r)=null then wait:=true -else begin wait:=false; s:=last_ins_ptr(r); link(s):=ins_ptr(p); - if best_ins_ptr(r)=p then - @<Wrap up the box specified by node |r|, splitting node |p| if - called for; set |wait:=true| if node |p| holds a remainder after - splitting@> - else begin while link(s)<>null do s:=link(s); - last_ins_ptr(r):=s; - end; - end; -@<Either append the insertion node |p| after node |q|, and remove it - from the current page, or delete |node(p)|@>; -end - -@ @<Wrap up the box specified by node |r|, splitting node |p| if...@>= -begin if type(r)=split_up then - if (broken_ins(r)=p)and(broken_ptr(r)<>null) then - begin while link(s)<>broken_ptr(r) do s:=link(s); - link(s):=null; - split_top_skip:=split_top_ptr(p); - ins_ptr(p):=prune_page_top(broken_ptr(r)); - if ins_ptr(p)<>null then - begin temp_ptr:=vpack(ins_ptr(p),natural); - height(p):=height(temp_ptr)+depth(temp_ptr); - free_node(temp_ptr,box_node_size); wait:=true; - end; - end; -best_ins_ptr(r):=null; -n:=qo(subtype(r)); -temp_ptr:=list_ptr(box(n)); -free_node(box(n),box_node_size); -box(n):=vpack(temp_ptr,natural); -end - -@ @<Either append the insertion node |p|...@>= -link(prev_p):=link(p); link(p):=null; -if wait then - begin link(q):=p; q:=p; incr(insert_penalties); - end -else begin delete_glue_ref(split_top_ptr(p)); - free_node(p,ins_node_size); - end; -p:=prev_p - -@ The list of heldover insertions, running from |link(page_head)| to -|page_tail|, must be moved to the contribution list when the user has -specified no output routine. - -@<Perform the default output routine@>= -begin if link(page_head)<>null then - begin if link(contrib_head)=null then - if nest_ptr=0 then tail:=page_tail@+else contrib_tail:=page_tail - else link(page_tail):=link(contrib_head); - link(contrib_head):=link(page_head); - link(page_head):=null; page_tail:=page_head; - end; -ship_out(box(255)); box(255):=null; -end - -@ @<Explain that too many dead cycles have occurred in a row@>= -begin print_err("Output loop---"); print_int(dead_cycles); -@.Output loop...@> -print(" consecutive dead cycles"); -help3("I've concluded that your \output is awry; it never does a")@/ -("\shipout, so I'm shipping \box255 out myself. Next time")@/ -("increase \maxdeadcycles if you want me to be more patient!"); error; -end - -@ @<Fire up the user's output routine and |return|@>= -begin output_active:=true; -incr(dead_cycles); -push_nest; mode:=-vmode; prev_depth:=ignore_depth; mode_line:=-line; -begin_token_list(output_routine,output_text); -new_save_level(output_group); normal_paragraph; -scan_left_brace; -return; -end - -@ When the user's output routine finishes, it has constructed a vlist -in internal vertical mode, and \TeX\ will do the following: - -@<Resume the page builder after an output routine has come to an end@>= -begin if (loc<>null) or - ((token_type<>output_text)and(token_type<>backed_up)) then - @<Recover from an unbalanced output routine@>; -end_token_list; {conserve stack space in case more outputs are triggered} -end_graf; unsave; output_active:=false; insert_penalties:=0;@/ -@<Ensure that box 255 is empty after output@>; -if tail<>head then {current list goes after heldover insertions} - begin link(page_tail):=link(head); - page_tail:=tail; - end; -if link(page_head)<>null then {and both go before heldover contributions} - begin if link(contrib_head)=null then contrib_tail:=page_tail; - link(page_tail):=link(contrib_head); - link(contrib_head):=link(page_head); - link(page_head):=null; page_tail:=page_head; - end; -pop_nest; build_page; -end - -@ @<Recover from an unbalanced output routine@>= -begin print_err("Unbalanced output routine"); -@.Unbalanced output routine@> -help2("Your sneaky output routine has problematic {'s and/or }'s.")@/ -("I can't handle that very well; good luck."); error; -repeat get_token; -until loc=null; -end {loops forever if reading from a file, since |null=min_halfword<=0|} - -@ @<Ensure that box 255 is empty after output@>= -if box(255)<>null then - begin print_err("Output routine didn't use all of "); - print_esc("box"); print_int(255); -@.Output routine didn't use...@> - help3("Your \output commands should empty \box255,")@/ - ("e.g., by saying `\shipout\box255'.")@/ - ("Proceed; I'll discard its present contents."); - box_error(255); - end - -@* \[46] The chief executive. -We come now to the |main_control| routine, which contains the master -switch that causes all the various pieces of \TeX\ to do their things, -in the right order. - -In a sense, this is the grand climax of the program: It applies all the -tools that we have worked so hard to construct. In another sense, this is -the messiest part of the program: It necessarily refers to other pieces -of code all over the place, so that a person can't fully understand what is -going on without paging back and forth to be reminded of conventions that -are defined elsewhere. We are now at the hub of the web, the central nervous -system that touches most of the other parts and ties them together. -@^brain@> - -The structure of |main_control| itself is quite simple. There's a label -called |big_switch|, at which point the next token of input is fetched -using |get_x_token|. Then the program branches at high speed into one of -about 100 possible directions, based on the value of the current -mode and the newly fetched command code; the sum |abs(mode)+cur_cmd| -indicates what to do next. For example, the case `|vmode+letter|' arises -when a letter occurs in vertical mode (or internal vertical mode); this -case leads to instructions that initialize a new paragraph and enter -horizontal mode. - -The big |case| statement that contains this multiway switch has been labeled -|reswitch|, so that the program can |goto reswitch| when the next token -has already been fetched. Most of the cases are quite short; they call -an ``action procedure'' that does the work for that case, and then they -either |goto reswitch| or they ``fall through'' to the end of the |case| -statement, which returns control back to |big_switch|. Thus, |main_control| -is not an extremely large procedure, in spite of the multiplicity of things -it must do; it is small enough to be handled by \PASCAL\ compilers that put -severe restrictions on procedure size. -@!@^action procedure@> - -One case is singled out for special treatment, because it accounts for most -of \TeX's activities in typical applications. The process of reading simple -text and converting it into |char_node| records, while looking for ligatures -and kerns, is part of \TeX's ``inner loop''; the whole program runs -efficiently when its inner loop is fast, so this part has been written -with particular care. - -@ We shall concentrate first on the inner loop of |main_control|, deferring -consideration of the other cases until later. -@^inner loop@> - -@d big_switch=60 {go here to branch on the next token of input} -@d main_loop=70 {go here to typeset a string of consecutive characters} -@d main_loop_wrapup=80 {go here to finish a character or ligature} -@d main_loop_move=90 {go here to advance the ligature cursor} -@d main_loop_move_lig=95 {same, when advancing past a generated ligature} -@d main_loop_lookahead=100 {go here to bring in another character, if any} -@d main_lig_loop=110 {go here to check for ligatures or kerning} -@d append_normal_space=120 {go here to append a normal space between words} - -@p @t\4@>@<Declare action procedures for use by |main_control|@>@; -@t\4@>@<Declare the procedure called |handle_right_brace|@>@; -procedure main_control; {governs \TeX's activities} -label big_switch,reswitch,main_loop,main_loop_wrapup, - main_loop_move,main_loop_move+1,main_loop_move+2,main_loop_move_lig, - main_loop_lookahead,main_loop_lookahead+1, - main_lig_loop,main_lig_loop+1,main_lig_loop+2, - append_normal_space,exit; -var@!t:integer; {general-purpose temporary variable} -begin if every_job<>null then begin_token_list(every_job,every_job_text); -big_switch: get_x_token;@/ -reswitch: @<Give diagnostic information, if requested@>; -case abs(mode)+cur_cmd of -hmode+letter,hmode+other_char,hmode+char_given: goto main_loop; -hmode+char_num: begin scan_char_num; cur_chr:=cur_val; goto main_loop;@+end; -hmode+no_boundary: begin get_x_token; - if (cur_cmd=letter)or(cur_cmd=other_char)or(cur_cmd=char_given)or - (cur_cmd=char_num) then cancel_boundary:=true; - goto reswitch; - end; -hmode+spacer: if space_factor=1000 then goto append_normal_space - else app_space; -hmode+ex_space,mmode+ex_space: goto append_normal_space; -@t\4@>@<Cases of |main_control| that are not part of the inner loop@>@; -end; {of the big |case| statement} -goto big_switch; -main_loop:@<Append character |cur_chr| and the following characters (if~any) - to the current hlist in the current font; |goto reswitch| when - a non-character has been fetched@>; -append_normal_space:@<Append a normal inter-word space to the current list, - then |goto big_switch|@>; -exit:end; - -@ When a new token has just been fetched at |big_switch|, we have an -ideal place to monitor \TeX's activity. -@^debugging@> - -@<Give diagnostic information, if requested@>= -if interrupt<>0 then if OK_to_interrupt then - begin back_input; check_interrupt; goto big_switch; - end; -@!debug if panicking then check_mem(false);@+@;@+gubed -if tracing_commands>0 then show_cur_cmd_chr - -@ The following part of the program was first written in a structured -manner, according to the philosophy that ``premature optimization is -the root of all evil.'' Then it was rearranged into pieces of -spaghetti so that the most common actions could proceed with little or -no redundancy. - -The original unoptimized form of this algorithm resembles the -|reconstitute| procedure, which was described earlier in connection with -hyphenation. Again we have an implied ``cursor'' between characters -|cur_l| and |cur_r|. The main difference is that the |lig_stack| can now -contain a charnode as well as pseudo-ligatures; that stack is now -usually nonempty, because the next character of input (if any) has been -appended to it. In |main_control| we have -$$|cur_r|=\cases{|character(lig_stack)|,&if |lig_stack>null|;\cr - |font_bchar[cur_font]|,&otherwise;\cr}$$ -except when |character(lig_stack)=font_false_bchar[cur_font]|. -Several additional global variables are needed. - -@<Glob...@>= -@!main_f:internal_font_number; {the current font} -@!main_i:four_quarters; {character information bytes for |cur_l|} -@!main_j:four_quarters; {ligature/kern command} -@!main_k:font_index; {index into |font_info|} -@!main_p:pointer; {temporary register for list manipulation} -@!main_s:integer; {space factor value} -@!bchar:halfword; {boundary character of current font, or |non_char|} -@!false_bchar:halfword; {nonexistent character matching |bchar|, or |non_char|} -@!cancel_boundary:boolean; {should the left boundary be ignored?} -@!ins_disc:boolean; {should we insert a discretionary node?} - -@ The boolean variables of the main loop are normally false, and always reset -to false before the loop is left. That saves us the extra work of initializing -each time. - -@<Set init...@>= -ligature_present:=false; cancel_boundary:=false; lft_hit:=false; rt_hit:=false; -ins_disc:=false; - -@ We leave the |space_factor| unchanged if |sf_code(cur_chr)=0|; otherwise we -set it equal to |sf_code(cur_chr)|, except that it should never change -from a value less than 1000 to a value exceeding 1000. The most common -case is |sf_code(cur_chr)=1000|, so we want that case to be fast. - -The overall structure of the main loop is presented here. Some program labels -are inside the individual sections. -@^inner loop@> - -@d adjust_space_factor==@t@>@;@/ - main_s:=sf_code(cur_chr); - if main_s=1000 then space_factor:=1000 - else if main_s<1000 then - begin if main_s>0 then space_factor:=main_s; - end - else if space_factor<1000 then space_factor:=1000 - else space_factor:=main_s - -@<Append character |cur_chr|...@>= -adjust_space_factor;@/ -main_f:=cur_font; -bchar:=font_bchar[main_f]; false_bchar:=font_false_bchar[main_f]; -if mode>0 then if language<>clang then fix_language; -fast_get_avail(lig_stack); font(lig_stack):=main_f; cur_l:=qi(cur_chr); -character(lig_stack):=cur_l;@/ -cur_q:=tail; -if cancel_boundary then - begin cancel_boundary:=false; main_k:=non_address; - end -else main_k:=bchar_label[main_f]; -if main_k=non_address then goto main_loop_move+2; {no left boundary processing} -cur_r:=cur_l; cur_l:=non_char; -goto main_lig_loop+1; {begin with cursor after left boundary} -@# -main_loop_wrapup:@<Make a ligature node, if |ligature_present|; - insert a null discretionary, if appropriate@>; -main_loop_move:@<If the cursor is immediately followed by the right boundary, - |goto reswitch|; if it's followed by an invalid character, |goto big_switch|; - otherwise move the cursor one step to the right and |goto main_lig_loop|@>; -main_loop_lookahead:@<Look ahead for another character, or leave |lig_stack| - empty if there's none there@>; -main_lig_loop:@<If there's a ligature/kern command relevant to |cur_l| and - |cur_r|, adjust the text appropriately; exit to |main_loop_wrapup|@>; -main_loop_move_lig:@<Move the cursor past a pseudo-ligature, then - |goto main_loop_lookahead| or |main_lig_loop|@> - -@ If |link(cur_q)| is nonnull when |wrapup| is invoked, |cur_q| points to -the list of characters that were consumed while building the ligature -character~|cur_l|. - -A discretionary break is not inserted for an explicit hyphen when we are in -restricted horizontal mode. In particular, this avoids putting discretionary -nodes inside of other discretionaries. -@^inner loop@> - -@d pack_lig(#)== {the parameter is either |rt_hit| or |false|} - begin main_p:=new_ligature(main_f,cur_l,link(cur_q)); - if lft_hit then - begin subtype(main_p):=2; lft_hit:=false; - end; - if # then if lig_stack=null then - begin incr(subtype(main_p)); rt_hit:=false; - end; - link(cur_q):=main_p; tail:=main_p; ligature_present:=false; - end - -@d wrapup(#)==if cur_l<non_char then - begin if link(cur_q)>null then - if character(tail)=qi(hyphen_char[main_f]) then ins_disc:=true; - if ligature_present then pack_lig(#); - if ins_disc then - begin ins_disc:=false; - if mode>0 then tail_append(new_disc); - end; - end - -@<Make a ligature node, if |ligature_present|;...@>= -wrapup(rt_hit) - -@ @<If the cursor is immediately followed by the right boundary...@>= -@^inner loop@> -if lig_stack=null then goto reswitch; -cur_q:=tail; cur_l:=character(lig_stack); -main_loop_move+1:if not is_char_node(lig_stack) then goto main_loop_move_lig; -main_loop_move+2:if(cur_chr<font_bc[main_f])or(cur_chr>font_ec[main_f]) then - begin char_warning(main_f,cur_chr); free_avail(lig_stack); goto big_switch; - end; -main_i:=char_info(main_f)(cur_l); -if not char_exists(main_i) then - begin char_warning(main_f,cur_chr); free_avail(lig_stack); goto big_switch; - end; -link(tail):=lig_stack; tail:=lig_stack {|main_loop_lookahead| is next} - -@ Here we are at |main_loop_move_lig|. -When we begin this code we have |cur_q=tail| and |cur_l=character(lig_stack)|. - -@<Move the cursor past a pseudo-ligature...@>= -main_p:=lig_ptr(lig_stack); -if main_p>null then tail_append(main_p); {append a single character} -temp_ptr:=lig_stack; lig_stack:=link(temp_ptr); -free_node(temp_ptr,small_node_size); -main_i:=char_info(main_f)(cur_l); ligature_present:=true; -if lig_stack=null then - if main_p>null then goto main_loop_lookahead - else cur_r:=bchar -else cur_r:=character(lig_stack); -goto main_lig_loop - -@ The result of \.{\\char} can participate in a ligature or kern, so we must -look ahead for it. - -@<Look ahead for another character...@>= -get_next; {set only |cur_cmd| and |cur_chr|, for speed} -if cur_cmd=letter then goto main_loop_lookahead+1; -if cur_cmd=other_char then goto main_loop_lookahead+1; -if cur_cmd=char_given then goto main_loop_lookahead+1; -x_token; {now expand and set |cur_cmd|, |cur_chr|, |cur_tok|} -if cur_cmd=letter then goto main_loop_lookahead+1; -if cur_cmd=other_char then goto main_loop_lookahead+1; -if cur_cmd=char_given then goto main_loop_lookahead+1; -if cur_cmd=char_num then - begin scan_char_num; cur_chr:=cur_val; goto main_loop_lookahead+1; - end; -if cur_cmd=no_boundary then bchar:=non_char; -cur_r:=bchar; lig_stack:=null; goto main_lig_loop; -main_loop_lookahead+1: adjust_space_factor; -fast_get_avail(lig_stack); font(lig_stack):=main_f; -cur_r:=qi(cur_chr); character(lig_stack):=cur_r; -if cur_r=false_bchar then cur_r:=non_char {this prevents spurious ligatures} - -@ Even though comparatively few characters have a lig/kern program, several -of the instructions here count as part of \TeX's inner loop, since a -@^inner loop@> -potentially long sequential search must be performed. For example, tests with -Computer Modern Roman showed that about 40 per cent of all characters -actually encountered in practice had a lig/kern program, and that about four -lig/kern commands were investigated for every such character. - -At the beginning of this code we have |main_i=char_info(main_f)(cur_l)|. - -@<If there's a ligature/kern command...@>= -if char_tag(main_i)<>lig_tag then goto main_loop_wrapup; -if cur_r=non_char then goto main_loop_wrapup; -main_k:=lig_kern_start(main_f)(main_i); main_j:=font_info[main_k].qqqq; -if skip_byte(main_j)<=stop_flag then goto main_lig_loop+2; -main_k:=lig_kern_restart(main_f)(main_j); -main_lig_loop+1:main_j:=font_info[main_k].qqqq; -main_lig_loop+2:if next_char(main_j)=cur_r then - if skip_byte(main_j)<=stop_flag then - @<Do ligature or kern command, returning to |main_lig_loop| - or |main_loop_wrapup| or |main_loop_move|@>; -if skip_byte(main_j)=qi(0) then incr(main_k) -else begin if skip_byte(main_j)>=stop_flag then goto main_loop_wrapup; - main_k:=main_k+qo(skip_byte(main_j))+1; - end; -goto main_lig_loop+1 - -@ When a ligature or kern instruction matches a character, we know from -|read_font_info| that the character exists in the font, even though we -haven't verified its existence in the normal way. - -This section could be made into a subroutine, if the code inside -|main_control| needs to be shortened. - -\chardef\?='174 % vertical line to indicate character retention - -@<Do ligature or kern command...@>= -begin if op_byte(main_j)>=kern_flag then - begin wrapup(rt_hit); - tail_append(new_kern(char_kern(main_f)(main_j))); goto main_loop_move; - end; -if cur_l=non_char then lft_hit:=true -else if lig_stack=null then rt_hit:=true; -check_interrupt; {allow a way out in case there's an infinite ligature loop} -case op_byte(main_j) of -qi(1),qi(5):begin cur_l:=rem_byte(main_j); {\.{=:\?}, \.{=:\?>}} - main_i:=char_info(main_f)(cur_l); ligature_present:=true; - end; -qi(2),qi(6):begin cur_r:=rem_byte(main_j); {\.{\?=:}, \.{\?=:>}} - if lig_stack=null then {right boundary character is being consumed} - begin lig_stack:=new_lig_item(cur_r); bchar:=non_char; - end - else if is_char_node(lig_stack) then {|link(lig_stack)=null|} - begin main_p:=lig_stack; lig_stack:=new_lig_item(cur_r); - lig_ptr(lig_stack):=main_p; - end - else character(lig_stack):=cur_r; - end; -qi(3):begin cur_r:=rem_byte(main_j); {\.{\?=:\?}} - main_p:=lig_stack; lig_stack:=new_lig_item(cur_r); - link(lig_stack):=main_p; - end; -qi(7),qi(11):begin wrapup(false); {\.{\?=:\?>}, \.{\?=:\?>>}} - cur_q:=tail; cur_l:=rem_byte(main_j); - main_i:=char_info(main_f)(cur_l); ligature_present:=true; - end; -othercases begin cur_l:=rem_byte(main_j); ligature_present:=true; {\.{=:}} - if lig_stack=null then goto main_loop_wrapup - else goto main_loop_move+1; - end -endcases; -if op_byte(main_j)>qi(4) then - if op_byte(main_j)<>qi(7) then goto main_loop_wrapup; -if cur_l<non_char then goto main_lig_loop; -main_k:=bchar_label[main_f]; goto main_lig_loop+1; -end - -@ The occurrence of blank spaces is almost part of \TeX's inner loop, -@^inner loop@> -since we usually encounter about one space for every five non-blank characters. -Therefore |main_control| gives second-highest priority to ordinary spaces. - -When a glue parameter like \.{\\spaceskip} is set to `\.{0pt}', we will -see to it later that the corresponding glue specification is precisely -|zero_glue|, not merely a pointer to some specification that happens -to be full of zeroes. Therefore it is simple to test whether a glue parameter -is zero or~not. - -@<Append a normal inter-word space...@>= -if space_skip=zero_glue then - begin @<Find the glue specification, |main_p|, for - text spaces in the current font@>; - temp_ptr:=new_glue(main_p); - end -else temp_ptr:=new_param_glue(space_skip_code); -link(tail):=temp_ptr; tail:=temp_ptr; -goto big_switch - -@ Having |font_glue| allocated for each text font saves both time and memory. -If any of the three spacing parameters are subsequently changed by the -use of \.{\\fontdimen}, the |find_font_dimen| procedure deallocates the -|font_glue| specification allocated here. - -@<Find the glue specification...@>= -begin main_p:=font_glue[cur_font]; -if main_p=null then - begin main_p:=new_spec(zero_glue); main_k:=param_base[cur_font]+space_code; - width(main_p):=font_info[main_k].sc; {that's |space(cur_font)|} - stretch(main_p):=font_info[main_k+1].sc; {and |space_stretch(cur_font)|} - shrink(main_p):=font_info[main_k+2].sc; {and |space_shrink(cur_font)|} - font_glue[cur_font]:=main_p; - end; -end - -@ @<Declare act...@>= -procedure app_space; {handle spaces when |space_factor<>1000|} -var@!q:pointer; {glue node} -begin if (space_factor>=2000)and(xspace_skip<>zero_glue) then - q:=new_param_glue(xspace_skip_code) -else begin if space_skip<>zero_glue then main_p:=space_skip - else @<Find the glue specification...@>; - main_p:=new_spec(main_p); - @<Modify the glue specification in |main_p| according to the space factor@>; - q:=new_glue(main_p); glue_ref_count(main_p):=null; - end; -link(tail):=q; tail:=q; -end; - -@ @<Modify the glue specification in |main_p| according to the space factor@>= -if space_factor>=2000 then width(main_p):=width(main_p)+extra_space(cur_font); -stretch(main_p):=xn_over_d(stretch(main_p),space_factor,1000); -shrink(main_p):=xn_over_d(shrink(main_p),1000,space_factor) - -@ Whew---that covers the main loop. We can now proceed at a leisurely -pace through the other combinations of possibilities. - -@d any_mode(#)==vmode+#,hmode+#,mmode+# {for mode-independent commands} - -@<Cases of |main_control| that are not part of the inner loop@>= -any_mode(relax),vmode+spacer,mmode+spacer,mmode+no_boundary:do_nothing; -any_mode(ignore_spaces): begin @<Get the next non-blank non-call...@>; - goto reswitch; - end; -vmode+stop: if its_all_over then return; {this is the only way out} -@t\4@>@<Forbidden cases detected in |main_control|@>@+@,any_mode(mac_param): - report_illegal_case; -@<Math-only cases in non-math modes, or vice versa@>: insert_dollar_sign; -@t\4@>@<Cases of |main_control| that build boxes and lists@>@; -@t\4@>@<Cases of |main_control| that don't depend on |mode|@>@; -@t\4@>@<Cases of |main_control| that are for extensions to \TeX@>@; - -@ Here is a list of cases where the user has probably gotten into or out of math -mode by mistake. \TeX\ will insert a dollar sign and rescan the current token. - -@d non_math(#)==vmode+#,hmode+# - -@<Math-only cases in non-math modes...@>= -non_math(sup_mark), non_math(sub_mark), non_math(math_char_num), -non_math(math_given), non_math(math_comp), non_math(delim_num), -non_math(left_right), non_math(above), non_math(radical), -non_math(math_style), non_math(math_choice), non_math(vcenter), -non_math(non_script), non_math(mkern), non_math(limit_switch), -non_math(mskip), non_math(math_accent), -mmode+endv, mmode+par_end, mmode+stop, mmode+vskip, mmode+un_vbox, -mmode+valign, mmode+hrule - -@ @<Declare action...@>= -procedure insert_dollar_sign; -begin back_input; cur_tok:=math_shift_token+"$"; -print_err("Missing $ inserted"); -@.Missing \$ inserted@> -help2("I've inserted a begin-math/end-math symbol since I think")@/ -("you left one out. Proceed, with fingers crossed."); ins_error; -end; - -@ When erroneous situations arise, \TeX\ usually issues an error message -specific to the particular error. For example, `\.{\\noalign}' should -not appear in any mode, since it is recognized by the |align_peek| routine -in all of its legitimate appearances; a special error message is given -when `\.{\\noalign}' occurs elsewhere. But sometimes the most appropriate -error message is simply that the user is not allowed to do what he or she -has attempted. For example, `\.{\\moveleft}' is allowed only in vertical mode, -and `\.{\\lower}' only in non-vertical modes. Such cases are enumerated -here and in the other sections referred to under `See also \dots.' - -@<Forbidden cases...@>= -vmode+vmove,hmode+hmove,mmode+hmove,any_mode(last_item), - -@ The `|you_cant|' procedure prints a line saying that the current command -is illegal in the current mode; it identifies these things symbolically. - -@<Declare action...@>= -procedure you_cant; -begin print_err("You can't use `"); -@.You can't use x in y mode@> -print_cmd_chr(cur_cmd,cur_chr); -print("' in "); print_mode(mode); -end; - -@ @<Declare act...@>= -procedure report_illegal_case; -begin you_cant; -help4("Sorry, but I'm not programmed to handle this case;")@/ -("I'll just pretend that you didn't ask for it.")@/ -("If you're in the wrong mode, you might be able to")@/ -("return to the right one by typing `I}' or `I$' or `I\par'.");@/ -error; -end; - -@ Some operations are allowed only in privileged modes, i.e., in cases -that |mode>0|. The |privileged| function is used to detect violations -of this rule; it issues an error message and returns |false| if the -current |mode| is negative. - -@<Declare act...@>= -function privileged:boolean; -begin if mode>0 then privileged:=true -else begin report_illegal_case; privileged:=false; - end; -end; - -@ Either \.{\\dump} or \.{\\end} will cause |main_control| to enter the -endgame, since both of them have `|stop|' as their command code. - -@<Put each...@>= -primitive("end",stop,0);@/ -@!@:end_}{\.{\\end} primitive@> -primitive("dump",stop,1);@/ -@!@:dump_}{\.{\\dump} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -stop:if chr_code=1 then print_esc("dump")@+else print_esc("end"); - -@ We don't want to leave |main_control| immediately when a |stop| command -is sensed, because it may be necessary to invoke an \.{\\output} routine -several times before things really grind to a halt. (The output routine -might even say `\.{\\gdef\\end\{...\}}', to prolong the life of the job.) -Therefore |its_all_over| is |true| only when the current page -and contribution list are empty, and when the last output was not a -``dead cycle.'' - -@<Declare act...@>= -function its_all_over:boolean; {do this when \.{\\end} or \.{\\dump} occurs} -label exit; -begin if privileged then - begin if (page_head=page_tail)and(head=tail)and(dead_cycles=0) then - begin its_all_over:=true; return; - end; - back_input; {we will try to end again after ejecting residual material} - tail_append(new_null_box); - width(tail):=hsize; - tail_append(new_glue(fill_glue)); - tail_append(new_penalty(-@'10000000000));@/ - build_page; {append \.{\\hbox to \\hsize\{\}\\vfill\\penalty-'10000000000}} - end; -its_all_over:=false; -exit:end; - -@* \[47] Building boxes and lists. -The most important parts of |main_control| are concerned with \TeX's -chief mission of box-making. We need to control the activities that put -entries on vlists and hlists, as well as the activities that convert -those lists into boxes. All of the necessary machinery has already been -developed; it remains for us to ``push the buttons'' at the right times. - -@ As an introduction to these routines, let's consider one of the simplest -cases: What happens when `\.{\\hrule}' occurs in vertical mode, or -`\.{\\vrule}' in horizontal mode or math mode? The code in |main_control| -is short, since the |scan_rule_spec| routine already does most of what is -required; thus, there is no need for a special action procedure. - -Note that baselineskip calculations are disabled after a rule in vertical -mode, by setting |prev_depth:=ignore_depth|. - -@<Cases of |main_control| that build...@>= -vmode+hrule,hmode+vrule,mmode+vrule: begin tail_append(scan_rule_spec); - if abs(mode)=vmode then prev_depth:=ignore_depth - else if abs(mode)=hmode then space_factor:=1000; - end; - -@ The processing of things like \.{\\hskip} and \.{\\vskip} is slightly -more complicated. But the code in |main_control| is very short, since -it simply calls on the action routine |append_glue|. Similarly, \.{\\kern} -activates |append_kern|. - -@<Cases of |main_control| that build...@>= -vmode+vskip,hmode+hskip,mmode+hskip,mmode+mskip: append_glue; -any_mode(kern),mmode+mkern: append_kern; - -@ The |hskip| and |vskip| command codes are used for control sequences -like \.{\\hss} and \.{\\vfil} as well as for \.{\\hskip} and \.{\\vskip}. -The difference is in the value of |cur_chr|. - -@d fil_code=0 {identifies \.{\\hfil} and \.{\\vfil}} -@d fill_code=1 {identifies \.{\\hfill} and \.{\\vfill}} -@d ss_code=2 {identifies \.{\\hss} and \.{\\vss}} -@d fil_neg_code=3 {identifies \.{\\hfilneg} and \.{\\vfilneg}} -@d skip_code=4 {identifies \.{\\hskip} and \.{\\vskip}} -@d mskip_code=5 {identifies \.{\\mskip}} - -@<Put each...@>= -primitive("hskip",hskip,skip_code);@/ -@!@:hskip_}{\.{\\hskip} primitive@> -primitive("hfil",hskip,fil_code); -@!@:hfil_}{\.{\\hfil} primitive@> -primitive("hfill",hskip,fill_code);@/ -@!@:hfill_}{\.{\\hfill} primitive@> -primitive("hss",hskip,ss_code); -@!@:hss_}{\.{\\hss} primitive@> -primitive("hfilneg",hskip,fil_neg_code);@/ -@!@:hfil_neg_}{\.{\\hfilneg} primitive@> -primitive("vskip",vskip,skip_code);@/ -@!@:vskip_}{\.{\\vskip} primitive@> -primitive("vfil",vskip,fil_code); -@!@:vfil_}{\.{\\vfil} primitive@> -primitive("vfill",vskip,fill_code);@/ -@!@:vfill_}{\.{\\vfill} primitive@> -primitive("vss",vskip,ss_code); -@!@:vss_}{\.{\\vss} primitive@> -primitive("vfilneg",vskip,fil_neg_code);@/ -@!@:vfil_neg_}{\.{\\vfilneg} primitive@> -primitive("mskip",mskip,mskip_code);@/ -@!@:mskip_}{\.{\\mskip} primitive@> -primitive("kern",kern,explicit); -@!@:kern_}{\.{\\kern} primitive@> -primitive("mkern",mkern,mu_glue);@/ -@!@:mkern_}{\.{\\mkern} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -hskip: case chr_code of - skip_code:print_esc("hskip"); - fil_code:print_esc("hfil"); - fill_code:print_esc("hfill"); - ss_code:print_esc("hss"); - othercases print_esc("hfilneg") - endcases; -vskip: case chr_code of - skip_code:print_esc("vskip"); - fil_code:print_esc("vfil"); - fill_code:print_esc("vfill"); - ss_code:print_esc("vss"); - othercases print_esc("vfilneg") - endcases; -mskip: print_esc("mskip"); -kern: print_esc("kern"); -mkern: print_esc("mkern"); - -@ All the work relating to glue creation has been relegated to the -following subroutine. It does not call |build_page|, because it is -used in at least one place where that would be a mistake. - -@<Declare action...@>= -procedure append_glue; -var s:small_number; {modifier of skip command} -begin s:=cur_chr; -case s of -fil_code: cur_val:=fil_glue; -fill_code: cur_val:=fill_glue; -ss_code: cur_val:=ss_glue; -fil_neg_code: cur_val:=fil_neg_glue; -skip_code: scan_glue(glue_val); -mskip_code: scan_glue(mu_val); -end; {now |cur_val| points to the glue specification} -tail_append(new_glue(cur_val)); -if s>=skip_code then - begin decr(glue_ref_count(cur_val)); - if s>skip_code then subtype(tail):=mu_glue; - end; -end; - -@ @<Declare act...@>= -procedure append_kern; -var s:quarterword; {|subtype| of the kern node} -begin s:=cur_chr; scan_dimen(s=mu_glue,false,false); -tail_append(new_kern(cur_val)); subtype(tail):=s; -end; - -@ Many of the actions related to box-making are triggered by the appearance -of braces in the input. For example, when the user says `\.{\\hbox} -\.{to} \.{100pt\{$\langle\,\hbox{\rm hlist}\,\rangle$\}}' in vertical mode, -the information about the box size (100pt, |exactly|) is put onto |save_stack| -with a level boundary word just above it, and |cur_group:=adjusted_hbox_group|; -\TeX\ enters restricted horizontal mode to process the hlist. The right -brace eventually causes |save_stack| to be restored to its former state, -at which time the information about the box size (100pt, |exactly|) is -available once again; a box is packaged and we leave restricted horizontal -mode, appending the new box to the current list of the enclosing mode -(in this case to the current list of vertical mode), followed by any -vertical adjustments that were removed from the box by |hpack|. - -The next few sections of the program are therefore concerned with the -treatment of left and right curly braces. - -@ If a left brace occurs in the middle of a page or paragraph, it simply -introduces a new level of grouping, and the matching right brace will not have -such a drastic effect. Such grouping affects neither the mode nor the -current list. - -@<Cases of |main_control| that build...@>= -non_math(left_brace): new_save_level(simple_group); -any_mode(begin_group): new_save_level(semi_simple_group); -any_mode(end_group): if cur_group=semi_simple_group then unsave - else off_save; - -@ We have to deal with errors in which braces and such things are not -properly nested. Sometimes the user makes an error of commission by -inserting an extra symbol, but sometimes the user makes an error of omission. -\TeX\ can't always tell one from the other, so it makes a guess and tries -to avoid getting into a loop. - -The |off_save| routine is called when the current group code is wrong. It tries -to insert something into the user's input that will help clean off -the top level. - -@<Declare act...@>= -procedure off_save; -var p:pointer; {inserted token} -begin if cur_group=bottom_level then - @<Drop current token and complain that it was unmatched@> -else begin back_input; p:=get_avail; link(temp_head):=p; - print_err("Missing "); - @<Prepare to insert a token that matches |cur_group|, - and print what it is@>; - print(" inserted"); ins_list(link(temp_head)); - help5("I've inserted something that you may have forgotten.")@/ - ("(See the <inserted text> above.)")@/ - ("With luck, this will get me unwedged. But if you")@/ - ("really didn't forget anything, try typing `2' now; then")@/ - ("my insertion and my current dilemma will both disappear."); - error; - end; -end; - -@ At this point, |link(temp_head)=p|, a pointer to an empty one-word node. - -@<Prepare to insert a token that matches |cur_group|...@>= -case cur_group of -semi_simple_group: begin info(p):=cs_token_flag+frozen_end_group; - print_esc("endgroup"); -@.Missing \\endgroup inserted@> - end; -math_shift_group: begin info(p):=math_shift_token+"$"; print_char("$"); -@.Missing \$ inserted@> - end; -math_left_group: begin info(p):=cs_token_flag+frozen_right; link(p):=get_avail; - p:=link(p); info(p):=other_token+"."; print_esc("right."); -@.Missing \\right\hbox{.} inserted@> -@^null delimiter@> - end; -othercases begin info(p):=right_brace_token+"}"; print_char("}"); -@.Missing \} inserted@> - end -endcases - -@ @<Drop current token and complain that it was unmatched@>= -begin print_err("Extra "); print_cmd_chr(cur_cmd,cur_chr); -@.Extra x@> -help1("Things are pretty mixed up, but I think the worst is over.");@/ -error; -end - -@ The routine for a |right_brace| character branches into many subcases, -since a variety of things may happen, depending on |cur_group|. Some -types of groups are not supposed to be ended by a right brace; error -messages are given in hopes of pinpointing the problem. Most branches -of this routine will be filled in later, when we are ready to understand -them; meanwhile, we must prepare ourselves to deal with such errors. - -@<Cases of |main_control| that build...@>= -any_mode(right_brace): handle_right_brace; - -@ @<Declare the procedure called |handle_right_brace|@>= -procedure handle_right_brace; -var p,@!q:pointer; {for short-term use} -@!d:scaled; {holds |split_max_depth| in |insert_group|} -@!f:integer; {holds |floating_penalty| in |insert_group|} -begin case cur_group of -simple_group: unsave; -bottom_level: begin print_err("Too many }'s"); -@.Too many \}'s@> - help2("You've closed more groups than you opened.")@/ - ("Such booboos are generally harmless, so keep going."); error; - end; -semi_simple_group,math_shift_group,math_left_group: extra_right_brace; -@t\4@>@<Cases of |handle_right_brace| where a |right_brace| triggers - a delayed action@>@; -othercases confusion("rightbrace") -@:this can't happen rightbrace}{\quad rightbrace@> -endcases; -end; - -@ @<Declare act...@>= -procedure extra_right_brace; -begin print_err("Extra }, or forgotten "); -@.Extra \}, or forgotten x@> -case cur_group of -semi_simple_group: print_esc("endgroup"); -math_shift_group: print_char("$"); -math_left_group: print_esc("right"); -end;@/ -help5("I've deleted a group-closing symbol because it seems to be")@/ -("spurious, as in `$x}$'. But perhaps the } is legitimate and")@/ -("you forgot something else, as in `\hbox{$x}'. In such cases")@/ -("the way to recover is to insert both the forgotten and the")@/ -("deleted material, e.g., by typing `I$}'."); error; -incr(align_state); -end; - -@ Here is where we clear the parameters that are supposed to revert to their -default values after every paragraph and when internal vertical mode is entered. - -@<Declare act...@>= -procedure normal_paragraph; -begin if looseness<>0 then eq_word_define(int_base+looseness_code,0); -if hang_indent<>0 then eq_word_define(dimen_base+hang_indent_code,0); -if hang_after<>1 then eq_word_define(int_base+hang_after_code,1); -if par_shape_ptr<>null then eq_define(par_shape_loc,shape_ref,null); -end; - -@ Now let's turn to the question of how \.{\\hbox} is treated. We actually -need to consider also a slightly larger context, since constructions like -`\.{\\setbox3=}\penalty0\.{\\hbox...}' and -`\.{\\leaders}\penalty0\.{\\hbox...}' and -`\.{\\lower3.8pt\\hbox...}' -are supposed to invoke quite -different actions after the box has been packaged. Conversely, -constructions like `\.{\\setbox3=}' can be followed by a variety of -different kinds of boxes, and we would like to encode such things in an -efficient way. - -In other words, there are two problems: to represent the context of a box, -and to represent its type. - -The first problem is solved by putting a ``context code'' on the |save_stack|, -just below the two entries that give the dimensions produced by |scan_spec|. -The context code is either a (signed) shift amount, or it is a large -integer |>=box_flag|, where |box_flag=@t$2^{30}$@>|. Codes |box_flag| through -|box_flag+255| represent `\.{\\setbox0}' through `\.{\\setbox255}'; -codes |box_flag+256| through |box_flag+511| represent `\.{\\global\\setbox0}' -through `\.{\\global\\setbox255}'; -code |box_flag+512| represents `\.{\\shipout}'; and codes |box_flag+513| -through |box_flag+515| represent `\.{\\leaders}', `\.{\\cleaders}', -and `\.{\\xleaders}'. - -The second problem is solved by giving the command code |make_box| to all -control sequences that produce a box, and by using the following |chr_code| -values to distinguish between them: |box_code|, |copy_code|, |last_box_code|, -|vsplit_code|, |vtop_code|, |vtop_code+vmode|, and |vtop_code+hmode|, where -the latter two are used to denote \.{\\vbox} and \.{\\hbox}, respectively. - -@d box_flag==@'10000000000 {context code for `\.{\\setbox0}'} -@d ship_out_flag==box_flag+512 {context code for `\.{\\shipout}'} -@d leader_flag==box_flag+513 {context code for `\.{\\leaders}'} -@d box_code=0 {|chr_code| for `\.{\\box}'} -@d copy_code=1 {|chr_code| for `\.{\\copy}'} -@d last_box_code=2 {|chr_code| for `\.{\\lastbox}'} -@d vsplit_code=3 {|chr_code| for `\.{\\vsplit}'} -@d vtop_code=4 {|chr_code| for `\.{\\vtop}'} - -@<Put each...@>= -primitive("moveleft",hmove,1); -@!@:move_left_}{\.{\\moveleft} primitive@> -primitive("moveright",hmove,0);@/ -@!@:move_right_}{\.{\\moveright} primitive@> -primitive("raise",vmove,1); -@!@:raise_}{\.{\\raise} primitive@> -primitive("lower",vmove,0); -@!@:lower_}{\.{\\lower} primitive@> -@# -primitive("box",make_box,box_code); -@!@:box_}{\.{\\box} primitive@> -primitive("copy",make_box,copy_code); -@!@:copy_}{\.{\\copy} primitive@> -primitive("lastbox",make_box,last_box_code); -@!@:last_box_}{\.{\\lastbox} primitive@> -primitive("vsplit",make_box,vsplit_code); -@!@:vsplit_}{\.{\\vsplit} primitive@> -primitive("vtop",make_box,vtop_code);@/ -@!@:vtop_}{\.{\\vtop} primitive@> -primitive("vbox",make_box,vtop_code+vmode); -@!@:vbox_}{\.{\\vbox} primitive@> -primitive("hbox",make_box,vtop_code+hmode);@/ -@!@:hbox_}{\.{\\hbox} primitive@> -primitive("shipout",leader_ship,a_leaders-1); {|ship_out_flag=leader_flag-1|} -@!@:ship_out_}{\.{\\shipout} primitive@> -primitive("leaders",leader_ship,a_leaders); -@!@:leaders_}{\.{\\leaders} primitive@> -primitive("cleaders",leader_ship,c_leaders); -@!@:c_leaders_}{\.{\\cleaders} primitive@> -primitive("xleaders",leader_ship,x_leaders); -@!@:x_leaders_}{\.{\\xleaders} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -hmove: if chr_code=1 then print_esc("moveleft")@+else print_esc("moveright"); -vmove: if chr_code=1 then print_esc("raise")@+else print_esc("lower"); -make_box: case chr_code of - box_code: print_esc("box"); - copy_code: print_esc("copy"); - last_box_code: print_esc("lastbox"); - vsplit_code: print_esc("vsplit"); - vtop_code: print_esc("vtop"); - vtop_code+vmode: print_esc("vbox"); - othercases print_esc("hbox") - endcases; -leader_ship: if chr_code=a_leaders then print_esc("leaders") - else if chr_code=c_leaders then print_esc("cleaders") - else if chr_code=x_leaders then print_esc("xleaders") - else print_esc("shipout"); - -@ Constructions that require a box are started by calling |scan_box| with -a specified context code. The |scan_box| routine verifies -that a |make_box| command comes next and then it calls |begin_box|. - -@<Cases of |main_control| that build...@>= -vmode+hmove,hmode+vmove,mmode+vmove: begin t:=cur_chr; - scan_normal_dimen; - if t=0 then scan_box(cur_val)@+else scan_box(-cur_val); - end; -any_mode(leader_ship): scan_box(leader_flag-a_leaders+cur_chr); -any_mode(make_box): begin_box(0); - -@ The global variable |cur_box| will point to a newly made box. If the box -is void, we will have |cur_box=null|. Otherwise we will have -|type(cur_box)=hlist_node| or |vlist_node| or |rule_node|; the |rule_node| -case can occur only with leaders. - -@<Glob...@>= -@!cur_box:pointer; {box to be placed into its context} - -@ The |box_end| procedure does the right thing with |cur_box|, if -|box_context| represents the context as explained above. - -@<Declare act...@>= -procedure box_end(@!box_context:integer); -var p:pointer; {|ord_noad| for new box in math mode} -begin if box_context<box_flag then @<Append box |cur_box| to the current list, - shifted by |box_context|@> -else if box_context<ship_out_flag then @<Store \(c)|cur_box| in a box register@> -else if cur_box<>null then - if box_context>ship_out_flag then @<Append a new leader node that - uses |cur_box|@> - else ship_out(cur_box); -end; - -@ The global variable |adjust_tail| will be non-null if and only if the -current box might include adjustments that should be appended to the -current vertical list. - -@<Append box |cur_box| to the current...@>= -begin if cur_box<>null then - begin shift_amount(cur_box):=box_context; - if abs(mode)=vmode then - begin append_to_vlist(cur_box); - if adjust_tail<>null then - begin if adjust_head<>adjust_tail then - begin link(tail):=link(adjust_head); tail:=adjust_tail; - end; - adjust_tail:=null; - end; - if mode>0 then build_page; - end - else begin if abs(mode)=hmode then space_factor:=1000 - else begin p:=new_noad; - math_type(nucleus(p)):=sub_box; - info(nucleus(p)):=cur_box; cur_box:=p; - end; - link(tail):=cur_box; tail:=cur_box; - end; - end; -end - -@ @<Store \(c)|cur_box| in a box register@>= -if box_context<box_flag+256 then - eq_define(box_base-box_flag+box_context,box_ref,cur_box) -else geq_define(box_base-box_flag-256+box_context,box_ref,cur_box) - -@ @<Append a new leader node ...@>= -begin @<Get the next non-blank non-relax...@>; -if ((cur_cmd=hskip)and(abs(mode)<>vmode))or@| - ((cur_cmd=vskip)and(abs(mode)=vmode)) then - begin append_glue; subtype(tail):=box_context-(leader_flag-a_leaders); - leader_ptr(tail):=cur_box; - end -else begin print_err("Leaders not followed by proper glue"); -@.Leaders not followed by...@> - help3("You should say `\leaders <box or rule><hskip or vskip>'.")@/ - ("I found the <box or rule>, but there's no suitable")@/ - ("<hskip or vskip>, so I'm ignoring these leaders."); back_error; - flush_node_list(cur_box); - end; -end - -@ Now that we can see what eventually happens to boxes, we can consider -the first steps in their creation. The |begin_box| routine is called when -|box_context| is a context specification, |cur_chr| specifies the type of -box desired, and |cur_cmd=make_box|. - -@<Declare act...@>= -procedure begin_box(@!box_context:integer); -label exit, done; -var @!p,@!q:pointer; {run through the current list} -@!m:quarterword; {the length of a replacement list} -@!k:halfword; {0 or |vmode| or |hmode|} -@!n:eight_bits; {a box number} -begin case cur_chr of -box_code: begin scan_eight_bit_int; cur_box:=box(cur_val); - box(cur_val):=null; {the box becomes void, at the same level} - end; -copy_code: begin scan_eight_bit_int; cur_box:=copy_node_list(box(cur_val)); - end; -last_box_code: @<If the current list ends with a box node, delete it from - the list and make |cur_box| point to it; otherwise set |cur_box:=null|@>; -vsplit_code: @<Split off part of a vertical box, make |cur_box| point to it@>; -othercases @<Initiate the construction of an hbox or vbox, then |return|@> -endcases;@/ -box_end(box_context); {in simple cases, we use the box immediately} -exit:end; - -@ Note that the condition |not is_char_node(tail)| implies that |head<>tail|, -since |head| is a one-word node. - -@<If the current list ends with a box node, delete it...@>= -begin cur_box:=null; -if abs(mode)=mmode then - begin you_cant; help1("Sorry; this \lastbox will be void."); error; - end -else if (mode=vmode)and(head=tail) then - begin you_cant; - help2("Sorry...I usually can't take things from the current page.")@/ - ("This \lastbox will therefore be void."); error; - end -else begin if not is_char_node(tail) then - if (type(tail)=hlist_node)or(type(tail)=vlist_node) then - @<Remove the last box, unless it's part of a discretionary@>; - end; -end - -@ @<Remove the last box...@>= -begin q:=head; -repeat p:=q; -if not is_char_node(q) then if type(q)=disc_node then - begin for m:=1 to replace_count(q) do p:=link(p); - if p=tail then goto done; - end; -q:=link(p); -until q=tail; -cur_box:=tail; shift_amount(cur_box):=0; -tail:=p; link(p):=null; -done:end - -@ Here we deal with things like `\.{\\vsplit 13 to 100pt}'. - -@<Split off part of a vertical box, make |cur_box| point to it@>= -begin scan_eight_bit_int; n:=cur_val; -if not scan_keyword("to") then -@.to@> - begin print_err("Missing `to' inserted"); -@.Missing `to' inserted@> - help2("I'm working on `\vsplit<box number> to <dimen>';")@/ - ("will look for the <dimen> next."); error; - end; -scan_normal_dimen; -cur_box:=vsplit(n,cur_val); -end - -@ Here is where we enter restricted horizontal mode or internal vertical -mode, in order to make a box. - -@<Initiate the construction of an hbox or vbox, then |return|@>= -begin k:=cur_chr-vtop_code; saved(0):=box_context; -if k=hmode then - if (box_context<box_flag)and(abs(mode)=vmode) then - scan_spec(adjusted_hbox_group,true) - else scan_spec(hbox_group,true) -else begin if k=vmode then scan_spec(vbox_group,true) - else begin scan_spec(vtop_group,true); k:=vmode; - end; - normal_paragraph; - end; -push_nest; mode:=-k; -if k=vmode then - begin prev_depth:=ignore_depth; - if every_vbox<>null then begin_token_list(every_vbox,every_vbox_text); - end -else begin space_factor:=1000; - if every_hbox<>null then begin_token_list(every_hbox,every_hbox_text); - end; -return; -end - -@ @<Declare act...@>= -procedure scan_box(@!box_context:integer); - {the next input should specify a box or perhaps a rule} -begin @<Get the next non-blank non-relax...@>; -if cur_cmd=make_box then begin_box(box_context) -else if (box_context>=leader_flag)and((cur_cmd=hrule)or(cur_cmd=vrule)) then - begin cur_box:=scan_rule_spec; box_end(box_context); - end -else begin@t@>@;@/ - print_err("A <box> was supposed to be here");@/ -@.A <box> was supposed to...@> - help3("I was expecting to see \hbox or \vbox or \copy or \box or")@/ - ("something like that. So you might find something missing in")@/ - ("your output. But keep trying; you can fix this later."); back_error; - end; -end; - -@ When the right brace occurs at the end of an \.{\\hbox} or \.{\\vbox} or -\.{\\vtop} construction, the |package| routine comes into action. We might -also have to finish a paragraph that hasn't ended. - -@<Cases of |handle...@>= -hbox_group: package(0); -adjusted_hbox_group: begin adjust_tail:=adjust_head; package(0); - end; -vbox_group: begin end_graf; package(0); - end; -vtop_group: begin end_graf; package(vtop_code); - end; - -@ @<Declare action...@>= -procedure package(@!c:small_number); -var h:scaled; {height of box} -@!p:pointer; {first node in a box} -@!d:scaled; {max depth} -begin d:=box_max_depth; unsave; save_ptr:=save_ptr-3; -if mode=-hmode then cur_box:=hpack(link(head),saved(2),saved(1)) -else begin cur_box:=vpackage(link(head),saved(2),saved(1),d); - if c=vtop_code then @<Readjust the height and depth of |cur_box|, - for \.{\\vtop}@>; - end; -pop_nest; box_end(saved(0)); -end; - -@ The height of a `\.{\\vtop}' box is inherited from the first item on its list, -if that item is an |hlist_node|, |vlist_node|, or |rule_node|; otherwise -the \.{\\vtop} height is zero. - - -@<Readjust the height...@>= -begin h:=0; p:=list_ptr(cur_box); -if p<>null then if type(p)<=rule_node then h:=height(p); -depth(cur_box):=depth(cur_box)-h+height(cur_box); height(cur_box):=h; -end - -@ A paragraph begins when horizontal-mode material occurs in vertical mode, -or when the paragraph is explicitly started by `\.{\\indent}' or -`\.{\\noindent}'. - -@<Put each...@>= -primitive("indent",start_par,1); -@!@:indent_}{\.{\\indent} primitive@> -primitive("noindent",start_par,0); -@!@:no_indent_}{\.{\\noindent} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -start_par: if chr_code=0 then print_esc("noindent")@+ else print_esc("indent"); - -@ @<Cases of |main_control| that build...@>= -vmode+start_par: new_graf(cur_chr>0); -vmode+letter,vmode+other_char,vmode+char_num,vmode+char_given, - vmode+math_shift,vmode+un_hbox,vmode+vrule, - vmode+accent,vmode+discretionary,vmode+hskip,vmode+valign, - vmode+ex_space,vmode+no_boundary:@t@>@;@/ - begin back_input; new_graf(true); - end; - -@ @<Declare act...@>= -function norm_min(@!h:integer):small_number; -begin if h<=0 then norm_min:=1@+else if h>=63 then norm_min:=63@+ -else norm_min:=h; -end; -@# -procedure new_graf(@!indented:boolean); -begin prev_graf:=0; -if (mode=vmode)or(head<>tail) then - tail_append(new_param_glue(par_skip_code)); -push_nest; mode:=hmode; space_factor:=1000; set_cur_lang; clang:=cur_lang; -prev_graf:=(norm_min(left_hyphen_min)*@'100+norm_min(right_hyphen_min)) - *@'200000+cur_lang; -if indented then - begin tail:=new_null_box; link(head):=tail; width(tail):=par_indent;@+ - end; -if every_par<>null then begin_token_list(every_par,every_par_text); -if nest_ptr=1 then build_page; {put |par_skip| glue on current page} -end; - -@ @<Cases of |main_control| that build...@>= -hmode+start_par,mmode+start_par: indent_in_hmode; - -@ @<Declare act...@>= -procedure indent_in_hmode; -var p,@!q:pointer; -begin if cur_chr>0 then {\.{\\indent}} - begin p:=new_null_box; width(p):=par_indent; - if abs(mode)=hmode then space_factor:=1000 - else begin q:=new_noad; math_type(nucleus(q)):=sub_box; - info(nucleus(q)):=p; p:=q; - end; - tail_append(p); - end; -end; - -@ A paragraph ends when a |par_end| command is sensed, or when we are in -horizontal mode when reaching the right brace of vertical-mode routines -like \.{\\vbox}, \.{\\insert}, or \.{\\output}. - -@<Cases of |main_control| that build...@>= -vmode+par_end: begin normal_paragraph; - if mode>0 then build_page; - end; -hmode+par_end: begin if align_state<0 then off_save; {this tries to - recover from an alignment that didn't end properly} - end_graf; {this takes us to the enclosing mode, if |mode>0|} - if mode=vmode then build_page; - end; -hmode+stop,hmode+vskip,hmode+hrule,hmode+un_vbox,hmode+halign: head_for_vmode; - -@ @<Declare act...@>= -procedure head_for_vmode; -begin if mode<0 then - if cur_cmd<>hrule then off_save - else begin print_err("You can't use `"); - print_esc("hrule"); print("' here except with leaders"); -@.You can't use \\hrule...@> - help2("To put a horizontal rule in an hbox or an alignment,")@/ - ("you should use \leaders or \hrulefill (see The TeXbook)."); - error; - end -else begin back_input; cur_tok:=par_token; back_input; token_type:=inserted; - end; -end; - -@ @<Declare act...@>= -procedure end_graf; -begin if mode=hmode then - begin if head=tail then pop_nest {null paragraphs are ignored} - else line_break(widow_penalty); - normal_paragraph; - error_count:=0; - end; -end; - -@ Insertion and adjustment and mark nodes are constructed by the following -pieces of the program. - -@<Cases of |main_control| that build...@>= -any_mode(insert),hmode+vadjust,mmode+vadjust: begin_insert_or_adjust; -any_mode(mark): make_mark; - -@ @<Forbidden...@>= -vmode+vadjust, - -@ @<Declare act...@>= -procedure begin_insert_or_adjust; -begin if cur_cmd=vadjust then cur_val:=255 -else begin scan_eight_bit_int; - if cur_val=255 then - begin print_err("You can't "); print_esc("insert"); print_int(255); -@.You can't \\insert255@> - help1("I'm changing to \insert0; box 255 is special."); - error; cur_val:=0; - end; - end; -saved(0):=cur_val; incr(save_ptr); -new_save_level(insert_group); scan_left_brace; normal_paragraph; -push_nest; mode:=-vmode; prev_depth:=ignore_depth; -end; - -@ @<Cases of |handle...@>= -insert_group: begin end_graf; q:=split_top_skip; add_glue_ref(q); - d:=split_max_depth; f:=floating_penalty; unsave; decr(save_ptr); - {now |saved(0)| is the insertion number, or 255 for |vadjust|} - p:=vpack(link(head),natural); pop_nest; - if saved(0)<255 then - begin tail_append(get_node(ins_node_size)); - type(tail):=ins_node; subtype(tail):=qi(saved(0)); - height(tail):=height(p)+depth(p); ins_ptr(tail):=list_ptr(p); - split_top_ptr(tail):=q; depth(tail):=d; float_cost(tail):=f; - end - else begin tail_append(get_node(small_node_size)); - type(tail):=adjust_node;@/ - subtype(tail):=0; {the |subtype| is not used} - adjust_ptr(tail):=list_ptr(p); delete_glue_ref(q); - end; - free_node(p,box_node_size); - if nest_ptr=0 then build_page; - end; -output_group: @<Resume the page builder...@>; - -@ @<Declare act...@>= -procedure make_mark; -var p:pointer; {new node} -begin p:=scan_toks(false,true); p:=get_node(small_node_size); -type(p):=mark_node; subtype(p):=0; {the |subtype| is not used} -mark_ptr(p):=def_ref; link(tail):=p; tail:=p; -end; - -@ Penalty nodes get into a list via the |break_penalty| command. -@^penalties@> - -@<Cases of |main_control| that build...@>= -any_mode(break_penalty): append_penalty; - -@ @<Declare action...@>= -procedure append_penalty; -begin scan_int; tail_append(new_penalty(cur_val)); -if mode=vmode then build_page; -end; - -@ The |remove_item| command removes a penalty, kern, or glue node if it -appears at the tail of the current list, using a brute-force linear scan. -Like \.{\\lastbox}, this command is not allowed in vertical mode (except -internal vertical mode), since the current list in vertical mode is sent -to the page builder. But if we happen to be able to implement it in -vertical mode, we do. - -@<Cases of |main_control| that build...@>= -any_mode(remove_item): delete_last; - -@ When |delete_last| is called, |cur_chr| is the |type| of node that -will be deleted, if present. - -@<Declare action...@>= -procedure delete_last; -label exit; -var @!p,@!q:pointer; {run through the current list} -@!m:quarterword; {the length of a replacement list} -begin if (mode=vmode)and(tail=head) then - @<Apologize for inability to do the operation now, - unless \.{\\unskip} follows non-glue@> -else begin if not is_char_node(tail) then if type(tail)=cur_chr then - begin q:=head; - repeat p:=q; - if not is_char_node(q) then if type(q)=disc_node then - begin for m:=1 to replace_count(q) do p:=link(p); - if p=tail then return; - end; - q:=link(p); - until q=tail; - link(p):=null; flush_node_list(tail); tail:=p; - end; - end; -exit:end; - -@ @<Apologize for inability to do the operation...@>= -begin if (cur_chr<>glue_node)or(last_glue<>max_halfword) then - begin you_cant; - help2("Sorry...I usually can't take things from the current page.")@/ - ("Try `I\vskip-\lastskip' instead."); - if cur_chr=kern_node then help_line[0]:= - ("Try `I\kern-\lastkern' instead.") - else if cur_chr<>glue_node then help_line[0]:=@| - ("Perhaps you can make the output routine do it."); - error; - end; -end - -@ @<Put each...@>= -primitive("unpenalty",remove_item,penalty_node);@/ -@!@:un_penalty_}{\.{\\unpenalty} primitive@> -primitive("unkern",remove_item,kern_node);@/ -@!@:un_kern_}{\.{\\unkern} primitive@> -primitive("unskip",remove_item,glue_node);@/ -@!@:un_skip_}{\.{\\unskip} primitive@> -primitive("unhbox",un_hbox,box_code);@/ -@!@:un_hbox_}{\.{\\unhbox} primitive@> -primitive("unhcopy",un_hbox,copy_code);@/ -@!@:un_hcopy_}{\.{\\unhcopy} primitive@> -primitive("unvbox",un_vbox,box_code);@/ -@!@:un_vbox_}{\.{\\unvbox} primitive@> -primitive("unvcopy",un_vbox,copy_code);@/ -@!@:un_vcopy_}{\.{\\unvcopy} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -remove_item: if chr_code=glue_node then print_esc("unskip") - else if chr_code=kern_node then print_esc("unkern") - else print_esc("unpenalty"); -un_hbox: if chr_code=copy_code then print_esc("unhcopy") - else print_esc("unhbox"); -un_vbox: if chr_code=copy_code then print_esc("unvcopy") - else print_esc("unvbox"); - -@ The |un_hbox| and |un_vbox| commands unwrap one of the 256 current boxes. - -@<Cases of |main_control| that build...@>= -vmode+un_vbox,hmode+un_hbox,mmode+un_hbox: unpackage; - -@ @<Declare act...@>= -procedure unpackage; -label exit; -var p:pointer; {the box} -@!c:box_code..copy_code; {should we copy?} -begin c:=cur_chr; scan_eight_bit_int; p:=box(cur_val); -if p=null then return; -if (abs(mode)=mmode)or((abs(mode)=vmode)and(type(p)<>vlist_node))or@| - ((abs(mode)=hmode)and(type(p)<>hlist_node)) then - begin print_err("Incompatible list can't be unboxed"); -@.Incompatible list...@> - help3("Sorry, Pandora. (You sneaky devil.)")@/ - ("I refuse to unbox an \hbox in vertical mode or vice versa.")@/ - ("And I can't open any boxes in math mode.");@/ - error; return; - end; -if c=copy_code then link(tail):=copy_node_list(list_ptr(p)) -else begin link(tail):=list_ptr(p); box(cur_val):=null; - free_node(p,box_node_size); - end; -while link(tail)<>null do tail:=link(tail); -exit:end; - -@ @<Forbidden...@>=vmode+ital_corr, - -@ Italic corrections are converted to kern nodes when the |ital_corr| command -follows a character. In math mode the same effect is achieved by appending -a kern of zero here, since italic corrections are supplied later. - -@<Cases of |main_control| that build...@>= -hmode+ital_corr: append_italic_correction; -mmode+ital_corr: tail_append(new_kern(0)); - -@ @<Declare act...@>= -procedure append_italic_correction; -label exit; -var p:pointer; {|char_node| at the tail of the current list} -@!f:internal_font_number; {the font in the |char_node|} -begin if tail<>head then - begin if is_char_node(tail) then p:=tail - else if type(tail)=ligature_node then p:=lig_char(tail) - else return; - f:=font(p); - tail_append(new_kern(char_italic(f)(char_info(f)(character(p))))); - subtype(tail):=explicit; - end; -exit:end; - -@ Discretionary nodes are easy in the common case `\.{\\-}', but in the -general case we must process three braces full of items. - -@<Put each...@>= -primitive("-",discretionary,1); -@!@:Single-character primitives -}{\quad\.{\\-}@> -primitive("discretionary",discretionary,0); -@!@:discretionary_}{\.{\\discretionary} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -discretionary: if chr_code=1 then - print_esc("-")@+else print_esc("discretionary"); - -@ @<Cases of |main_control| that build...@>= -hmode+discretionary,mmode+discretionary: append_discretionary; - -@ The space factor does not change when we append a discretionary node, -but it starts out as 1000 in the subsidiary lists. - -@<Declare act...@>= -procedure append_discretionary; -var c:integer; {hyphen character} -begin tail_append(new_disc); -if cur_chr=1 then - begin c:=hyphen_char[cur_font]; - if c>=0 then if c<256 then pre_break(tail):=new_character(cur_font,c); - end -else begin incr(save_ptr); saved(-1):=0; new_save_level(disc_group); - scan_left_brace; push_nest; mode:=-hmode; space_factor:=1000; - end; -end; - -@ The three discretionary lists are constructed somewhat as if they were -hboxes. A~subroutine called |build_discretionary| handles the transitions. -(This is sort of fun.) - -@<Cases of |handle...@>= -disc_group: build_discretionary; - -@ @<Declare act...@>= -procedure build_discretionary; -label done,exit; -var p,@!q:pointer; {for link manipulation} -@!n:integer; {length of discretionary list} -begin unsave; -@<Prune the current list, if necessary, until it contains only - |char_node|, |kern_node|, |hlist_node|, |vlist_node|, |rule_node|, - and |ligature_node| items; set |n| to the length of the list, - and set |q| to the list's tail@>; -p:=link(head); pop_nest; -case saved(-1) of -0:pre_break(tail):=p; -1:post_break(tail):=p; -2:@<Attach list |p| to the current list, and record its length; - then finish up and |return|@>; -end; {there are no other cases} -incr(saved(-1)); new_save_level(disc_group); scan_left_brace; -push_nest; mode:=-hmode; space_factor:=1000; -exit:end; - -@ @<Attach list |p| to the current...@>= -begin if (n>0)and(abs(mode)=mmode) then - begin print_err("Illegal math "); print_esc("discretionary"); -@.Illegal math \\disc...@> - help2("Sorry: The third part of a discretionary break must be")@/ - ("empty, in math formulas. I had to delete your third part."); - flush_node_list(p); n:=0; error; - end -else link(tail):=p; -if n<=max_quarterword then replace_count(tail):=n -else begin print_err("Discretionary list is too long"); -@.Discretionary list is too long@> - help2("Wow---I never thought anybody would tweak me here.")@/ - ("You can't seriously need such a huge discretionary list?"); - error; - end; -if n>0 then tail:=q; -decr(save_ptr); return; -end - -@ During this loop, |p=link(q)| and there are |n| items preceding |p|. - -@<Prune the current list, if necessary...@>= -q:=head; p:=link(q); n:=0; -while p<>null do - begin if not is_char_node(p) then if type(p)>rule_node then - if type(p)<>kern_node then if type(p)<>ligature_node then - begin print_err("Improper discretionary list"); -@.Improper discretionary list@> - help1("Discretionary lists must contain only boxes and kerns.");@/ - error; - begin_diagnostic; - print_nl("The following discretionary sublist has been deleted:"); -@.The following...deleted@> - show_box(p); - end_diagnostic(true); - flush_node_list(p); link(q):=null; goto done; - end; - q:=p; p:=link(q); incr(n); - end; -done: - -@ We need only one more thing to complete the horizontal mode routines, namely -the \.{\\accent} primitive. - -@<Cases of |main_control| that build...@>= -hmode+accent: make_accent; - -@ The positioning of accents is straightforward but tedious. Given an accent -of width |a|, designed for characters of height |x| and slant |s|; -and given a character of width |w|, height |h|, and slant |t|: We will shift -the accent down by |x-h|, and we will insert kern nodes that have the effect of -centering the accent over the character and shifting the accent to the -right by $\delta={1\over2}(w-a)+h\cdot t-x\cdot s$. If either character is -absent from the font, we will simply use the other, without shifting. - -@<Declare act...@>= -procedure make_accent; -var s,@!t: real; {amount of slant} -@!p,@!q,@!r:pointer; {character, box, and kern nodes} -@!f:internal_font_number; {relevant font} -@!a,@!h,@!x,@!w,@!delta:scaled; {heights and widths, as explained above} -@!i:four_quarters; {character information} -begin scan_char_num; f:=cur_font; p:=new_character(f,cur_val); -if p<>null then - begin x:=x_height(f); s:=slant(f)/float_constant(65536); -@^real division@> - a:=char_width(f)(char_info(f)(character(p)));@/ - do_assignments;@/ - @<Create a character node |q| for the next character, - but set |q:=null| if problems arise@>; - if q<>null then @<Append the accent with appropriate kerns, - then set |p:=q|@>; - link(tail):=p; tail:=p; space_factor:=1000; - end; -end; - -@ @<Create a character node |q| for the next...@>= -q:=null; f:=cur_font; -if (cur_cmd=letter)or(cur_cmd=other_char)or(cur_cmd=char_given) then - q:=new_character(f,cur_chr) -else if cur_cmd=char_num then - begin scan_char_num; q:=new_character(f,cur_val); - end -else back_input - -@ The kern nodes appended here must be distinguished from other kerns, lest -they be wiped away by the hyphenation algorithm or by a previous line break. - -The two kerns are computed with (machine-dependent) |real| arithmetic, but -their sum is machine-independent; the net effect is machine-independent, -because the user cannot remove these nodes nor access them via \.{\\lastkern}. - -@<Append the accent with appropriate kerns...@>= -begin t:=slant(f)/float_constant(65536); -@^real division@> -i:=char_info(f)(character(q)); -w:=char_width(f)(i); h:=char_height(f)(height_depth(i)); -if h<>x then {the accent must be shifted up or down} - begin p:=hpack(p,natural); shift_amount(p):=x-h; - end; -delta:=round((w-a)/float_constant(2)+h*t-x*s); -@^real multiplication@> -@^real addition@> -r:=new_kern(delta); subtype(r):=acc_kern; link(tail):=r; link(r):=p; -tail:=new_kern(-a-delta); subtype(tail):=acc_kern; link(p):=tail; p:=q; -end - -@ When `\.{\\cr}' or `\.{\\span}' or a tab mark comes through the scanner -into |main_control|, it might be that the user has foolishly inserted -one of them into something that has nothing to do with alignment. But it is -far more likely that a left brace or right brace has been omitted, since -|get_next| takes actions appropriate to alignment only when `\.{\\cr}' -or `\.{\\span}' or tab marks occur with |align_state=0|. The following -program attempts to make an appropriate recovery. - -@<Cases of |main_control| that build...@>= -any_mode(car_ret), any_mode(tab_mark): align_error; -any_mode(no_align): no_align_error; -any_mode(omit): omit_error; - -@ @<Declare act...@>= -procedure align_error; -begin if abs(align_state)>2 then - @<Express consternation over the fact that no alignment is in progress@> -else begin back_input; - if align_state<0 then - begin print_err("Missing { inserted"); -@.Missing \{ inserted@> - incr(align_state); cur_tok:=left_brace_token+"{"; - end - else begin print_err("Missing } inserted"); -@.Missing \} inserted@> - decr(align_state); cur_tok:=right_brace_token+"}"; - end; - help3("I've put in what seems to be necessary to fix")@/ - ("the current column of the current alignment.")@/ - ("Try to go on, since this might almost work."); ins_error; - end; -end; - -@ @<Express consternation...@>= -begin print_err("Misplaced "); print_cmd_chr(cur_cmd,cur_chr); -@.Misplaced \&@> -@.Misplaced \\span@> -@.Misplaced \\cr@> -if cur_tok=tab_token+"&" then - begin help6("I can't figure out why you would want to use a tab mark")@/ - ("here. If you just want an ampersand, the remedy is")@/ - ("simple: Just type `I\&' now. But if some right brace")@/ - ("up above has ended a previous alignment prematurely,")@/ - ("you're probably due for more error messages, and you")@/ - ("might try typing `S' now just to see what is salvageable."); - end -else begin help5("I can't figure out why you would want to use a tab mark")@/ - ("or \cr or \span just now. If something like a right brace")@/ - ("up above has ended a previous alignment prematurely,")@/ - ("you're probably due for more error messages, and you")@/ - ("might try typing `S' now just to see what is salvageable."); - end; -error; -end - -@ The help messages here contain a little white lie, since \.{\\noalign} -and \.{\\omit} are allowed also after `\.{\\noalign\{...\}}'. - -@<Declare act...@>= -procedure no_align_error; -begin print_err("Misplaced "); print_esc("noalign"); -@.Misplaced \\noalign@> -help2("I expect to see \noalign only after the \cr of")@/ - ("an alignment. Proceed, and I'll ignore this case."); error; -end; -procedure omit_error; -begin print_err("Misplaced "); print_esc("omit"); -@.Misplaced \\omit@> -help2("I expect to see \omit only after tab marks or the \cr of")@/ - ("an alignment. Proceed, and I'll ignore this case."); error; -end; - -@ We've now covered most of the abuses of \.{\\halign} and \.{\\valign}. -Let's take a look at what happens when they are used correctly. - -@<Cases of |main_control| that build...@>= -vmode+halign,hmode+valign:init_align; -mmode+halign: if privileged then - if cur_group=math_shift_group then init_align - else off_save; -vmode+endv,hmode+endv: do_endv; - -@ An |align_group| code is supposed to remain on the |save_stack| -during an entire alignment, until |fin_align| removes it. - -A devious user might force an |endv| command to occur just about anywhere; -we must defeat such hacks. - -@<Declare act...@>= -procedure do_endv; -begin base_ptr:=input_ptr; input_stack[base_ptr]:=cur_input; -while (input_stack[base_ptr].index_field<>v_template) and - (input_stack[base_ptr].loc_field=null) and - (input_stack[base_ptr].state_field=token_list) do decr(base_ptr); -if (input_stack[base_ptr].index_field<>v_template) or - (input_stack[base_ptr].loc_field<>null) or - (input_stack[base_ptr].state_field<>token_list) then - fatal_error("(interwoven alignment preambles are not allowed)"); -@.interwoven alignment preambles...@> - if cur_group=align_group then - begin end_graf; - if fin_col then fin_row; - end -else off_save; -end; - -@ @<Cases of |handle_right_brace|...@>= -align_group: begin back_input; cur_tok:=cs_token_flag+frozen_cr; - print_err("Missing "); print_esc("cr"); print(" inserted"); -@.Missing \\cr inserted@> - help1("I'm guessing that you meant to end an alignment here."); - ins_error; - end; - -@ @<Cases of |handle_right_brace|...@>= -no_align_group: begin end_graf; unsave; align_peek; - end; - -@ Finally, \.{\\endcsname} is not supposed to get through to |main_control|. - -@<Cases of |main_control| that build...@>= -any_mode(end_cs_name): cs_error; - -@ @<Declare act...@>= -procedure cs_error; -begin print_err("Extra "); print_esc("endcsname"); -@.Extra \\endcsname@> -help1("I'm ignoring this, since I wasn't doing a \csname."); -error; -end; - -@* \[48] Building math lists. -The routines that \TeX\ uses to create mlists are similar to those we have -just seen for the generation of hlists and vlists. But it is necessary to -make ``noads'' as well as nodes, so the reader should review the -discussion of math mode data structures before trying to make sense out of -the following program. - -Here is a little routine that needs to be done whenever a subformula -is about to be processed. The parameter is a code like |math_group|. - -@<Declare act...@>= -procedure push_math(@!c:group_code); -begin push_nest; mode:=-mmode; incompleat_noad:=null; new_save_level(c); -end; - -@ We get into math mode from horizontal mode when a `\.\$' (i.e., a -|math_shift| character) is scanned. We must check to see whether this -`\.\$' is immediately followed by another, in case display math mode is -called for. - -@<Cases of |main_control| that build...@>= -hmode+math_shift:init_math; - -@ @<Declare act...@>= -procedure init_math; -label reswitch,found,not_found,done; -var w:scaled; {new or partial |pre_display_size|} -@!l:scaled; {new |display_width|} -@!s:scaled; {new |display_indent|} -@!p:pointer; {current node when calculating |pre_display_size|} -@!q:pointer; {glue specification when calculating |pre_display_size|} -@!f:internal_font_number; {font in current |char_node|} -@!n:integer; {scope of paragraph shape specification} -@!v:scaled; {|w| plus possible glue amount} -@!d:scaled; {increment to |v|} -begin get_token; {|get_x_token| would fail on \.{\\ifmmode}\thinspace!} -if (cur_cmd=math_shift)and(mode>0) then @<Go into display math mode@> -else begin back_input; @<Go into ordinary math mode@>; - end; -end; - -@ @<Go into ordinary math mode@>= -begin push_math(math_shift_group); eq_word_define(int_base+cur_fam_code,-1); -if every_math<>null then begin_token_list(every_math,every_math_text); -end - -@ We get into ordinary math mode from display math mode when `\.{\\eqno}' or -`\.{\\leqno}' appears. In such cases |cur_chr| will be 0 or~1, respectively; -the value of |cur_chr| is placed onto |save_stack| for safe keeping. - -@<Cases of |main_control| that build...@>= -mmode+eq_no: if privileged then - if cur_group=math_shift_group then start_eq_no - else off_save; - -@ @<Put each...@>= -primitive("eqno",eq_no,0); -@!@:eq_no_}{\.{\\eqno} primitive@> -primitive("leqno",eq_no,1); -@!@:leq_no_}{\.{\\leqno} primitive@> - -@ When \TeX\ is in display math mode, |cur_group=math_shift_group|, -so it is not necessary for the |start_eq_no| procedure to test for -this condition. - -@<Declare act...@>= -procedure start_eq_no; -begin saved(0):=cur_chr; incr(save_ptr); -@<Go into ordinary math mode@>; -end; - -@ @<Cases of |print_cmd_chr|...@>= -eq_no:if chr_code=1 then print_esc("leqno")@+else print_esc("eqno"); - -@ @<Forbidden...@>=non_math(eq_no), - -@ When we enter display math mode, we need to call |line_break| to -process the partial paragraph that has just been interrupted by the -display. Then we can set the proper values of |display_width| and -|display_indent| and |pre_display_size|. - -@<Go into display math mode@>= -begin if head=tail then {`\.{\\noindent\$\$}' or `\.{\$\${ }\$\$}'} - begin pop_nest; w:=-max_dimen; - end -else begin line_break(display_widow_penalty);@/ - @<Calculate the natural width, |w|, by which the characters of the - final line extend to the right of the reference point, - plus two ems; or set |w:=max_dimen| if the non-blank information - on that line is affected by stretching or shrinking@>; - end; -{now we are in vertical mode, working on the list that will contain the display} -@<Calculate the length, |l|, and the shift amount, |s|, of the display lines@>; -push_math(math_shift_group); mode:=mmode; -eq_word_define(int_base+cur_fam_code,-1);@/ -eq_word_define(dimen_base+pre_display_size_code,w); -eq_word_define(dimen_base+display_width_code,l); -eq_word_define(dimen_base+display_indent_code,s); -if every_display<>null then begin_token_list(every_display,every_display_text); -if nest_ptr=1 then build_page; -end - -@ @<Calculate the natural width, |w|, by which...@>= -v:=shift_amount(just_box)+2*quad(cur_font); w:=-max_dimen; -p:=list_ptr(just_box); -while p<>null do - begin @<Let |d| be the natural width of node |p|; - if the node is ``visible,'' |goto found|; - if the node is glue that stretches or shrinks, set |v:=max_dimen|@>; - if v<max_dimen then v:=v+d; - goto not_found; - found: if v<max_dimen then - begin v:=v+d; w:=v; - end - else begin w:=max_dimen; goto done; - end; - not_found: p:=link(p); - end; -done: - -@ @<Let |d| be the natural width of node |p|...@>= -reswitch: if is_char_node(p) then - begin f:=font(p); d:=char_width(f)(char_info(f)(character(p))); - goto found; - end; -case type(p) of -hlist_node,vlist_node,rule_node: begin d:=width(p); goto found; - end; -ligature_node:@<Make node |p| look like a |char_node|...@>; -kern_node,math_node: d:=width(p); -glue_node:@<Let |d| be the natural width of this glue; if stretching - or shrinking, set |v:=max_dimen|; |goto found| in the case of leaders@>; -whatsit_node: @<Let |d| be the width of the whatsit |p|@>; -othercases d:=0 -endcases - -@ We need to be careful that |w|, |v|, and |d| do not depend on any |glue_set| -values, since such values are subject to system-dependent rounding. -System-dependent numbers are not allowed to infiltrate parameters like -|pre_display_size|, since \TeX82 is supposed to make the same decisions on all -machines. - -@<Let |d| be the natural width of this glue...@>= -begin q:=glue_ptr(p); d:=width(q); -if glue_sign(just_box)=stretching then - begin if (glue_order(just_box)=stretch_order(q))and@| - (stretch(q)<>0) then - v:=max_dimen; - end -else if glue_sign(just_box)=shrinking then - begin if (glue_order(just_box)=shrink_order(q))and@| - (shrink(q)<>0) then - v:=max_dimen; - end; -if subtype(p)>=a_leaders then goto found; -end - -@ A displayed equation is considered to be three lines long, so we -calculate the length and offset of line number |prev_graf+2|. - -@<Calculate the length, |l|, ...@>= -if par_shape_ptr=null then - if (hang_indent<>0)and@| - (((hang_after>=0)and(prev_graf+2>hang_after))or@| - (prev_graf+1<-hang_after)) then - begin l:=hsize-abs(hang_indent); - if hang_indent>0 then s:=hang_indent@+else s:=0; - end - else begin l:=hsize; s:=0; - end -else begin n:=info(par_shape_ptr); - if prev_graf+2>=n then p:=par_shape_ptr+2*n - else p:=par_shape_ptr+2*(prev_graf+2); - s:=mem[p-1].sc; l:=mem[p].sc; - end - -@ Subformulas of math formulas cause a new level of math mode to be entered, -on the semantic nest as well as the save stack. These subformulas arise in -several ways: (1)~A left brace by itself indicates the beginning of a -subformula that will be put into a box, thereby freezing its glue and -preventing line breaks. (2)~A subscript or superscript is treated as a -subformula if it is not a single character; the same applies to -the nucleus of things like \.{\\underline}. (3)~The \.{\\left} primitive -initiates a subformula that will be terminated by a matching \.{\\right}. -The group codes placed on |save_stack| in these three cases are -|math_group|, |math_group|, and |math_left_group|, respectively. - -Here is the code that handles case (1); the other cases are not quite as -trivial, so we shall consider them later. - -@<Cases of |main_control| that build...@>= -mmode+left_brace: begin tail_append(new_noad); - back_input; scan_math(nucleus(tail)); - end; - -@ Recall that the |nucleus|, |subscr|, and |supscr| fields in a noad are -broken down into subfields called |math_type| and either |info| or -|(fam,character)|. The job of |scan_math| is to figure out what to place -in one of these principal fields; it looks at the subformula that -comes next in the input, and places an encoding of that subformula -into a given word of |mem|. - -@d fam_in_range==((cur_fam>=0)and(cur_fam<16)) - -@<Declare act...@>= -procedure scan_math(@!p:pointer); -label restart,reswitch,exit; -var c:integer; {math character code} -begin restart:@<Get the next non-blank non-relax...@>; -reswitch:case cur_cmd of -letter,other_char,char_given: begin c:=ho(math_code(cur_chr)); - if c=@'100000 then - begin @<Treat |cur_chr| as an active character@>; - goto restart; - end; - end; -char_num: begin scan_char_num; cur_chr:=cur_val; cur_cmd:=char_given; - goto reswitch; - end; -math_char_num: begin scan_fifteen_bit_int; c:=cur_val; - end; -math_given: c:=cur_chr; -delim_num: begin scan_twenty_seven_bit_int; c:=cur_val div @'10000; - end; -othercases @<Scan a subformula enclosed in braces and |return|@> -endcases;@/ -math_type(p):=math_char; character(p):=qi(c mod 256); -if (c>=var_code)and fam_in_range then fam(p):=cur_fam -else fam(p):=(c div 256) mod 16; -exit:end; - -@ An active character that is an |outer_call| is allowed here. - -@<Treat |cur_chr|...@>= -begin cur_cs:=cur_chr+active_base; -cur_cmd:=eq_type(cur_cs); cur_chr:=equiv(cur_cs); -x_token; back_input; -end - -@ The pointer |p| is placed on |save_stack| while a complex subformula -is being scanned. - -@<Scan a subformula...@>= -begin back_input; scan_left_brace;@/ -saved(0):=p; incr(save_ptr); push_math(math_group); return; -end - -@ The simplest math formula is, of course, `\.{\${ }\$}', when no noads are -generated. The next simplest cases involve a single character, e.g., -`\.{\$x\$}'. Even though such cases may not seem to be very interesting, -the reader can perhaps understand how happy the author was when `\.{\$x\$}' -was first properly typeset by \TeX. The code in this section was used. -@^Knuth, Donald Ervin@> - -@<Cases of |main_control| that build...@>= -mmode+letter,mmode+other_char,mmode+char_given: - set_math_char(ho(math_code(cur_chr))); -mmode+char_num: begin scan_char_num; cur_chr:=cur_val; - set_math_char(ho(math_code(cur_chr))); - end; -mmode+math_char_num: begin scan_fifteen_bit_int; set_math_char(cur_val); - end; -mmode+math_given: set_math_char(cur_chr); -mmode+delim_num: begin scan_twenty_seven_bit_int; - set_math_char(cur_val div @'10000); - end; - -@ The |set_math_char| procedure creates a new noad appropriate to a given -math code, and appends it to the current mlist. However, if the math code -is sufficiently large, the |cur_chr| is treated as an active character and -nothing is appended. - -@<Declare act...@>= -procedure set_math_char(@!c:integer); -var p:pointer; {the new noad} -begin if c>=@'100000 then - @<Treat |cur_chr|...@> -else begin p:=new_noad; math_type(nucleus(p)):=math_char; - character(nucleus(p)):=qi(c mod 256); - fam(nucleus(p)):=(c div 256) mod 16; - if c>=var_code then - begin if fam_in_range then fam(nucleus(p)):=cur_fam; - type(p):=ord_noad; - end - else type(p):=ord_noad+(c div @'10000); - link(tail):=p; tail:=p; - end; -end; - -@ Primitive math operators like \.{\\mathop} and \.{\\underline} are given -the command code |math_comp|, supplemented by the noad type that they -generate. - -@<Put each...@>= -primitive("mathord",math_comp,ord_noad); -@!@:math_ord_}{\.{\\mathord} primitive@> -primitive("mathop",math_comp,op_noad); -@!@:math_op_}{\.{\\mathop} primitive@> -primitive("mathbin",math_comp,bin_noad); -@!@:math_bin_}{\.{\\mathbin} primitive@> -primitive("mathrel",math_comp,rel_noad); -@!@:math_rel_}{\.{\\mathrel} primitive@> -primitive("mathopen",math_comp,open_noad); -@!@:math_open_}{\.{\\mathopen} primitive@> -primitive("mathclose",math_comp,close_noad); -@!@:math_close_}{\.{\\mathclose} primitive@> -primitive("mathpunct",math_comp,punct_noad); -@!@:math_punct_}{\.{\\mathpunct} primitive@> -primitive("mathinner",math_comp,inner_noad); -@!@:math_inner_}{\.{\\mathinner} primitive@> -primitive("underline",math_comp,under_noad); -@!@:underline_}{\.{\\underline} primitive@> -primitive("overline",math_comp,over_noad);@/ -@!@:overline_}{\.{\\overline} primitive@> -primitive("displaylimits",limit_switch,normal); -@!@:display_limits_}{\.{\\displaylimits} primitive@> -primitive("limits",limit_switch,limits); -@!@:limits_}{\.{\\limits} primitive@> -primitive("nolimits",limit_switch,no_limits); -@!@:no_limits_}{\.{\\nolimits} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -math_comp: case chr_code of - ord_noad: print_esc("mathord"); - op_noad: print_esc("mathop"); - bin_noad: print_esc("mathbin"); - rel_noad: print_esc("mathrel"); - open_noad: print_esc("mathopen"); - close_noad: print_esc("mathclose"); - punct_noad: print_esc("mathpunct"); - inner_noad: print_esc("mathinner"); - under_noad: print_esc("underline"); - othercases print_esc("overline") - endcases; -limit_switch: if chr_code=limits then print_esc("limits") - else if chr_code=no_limits then print_esc("nolimits") - else print_esc("displaylimits"); - -@ @<Cases of |main_control| that build...@>= -mmode+math_comp: begin tail_append(new_noad); - type(tail):=cur_chr; scan_math(nucleus(tail)); - end; -mmode+limit_switch: math_limit_switch; - -@ @<Declare act...@>= -procedure math_limit_switch; -label exit; -begin if head<>tail then if type(tail)=op_noad then - begin subtype(tail):=cur_chr; return; - end; -print_err("Limit controls must follow a math operator"); -@.Limit controls must follow...@> -help1("I'm ignoring this misplaced \limits or \nolimits command."); error; -exit:end; - -@ Delimiter fields of noads are filled in by the |scan_delimiter| routine. -The first parameter of this procedure is the |mem| address where the -delimiter is to be placed; the second tells if this delimiter follows -\.{\\radical} or not. - -@<Declare act...@>= -procedure scan_delimiter(@!p:pointer;@!r:boolean); -begin if r then scan_twenty_seven_bit_int -else begin @<Get the next non-blank non-relax...@>; - case cur_cmd of - letter,other_char: cur_val:=del_code(cur_chr); - delim_num: scan_twenty_seven_bit_int; - othercases cur_val:=-1 - endcases; - end; -if cur_val<0 then @<Report that an invalid delimiter code is being changed - to null; set~|cur_val:=0|@>; -small_fam(p):=(cur_val div @'4000000) mod 16; -small_char(p):=qi((cur_val div @'10000) mod 256); -large_fam(p):=(cur_val div 256) mod 16; -large_char(p):=qi(cur_val mod 256); -end; - -@ @<Report that an invalid delimiter...@>= -begin print_err("Missing delimiter (. inserted)"); -@.Missing delimiter...@> -help6("I was expecting to see something like `(' or `\{' or")@/ - ("`\}' here. If you typed, e.g., `{' instead of `\{', you")@/ - ("should probably delete the `{' by typing `1' now, so that")@/ - ("braces don't get unbalanced. Otherwise just proceed.")@/ - ("Acceptable delimiters are characters whose \delcode is")@/ - ("nonnegative, or you can use `\delimiter <delimiter code>'."); -back_error; cur_val:=0; -end - -@ @<Cases of |main_control| that build...@>= -mmode+radical:math_radical; - -@ @<Declare act...@>= -procedure math_radical; -begin tail_append(get_node(radical_noad_size)); -type(tail):=radical_noad; subtype(tail):=normal; -mem[nucleus(tail)].hh:=empty_field; -mem[subscr(tail)].hh:=empty_field; -mem[supscr(tail)].hh:=empty_field; -scan_delimiter(left_delimiter(tail),true); scan_math(nucleus(tail)); -end; - -@ @<Cases of |main_control| that build...@>= -mmode+accent,mmode+math_accent:math_ac; - -@ @<Declare act...@>= -procedure math_ac; -begin if cur_cmd=accent then - @<Complain that the user should have said \.{\\mathaccent}@>; -tail_append(get_node(accent_noad_size)); -type(tail):=accent_noad; subtype(tail):=normal; -mem[nucleus(tail)].hh:=empty_field; -mem[subscr(tail)].hh:=empty_field; -mem[supscr(tail)].hh:=empty_field; -math_type(accent_chr(tail)):=math_char; -scan_fifteen_bit_int; -character(accent_chr(tail)):=qi(cur_val mod 256); -if (cur_val>=var_code)and fam_in_range then fam(accent_chr(tail)):=cur_fam -else fam(accent_chr(tail)):=(cur_val div 256) mod 16; -scan_math(nucleus(tail)); -end; - -@ @<Complain that the user should have said \.{\\mathaccent}@>= -begin print_err("Please use "); print_esc("mathaccent"); -print(" for accents in math mode"); -@.Please use \\mathaccent...@> -help2("I'm changing \accent to \mathaccent here; wish me luck.")@/ - ("(Accents are not the same in formulas as they are in text.)"); -error; -end - -@ @<Cases of |main_control| that build...@>= -mmode+vcenter: begin scan_spec(vcenter_group,false); normal_paragraph; - push_nest; mode:=-vmode; prev_depth:=ignore_depth; - if every_vbox<>null then begin_token_list(every_vbox,every_vbox_text); - end; - -@ @<Cases of |handle...@>= -vcenter_group: begin end_graf; unsave; save_ptr:=save_ptr-2; - p:=vpack(link(head),saved(1),saved(0)); pop_nest; - tail_append(new_noad); type(tail):=vcenter_noad; - math_type(nucleus(tail)):=sub_box; info(nucleus(tail)):=p; - end; - -@ The routine that inserts a |style_node| holds no surprises. - -@<Put each...@>= -primitive("displaystyle",math_style,display_style); -@!@:display_style_}{\.{\\displaystyle} primitive@> -primitive("textstyle",math_style,text_style); -@!@:text_style_}{\.{\\textstyle} primitive@> -primitive("scriptstyle",math_style,script_style); -@!@:script_style_}{\.{\\scriptstyle} primitive@> -primitive("scriptscriptstyle",math_style,script_script_style); -@!@:script_script_style_}{\.{\\scriptscriptstyle} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -math_style: print_style(chr_code); - -@ @<Cases of |main_control| that build...@>= -mmode+math_style: tail_append(new_style(cur_chr)); -mmode+non_script: begin tail_append(new_glue(zero_glue)); - subtype(tail):=cond_math_glue; - end; -mmode+math_choice: append_choices; - -@ The routine that scans the four mlists of a \.{\\mathchoice} is very -much like the routine that builds discretionary nodes. - -@<Declare act...@>= -procedure append_choices; -begin tail_append(new_choice); incr(save_ptr); saved(-1):=0; -push_math(math_choice_group); scan_left_brace; -end; - -@ @<Cases of |handle_right_brace|...@>= -math_choice_group: build_choices; - -@ @<Declare act...@>= -@t\4@>@<Declare the function called |fin_mlist|@>@t@>@;@/ -procedure build_choices; -label exit; -var p:pointer; {the current mlist} -begin unsave; p:=fin_mlist(null); -case saved(-1) of -0:display_mlist(tail):=p; -1:text_mlist(tail):=p; -2:script_mlist(tail):=p; -3:begin script_script_mlist(tail):=p; decr(save_ptr); return; - end; -end; {there are no other cases} -incr(saved(-1)); push_math(math_choice_group); scan_left_brace; -exit:end; - -@ Subscripts and superscripts are attached to the previous nucleus by the -@^superscripts@>@^subscripts@> -action procedure called |sub_sup|. We use the facts that |sub_mark=sup_mark+1| -and |subscr(p)=supscr(p)+1|. - -@<Cases of |main_control| that build...@>= -mmode+sub_mark,mmode+sup_mark: sub_sup; - -@ @<Declare act...@>= -procedure sub_sup; -var t:small_number; {type of previous sub/superscript} -@!p:pointer; {field to be filled by |scan_math|} -begin t:=empty; p:=null; -if tail<>head then if scripts_allowed(tail) then - begin p:=supscr(tail)+cur_cmd-sup_mark; {|supscr| or |subscr|} - t:=math_type(p); - end; -if (p=null)or(t<>empty) then @<Insert a dummy noad to be sub/superscripted@>; -scan_math(p); -end; - -@ @<Insert a dummy...@>= -begin tail_append(new_noad); -p:=supscr(tail)+cur_cmd-sup_mark; {|supscr| or |subscr|} -if t<>empty then - begin if cur_cmd=sup_mark then - begin print_err("Double superscript"); -@.Double superscript@> - help1("I treat `x^1^2' essentially like `x^1{}^2'."); - end - else begin print_err("Double subscript"); -@.Double subscript@> - help1("I treat `x_1_2' essentially like `x_1{}_2'."); - end; - error; - end; -end - -@ An operation like `\.{\\over}' causes the current mlist to go into a -state of suspended animation: |incompleat_noad| points to a |fraction_noad| -that contains the mlist-so-far as its numerator, while the denominator -is yet to come. Finally when the mlist is finished, the denominator will -go into the incompleat fraction noad, and that noad will become the -whole formula, unless it is surrounded by `\.{\\left}' and `\.{\\right}' -delimiters. - -@d above_code=0 { `\.{\\above}' } -@d over_code=1 { `\.{\\over}' } -@d atop_code=2 { `\.{\\atop}' } -@d delimited_code=3 { `\.{\\abovewithdelims}', etc.} - -@<Put each...@>= -primitive("above",above,above_code);@/ -@!@:above_}{\.{\\above} primitive@> -primitive("over",above,over_code);@/ -@!@:over_}{\.{\\over} primitive@> -primitive("atop",above,atop_code);@/ -@!@:atop_}{\.{\\atop} primitive@> -primitive("abovewithdelims",above,delimited_code+above_code);@/ -@!@:above_with_delims_}{\.{\\abovewithdelims} primitive@> -primitive("overwithdelims",above,delimited_code+over_code);@/ -@!@:over_with_delims_}{\.{\\overwithdelims} primitive@> -primitive("atopwithdelims",above,delimited_code+atop_code); -@!@:atop_with_delims_}{\.{\\atopwithdelims} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -above: case chr_code of - over_code:print_esc("over"); - atop_code:print_esc("atop"); - delimited_code+above_code:print_esc("abovewithdelims"); - delimited_code+over_code:print_esc("overwithdelims"); - delimited_code+atop_code:print_esc("atopwithdelims"); - othercases print_esc("above") - endcases; - -@ @<Cases of |main_control| that build...@>= -mmode+above: math_fraction; - -@ @<Declare act...@>= -procedure math_fraction; -var c:small_number; {the type of generalized fraction we are scanning} -begin c:=cur_chr; -if incompleat_noad<>null then - @<Ignore the fraction operation and complain about this ambiguous case@> -else begin incompleat_noad:=get_node(fraction_noad_size); - type(incompleat_noad):=fraction_noad; - subtype(incompleat_noad):=normal; - math_type(numerator(incompleat_noad)):=sub_mlist; - info(numerator(incompleat_noad)):=link(head); - mem[denominator(incompleat_noad)].hh:=empty_field; - mem[left_delimiter(incompleat_noad)].qqqq:=null_delimiter; - mem[right_delimiter(incompleat_noad)].qqqq:=null_delimiter;@/ - link(head):=null; tail:=head; - @<Use code |c| to distinguish between generalized fractions@>; - end; -end; - -@ @<Use code |c|...@>= -if c>=delimited_code then - begin scan_delimiter(left_delimiter(incompleat_noad),false); - scan_delimiter(right_delimiter(incompleat_noad),false); - end; -case c mod delimited_code of -above_code: begin scan_normal_dimen; - thickness(incompleat_noad):=cur_val; - end; -over_code: thickness(incompleat_noad):=default_code; -atop_code: thickness(incompleat_noad):=0; -end {there are no other cases} - -@ @<Ignore the fraction...@>= -begin if c>=delimited_code then - begin scan_delimiter(garbage,false); scan_delimiter(garbage,false); - end; -if c mod delimited_code=above_code then scan_normal_dimen; -print_err("Ambiguous; you need another { and }"); -@.Ambiguous...@> -help3("I'm ignoring this fraction specification, since I don't")@/ - ("know whether a construction like `x \over y \over z'")@/ - ("means `{x \over y} \over z' or `x \over {y \over z}'."); -error; -end - -@ At the end of a math formula or subformula, the |fin_mlist| routine is -called upon to return a pointer to the newly completed mlist, and to -pop the nest back to the enclosing semantic level. The parameter to -|fin_mlist|, if not null, points to a |right_noad| that ends the -current mlist; this |right_noad| has not yet been appended. - -@<Declare the function called |fin_mlist|@>= -function fin_mlist(@!p:pointer):pointer; -var q:pointer; {the mlist to return} -begin if incompleat_noad<>null then @<Compleat the incompleat noad@> -else begin link(tail):=p; q:=link(head); - end; -pop_nest; fin_mlist:=q; -end; - -@ @<Compleat...@>= -begin math_type(denominator(incompleat_noad)):=sub_mlist; -info(denominator(incompleat_noad)):=link(head); -if p=null then q:=incompleat_noad -else begin q:=info(numerator(incompleat_noad)); - if type(q)<>left_noad then confusion("right"); -@:this can't happen right}{\quad right@> - info(numerator(incompleat_noad)):=link(q); - link(q):=incompleat_noad; link(incompleat_noad):=p; - end; -end - -@ Now at last we're ready to see what happens when a right brace occurs -in a math formula. Two special cases are simplified here: Braces are effectively -removed when they surround a single Ord without sub/superscripts, or when they -surround an accent that is the nucleus of an Ord atom. - -@<Cases of |handle...@>= -math_group: begin unsave; decr(save_ptr);@/ - math_type(saved(0)):=sub_mlist; p:=fin_mlist(null); info(saved(0)):=p; - if p<>null then if link(p)=null then - if type(p)=ord_noad then - begin if math_type(subscr(p))=empty then - if math_type(supscr(p))=empty then - begin mem[saved(0)].hh:=mem[nucleus(p)].hh; - free_node(p,noad_size); - end; - end - else if type(p)=accent_noad then if saved(0)=nucleus(tail) then - if type(tail)=ord_noad then @<Replace the tail of the list by |p|@>; - end; - -@ @<Replace the tail...@>= -begin q:=head; while link(q)<>tail do q:=link(q); -link(q):=p; free_node(tail,noad_size); tail:=p; -end - -@ We have dealt with all constructions of math mode except `\.{\\left}' and -`\.{\\right}', so the picture is completed by the following sections of -the program. - -@<Put each...@>= -primitive("left",left_right,left_noad); -@!@:left_}{\.{\\left} primitive@> -primitive("right",left_right,right_noad); -@!@:right_}{\.{\\right} primitive@> -text(frozen_right):="right"; eqtb[frozen_right]:=eqtb[cur_val]; - -@ @<Cases of |print_cmd_chr|...@>= -left_right: if chr_code=left_noad then print_esc("left") -else print_esc("right"); - -@ @<Cases of |main_control| that build...@>= -mmode+left_right: math_left_right; - -@ @<Declare act...@>= -procedure math_left_right; -var t:small_number; {|left_noad| or |right_noad|} -@!p:pointer; {new noad} -begin t:=cur_chr; -if (t=right_noad)and(cur_group<>math_left_group) then - @<Try to recover from mismatched \.{\\right}@> -else begin p:=new_noad; type(p):=t; - scan_delimiter(delimiter(p),false); - if t=left_noad then - begin push_math(math_left_group); link(head):=p; tail:=p; - end - else begin p:=fin_mlist(p); unsave; {end of |math_left_group|} - tail_append(new_noad); type(tail):=inner_noad; - math_type(nucleus(tail)):=sub_mlist; - info(nucleus(tail)):=p; - end; - end; -end; - -@ @<Try to recover from mismatch...@>= -begin if cur_group=math_shift_group then - begin scan_delimiter(garbage,false); - print_err("Extra "); print_esc("right"); -@.Extra \\right.@> - help1("I'm ignoring a \right that had no matching \left."); - error; - end -else off_save; -end - -@ Here is the only way out of math mode. - -@<Cases of |main_control| that build...@>= -mmode+math_shift: if cur_group=math_shift_group then after_math - else off_save; - -@ @<Declare act...@>= -procedure after_math; -var l:boolean; {`\.{\\leqno}' instead of `\.{\\eqno}'} -@!danger:boolean; {not enough symbol fonts are present} -@!m:integer; {|mmode| or |-mmode|} -@!p:pointer; {the formula} -@!a:pointer; {box containing equation number} -@<Local variables for finishing a displayed formula@>@; -begin danger:=false; -@<Check that the necessary fonts for math symbols are present; - if not, flush the current math lists and set |danger:=true|@>; -m:=mode; l:=false; p:=fin_mlist(null); {this pops the nest} -if mode=-m then {end of equation number} - begin @<Check that another \.\$ follows@>; - cur_mlist:=p; cur_style:=text_style; mlist_penalties:=false; - mlist_to_hlist; a:=hpack(link(temp_head),natural); - unsave; decr(save_ptr); {now |cur_group=math_shift_group|} - if saved(0)=1 then l:=true; - danger:=false; - @<Check that the necessary fonts for math symbols are present; - if not, flush the current math lists and set |danger:=true|@>; - m:=mode; p:=fin_mlist(null); - end -else a:=null; -if m<0 then @<Finish math in text@> -else begin if a=null then @<Check that another \.\$ follows@>; - @<Finish displayed math@>; - end; -end; - -@ @<Check that the necessary fonts...@>= -if (font_params[fam_fnt(2+text_size)]<total_mathsy_params)or@| - (font_params[fam_fnt(2+script_size)]<total_mathsy_params)or@| - (font_params[fam_fnt(2+script_script_size)]<total_mathsy_params) then - begin print_err("Math formula deleted: Insufficient symbol fonts");@/ -@.Math formula deleted...@> - help3("Sorry, but I can't typeset math unless \textfont 2")@/ - ("and \scriptfont 2 and \scriptscriptfont 2 have all")@/ - ("the \fontdimen values needed in math symbol fonts."); - error; flush_math; danger:=true; - end -else if (font_params[fam_fnt(3+text_size)]<total_mathex_params)or@| - (font_params[fam_fnt(3+script_size)]<total_mathex_params)or@| - (font_params[fam_fnt(3+script_script_size)]<total_mathex_params) then - begin print_err("Math formula deleted: Insufficient extension fonts");@/ - help3("Sorry, but I can't typeset math unless \textfont 3")@/ - ("and \scriptfont 3 and \scriptscriptfont 3 have all")@/ - ("the \fontdimen values needed in math extension fonts."); - error; flush_math; danger:=true; - end - -@ The |unsave| is done after everything else here; hence an appearance of -`\.{\\mathsurround}' inside of `\.{\$...\$}' affects the spacing at these -particular \.\$'s. This is consistent with the conventions of -`\.{\$\$...\$\$}', since `\.{\\abovedisplayskip}' inside a display affects the -space above that display. - -@<Finish math in text@>= -begin tail_append(new_math(math_surround,before)); -cur_mlist:=p; cur_style:=text_style; mlist_penalties:=(mode>0); mlist_to_hlist; -link(tail):=link(temp_head); -while link(tail)<>null do tail:=link(tail); -tail_append(new_math(math_surround,after)); -space_factor:=1000; unsave; -end - -@ \TeX\ gets to the following part of the program when the first `\.\$' ending -a display has been scanned. - -@<Check that another \.\$ follows@>= -begin get_x_token; -if cur_cmd<>math_shift then - begin print_err("Display math should end with $$"); -@.Display math...with \$\$@> - help2("The `$' that I just saw supposedly matches a previous `$$'.")@/ - ("So I shall assume that you typed `$$' both times."); - back_error; - end; -end - -@ We have saved the worst for last: The fussiest part of math mode processing -occurs when a displayed formula is being centered and placed with an optional -equation number. - -@<Local variables for finishing...@>= -@!b:pointer; {box containing the equation} -@!w:scaled; {width of the equation} -@!z:scaled; {width of the line} -@!e:scaled; {width of equation number} -@!q:scaled; {width of equation number plus space to separate from equation} -@!d:scaled; {displacement of equation in the line} -@!s:scaled; {move the line right this much} -@!g1,@!g2:small_number; {glue parameter codes for before and after} -@!r:pointer; {kern node used to position the display} -@!t:pointer; {tail of adjustment list} - -@ At this time |p| points to the mlist for the formula; |a| is either -|null| or it points to a box containing the equation number; and we are in -vertical mode (or internal vertical mode). - -@<Finish displayed math@>= -cur_mlist:=p; cur_style:=display_style; mlist_penalties:=false; -mlist_to_hlist; p:=link(temp_head);@/ -adjust_tail:=adjust_head; b:=hpack(p,natural); p:=list_ptr(b); -t:=adjust_tail; adjust_tail:=null;@/ -w:=width(b); z:=display_width; s:=display_indent; -if (a=null)or danger then - begin e:=0; q:=0; - end -else begin e:=width(a); q:=e+math_quad(text_size); - end; -if w+q>z then - @<Squeeze the equation as much as possible; if there is an equation - number that should go on a separate line by itself, - set~|e:=0|@>; -@<Determine the displacement, |d|, of the left edge of the equation, with - respect to the line size |z|, assuming that |l=false|@>; -@<Append the glue or equation number preceding the display@>; -@<Append the display and perhaps also the equation number@>; -@<Append the glue or equation number following the display@>; -resume_after_display - -@ @<Declare act...@>= -procedure resume_after_display; -begin if cur_group<>math_shift_group then confusion("display"); -@:this can't happen display}{\quad display@> -unsave; prev_graf:=prev_graf+3; -push_nest; mode:=hmode; space_factor:=1000; set_cur_lang; clang:=cur_lang; -prev_graf:=(norm_min(left_hyphen_min)*@'100+norm_min(right_hyphen_min)) - *@'200000+cur_lang; -@<Scan an optional space@>; -if nest_ptr=1 then build_page; -end; - -@ The user can force the equation number to go on a separate line -by causing its width to be zero. - -@<Squeeze the equation as much as possible...@>= -begin if (e<>0)and((w-total_shrink[normal]+q<=z)or@| - (total_shrink[fil]<>0)or(total_shrink[fill]<>0)or - (total_shrink[filll]<>0)) then - begin free_node(b,box_node_size); - b:=hpack(p,z-q,exactly); - end -else begin e:=0; - if w>z then - begin free_node(b,box_node_size); - b:=hpack(p,z,exactly); - end; - end; -w:=width(b); -end - -@ We try first to center the display without regard to the existence of -the equation number. If that would make it too close (where ``too close'' -means that the space between display and equation number is less than the -width of the equation number), we either center it in the remaining space -or move it as far from the equation number as possible. The latter alternative -is taken only if the display begins with glue, since we assume that the -user put glue there to control the spacing precisely. - -@<Determine the displacement, |d|, of the left edge of the equation...@>= -d:=half(z-w); -if (e>0)and(d<2*e) then {too close} - begin d:=half(z-w-e); - if p<>null then if not is_char_node(p) then if type(p)=glue_node then d:=0; - end - -@ If the equation number is set on a line by itself, either before or -after the formula, we append an infinite penalty so that no page break will -separate the display from its number; and we use the same size and -displacement for all three potential lines of the display, even though -`\.{\\parshape}' may specify them differently. - -@<Append the glue or equation number preceding the display@>= -tail_append(new_penalty(pre_display_penalty));@/ -if (d+s<=pre_display_size)or l then {not enough clearance} - begin g1:=above_display_skip_code; g2:=below_display_skip_code; - end -else begin g1:=above_display_short_skip_code; - g2:=below_display_short_skip_code; - end; -if l and(e=0) then {it follows that |type(a)=hlist_node|} - begin shift_amount(a):=s; append_to_vlist(a); - tail_append(new_penalty(inf_penalty)); - end -else tail_append(new_param_glue(g1)) - -@ @<Append the display and perhaps also the equation number@>= -if e<>0 then - begin r:=new_kern(z-w-e-d); - if l then - begin link(a):=r; link(r):=b; b:=a; d:=0; - end - else begin link(b):=r; link(r):=a; - end; - b:=hpack(b,natural); - end; -shift_amount(b):=s+d; append_to_vlist(b) - -@ @<Append the glue or equation number following the display@>= -if (a<>null)and(e=0)and not l then - begin tail_append(new_penalty(inf_penalty)); - shift_amount(a):=s+z-width(a); - append_to_vlist(a); - g2:=0; - end; -if t<>adjust_head then {migrating material comes after equation number} - begin link(tail):=link(adjust_head); tail:=t; - end; -tail_append(new_penalty(post_display_penalty)); -if g2>0 then tail_append(new_param_glue(g2)) - -@ When \.{\\halign} appears in a display, the alignment routines operate -essentially as they do in vertical mode. Then the following program is -activated, with |p| and |q| pointing to the beginning and end of the -resulting list, and with |aux_save| holding the |prev_depth| value. - -@<Finish an alignment in a display@>= -begin do_assignments; -if cur_cmd<>math_shift then @<Pontificate about improper alignment in display@> -else @<Check that another \.\$ follows@>; -pop_nest; -tail_append(new_penalty(pre_display_penalty)); -tail_append(new_param_glue(above_display_skip_code)); -link(tail):=p; -if p<>null then tail:=q; -tail_append(new_penalty(post_display_penalty)); -tail_append(new_param_glue(below_display_skip_code)); -prev_depth:=aux_save.sc; resume_after_display; -end - -@ @<Pontificate...@>= -begin print_err("Missing $$ inserted"); -@.Missing {\$\$} inserted@> -help2("Displays can use special alignments (like \eqalignno)")@/ - ("only if nothing but the alignment itself is between $$'s."); -back_error; -end - -@* \[49] Mode-independent processing. -The long |main_control| procedure has now been fully specified, except for -certain activities that are independent of the current mode. These activities -do not change the current vlist or hlist or mlist; if they change anything, -it is the value of a parameter or the meaning of a control sequence. - -Assignments to values in |eqtb| can be global or local. Furthermore, a -control sequence can be defined to be `\.{\\long}' or `\.{\\outer}', and -it might or might not be expanded. The prefixes `\.{\\global}', `\.{\\long}', -and `\.{\\outer}' can occur in any order. Therefore we assign binary numeric -codes, making it possible to accumulate the union of all specified prefixes -by adding the corresponding codes. (\PASCAL's |set| operations could also -have been used.) - -@<Put each...@>= -primitive("long",prefix,1); -@!@:long_}{\.{\\long} primitive@> -primitive("outer",prefix,2); -@!@:outer_}{\.{\\outer} primitive@> -primitive("global",prefix,4); -@!@:global_}{\.{\\global} primitive@> -primitive("def",def,0); -@!@:def_}{\.{\\def} primitive@> -primitive("gdef",def,1); -@!@:gdef_}{\.{\\gdef} primitive@> -primitive("edef",def,2); -@!@:edef_}{\.{\\edef} primitive@> -primitive("xdef",def,3); -@!@:xdef_}{\.{\\xdef} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -prefix: if chr_code=1 then print_esc("long") - else if chr_code=2 then print_esc("outer") - else print_esc("global"); -def: if chr_code=0 then print_esc("def") - else if chr_code=1 then print_esc("gdef") - else if chr_code=2 then print_esc("edef") - else print_esc("xdef"); - -@ Every prefix, and every command code that might or might not be prefixed, -calls the action procedure |prefixed_command|. This routine accumulates -a sequence of prefixes until coming to a non-prefix, then it carries out -the command. - -@<Cases of |main_control| that don't...@>= -any_mode(toks_register), -any_mode(assign_toks), -any_mode(assign_int), -any_mode(assign_dimen), -any_mode(assign_glue), -any_mode(assign_mu_glue), -any_mode(assign_font_dimen), -any_mode(assign_font_int), -any_mode(set_aux), -any_mode(set_prev_graf), -any_mode(set_page_dimen), -any_mode(set_page_int), -any_mode(set_box_dimen), -any_mode(set_shape), -any_mode(def_code), -any_mode(def_family), -any_mode(set_font), -any_mode(def_font), -any_mode(register), -any_mode(advance), -any_mode(multiply), -any_mode(divide), -any_mode(prefix), -any_mode(let), -any_mode(shorthand_def), -any_mode(read_to_cs), -any_mode(def), -any_mode(set_box), -any_mode(hyph_data), -any_mode(set_interaction):prefixed_command; - -@ If the user says, e.g., `\.{\\global\\global}', the redundancy is -silently accepted. - -@<Declare act...@>= -@t\4@>@<Declare subprocedures for |prefixed_command|@>@t@>@;@/ -procedure prefixed_command; -label done,exit; -var a:small_number; {accumulated prefix codes so far} -@!f:internal_font_number; {identifies a font} -@!j:halfword; {index into a \.{\\parshape} specification} -@!k:font_index; {index into |font_info|} -@!p,@!q:pointer; {for temporary short-term use} -@!n:integer; {ditto} -@!e:boolean; {should a definition be expanded? or was \.{\\let} not done?} -begin a:=0; -while cur_cmd=prefix do - begin if not odd(a div cur_chr) then a:=a+cur_chr; - @<Get the next non-blank non-relax...@>; - if cur_cmd<=max_non_prefixed_command then - @<Discard erroneous prefixes and |return|@>; - end; -@<Discard the prefixes \.{\\long} and \.{\\outer} if they are irrelevant@>; -@<Adjust \(f)for the setting of \.{\\globaldefs}@>; -case cur_cmd of -@t\4@>@<Assignments@>@; -othercases confusion("prefix") -@:this can't happen prefix}{\quad prefix@> -endcases; -done: @<Insert a token saved by \.{\\afterassignment}, if any@>; -exit:end; - -@ @<Discard erroneous...@>= -begin print_err("You can't use a prefix with `"); -@.You can't use a prefix with x@> -print_cmd_chr(cur_cmd,cur_chr); print_char("'"); -help1("I'll pretend you didn't say \long or \outer or \global."); -back_error; return; -end - -@ @<Discard the prefixes...@>= -if (cur_cmd<>def)and(a mod 4<>0) then - begin print_err("You can't use `"); print_esc("long"); print("' or `"); - print_esc("outer"); print("' with `"); -@.You can't use \\long...@> - print_cmd_chr(cur_cmd,cur_chr); print_char("'"); - help1("I'll pretend you didn't say \long or \outer here."); - error; - end - -@ The previous routine does not have to adjust |a| so that |a mod 4=0|, -since the following routines test for the \.{\\global} prefix as follows. - -@d global==(a>=4) -@d define(#)==if global then geq_define(#)@+else eq_define(#) -@d word_define(#)==if global then geq_word_define(#)@+else eq_word_define(#) - -@<Adjust \(f)for the setting of \.{\\globaldefs}@>= -if global_defs<>0 then - if global_defs<0 then - begin if global then a:=a-4; - end - else begin if not global then a:=a+4; - end - -@ When a control sequence is to be defined, by \.{\\def} or \.{\\let} or -something similar, the |get_r_token| routine will substitute a special -control sequence for a token that is not redefinable. - -@<Declare subprocedures for |prefixed_command|@>= -procedure get_r_token; -label restart; -begin restart: repeat get_token; -until cur_tok<>space_token; -if (cur_cs=0)or(cur_cs>frozen_control_sequence) then - begin print_err("Missing control sequence inserted"); -@.Missing control...@> - help5("Please don't say `\def cs{...}', say `\def\cs{...}'.")@/ - ("I've inserted an inaccessible control sequence so that your")@/ - ("definition will be completed without mixing me up too badly.")@/ - ("You can recover graciously from this error, if you're")@/ - ("careful; see exercise 27.2 in The TeXbook."); -@:TeXbook}{\sl The \TeX book@> - if cur_cs=0 then back_input; - cur_tok:=cs_token_flag+frozen_protection; ins_error; goto restart; - end; -end; - -@ @<Initialize table entries...@>= -text(frozen_protection):="inaccessible"; -@.inaccessible@> - -@ Here's an example of the way many of the following routines operate. -(Unfortunately, they aren't all as simple as this.) - -@<Assignments@>= -set_font: define(cur_font_loc,data,cur_chr); - -@ When a |def| command has been scanned, -|cur_chr| is odd if the definition is supposed to be global, and -|cur_chr>=2| if the definition is supposed to be expanded. - -@<Assignments@>= -def: begin if odd(cur_chr)and not global and(global_defs>=0) then a:=a+4; - e:=(cur_chr>=2); get_r_token; p:=cur_cs; - q:=scan_toks(true,e); define(p,call+(a mod 4),def_ref); - end; - -@ Both \.{\\let} and \.{\\futurelet} share the command code |let|. - -@<Put each...@>= -primitive("let",let,normal);@/ -@!@:let_}{\.{\\let} primitive@> -primitive("futurelet",let,normal+1);@/ -@!@:future_let_}{\.{\\futurelet} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -let: if chr_code<>normal then print_esc("futurelet")@+else print_esc("let"); - -@ @<Assignments@>= -let: begin n:=cur_chr; - get_r_token; p:=cur_cs; - if n=normal then - begin repeat get_token; - until cur_cmd<>spacer; - if cur_tok=other_token+"=" then - begin get_token; - if cur_cmd=spacer then get_token; - end; - end - else begin get_token; q:=cur_tok; get_token; back_input; - cur_tok:=q; back_input; {look ahead, then back up} - end; {note that |back_input| doesn't affect |cur_cmd|, |cur_chr|} - if cur_cmd>=call then add_token_ref(cur_chr); - define(p,cur_cmd,cur_chr); - end; - -@ A \.{\\chardef} creates a control sequence whose |cmd| is |char_given|; -a \.{\\mathchardef} creates a control sequence whose |cmd| is |math_given|; -and the corresponding |chr| is the character code or math code. A \.{\\countdef} -or \.{\\dimendef} or \.{\\skipdef} or \.{\\muskipdef} creates a control -sequence whose |cmd| is |assign_int| or \dots\ or |assign_mu_glue|, and the -corresponding |chr| is the |eqtb| location of the internal register in question. - -@d char_def_code=0 {|shorthand_def| for \.{\\chardef}} -@d math_char_def_code=1 {|shorthand_def| for \.{\\mathchardef}} -@d count_def_code=2 {|shorthand_def| for \.{\\countdef}} -@d dimen_def_code=3 {|shorthand_def| for \.{\\dimendef}} -@d skip_def_code=4 {|shorthand_def| for \.{\\skipdef}} -@d mu_skip_def_code=5 {|shorthand_def| for \.{\\muskipdef}} -@d toks_def_code=6 {|shorthand_def| for \.{\\toksdef}} - -@<Put each...@>= -primitive("chardef",shorthand_def,char_def_code);@/ -@!@:char_def_}{\.{\\chardef} primitive@> -primitive("mathchardef",shorthand_def,math_char_def_code);@/ -@!@:math_char_def_}{\.{\\mathchardef} primitive@> -primitive("countdef",shorthand_def,count_def_code);@/ -@!@:count_def_}{\.{\\countdef} primitive@> -primitive("dimendef",shorthand_def,dimen_def_code);@/ -@!@:dimen_def_}{\.{\\dimendef} primitive@> -primitive("skipdef",shorthand_def,skip_def_code);@/ -@!@:skip_def_}{\.{\\skipdef} primitive@> -primitive("muskipdef",shorthand_def,mu_skip_def_code);@/ -@!@:mu_skip_def_}{\.{\\muskipdef} primitive@> -primitive("toksdef",shorthand_def,toks_def_code);@/ -@!@:toks_def_}{\.{\\toksdef} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -shorthand_def: case chr_code of - char_def_code: print_esc("chardef"); - math_char_def_code: print_esc("mathchardef"); - count_def_code: print_esc("countdef"); - dimen_def_code: print_esc("dimendef"); - skip_def_code: print_esc("skipdef"); - mu_skip_def_code: print_esc("muskipdef"); - othercases print_esc("toksdef") - endcases; -char_given: begin print_esc("char"); print_hex(chr_code); - end; -math_given: begin print_esc("mathchar"); print_hex(chr_code); - end; - -@ We temporarily define |p| to be |relax|, so that an occurrence of |p| -while scanning the definition will simply stop the scanning instead of -producing an ``undefined control sequence'' error or expanding the -previous meaning. This allows, for instance, `\.{\\chardef\\foo=123\\foo}'. - -@<Assignments@>= -shorthand_def: begin n:=cur_chr; get_r_token; p:=cur_cs; define(p,relax,256); - scan_optional_equals; - case n of - char_def_code: begin scan_char_num; define(p,char_given,cur_val); - end; - math_char_def_code: begin scan_fifteen_bit_int; define(p,math_given,cur_val); - end; - othercases begin scan_eight_bit_int; - case n of - count_def_code: define(p,assign_int,count_base+cur_val); - dimen_def_code: define(p,assign_dimen,scaled_base+cur_val); - skip_def_code: define(p,assign_glue,skip_base+cur_val); - mu_skip_def_code: define(p,assign_mu_glue,mu_skip_base+cur_val); - toks_def_code: define(p,assign_toks,toks_base+cur_val); - end; {there are no other cases} - end - endcases; - end; - -@ @<Assignments@>= -read_to_cs: begin scan_int; n:=cur_val; - if not scan_keyword("to") then -@.to@> - begin print_err("Missing `to' inserted"); -@.Missing `to'...@> - help2("You should have said `\read<number> to \cs'.")@/ - ("I'm going to look for the \cs now."); error; - end; - get_r_token; - p:=cur_cs; read_toks(n,p); define(p,call,cur_val); - end; - -@ The token-list parameters, \.{\\output} and \.{\\everypar}, etc., receive -their values in the following way. (For safety's sake, we place an -enclosing pair of braces around an \.{\\output} list.) - -@<Assignments@>= -toks_register,assign_toks: begin q:=cur_cs; - if cur_cmd=toks_register then - begin scan_eight_bit_int; p:=toks_base+cur_val; - end - else p:=cur_chr; {|p=every_par_loc| or |output_routine_loc| or \dots} - scan_optional_equals; - @<Get the next non-blank non-relax non-call token@>; - if cur_cmd<>left_brace then @<If the right-hand side is a token parameter - or token register, finish the assignment and |goto done|@>; - back_input; cur_cs:=q; q:=scan_toks(false,false); - if link(def_ref)=null then {empty list: revert to the default} - begin define(p,undefined_cs,null); free_avail(def_ref); - end - else begin if p=output_routine_loc then {enclose in curlies} - begin link(q):=get_avail; q:=link(q); - info(q):=right_brace_token+"}"; - q:=get_avail; info(q):=left_brace_token+"{"; - link(q):=link(def_ref); link(def_ref):=q; - end; - define(p,call,def_ref); - end; - end; - -@ @<If the right-hand side is a token parameter...@>= -begin if cur_cmd=toks_register then - begin scan_eight_bit_int; cur_cmd:=assign_toks; cur_chr:=toks_base+cur_val; - end; -if cur_cmd=assign_toks then - begin q:=equiv(cur_chr); - if q=null then define(p,undefined_cs,null) - else begin add_token_ref(q); define(p,call,q); - end; - goto done; - end; -end - -@ Similar routines are used to assign values to the numeric parameters. - -@<Assignments@>= -assign_int: begin p:=cur_chr; scan_optional_equals; scan_int; - word_define(p,cur_val); - end; -assign_dimen: begin p:=cur_chr; scan_optional_equals; - scan_normal_dimen; word_define(p,cur_val); - end; -assign_glue,assign_mu_glue: begin p:=cur_chr; n:=cur_cmd; scan_optional_equals; - if n=assign_mu_glue then scan_glue(mu_val)@+else scan_glue(glue_val); - trap_zero_glue; - define(p,glue_ref,cur_val); - end; - -@ When a glue register or parameter becomes zero, it will always point to -|zero_glue| because of the following procedure. (Exception: The tabskip -glue isn't trapped while preambles are being scanned.) - -@<Declare subprocedures for |prefixed_command|@>= -procedure trap_zero_glue; -begin if (width(cur_val)=0)and(stretch(cur_val)=0)and(shrink(cur_val)=0) then - begin add_glue_ref(zero_glue); - delete_glue_ref(cur_val); cur_val:=zero_glue; - end; -end; - -@ The various character code tables are changed by the |def_code| commands, -and the font families are declared by |def_family|. - -@<Put each...@>= -primitive("catcode",def_code,cat_code_base); -@!@:cat_code_}{\.{\\catcode} primitive@> -primitive("mathcode",def_code,math_code_base); -@!@:math_code_}{\.{\\mathcode} primitive@> -primitive("lccode",def_code,lc_code_base); -@!@:lc_code_}{\.{\\lccode} primitive@> -primitive("uccode",def_code,uc_code_base); -@!@:uc_code_}{\.{\\uccode} primitive@> -primitive("sfcode",def_code,sf_code_base); -@!@:sf_code_}{\.{\\sfcode} primitive@> -primitive("delcode",def_code,del_code_base); -@!@:del_code_}{\.{\\delcode} primitive@> -primitive("textfont",def_family,math_font_base); -@!@:text_font_}{\.{\\textfont} primitive@> -primitive("scriptfont",def_family,math_font_base+script_size); -@!@:script_font_}{\.{\\scriptfont} primitive@> -primitive("scriptscriptfont",def_family,math_font_base+script_script_size); -@!@:script_script_font_}{\.{\\scriptscriptfont} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -def_code: if chr_code=cat_code_base then print_esc("catcode") - else if chr_code=math_code_base then print_esc("mathcode") - else if chr_code=lc_code_base then print_esc("lccode") - else if chr_code=uc_code_base then print_esc("uccode") - else if chr_code=sf_code_base then print_esc("sfcode") - else print_esc("delcode"); -def_family: print_size(chr_code-math_font_base); - -@ The different types of code values have different legal ranges; the -following program is careful to check each case properly. - -@<Assignments@>= -def_code: begin @<Let |n| be the largest legal code value, based on |cur_chr|@>; - p:=cur_chr; scan_char_num; p:=p+cur_val; scan_optional_equals; - scan_int; - if ((cur_val<0)and(p<del_code_base))or(cur_val>n) then - begin print_err("Invalid code ("); print_int(cur_val); -@.Invalid code@> - if p<del_code_base then print("), should be in the range 0..") - else print("), should be at most "); - print_int(n); - help1("I'm going to use 0 instead of that illegal code value.");@/ - error; cur_val:=0; - end; - if p<math_code_base then define(p,data,cur_val) - else if p<del_code_base then define(p,data,hi(cur_val)) - else word_define(p,cur_val); - end; - -@ @<Let |n| be the largest...@>= -if cur_chr=cat_code_base then n:=max_char_code -else if cur_chr=math_code_base then n:=@'100000 -else if cur_chr=sf_code_base then n:=@'77777 -else if cur_chr=del_code_base then n:=@'77777777 -else n:=255 - -@ @<Assignments@>= -def_family: begin p:=cur_chr; scan_four_bit_int; p:=p+cur_val; - scan_optional_equals; scan_font_ident; define(p,data,cur_val); - end; - -@ Next we consider changes to \TeX's numeric registers. - -@<Assignments@>= -register,advance,multiply,divide: do_register_command(a); - -@ We use the fact that |register<advance<multiply<divide|. - -@<Declare subprocedures for |prefixed_command|@>= -procedure do_register_command(@!a:small_number); -label found,exit; -var l,@!q,@!r,@!s:pointer; {for list manipulation} -@!p:int_val..mu_val; {type of register involved} -begin q:=cur_cmd; -@<Compute the register location |l| and its type |p|; but |return| if invalid@>; -if q=register then scan_optional_equals -else if scan_keyword("by") then do_nothing; {optional `\.{by}'} -@.by@> -arith_error:=false; -if q<multiply then @<Compute result of |register| or - |advance|, put it in |cur_val|@> -else @<Compute result of |multiply| or |divide|, put it in |cur_val|@>; -if arith_error then - begin print_err("Arithmetic overflow"); -@.Arithmetic overflow@> - help2("I can't carry out that multiplication or division,")@/ - ("since the result is out of range."); - if p>=glue_val then delete_glue_ref(cur_val); - error; return; - end; -if p<glue_val then word_define(l,cur_val) -else begin trap_zero_glue; define(l,glue_ref,cur_val); - end; -exit: end; - -@ Here we use the fact that the consecutive codes |int_val..mu_val| and -|assign_int..assign_mu_glue| correspond to each other nicely. - -@<Compute the register location |l| and its type |p|...@>= -begin if q<>register then - begin get_x_token; - if (cur_cmd>=assign_int)and(cur_cmd<=assign_mu_glue) then - begin l:=cur_chr; p:=cur_cmd-assign_int; goto found; - end; - if cur_cmd<>register then - begin print_err("You can't use `"); print_cmd_chr(cur_cmd,cur_chr); -@.You can't use x after ...@> - print("' after "); print_cmd_chr(q,0); - help1("I'm forgetting what you said and not changing anything."); - error; return; - end; - end; -p:=cur_chr; scan_eight_bit_int; -case p of -int_val: l:=cur_val+count_base; -dimen_val: l:=cur_val+scaled_base; -glue_val: l:=cur_val+skip_base; -mu_val: l:=cur_val+mu_skip_base; -end; {there are no other cases} -end; -found: - -@ @<Compute result of |register| or |advance|...@>= -if p<glue_val then - begin if p=int_val then scan_int@+else scan_normal_dimen; - if q=advance then cur_val:=cur_val+eqtb[l].int; - end -else begin scan_glue(p); - if q=advance then @<Compute the sum of two glue specs@>; - end - -@ @<Compute the sum of two glue specs@>= -begin q:=new_spec(cur_val); r:=equiv(l); -delete_glue_ref(cur_val); -width(q):=width(q)+width(r); -if stretch(q)=0 then stretch_order(q):=normal; -if stretch_order(q)=stretch_order(r) then stretch(q):=stretch(q)+stretch(r) -else if (stretch_order(q)<stretch_order(r))and(stretch(r)<>0) then - begin stretch(q):=stretch(r); stretch_order(q):=stretch_order(r); - end; -if shrink(q)=0 then shrink_order(q):=normal; -if shrink_order(q)=shrink_order(r) then shrink(q):=shrink(q)+shrink(r) -else if (shrink_order(q)<shrink_order(r))and(shrink(r)<>0) then - begin shrink(q):=shrink(r); shrink_order(q):=shrink_order(r); - end; -cur_val:=q; -end - -@ @<Compute result of |multiply| or |divide|...@>= -begin scan_int; -if p<glue_val then - if q=multiply then - if p=int_val then cur_val:=mult_integers(eqtb[l].int,cur_val) - else cur_val:=nx_plus_y(eqtb[l].int,cur_val,0) - else cur_val:=x_over_n(eqtb[l].int,cur_val) -else begin s:=equiv(l); r:=new_spec(s); - if q=multiply then - begin width(r):=nx_plus_y(width(s),cur_val,0); - stretch(r):=nx_plus_y(stretch(s),cur_val,0); - shrink(r):=nx_plus_y(shrink(s),cur_val,0); - end - else begin width(r):=x_over_n(width(s),cur_val); - stretch(r):=x_over_n(stretch(s),cur_val); - shrink(r):=x_over_n(shrink(s),cur_val); - end; - cur_val:=r; - end; -end - -@ The processing of boxes is somewhat different, because we may need -to scan and create an entire box before we actually change the value of the old -one. - -@<Assignments@>= -set_box: begin scan_eight_bit_int; - if global then n:=256+cur_val@+else n:=cur_val; - scan_optional_equals; - if set_box_allowed then scan_box(box_flag+n) - else begin print_err("Improper "); print_esc("setbox"); -@.Improper \\setbox@> - help2("Sorry, \setbox is not allowed after \halign in a display,")@/ - ("or between \accent and an accented character."); error; - end; - end; - -@ The |space_factor| or |prev_depth| settings are changed when a |set_aux| -command is sensed. Similarly, |prev_graf| is changed in the presence of -|set_prev_graf|, and |dead_cycles| or |insert_penalties| in the presence of -|set_page_int|. These definitions are always global. - -When some dimension of a box register is changed, the change isn't exactly -global; but \TeX\ does not look at the \.{\\global} switch. - -@<Assignments@>= -set_aux:alter_aux; -set_prev_graf:alter_prev_graf; -set_page_dimen:alter_page_so_far; -set_page_int:alter_integer; -set_box_dimen:alter_box_dimen; - -@ @<Declare subprocedures for |prefixed_command|@>= -procedure alter_aux; -var c:halfword; {|hmode| or |vmode|} -begin if cur_chr<>abs(mode) then report_illegal_case -else begin c:=cur_chr; scan_optional_equals; - if c=vmode then - begin scan_normal_dimen; prev_depth:=cur_val; - end - else begin scan_int; - if (cur_val<=0)or(cur_val>32767) then - begin print_err("Bad space factor"); -@.Bad space factor@> - help1("I allow only values in the range 1..32767 here."); - int_error(cur_val); - end - else space_factor:=cur_val; - end; - end; -end; - -@ @<Declare subprocedures for |prefixed_command|@>= -procedure alter_prev_graf; -var p:0..nest_size; {index into |nest|} -begin nest[nest_ptr]:=cur_list; p:=nest_ptr; -while abs(nest[p].mode_field)<>vmode do decr(p); -scan_optional_equals; scan_int; -if cur_val<0 then - begin print_err("Bad "); print_esc("prevgraf"); -@.Bad \\prevgraf@> - help1("I allow only nonnegative values here."); - int_error(cur_val); - end -else begin nest[p].pg_field:=cur_val; cur_list:=nest[nest_ptr]; - end; -end; - -@ @<Declare subprocedures for |prefixed_command|@>= -procedure alter_page_so_far; -var c:0..7; {index into |page_so_far|} -begin c:=cur_chr; scan_optional_equals; scan_normal_dimen; -page_so_far[c]:=cur_val; -end; - -@ @<Declare subprocedures for |prefixed_command|@>= -procedure alter_integer; -var c:0..1; {0 for \.{\\deadcycles}, 1 for \.{\\insertpenalties}} -begin c:=cur_chr; scan_optional_equals; scan_int; -if c=0 then dead_cycles:=cur_val -else insert_penalties:=cur_val; -end; - -@ @<Declare subprocedures for |prefixed_command|@>= -procedure alter_box_dimen; -var c:small_number; {|width_offset| or |height_offset| or |depth_offset|} -@!b:eight_bits; {box number} -begin c:=cur_chr; scan_eight_bit_int; b:=cur_val; scan_optional_equals; -scan_normal_dimen; -if box(b)<>null then mem[box(b)+c].sc:=cur_val; -end; - -@ Paragraph shapes are set up in the obvious way. - -@<Assignments@>= -set_shape: begin scan_optional_equals; scan_int; n:=cur_val; - if n<=0 then p:=null - else begin p:=get_node(2*n+1); info(p):=n; - for j:=1 to n do - begin scan_normal_dimen; - mem[p+2*j-1].sc:=cur_val; {indentation} - scan_normal_dimen; - mem[p+2*j].sc:=cur_val; {width} - end; - end; - define(par_shape_loc,shape_ref,p); - end; - -@ Here's something that isn't quite so obvious. It guarantees that -|info(par_shape_ptr)| can hold any positive~|n| for which |get_node(2*n+1)| -doesn't overflow the memory capacity. - -@<Check the ``constant''...@>= -if 2*max_halfword<mem_top-mem_min then bad:=41; - -@ New hyphenation data is loaded by the |hyph_data| command. - -@<Put each...@>= -primitive("hyphenation",hyph_data,0); -@!@:hyphenation_}{\.{\\hyphenation} primitive@> -primitive("patterns",hyph_data,1); -@!@:patterns_}{\.{\\patterns} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -hyph_data: if chr_code=1 then print_esc("patterns") - else print_esc("hyphenation"); - -@ @<Assignments@>= -hyph_data: if cur_chr=1 then - begin @!init new_patterns; goto done;@;@+tini@/ - print_err("Patterns can be loaded only by INITEX"); -@.Patterns can be...@> - help0; error; - repeat get_token; until cur_cmd=right_brace; {flush the patterns} - return; - end - else begin new_hyph_exceptions; goto done; - end; - -@ All of \TeX's parameters are kept in |eqtb| except the font information, -the interaction mode, and the hyphenation tables; these are strictly global. - -@<Assignments@>= -assign_font_dimen: begin find_font_dimen(true); k:=cur_val; - scan_optional_equals; scan_normal_dimen; font_info[k].sc:=cur_val; - end; -assign_font_int: begin n:=cur_chr; scan_font_ident; f:=cur_val; - scan_optional_equals; scan_int; - if n=0 then hyphen_char[f]:=cur_val@+else skew_char[f]:=cur_val; - end; - -@ @<Put each...@>= -primitive("hyphenchar",assign_font_int,0); -@!@:hyphen_char_}{\.{\\hyphenchar} primitive@> -primitive("skewchar",assign_font_int,1); -@!@:skew_char_}{\.{\\skewchar} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -assign_font_int: if chr_code=0 then print_esc("hyphenchar") - else print_esc("skewchar"); - -@ Here is where the information for a new font gets loaded. - -@<Assignments@>= -def_font: new_font(a); - -@ @<Declare subprocedures for |prefixed_command|@>= -procedure new_font(@!a:small_number); -label common_ending; -var u:pointer; {user's font identifier} -@!s:scaled; {stated ``at'' size, or negative of scaled magnification} -@!f:internal_font_number; {runs through existing fonts} -@!t:str_number; {name for the frozen font identifier} -@!old_setting:0..max_selector; {holds |selector| setting} -@!flushable_string:str_number; {string not yet referenced} -begin if job_name=0 then open_log_file; - {avoid confusing \.{texput} with the font name} -@.texput@> -get_r_token; u:=cur_cs; -if u>=hash_base then t:=text(u) -else if u>=single_base then - if u=null_cs then t:="FONT"@+else t:=u-single_base -else begin old_setting:=selector; selector:=new_string; - print("FONT"); print(u-active_base); selector:=old_setting; -@.FONTx@> - str_room(1); t:=make_string; - end; -define(u,set_font,null_font); scan_optional_equals; scan_file_name; -@<Scan the font size specification@>; -@<If this font has already been loaded, set |f| to the internal - font number and |goto common_ending|@>; -f:=read_font_info(u,cur_name,cur_area,s); -common_ending: equiv(u):=f; eqtb[font_id_base+f]:=eqtb[u]; font_id_text(f):=t; -end; - -@ @<Scan the font size specification@>= -name_in_progress:=true; {this keeps |cur_name| from being changed} -if scan_keyword("at") then @<Put the \(p)(positive) `at' size into |s|@> -@.at@> -else if scan_keyword("scaled") then -@.scaled@> - begin scan_int; s:=-cur_val; - if (cur_val<=0)or(cur_val>32768) then - begin print_err("Illegal magnification has been changed to 1000");@/ -@.Illegal magnification...@> - help1("The magnification ratio must be between 1 and 32768."); - int_error(cur_val); s:=-1000; - end; - end -else s:=-1000; -name_in_progress:=false - -@ @<Put the \(p)(positive) `at' size into |s|@>= -begin scan_normal_dimen; s:=cur_val; -if (s<=0)or(s>=@'1000000000) then - begin print_err("Improper `at' size ("); - print_scaled(s); print("pt), replaced by 10pt"); -@.Improper `at' size...@> - help2("I can only handle fonts at positive sizes that are")@/ - ("less than 2048pt, so I've changed what you said to 10pt."); - error; s:=10*unity; - end; -end - -@ When the user gives a new identifier to a font that was previously loaded, -the new name becomes the font identifier of record. Font names `\.{xyz}' and -`\.{XYZ}' are considered to be different. - -@<If this font has already been loaded...@>= -flushable_string:=str_ptr-1; -for f:=font_base+1 to font_ptr do - if str_eq_str(font_name[f],cur_name)and str_eq_str(font_area[f],cur_area) then - begin if cur_name=flushable_string then - begin flush_string; cur_name:=font_name[f]; - end; - if s>0 then - begin if s=font_size[f] then goto common_ending; - end - else if font_size[f]=xn_over_d(font_dsize[f],-s,1000) then - goto common_ending; - end - -@ @<Cases of |print_cmd_chr|...@>= -set_font:begin print("select font "); slow_print(font_name[chr_code]); - if font_size[chr_code]<>font_dsize[chr_code] then - begin print(" at "); print_scaled(font_size[chr_code]); - print("pt"); - end; - end; - -@ @<Put each...@>= -primitive("batchmode",set_interaction,batch_mode); -@!@:batch_mode_}{\.{\\batchmode} primitive@> -primitive("nonstopmode",set_interaction,nonstop_mode); -@!@:nonstop_mode_}{\.{\\nonstopmode} primitive@> -primitive("scrollmode",set_interaction,scroll_mode); -@!@:scroll_mode_}{\.{\\scrollmode} primitive@> -primitive("errorstopmode",set_interaction,error_stop_mode); -@!@:error_stop_mode_}{\.{\\errorstopmode} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -set_interaction: case chr_code of - batch_mode: print_esc("batchmode"); - nonstop_mode: print_esc("nonstopmode"); - scroll_mode: print_esc("scrollmode"); - othercases print_esc("errorstopmode") - endcases; - -@ @<Assignments@>= -set_interaction: new_interaction; - -@ @<Declare subprocedures for |prefixed_command|@>= -procedure new_interaction; -begin print_ln; -interaction:=cur_chr; -@<Initialize the print |selector| based on |interaction|@>; -if log_opened then selector:=selector+2; -end; - -@ The \.{\\afterassignment} command puts a token into the global -variable |after_token|. This global variable is examined just after -every assignment has been performed. - -@<Glob...@>= -@!after_token:halfword; {zero, or a saved token} - -@ @<Set init...@>= -after_token:=0; - -@ @<Cases of |main_control| that don't...@>= -any_mode(after_assignment):begin get_token; after_token:=cur_tok; - end; - -@ @<Insert a token saved by \.{\\afterassignment}, if any@>= -if after_token<>0 then - begin cur_tok:=after_token; back_input; after_token:=0; - end - -@ Here is a procedure that might be called `Get the next non-blank non-relax -non-call non-assignment token'. - -@<Declare act...@>= -procedure do_assignments; -label exit; -begin loop begin @<Get the next non-blank non-relax...@>; - if cur_cmd<=max_non_prefixed_command then return; - set_box_allowed:=false; prefixed_command; set_box_allowed:=true; - end; -exit:end; - -@ @<Cases of |main_control| that don't...@>= -any_mode(after_group):begin get_token; save_for_after(cur_tok); - end; - -@ Files for \.{\\read} are opened and closed by the |in_stream| command. - -@<Put each...@>= -primitive("openin",in_stream,1); -@!@:open_in_}{\.{\\openin} primitive@> -primitive("closein",in_stream,0); -@!@:close_in_}{\.{\\closein} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -in_stream: if chr_code=0 then print_esc("closein") - else print_esc("openin"); - -@ @<Cases of |main_control| that don't...@>= -any_mode(in_stream): open_or_close_in; - -@ @<Declare act...@>= -procedure open_or_close_in; -var c:0..1; {1 for \.{\\openin}, 0 for \.{\\closein}} -@!n:0..15; {stream number} -begin c:=cur_chr; scan_four_bit_int; n:=cur_val; -if read_open[n]<>closed then - begin a_close(read_file[n]); read_open[n]:=closed; - end; -if c<>0 then - begin scan_optional_equals; scan_file_name; - if cur_ext="" then cur_ext:=".tex"; - pack_cur_name; - if a_open_in(read_file[n]) then read_open[n]:=just_open; - end; -end; - -@ The user can issue messages to the terminal, regardless of the -current mode. - -@<Cases of |main_control| that don't...@>= -any_mode(message):issue_message; - -@ @<Put each...@>= -primitive("message",message,0); -@!@:message_}{\.{\\message} primitive@> -primitive("errmessage",message,1); -@!@:err_message_}{\.{\\errmessage} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -message: if chr_code=0 then print_esc("message") - else print_esc("errmessage"); - -@ @<Declare act...@>= -procedure issue_message; -var old_setting:0..max_selector; {holds |selector| setting} -@!c:0..1; {identifies \.{\\message} and \.{\\errmessage}} -@!s:str_number; {the message} -begin c:=cur_chr; link(garbage):=scan_toks(false,true); -old_setting:=selector; selector:=new_string; -token_show(def_ref); selector:=old_setting; -flush_list(def_ref); -str_room(1); s:=make_string; -if c=0 then @<Print string |s| on the terminal@> -else @<Print string |s| as an error message@>; -flush_string; -end; - -@ @<Print string |s| on the terminal@>= -begin if term_offset+length(s)>max_print_line-2 then print_ln -else if (term_offset>0)or(file_offset>0) then print_char(" "); -slow_print(s); update_terminal; -end - -@ If \.{\\errmessage} occurs often in |scroll_mode|, without user-defined -\.{\\errhelp}, we don't want to give a long help message each time. So we -give a verbose explanation only once. - -@<Glob...@>= -@!long_help_seen:boolean; {has the long \.{\\errmessage} help been used?} - -@ @<Set init...@>=long_help_seen:=false; - -@ @<Print string |s| as an error message@>= -begin print_err(""); slow_print(s); -if err_help<>null then use_err_help:=true -else if long_help_seen then help1("(That was another \errmessage.)") -else begin if interaction<error_stop_mode then long_help_seen:=true; - help4("This error message was generated by an \errmessage")@/ - ("command, so I can't give any explicit help.")@/ - ("Pretend that you're Hercule Poirot: Examine all clues,")@/ -@^Poirot, Hercule@> - ("and deduce the truth by order and method."); - end; -error; use_err_help:=false; -end - -@ The |error| routine calls on |give_err_help| if help is requested from -the |err_help| parameter. - -@p procedure give_err_help; -begin token_show(err_help); -end; - -@ The \.{\\uppercase} and \.{\\lowercase} commands are implemented by -building a token list and then changing the cases of the letters in it. - -@<Cases of |main_control| that don't...@>= -any_mode(case_shift):shift_case; - -@ @<Put each...@>= -primitive("lowercase",case_shift,lc_code_base); -@!@:lowercase_}{\.{\\lowercase} primitive@> -primitive("uppercase",case_shift,uc_code_base); -@!@:uppercase_}{\.{\\uppercase} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -case_shift:if chr_code=lc_code_base then print_esc("lowercase") - else print_esc("uppercase"); - -@ @<Declare act...@>= -procedure shift_case; -var b:pointer; {|lc_code_base| or |uc_code_base|} -@!p:pointer; {runs through the token list} -@!t:halfword; {token} -@!c:eight_bits; {character code} -begin b:=cur_chr; p:=scan_toks(false,false); p:=link(def_ref); -while p<>null do - begin @<Change the case of the token in |p|, if a change is appropriate@>; - p:=link(p); - end; -back_list(link(def_ref)); free_avail(def_ref); {omit reference count} -end; - -@ When the case of a |chr_code| changes, we don't change the |cmd|. -We also change active characters, using the fact that -|cs_token_flag+active_base| is a multiple of~256. -@^data structure assumptions@> - -@<Change the case of the token in |p|, if a change is appropriate@>= -t:=info(p); -if t<cs_token_flag+single_base then - begin c:=t mod 256; - if equiv(b+c)<>0 then info(p):=t-c+equiv(b+c); - end - -@ We come finally to the last pieces missing from |main_control|, namely the -`\.{\\show}' commands that are useful when debugging. - -@<Cases of |main_control| that don't...@>= -any_mode(xray): show_whatever; - -@ @d show_code=0 { \.{\\show} } -@d show_box_code=1 { \.{\\showbox} } -@d show_the_code=2 { \.{\\showthe} } -@d show_lists_code=3 { \.{\\showlists} } - -@<Put each...@>= -primitive("show",xray,show_code); -@!@:show_}{\.{\\show} primitive@> -primitive("showbox",xray,show_box_code); -@!@:show_box_}{\.{\\showbox} primitive@> -primitive("showthe",xray,show_the_code); -@!@:show_the_}{\.{\\showthe} primitive@> -primitive("showlists",xray,show_lists_code); -@!@:show_lists_code_}{\.{\\showlists} primitive@> - -@ @<Cases of |print_cmd_chr|...@>= -xray: case chr_code of - show_box_code:print_esc("showbox"); - show_the_code:print_esc("showthe"); - show_lists_code:print_esc("showlists"); - othercases print_esc("show") - endcases; - -@ @<Declare act...@>= -procedure show_whatever; -label common_ending; -var p:pointer; {tail of a token list to show} -begin case cur_chr of -show_lists_code: begin begin_diagnostic; show_activities; - end; -show_box_code: @<Show the current contents of a box@>; -show_code: @<Show the current meaning of a token, then |goto common_ending|@>; -othercases @<Show the current value of some parameter or register, - then |goto common_ending|@> -endcases;@/ -@<Complete a potentially long \.{\\show} command@>; -common_ending: if interaction<error_stop_mode then - begin help0; decr(error_count); - end -else if tracing_online>0 then - begin@t@>@;@/ - help3("This isn't an error message; I'm just \showing something.")@/ - ("Type `I\show...' to show more (e.g., \show\cs,")@/ - ("\showthe\count10, \showbox255, \showlists)."); - end -else begin@t@>@;@/ - help5("This isn't an error message; I'm just \showing something.")@/ - ("Type `I\show...' to show more (e.g., \show\cs,")@/ - ("\showthe\count10, \showbox255, \showlists).")@/ - ("And type `I\tracingonline=1\show...' to show boxes and")@/ - ("lists on your terminal as well as in the transcript file."); - end; -error; -end; - -@ @<Show the current meaning of a token...@>= -begin get_token; -if interaction=error_stop_mode then wake_up_terminal; -print_nl("> "); -if cur_cs<>0 then - begin sprint_cs(cur_cs); print_char("="); - end; -print_meaning; goto common_ending; -end - -@ @<Cases of |print_cmd_chr|...@>= -undefined_cs: print("undefined"); -call: print("macro"); -long_call: print_esc("long macro"); -outer_call: print_esc("outer macro"); -long_outer_call: begin print_esc("long"); print_esc("outer macro"); - end; -end_template: print_esc("outer endtemplate"); - -@ @<Show the current contents of a box@>= -begin scan_eight_bit_int; begin_diagnostic; -print_nl("> \box"); print_int(cur_val); print_char("="); -if box(cur_val)=null then print("void") -else show_box(box(cur_val)); -end - -@ @<Show the current value of some parameter...@>= -begin p:=the_toks; -if interaction=error_stop_mode then wake_up_terminal; -print_nl("> "); token_show(temp_head); -flush_list(link(temp_head)); goto common_ending; -end - -@ @<Complete a potentially long \.{\\show} command@>= -end_diagnostic(true); print_err("OK"); -@.OK@> -if selector=term_and_log then if tracing_online<=0 then - begin selector:=term_only; print(" (see the transcript file)"); - selector:=term_and_log; - end - -@* \[50] Dumping and undumping the tables. -After \.{INITEX} has seen a collection of fonts and macros, it -can write all the necessary information on an auxiliary file so -that production versions of \TeX\ are able to initialize their -memory at high speed. The present section of the program takes -care of such output and input. We shall consider simultaneously -the processes of storing and restoring, -so that the inverse relation between them is clear. -@.INITEX@> - -The global variable |format_ident| is a string that is printed right -after the |banner| line when \TeX\ is ready to start. For \.{INITEX} this -string says simply `\.{ (INITEX)}'; for other versions of \TeX\ it says, -for example, `\.{ (preloaded format=plain 1982.11.19)}', showing the year, -month, and day that the format file was created. We have |format_ident=0| -before \TeX's tables are loaded. - -@<Glob...@>= -@!format_ident:str_number; - -@ @<Set init...@>= -format_ident:=0; - -@ @<Initialize table entries...@>= -format_ident:=" (INITEX)"; - -@ @<Declare act...@>= -@!init procedure store_fmt_file; -label found1,found2,done1,done2; -var j,@!k,@!l:integer; {all-purpose indices} -@!p,@!q: pointer; {all-purpose pointers} -@!x: integer; {something to dump} -@!w: four_quarters; {four ASCII codes} -begin @<If dumping is not allowed, abort@>; -@<Create the |format_ident|, open the format file, - and inform the user that dumping has begun@>; -@<Dump constants for consistency check@>; -@<Dump the string pool@>; -@<Dump the dynamic memory@>; -@<Dump the table of equivalents@>; -@<Dump the font information@>; -@<Dump the hyphenation tables@>; -@<Dump a couple more things and the closing check word@>; -@<Close the format file@>; -end; -tini - -@ Corresponding to the procedure that dumps a format file, we have a function -that reads one in. The function returns |false| if the dumped format is -incompatible with the present \TeX\ table sizes, etc. - -@d bad_fmt=6666 {go here if the format file is unacceptable} -@d too_small(#)==begin wake_up_terminal; - wterm_ln('---! Must increase the ',#); -@.Must increase the x@> - goto bad_fmt; - end - -@p @t\4@>@<Declare the function called |open_fmt_file|@>@; -function load_fmt_file:boolean; -label bad_fmt,exit; -var j,@!k:integer; {all-purpose indices} -@!p,@!q: pointer; {all-purpose pointers} -@!x: integer; {something undumped} -@!w: four_quarters; {four ASCII codes} -begin @<Undump constants for consistency check@>; -@<Undump the string pool@>; -@<Undump the dynamic memory@>; -@<Undump the table of equivalents@>; -@<Undump the font information@>; -@<Undump the hyphenation tables@>; -@<Undump a couple more things and the closing check word@>; -load_fmt_file:=true; return; {it worked!} -bad_fmt: wake_up_terminal; - wterm_ln('(Fatal format file error; I''m stymied)'); -@.Fatal format file error@> -load_fmt_file:=false; -exit:end; - -@ The user is not allowed to dump a format file unless |save_ptr=0|. -This condition implies that |cur_level=level_one|, hence -the |xeq_level| array is constant and it need not be dumped. - -@<If dumping is not allowed, abort@>= -if save_ptr<>0 then - begin print_err("You can't dump inside a group"); -@.You can't dump...@> - help1("`{...\dump}' is a no-no."); succumb; - end - -@ Format files consist of |memory_word| items, and we use the following -macros to dump words of different types: - -@d dump_wd(#)==begin fmt_file^:=#; put(fmt_file);@+end -@d dump_int(#)==begin fmt_file^.int:=#; put(fmt_file);@+end -@d dump_hh(#)==begin fmt_file^.hh:=#; put(fmt_file);@+end -@d dump_qqqq(#)==begin fmt_file^.qqqq:=#; put(fmt_file);@+end - -@<Glob...@>= -@!fmt_file:word_file; {for input or output of format information} - -@ The inverse macros are slightly more complicated, since we need to check -the range of the values we are reading in. We say `|undump(a)(b)(x)|' to -read an integer value |x| that is supposed to be in the range |a<=x<=b|. -System error messages should be suppressed when undumping. -@^system dependencies@> - -@d undump_wd(#)==begin get(fmt_file); #:=fmt_file^;@+end -@d undump_int(#)==begin get(fmt_file); #:=fmt_file^.int;@+end -@d undump_hh(#)==begin get(fmt_file); #:=fmt_file^.hh;@+end -@d undump_qqqq(#)==begin get(fmt_file); #:=fmt_file^.qqqq;@+end -@d undump_end_end(#)==#:=x;@+end -@d undump_end(#)==(x>#) then goto bad_fmt@+else undump_end_end -@d undump(#)==begin undump_int(x); if (x<#) or undump_end -@d undump_size_end_end(#)==too_small(#)@+else undump_end_end -@d undump_size_end(#)==if x># then undump_size_end_end -@d undump_size(#)==begin undump_int(x); - if x<# then goto bad_fmt; undump_size_end - -@ The next few sections of the program should make it clear how we use the -dump/undump macros. - -@<Dump constants for consistency check@>= -dump_int(@$);@/ -dump_int(mem_bot);@/ -dump_int(mem_top);@/ -dump_int(eqtb_size);@/ -dump_int(hash_prime);@/ -dump_int(hyph_size) - -@ Sections of a \.{WEB} program that are ``commented out'' still contribute -strings to the string pool; therefore \.{INITEX} and \TeX\ will have -the same strings. (And it is, of course, a good thing that they do.) -@.WEB@> -@^string pool@> - -@<Undump constants for consistency check@>= -x:=fmt_file^.int; -if x<>@$ then goto bad_fmt; {check that strings are the same} -undump_int(x); -if x<>mem_bot then goto bad_fmt; -undump_int(x); -if x<>mem_top then goto bad_fmt; -undump_int(x); -if x<>eqtb_size then goto bad_fmt; -undump_int(x); -if x<>hash_prime then goto bad_fmt; -undump_int(x); -if x<>hyph_size then goto bad_fmt - -@ @d dump_four_ASCII== - w.b0:=qi(so(str_pool[k])); w.b1:=qi(so(str_pool[k+1])); - w.b2:=qi(so(str_pool[k+2])); w.b3:=qi(so(str_pool[k+3])); - dump_qqqq(w) - -@<Dump the string pool@>= -dump_int(pool_ptr); -dump_int(str_ptr); -for k:=0 to str_ptr do dump_int(str_start[k]); -k:=0; -while k+4<pool_ptr do - begin dump_four_ASCII; k:=k+4; - end; -k:=pool_ptr-4; dump_four_ASCII; -print_ln; print_int(str_ptr); print(" strings of total length "); -print_int(pool_ptr) - -@ @d undump_four_ASCII== - undump_qqqq(w); - str_pool[k]:=si(qo(w.b0)); str_pool[k+1]:=si(qo(w.b1)); - str_pool[k+2]:=si(qo(w.b2)); str_pool[k+3]:=si(qo(w.b3)) - -@<Undump the string pool@>= -undump_size(0)(pool_size)('string pool size')(pool_ptr); -undump_size(0)(max_strings)('max strings')(str_ptr); -for k:=0 to str_ptr do undump(0)(pool_ptr)(str_start[k]); -k:=0; -while k+4<pool_ptr do - begin undump_four_ASCII; k:=k+4; - end; -k:=pool_ptr-4; undump_four_ASCII; -init_str_ptr:=str_ptr; init_pool_ptr:=pool_ptr - -@ By sorting the list of available spaces in the variable-size portion of -|mem|, we are usually able to get by without having to dump very much -of the dynamic memory. - -We recompute |var_used| and |dyn_used|, so that \.{INITEX} dumps valid -information even when it has not been gathering statistics. - -@<Dump the dynamic memory@>= -sort_avail; var_used:=0; -dump_int(lo_mem_max); dump_int(rover); -p:=mem_bot; q:=rover; x:=0; -repeat for k:=p to q+1 do dump_wd(mem[k]); -x:=x+q+2-p; var_used:=var_used+q-p; -p:=q+node_size(q); q:=rlink(q); -until q=rover; -var_used:=var_used+lo_mem_max-p; dyn_used:=mem_end+1-hi_mem_min;@/ -for k:=p to lo_mem_max do dump_wd(mem[k]); -x:=x+lo_mem_max+1-p; -dump_int(hi_mem_min); dump_int(avail); -for k:=hi_mem_min to mem_end do dump_wd(mem[k]); -x:=x+mem_end+1-hi_mem_min; -p:=avail; -while p<>null do - begin decr(dyn_used); p:=link(p); - end; -dump_int(var_used); dump_int(dyn_used); -print_ln; print_int(x); -print(" memory locations dumped; current usage is "); -print_int(var_used); print_char("&"); print_int(dyn_used) - -@ @<Undump the dynamic memory@>= -undump(lo_mem_stat_max+1000)(hi_mem_stat_min-1)(lo_mem_max); -undump(lo_mem_stat_max+1)(lo_mem_max)(rover); -p:=mem_bot; q:=rover; -repeat for k:=p to q+1 do undump_wd(mem[k]); -p:=q+node_size(q); -if (p>lo_mem_max)or((q>=rlink(q))and(rlink(q)<>rover)) then goto bad_fmt; -q:=rlink(q); -until q=rover; -for k:=p to lo_mem_max do undump_wd(mem[k]); -if mem_min<mem_bot-2 then {make more low memory available} - begin p:=llink(rover); q:=mem_min+1; - link(mem_min):=null; info(mem_min):=null; {we don't use the bottom word} - rlink(p):=q; llink(rover):=q;@/ - rlink(q):=rover; llink(q):=p; link(q):=empty_flag; - node_size(q):=mem_bot-q; - end; -undump(lo_mem_max+1)(hi_mem_stat_min)(hi_mem_min); -undump(null)(mem_top)(avail); mem_end:=mem_top; -for k:=hi_mem_min to mem_end do undump_wd(mem[k]); -undump_int(var_used); undump_int(dyn_used) - -@ @<Dump the table of equivalents@>= -@<Dump regions 1 to 4 of |eqtb|@>; -@<Dump regions 5 and 6 of |eqtb|@>; -dump_int(par_loc); dump_int(write_loc);@/ -@<Dump the hash table@> - -@ @<Undump the table of equivalents@>= -@<Undump regions 1 to 6 of |eqtb|@>; -undump(hash_base)(frozen_control_sequence)(par_loc); -par_token:=cs_token_flag+par_loc;@/ -undump(hash_base)(frozen_control_sequence)(write_loc);@/ -@<Undump the hash table@> - -@ The table of equivalents usually contains repeated information, so we dump it -in compressed form: The sequence of $n+2$ values $(n,x_1,\ldots,x_n,m)$ in the -format file represents $n+m$ consecutive entries of |eqtb|, with |m| extra -copies of $x_n$, namely $(x_1,\ldots,x_n,x_n,\ldots,x_n)$. - -@<Dump regions 1 to 4 of |eqtb|@>= -k:=active_base; -repeat j:=k; -while j<int_base-1 do - begin if (equiv(j)=equiv(j+1))and(eq_type(j)=eq_type(j+1))and@| - (eq_level(j)=eq_level(j+1)) then goto found1; - incr(j); - end; -l:=int_base; goto done1; {|j=int_base-1|} -found1: incr(j); l:=j; -while j<int_base-1 do - begin if (equiv(j)<>equiv(j+1))or(eq_type(j)<>eq_type(j+1))or@| - (eq_level(j)<>eq_level(j+1)) then goto done1; - incr(j); - end; -done1:dump_int(l-k); -while k<l do - begin dump_wd(eqtb[k]); incr(k); - end; -k:=j+1; dump_int(k-l); -until k=int_base - -@ @<Dump regions 5 and 6 of |eqtb|@>= -repeat j:=k; -while j<eqtb_size do - begin if eqtb[j].int=eqtb[j+1].int then goto found2; - incr(j); - end; -l:=eqtb_size+1; goto done2; {|j=eqtb_size|} -found2: incr(j); l:=j; -while j<eqtb_size do - begin if eqtb[j].int<>eqtb[j+1].int then goto done2; - incr(j); - end; -done2:dump_int(l-k); -while k<l do - begin dump_wd(eqtb[k]); incr(k); - end; -k:=j+1; dump_int(k-l); -until k>eqtb_size - -@ @<Undump regions 1 to 6 of |eqtb|@>= -k:=active_base; -repeat undump_int(x); -if (x<1)or(k+x>eqtb_size+1) then goto bad_fmt; -for j:=k to k+x-1 do undump_wd(eqtb[j]); -k:=k+x; -undump_int(x); -if (x<0)or(k+x>eqtb_size+1) then goto bad_fmt; -for j:=k to k+x-1 do eqtb[j]:=eqtb[k-1]; -k:=k+x; -until k>eqtb_size - -@ A different scheme is used to compress the hash table, since its lower -region is usually sparse. When |text(p)<>0| for |p<=hash_used|, we output -two words, |p| and |hash[p]|. The hash table is, of course, densely packed -for |p>=hash_used|, so the remaining entries are output in a~block. - -@<Dump the hash table@>= -dump_int(hash_used); cs_count:=frozen_control_sequence-1-hash_used; -for p:=hash_base to hash_used do if text(p)<>0 then - begin dump_int(p); dump_hh(hash[p]); incr(cs_count); - end; -for p:=hash_used+1 to undefined_control_sequence-1 do dump_hh(hash[p]); -dump_int(cs_count);@/ -print_ln; print_int(cs_count); print(" multiletter control sequences") - -@ @<Undump the hash table@>= -undump(hash_base)(frozen_control_sequence)(hash_used); p:=hash_base-1; -repeat undump(p+1)(hash_used)(p); undump_hh(hash[p]); -until p=hash_used; -for p:=hash_used+1 to undefined_control_sequence-1 do undump_hh(hash[p]); -undump_int(cs_count) - -@ @<Dump the font information@>= -dump_int(fmem_ptr); -for k:=0 to fmem_ptr-1 do dump_wd(font_info[k]); -dump_int(font_ptr); -for k:=null_font to font_ptr do - @<Dump the array info for internal font number |k|@>; -print_ln; print_int(fmem_ptr-7); print(" words of font info for "); -print_int(font_ptr-font_base); print(" preloaded font"); -if font_ptr<>font_base+1 then print_char("s") - -@ @<Undump the font information@>= -undump_size(7)(font_mem_size)('font mem size')(fmem_ptr); -for k:=0 to fmem_ptr-1 do undump_wd(font_info[k]); -undump_size(font_base)(font_max)('font max')(font_ptr); -for k:=null_font to font_ptr do - @<Undump the array info for internal font number |k|@> - -@ @<Dump the array info for internal font number |k|@>= -begin dump_qqqq(font_check[k]); -dump_int(font_size[k]); -dump_int(font_dsize[k]); -dump_int(font_params[k]);@/ -dump_int(hyphen_char[k]); -dump_int(skew_char[k]);@/ -dump_int(font_name[k]); -dump_int(font_area[k]);@/ -dump_int(font_bc[k]); -dump_int(font_ec[k]);@/ -dump_int(char_base[k]); -dump_int(width_base[k]); -dump_int(height_base[k]);@/ -dump_int(depth_base[k]); -dump_int(italic_base[k]); -dump_int(lig_kern_base[k]);@/ -dump_int(kern_base[k]); -dump_int(exten_base[k]); -dump_int(param_base[k]);@/ -dump_int(font_glue[k]);@/ -dump_int(bchar_label[k]); -dump_int(font_bchar[k]); -dump_int(font_false_bchar[k]);@/ -print_nl("\font"); print_esc(font_id_text(k)); print_char("="); -print_file_name(font_name[k],font_area[k],""); -if font_size[k]<>font_dsize[k] then - begin print(" at "); print_scaled(font_size[k]); print("pt"); - end; -end - -@ @<Undump the array info for internal font number |k|@>= -begin undump_qqqq(font_check[k]);@/ -undump_int(font_size[k]); -undump_int(font_dsize[k]); -undump(min_halfword)(max_halfword)(font_params[k]);@/ -undump_int(hyphen_char[k]); -undump_int(skew_char[k]);@/ -undump(0)(str_ptr)(font_name[k]); -undump(0)(str_ptr)(font_area[k]);@/ -undump(0)(255)(font_bc[k]); -undump(0)(255)(font_ec[k]);@/ -undump_int(char_base[k]); -undump_int(width_base[k]); -undump_int(height_base[k]);@/ -undump_int(depth_base[k]); -undump_int(italic_base[k]); -undump_int(lig_kern_base[k]);@/ -undump_int(kern_base[k]); -undump_int(exten_base[k]); -undump_int(param_base[k]);@/ -undump(min_halfword)(lo_mem_max)(font_glue[k]);@/ -undump(0)(fmem_ptr-1)(bchar_label[k]); -undump(min_quarterword)(non_char)(font_bchar[k]); -undump(min_quarterword)(non_char)(font_false_bchar[k]); -end - -@ @<Dump the hyphenation tables@>= -dump_int(hyph_count); -for k:=0 to hyph_size do if hyph_word[k]<>0 then - begin dump_int(k); dump_int(hyph_word[k]); dump_int(hyph_list[k]); - end; -print_ln; print_int(hyph_count); print(" hyphenation exception"); -if hyph_count<>1 then print_char("s"); -if trie_not_ready then init_trie; -dump_int(trie_max); -for k:=0 to trie_max do dump_hh(trie[k]); -dump_int(trie_op_ptr); -for k:=1 to trie_op_ptr do - begin dump_int(hyf_distance[k]); - dump_int(hyf_num[k]); - dump_int(hyf_next[k]); - end; -print_nl("Hyphenation trie of length "); print_int(trie_max); -@.Hyphenation trie...@> -print(" has "); print_int(trie_op_ptr); print(" op"); -if trie_op_ptr<>1 then print_char("s"); -print(" out of "); print_int(trie_op_size); -for k:=255 downto 0 do if trie_used[k]>min_quarterword then - begin print_nl(" "); print_int(qo(trie_used[k])); - print(" for language "); print_int(k); - dump_int(k); dump_int(qo(trie_used[k])); - end - -@ Only ``nonempty'' parts of |op_start| need to be restored. - -@<Undump the hyphenation tables@>= -undump(0)(hyph_size)(hyph_count); -for k:=1 to hyph_count do - begin undump(0)(hyph_size)(j); - undump(0)(str_ptr)(hyph_word[j]); - undump(min_halfword)(max_halfword)(hyph_list[j]); - end; -undump_size(0)(trie_size)('trie size')(j); @+init trie_max:=j;@+tini -for k:=0 to j do undump_hh(trie[k]); -undump_size(0)(trie_op_size)('trie op size')(j); @+init trie_op_ptr:=j;@+tini -for k:=1 to j do - begin undump(0)(63)(hyf_distance[k]); {a |small_number|} - undump(0)(63)(hyf_num[k]); - undump(min_quarterword)(max_quarterword)(hyf_next[k]); - end; -init for k:=0 to 255 do trie_used[k]:=min_quarterword;@+tini@;@/ -k:=256; -while j>0 do - begin undump(0)(k-1)(k); undump(1)(j)(x);@+init trie_used[k]:=qi(x);@+tini@;@/ - j:=j-x; op_start[k]:=qo(j); - end; -@!init trie_not_ready:=false @+tini - -@ We have already printed a lot of statistics, so we set |tracing_stats:=0| -to prevent them from appearing again. - -@<Dump a couple more things and the closing check word@>= -dump_int(interaction); dump_int(format_ident); dump_int(69069); -tracing_stats:=0 - -@ @<Undump a couple more things and the closing check word@>= -undump(batch_mode)(error_stop_mode)(interaction); -undump(0)(str_ptr)(format_ident); -undump_int(x); -if (x<>69069)or eof(fmt_file) then goto bad_fmt - -@ @<Create the |format_ident|...@>= -selector:=new_string; -print(" (preloaded format="); print(job_name); print_char(" "); -print_int(year); print_char("."); -print_int(month); print_char("."); print_int(day); print_char(")"); -if interaction=batch_mode then selector:=log_only -else selector:=term_and_log; -str_room(1); -format_ident:=make_string; -pack_job_name(format_extension); -while not w_open_out(fmt_file) do - prompt_file_name("format file name",format_extension); -print_nl("Beginning to dump on file "); -@.Beginning to dump...@> -slow_print(w_make_name_string(fmt_file)); flush_string; -print_nl(""); slow_print(format_ident) - -@ @<Close the format file@>= -w_close(fmt_file) - -@* \[51] The main program. -This is it: the part of \TeX\ that executes all those procedures we have -written. - -Well---almost. Let's leave space for a few more routines that we may -have forgotten. - -@p @<Last-minute procedures@> - -@ We have noted that there are two versions of \TeX82. One, called \.{INITEX}, -@.INITEX@> -has to be run first; it initializes everything from scratch, without -reading a format file, and it has the capability of dumping a format file. -The other one is called `\.{VIRTEX}'; it is a ``virgin'' program that needs -@.VIRTEX@> -to input a format file in order to get started. \.{VIRTEX} typically has -more memory capacity than \.{INITEX}, because it does not need the space -consumed by the auxiliary hyphenation tables and the numerous calls on -|primitive|, etc. - -The \.{VIRTEX} program cannot read a format file instantaneously, of course; -the best implementations therefore allow for production versions of \TeX\ that -not only avoid the loading routine for \PASCAL\ object code, they also have -a format file pre-loaded. This is impossible to do if we stick to standard -\PASCAL; but there is a simple way to fool many systems into avoiding the -initialization, as follows:\quad(1)~We declare a global integer variable -called |ready_already|. The probability is negligible that this -variable holds any particular value like 314159 when \.{VIRTEX} is first -loaded.\quad(2)~After we have read in a format file and initialized -everything, we set |ready_already:=314159|.\quad(3)~Soon \.{VIRTEX} -will print `\.*', waiting for more input; and at this point we -interrupt the program and save its core image in some form that the -operating system can reload speedily.\quad(4)~When that core image is -activated, the program starts again at the beginning; but now -|ready_already=314159| and all the other global variables have -their initial values too. The former chastity has vanished! - -In other words, if we allow ourselves to test the condition -|ready_already=314159|, before |ready_already| has been -assigned a value, we can avoid the lengthy initialization. Dirty tricks -rarely pay off so handsomely. -@^dirty \PASCAL@> -@^system dependencies@> - -On systems that allow such preloading, the standard program called \.{TeX} -should be the one that has \.{plain} format preloaded, since that agrees -with {\sl The \TeX book}. Other versions, e.g., \.{AmSTeX}, should also -@:TeXbook}{\sl The \TeX book@> -@.AmSTeX@> -@.plain@> -be provided for commonly used formats. - -@<Glob...@>= -@!ready_already:integer; {a sacrifice of purity for economy} - -@ Now this is really it: \TeX\ starts and ends here. - -The initial test involving |ready_already| should be deleted if the -\PASCAL\ runtime system is smart enough to detect such a ``mistake.'' -@^system dependencies@> - -@p begin @!{|start_here|} -history:=fatal_error_stop; {in case we quit during initialization} -t_open_out; {open the terminal for output} -if ready_already=314159 then goto start_of_TEX; -@<Check the ``constant'' values...@>@; -if bad>0 then - begin wterm_ln('Ouch---my internal constants have been clobbered!', - '---case ',bad:1); -@.Ouch...clobbered@> - goto final_end; - end; -initialize; {set global variables to their starting values} -@!init if not get_strings_started then goto final_end; -init_prim; {call |primitive| for each primitive} -init_str_ptr:=str_ptr; init_pool_ptr:=pool_ptr; fix_date_and_time; -tini@/ -ready_already:=314159; -start_of_TEX: @<Initialize the output routines@>; -@<Get the first line of input and prepare to start@>; -history:=spotless; {ready to go!} -main_control; {come to life} -final_cleanup; {prepare for death} -end_of_TEX: close_files_and_terminate; -final_end: ready_already:=0; -end. - -@ Here we do whatever is needed to complete \TeX's job gracefully on the -local operating system. The code here might come into play after a fatal -error; it must therefore consist entirely of ``safe'' operations that -cannot produce error messages. For example, it would be a mistake to call -|str_room| or |make_string| at this time, because a call on |overflow| -might lead to an infinite loop. -@^system dependencies@> -(Actually there's one way to get error messages, via |prepare_mag|; -but that can't cause infinite recursion.) -@^recursion@> - -If |final_cleanup| is bypassed, this program doesn't bother to close -the input files that may still be open. - -@<Last-minute...@>= -procedure close_files_and_terminate; -var k:integer; {all-purpose index} -begin @<Finish the extensions@>; new_line_char:=-1; -@!stat if tracing_stats>0 then @<Output statistics about this job@>;@;@+tats@/ -wake_up_terminal; @<Finish the \.{DVI} file@>; -if log_opened then - begin wlog_cr; a_close(log_file); selector:=selector-2; - if selector=term_only then - begin print_nl("Transcript written on "); -@.Transcript written...@> - slow_print(log_name); print_char("."); - end; - end; -end; - -@ The present section goes directly to the log file instead of using -|print| commands, because there's no need for these strings to take -up |str_pool| memory when a non-{\bf stat} version of \TeX\ is being used. - -@<Output statistics...@>= -if log_opened then - begin wlog_ln(' '); - wlog_ln('Here is how much of TeX''s memory',' you used:'); -@.Here is how much...@> - wlog(' ',str_ptr-init_str_ptr:1,' string'); - if str_ptr<>init_str_ptr+1 then wlog('s'); - wlog_ln(' out of ', max_strings-init_str_ptr:1);@/ - wlog_ln(' ',pool_ptr-init_pool_ptr:1,' string characters out of ', - pool_size-init_pool_ptr:1);@/ - wlog_ln(' ',lo_mem_max-mem_min+mem_end-hi_mem_min+2:1,@| - ' words of memory out of ',mem_end+1-mem_min:1);@/ - wlog_ln(' ',cs_count:1,' multiletter control sequences out of ', - hash_size:1);@/ - wlog(' ',fmem_ptr:1,' words of font info for ', - font_ptr-font_base:1,' font'); - if font_ptr<>font_base+1 then wlog('s'); - wlog_ln(', out of ',font_mem_size:1,' for ',font_max-font_base:1);@/ - wlog(' ',hyph_count:1,' hyphenation exception'); - if hyph_count<>1 then wlog('s'); - wlog_ln(' out of ',hyph_size:1);@/ - wlog_ln(' ',max_in_stack:1,'i,',max_nest_stack:1,'n,',@| - max_param_stack:1,'p,',@| - max_buf_stack+1:1,'b,',@| - max_save_stack+6:1,'s stack positions out of ',@| - stack_size:1,'i,', - nest_size:1,'n,', - param_size:1,'p,', - buf_size:1,'b,', - save_size:1,'s'); - end - -@ We get to the |final_cleanup| routine when \.{\\end} or \.{\\dump} has -been scanned and |its_all_over|\kern-2pt. - -@<Last-minute...@>= -procedure final_cleanup; -label exit; -var c:small_number; {0 for \.{\\end}, 1 for \.{\\dump}} -begin c:=cur_chr; if c<>1 then new_line_char:=-1; -if job_name=0 then open_log_file; -while input_ptr>0 do - if state=token_list then end_token_list@+else end_file_reading; -while open_parens>0 do - begin print(" )"); decr(open_parens); - end; -if cur_level>level_one then - begin print_nl("("); print_esc("end occurred "); - print("inside a group at level "); -@:end_}{\.{(\\end occurred...)}@> - print_int(cur_level-level_one); print_char(")"); - end; -while cond_ptr<>null do - begin print_nl("("); print_esc("end occurred "); - print("when "); print_cmd_chr(if_test,cur_if); - if if_line<>0 then - begin print(" on line "); print_int(if_line); - end; - print(" was incomplete)"); - if_line:=if_line_field(cond_ptr); - cur_if:=subtype(cond_ptr); temp_ptr:=cond_ptr; - cond_ptr:=link(cond_ptr); free_node(temp_ptr,if_node_size); - end; -if history<>spotless then - if ((history=warning_issued)or(interaction<error_stop_mode)) then - if selector=term_and_log then - begin selector:=term_only; - print_nl("(see the transcript file for additional information)"); -@.see the transcript file...@> - selector:=term_and_log; - end; -if c=1 then - begin @!init for c:=top_mark_code to split_bot_mark_code do - if cur_mark[c]<>null then delete_token_ref(cur_mark[c]); - if last_glue<>max_halfword then delete_glue_ref(last_glue); - store_fmt_file; return;@+tini@/ - print_nl("(\dump is performed only by INITEX)"); return; -@:dump_}{\.{\\dump...only by INITEX}@> - end; -exit:end; - -@ @<Last-minute...@>= -@!init procedure init_prim; {initialize all the primitives} -begin no_new_control_sequence:=false; -@<Put each...@>; -no_new_control_sequence:=true; -end; -tini - -@ When we begin the following code, \TeX's tables may still contain garbage; -the strings might not even be present. Thus we must proceed cautiously to get -bootstrapped in. - -But when we finish this part of the program, \TeX\ is ready to call on the -|main_control| routine to do its work. - -@<Get the first line...@>= -begin @<Initialize the input routines@>; -if (format_ident=0)or(buffer[loc]="&") then - begin if format_ident<>0 then initialize; {erase preloaded format} - if not open_fmt_file then goto final_end; - if not load_fmt_file then - begin w_close(fmt_file); goto final_end; - end; - w_close(fmt_file); - while (loc<limit)and(buffer[loc]=" ") do incr(loc); - end; -if end_line_char_inactive then decr(limit) -else buffer[limit]:=end_line_char; -fix_date_and_time;@/ -@<Compute the magic offset@>; -@<Initialize the print |selector|...@>; -if (loc<limit)and(cat_code(buffer[loc])<>escape) then start_input; - {\.{\\input} assumed} -end - -@* \[52] Debugging. -Once \TeX\ is working, you should be able to diagnose most errors with -the \.{\\show} commands and other diagnostic features. But for the initial -stages of debugging, and for the revelation of really deep mysteries, you -can compile \TeX\ with a few more aids, including the \PASCAL\ runtime -checks and its debugger. An additional routine called |debug_help| -will also come into play when you type `\.D' after an error message; -|debug_help| also occurs just before a fatal error causes \TeX\ to succumb. -@^debugging@> -@^system dependencies@> - -The interface to |debug_help| is primitive, but it is good enough when used -with a \PASCAL\ debugger that allows you to set breakpoints and to read -variables and change their values. After getting the prompt `\.{debug \#}', you -type either a negative number (this exits |debug_help|), or zero (this -goes to a location where you can set a breakpoint, thereby entering into -dialog with the \PASCAL\ debugger), or a positive number |m| followed by -an argument |n|. The meaning of |m| and |n| will be clear from the -program below. (If |m=13|, there is an additional argument, |l|.) -@.debug \#@> - -@d breakpoint=888 {place where a breakpoint is desirable} - -@<Last-minute...@>= -@!debug procedure debug_help; {routine to display various things} -label breakpoint,exit; -var k,@!l,@!m,@!n:integer; -begin clear_terminal; - loop begin wake_up_terminal; - print_nl("debug # (-1 to exit):"); update_terminal; -@.debug \#@> - read(term_in,m); - if m<0 then return - else if m=0 then - begin goto breakpoint;@/ {go to every declared label at least once} - breakpoint: m:=0; @{'BREAKPOINT'@}@/ - end - else begin read(term_in,n); - case m of - @t\4@>@<Numbered cases for |debug_help|@>@; - othercases print("?") - endcases; - end; - end; -exit:end; -gubed - -@ @<Numbered cases...@>= -1: print_word(mem[n]); {display |mem[n]| in all forms} -2: print_int(info(n)); -3: print_int(link(n)); -4: print_word(eqtb[n]); -5: print_word(font_info[n]); -6: print_word(save_stack[n]); -7: show_box(n); - {show a box, abbreviated by |show_box_depth| and |show_box_breadth|} -8: begin breadth_max:=10000; depth_threshold:=pool_size-pool_ptr-10; - show_node_list(n); {show a box in its entirety} - end; -9: show_token_list(n,null,1000); -10: slow_print(n); -11: check_mem(n>0); {check wellformedness; print new busy locations if |n>0|} -12: search_mem(n); {look for pointers to |n|} -13: begin read(term_in,l); print_cmd_chr(n,l); - end; -14: for k:=0 to n do print(buffer[k]); -15: begin font_in_short_display:=null_font; short_display(n); - end; -16: panicking:=not panicking; - -@* \[53] Extensions. -The program above includes a bunch of ``hooks'' that allow further -capabilities to be added without upsetting \TeX's basic structure. -Most of these hooks are concerned with ``whatsit'' nodes, which are -intended to be used for special purposes; whenever a new extension to -\TeX\ involves a new kind of whatsit node, a corresponding change needs -to be made to the routines below that deal with such nodes, -but it will usually be unnecessary to make many changes to the -other parts of this program. - -In order to demonstrate how extensions can be made, we shall treat -`\.{\\write}', `\.{\\openout}', `\.{\\closeout}', `\.{\\immediate}', -`\.{\\special}', and `\.{\\setlanguage}' as if they were extensions. -These commands are actually primitives of \TeX, and they should -appear in all implementations of the system; but let's try to imagine -that they aren't. Then the program below illustrates how a person -could add them. - -Sometimes, of course, an extension will require changes to \TeX\ itself; -no system of hooks could be complete enough for all conceivable extensions. -The features associated with `\.{\\write}' are almost all confined to the -following paragraphs, but there are small parts of the |print_ln| and -|print_char| procedures that were introduced specifically to \.{\\write} -characters. Furthermore one of the token lists recognized by the scanner -is a |write_text|; and there are a few other miscellaneous places where we -have already provided for some aspect of \.{\\write}. The goal of a \TeX\ -extender should be to minimize alterations to the standard parts of the -program, and to avoid them completely if possible. He or she should also -be quite sure that there's no easy way to accomplish the desired goals -with the standard features that \TeX\ already has. ``Think thrice before -extending,'' because that may save a lot of work, and it will also keep -incompatible extensions of \TeX\ from proliferating. -@^system dependencies@> -@^extensions to \TeX@> - -@ First let's consider the format of whatsit nodes that are used to represent -the data associated with \.{\\write} and its relatives. Recall that a whatsit -has |type=whatsit_node|, and the |subtype| is supposed to distinguish -different kinds of whatsits. Each node occupies two or more words; the -exact number is immaterial, as long as it is readily determined from the -|subtype| or other data. - -We shall introduce five |subtype| values here, corresponding to the -control sequences \.{\\openout}, \.{\\write}, \.{\\closeout}, \.{\\special}, and -\.{\\setlanguage}. The second word of I/O whatsits has a |write_stream| field -that identifies the write-stream number (0 to 15, or 16 for out-of-range and -positive, or 17 for out-of-range and negative). -In the case of \.{\\write} and \.{\\special}, there is also a field that -points to the reference count of a token list that should be sent. In the -case of \.{\\openout}, we need three words and three auxiliary subfields -to hold the string numbers for name, area, and extension. - -@d write_node_size=2 {number of words in a write/whatsit node} -@d open_node_size=3 {number of words in an open/whatsit node} -@d open_node=0 {|subtype| in whatsits that represent files to \.{\\openout}} -@d write_node=1 {|subtype| in whatsits that represent things to \.{\\write}} -@d close_node=2 {|subtype| in whatsits that represent streams to \.{\\closeout}} -@d special_node=3 {|subtype| in whatsits that represent \.{\\special} things} -@d language_node=4 {|subtype| in whatsits that change the current language} -@d what_lang(#)==link(#+1) {language number, in the range |0..255|} -@d what_lhm(#)==type(#+1) {minimum left fragment, in the range |1..63|} -@d what_rhm(#)==subtype(#+1) {minimum right fragment, in the range |1..63|} -@d write_tokens(#) == link(#+1) {reference count of token list to write} -@d write_stream(#) == info(#+1) {stream number (0 to 17)} -@d open_name(#) == link(#+1) {string number of file name to open} -@d open_area(#) == info(#+2) {string number of file area for |open_name|} -@d open_ext(#) == link(#+2) {string number of file extension for |open_name|} - -@ The sixteen possible \.{\\write} streams are represented by the |write_file| -array. The |j|th file is open if and only if |write_open[j]=true|. The last -two streams are special; |write_open[16]| represents a stream number -greater than 15, while |write_open[17]| represents a negative stream number, -and both of these variables are always |false|. - -@<Glob...@>= -@!write_file:array[0..15] of alpha_file; -@!write_open:array[0..17] of boolean; - -@ @<Set init...@>= -for k:=0 to 17 do write_open[k]:=false; - -@ Extensions might introduce new command codes; but it's best to use -|extension| with a modifier, whenever possible, so that |main_control| -stays the same. - -@d immediate_code=4 {command modifier for \.{\\immediate}} -@d set_language_code=5 {command modifier for \.{\\setlanguage}} - -@<Put each...@>= -primitive("openout",extension,open_node);@/ -@!@:open_out_}{\.{\\openout} primitive@> -primitive("write",extension,write_node); write_loc:=cur_val;@/ -@!@:write_}{\.{\\write} primitive@> -primitive("closeout",extension,close_node);@/ -@!@:close_out_}{\.{\\closeout} primitive@> -primitive("special",extension,special_node);@/ -@!@:special_}{\.{\\special} primitive@> -primitive("immediate",extension,immediate_code);@/ -@!@:immediate_}{\.{\\immediate} primitive@> -primitive("setlanguage",extension,set_language_code);@/ -@!@:set_language_}{\.{\\setlanguage} primitive@> - -@ The variable |write_loc| just introduced is used to provide an -appropriate error message in case of ``runaway'' write texts. - -@<Glob...@>= -@!write_loc:pointer; {|eqtb| address of \.{\\write}} - -@ @<Cases of |print_cmd_chr|...@>= -extension: case chr_code of - open_node:print_esc("openout"); - write_node:print_esc("write"); - close_node:print_esc("closeout"); - special_node:print_esc("special"); - immediate_code:print_esc("immediate"); - set_language_code:print_esc("setlanguage"); - othercases print("[unknown extension!]") - endcases; - -@ When an |extension| command occurs in |main_control|, in any mode, -the |do_extension| routine is called. - -@<Cases of |main_control| that are for extensions...@>= -any_mode(extension):do_extension; - -@ @<Declare act...@>= -@t\4@>@<Declare procedures needed in |do_extension|@>@; -procedure do_extension; -var i,@!j,@!k:integer; {all-purpose integers} -@!p,@!q,@!r:pointer; {all-purpose pointers} -begin case cur_chr of -open_node:@<Implement \.{\\openout}@>; -write_node:@<Implement \.{\\write}@>; -close_node:@<Implement \.{\\closeout}@>; -special_node:@<Implement \.{\\special}@>; -immediate_code:@<Implement \.{\\immediate}@>; -set_language_code:@<Implement \.{\\setlanguage}@>; -othercases confusion("ext1") -@:this can't happen ext1}{\quad ext1@> -endcases; -end; - -@ Here is a subroutine that creates a whatsit node having a given |subtype| -and a given number of words. It initializes only the first word of the whatsit, -and appends it to the current list. - -@<Declare procedures needed in |do_extension|@>= -procedure new_whatsit(@!s:small_number;@!w:small_number); -var p:pointer; {the new node} -begin p:=get_node(w); type(p):=whatsit_node; subtype(p):=s; -link(tail):=p; tail:=p; -end; - -@ The next subroutine uses |cur_chr| to decide what sort of whatsit is -involved, and also inserts a |write_stream| number. - -@<Declare procedures needed in |do_ext...@>= -procedure new_write_whatsit(@!w:small_number); -begin new_whatsit(cur_chr,w); -if w<>write_node_size then scan_four_bit_int -else begin scan_int; - if cur_val<0 then cur_val:=17 - else if cur_val>15 then cur_val:=16; - end; -write_stream(tail):=cur_val; -end; - -@ @<Implement \.{\\openout}@>= -begin new_write_whatsit(open_node_size); -scan_optional_equals; scan_file_name;@/ -open_name(tail):=cur_name; open_area(tail):=cur_area; open_ext(tail):=cur_ext; -end - -@ When `\.{\\write 12\{...\}}' appears, we scan the token list `\.{\{...\}}' -without expanding its macros; the macros will be expanded later when this -token list is rescanned. - -@<Implement \.{\\write}@>= -begin k:=cur_cs; new_write_whatsit(write_node_size);@/ -cur_cs:=k; p:=scan_toks(false,false); write_tokens(tail):=def_ref; -end - -@ @<Implement \.{\\closeout}@>= -begin new_write_whatsit(write_node_size); write_tokens(tail):=null; -end - -@ When `\.{\\special\{...\}}' appears, we expand the macros in the token -list as in \.{\\xdef} and \.{\\mark}. - -@<Implement \.{\\special}@>= -begin new_whatsit(special_node,write_node_size); write_stream(tail):=null; -p:=scan_toks(false,true); write_tokens(tail):=def_ref; -end - -@ Each new type of node that appears in our data structure must be capable -of being displayed, copied, destroyed, and so on. The routines that we -need for write-oriented whatsits are somewhat like those for mark nodes; -other extensions might, of course, involve more subtlety here. - -@<Basic printing...@>= -procedure print_write_whatsit(@!s:str_number;@!p:pointer); -begin print_esc(s); -if write_stream(p)<16 then print_int(write_stream(p)) -else if write_stream(p)=16 then print_char("*") -@.*\relax@> -else print_char("-"); -end; - -@ @<Display the whatsit...@>= -case subtype(p) of -open_node:begin print_write_whatsit("openout",p); - print_char("="); print_file_name(open_name(p),open_area(p),open_ext(p)); - end; -write_node:begin print_write_whatsit("write",p); - print_mark(write_tokens(p)); - end; -close_node:print_write_whatsit("closeout",p); -special_node:begin print_esc("special"); - print_mark(write_tokens(p)); - end; -language_node:begin print_esc("setlanguage"); - print_int(what_lang(p)); print(" (hyphenmin "); - print_int(what_lhm(p)); print_char(","); - print_int(what_rhm(p)); print_char(")"); - end; -othercases print("whatsit?") -endcases - -@ @<Make a partial copy of the whatsit...@>= -case subtype(p) of -open_node: begin r:=get_node(open_node_size); words:=open_node_size; - end; -write_node,special_node: begin r:=get_node(write_node_size); - add_token_ref(write_tokens(p)); words:=write_node_size; - end; -close_node,language_node: begin r:=get_node(small_node_size); - words:=small_node_size; - end; -othercases confusion("ext2") -@:this can't happen ext2}{\quad ext2@> -endcases - -@ @<Wipe out the whatsit...@>= -begin case subtype(p) of -open_node: free_node(p,open_node_size); -write_node,special_node: begin delete_token_ref(write_tokens(p)); - free_node(p,write_node_size); goto done; - end; -close_node,language_node: free_node(p,small_node_size); -othercases confusion("ext3") -@:this can't happen ext3}{\quad ext3@> -endcases;@/ -goto done; -end - -@ @<Incorporate a whatsit node into a vbox@>=do_nothing - -@ @<Incorporate a whatsit node into an hbox@>=do_nothing - -@ @<Let |d| be the width of the whatsit |p|@>=d:=0 - -@ @d adv_past(#)==@+if subtype(#)=language_node then - begin cur_lang:=what_lang(#); l_hyf:=what_lhm(#); r_hyf:=what_rhm(#);@+end - -@<Advance \(p)past a whatsit node in the \(l)|line_break| loop@>=@+ -adv_past(cur_p) - -@ @<Advance \(p)past a whatsit node in the \(p)pre-hyphenation loop@>=@+ -adv_past(s) - -@ @<Prepare to move whatsit |p| to the current page, then |goto contribute|@>= -goto contribute - -@ @<Process whatsit |p| in |vert_break| loop, |goto not_found|@>= -goto not_found - -@ @<Output the whatsit node |p| in a vlist@>= -out_what(p) - -@ @<Output the whatsit node |p| in an hlist@>= -out_what(p) - -@ After all this preliminary shuffling, we come finally to the routines -that actually send out the requested data. Let's do \.{\\special} first -(it's easier). - -@<Declare procedures needed in |hlist_out|, |vlist_out|@>= -procedure special_out(@!p:pointer); -var old_setting:0..max_selector; {holds print |selector|} -@!k:pool_pointer; {index into |str_pool|} -begin synch_h; synch_v;@/ -old_setting:=selector; selector:=new_string; -show_token_list(link(write_tokens(p)),null,pool_size-pool_ptr); -selector:=old_setting; -str_room(1); -if cur_length<256 then - begin dvi_out(xxx1); dvi_out(cur_length); - end -else begin dvi_out(xxx4); dvi_four(cur_length); - end; -for k:=str_start[str_ptr] to pool_ptr-1 do dvi_out(so(str_pool[k])); -pool_ptr:=str_start[str_ptr]; {erase the string} -end; - -@ To write a token list, we must run it through \TeX's scanner, expanding -macros and \.{\\the} and \.{\\number}, etc. This might cause runaways, -if a delimited macro parameter isn't matched, and runaways would be -extremely confusing since we are calling on \TeX's scanner in the middle -of a \.{\\shipout} command. Therefore we will put a dummy control sequence as -a ``stopper,'' right after the token list. This control sequence is -artificially defined to be \.{\\outer}. -@:end_write_}{\.{\\endwrite}@> - -@<Initialize table...@>= -text(end_write):="endwrite"; eq_level(end_write):=level_one; -eq_type(end_write):=outer_call; equiv(end_write):=null; - -@ @<Declare procedures needed in |hlist_out|, |vlist_out|@>= -procedure write_out(@!p:pointer); -var old_setting:0..max_selector; {holds print |selector|} -@!old_mode:integer; {saved |mode|} -@!j:small_number; {write stream number} -@!q,@!r:pointer; {temporary variables for list manipulation} -begin @<Expand macros in the token list - and make |link(def_ref)| point to the result@>; -old_setting:=selector; j:=write_stream(p); -if write_open[j] then selector:=j -else begin {write to the terminal if file isn't open} - if (j=17)and(selector=term_and_log) then selector:=log_only; - print_nl(""); - end; -token_show(def_ref); print_ln; -flush_list(def_ref); selector:=old_setting; -end; - -@ The final line of this routine is slightly subtle; at least, the author -didn't think about it until getting burnt! There is a used-up token list -@^Knuth, Donald Ervin@> -on the stack, namely the one that contained |end_write_token|. (We -insert this artificial `\.{\\endwrite}' to prevent runaways, as explained -above.) If it were not removed, and if there were numerous writes on a -single page, the stack would overflow. - -@d end_write_token==cs_token_flag+end_write - -@<Expand macros in the token list and...@>= -q:=get_avail; info(q):=right_brace_token+"}";@/ -r:=get_avail; link(q):=r; info(r):=end_write_token; ins_list(q);@/ -begin_token_list(write_tokens(p),write_text);@/ -q:=get_avail; info(q):=left_brace_token+"{"; ins_list(q); -{now we're ready to scan - `\.\{$\langle\,$token list$\,\rangle$\.{\} \\endwrite}'} -old_mode:=mode; mode:=0; - {disable \.{\\prevdepth}, \.{\\spacefactor}, \.{\\lastskip}, \.{\\prevgraf}} -cur_cs:=write_loc; q:=scan_toks(false,true); {expand macros, etc.} -get_token;@+if cur_tok<>end_write_token then - @<Recover from an unbalanced write command@>; -mode:=old_mode; -end_token_list {conserve stack space} - -@ @<Recover from an unbalanced write command@>= -begin print_err("Unbalanced write command"); -@.Unbalanced write...@> -help2("On this page there's a \write with fewer real {'s than }'s.")@/ -("I can't handle that very well; good luck."); error; -repeat get_token; -until cur_tok=end_write_token; -end - -@ The |out_what| procedure takes care of outputting whatsit nodes for -|vlist_out| and |hlist_out|\kern-.3pt. - -@<Declare procedures needed in |hlist_out|, |vlist_out|@>= -procedure out_what(@!p:pointer); -var j:small_number; {write stream number} -begin case subtype(p) of -open_node,write_node,close_node:@<Do some work that has been queued up - for \.{\\write}@>; -special_node:special_out(p); -language_node:do_nothing; -othercases confusion("ext4") -@:this can't happen ext4}{\quad ext4@> -endcases; -end; - -@ We don't implement \.{\\write} inside of leaders. (The reason is that -the number of times a leader box appears might be different in different -implementations, due to machine-dependent rounding in the glue calculations.) -@^leaders@> - -@<Do some work that has been queued up...@>= -if not doing_leaders then - begin j:=write_stream(p); - if subtype(p)=write_node then write_out(p) - else begin if write_open[j] then a_close(write_file[j]); - if subtype(p)=close_node then write_open[j]:=false - else if j<16 then - begin cur_name:=open_name(p); cur_area:=open_area(p); - cur_ext:=open_ext(p); - if cur_ext="" then cur_ext:=".tex"; - pack_cur_name; - while not a_open_out(write_file[j]) do - prompt_file_name("output file name",".tex"); - write_open[j]:=true; - end; - end; - end - -@ The presence of `\.{\\immediate}' causes the |do_extension| procedure -to descend to one level of recursion. Nothing happens unless \.{\\immediate} -is followed by `\.{\\openout}', `\.{\\write}', or `\.{\\closeout}'. -@^recursion@> - -@<Implement \.{\\immediate}@>= -begin get_x_token; -if (cur_cmd=extension)and(cur_chr<=close_node) then - begin p:=tail; do_extension; {append a whatsit node} - out_what(tail); {do the action immediately} - flush_node_list(tail); tail:=p; link(p):=null; - end -else back_input; -end - -@ The \.{\\language} extension is somewhat different. -We need a subroutine that comes into play when a character of -a non-|clang| language is being appended to the current paragraph. - -@<Declare action...@>= -procedure fix_language; -var @!l:ASCII_code; {the new current language} -begin if language<=0 then l:=0 -else if language>255 then l:=0 -else l:=language; -if l<>clang then - begin new_whatsit(language_node,small_node_size); - what_lang(tail):=l; clang:=l;@/ - what_lhm(tail):=norm_min(left_hyphen_min); - what_rhm(tail):=norm_min(right_hyphen_min); - end; -end; - -@ @<Implement \.{\\setlanguage}@>= -if abs(mode)<>hmode then report_illegal_case -else begin new_whatsit(language_node,small_node_size); - scan_int; - if cur_val<=0 then clang:=0 - else if cur_val>255 then clang:=0 - else clang:=cur_val; - what_lang(tail):=clang; - what_lhm(tail):=norm_min(left_hyphen_min); - what_rhm(tail):=norm_min(right_hyphen_min); - end - -@ @<Finish the extensions@>= -for k:=0 to 15 do if write_open[k] then a_close(write_file[k]) - -@* \[54] System-dependent changes. -This section should be replaced, if necessary, by any special -modifications of the program -that are necessary to make \TeX\ work at a particular installation. -It is usually best to design your change file so that all changes to -previous sections preserve the section numbering; then everybody's version -will be consistent with the published program. More extensive changes, -which introduce new sections, can be inserted here; then only the index -itself will get a new section number. -@^system dependencies@> - -@* \[55] Index. -Here is where you can find all uses of each identifier in the program, -with underlined entries pointing to where the identifier was defined. -If the identifier is only one letter long, however, you get to see only -the underlined entries. {\sl All references are to section numbers instead of -page numbers.} - -This index also lists error messages and other aspects of the program -that you might want to look up some day. For example, the entry -for ``system dependencies'' lists all sections that should receive -special attention from people who are installing \TeX\ in a new -operating environment. A list of various things that can't happen appears -under ``this can't happen''. Approximately 40 sections are listed under -``inner loop''; these account for about 60\pct! of \TeX's running time, -exclusive of input and output. |