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+Date: Tue, 31 Jan 1995 21:15:16 +0100
+Sender: NTS-L Distribution list <NTS-L@DHDURZ1.EARN>
+From: "J%org Knappen, Mainz" <KNAPPEN@VKPMZD.KPH.UNI-MAINZ.DE>
+Subject: Frequently asked questions of NTS-L, 5th edition
+X-To: nts-l <nts-l@dhdurz1.bitnet>
+To: Multiple recipients of list NTS-L <NTS-L@DHDURZ1.EARN>
+
+    Frequently Asked Questions of NTS-L
+ 
+Fifth edition
+Date: 31-JAN-1995
+Archive name: nts-l-faq
+Currently maintained by: knappen@vkpmzd.kph.uni-mainz.de (J%org Knappen)
+ 
+Remark about the format:
+ 
+This faq is divided into several sections and subsections. Each section
+contains a subsection general with some ideas which have not yet been
+discussed. I added a date to some subsections to allow you to retrieve
+fuller discussions from the archives. The transactions of this group are
+archived on
+ 
+        ftp.th-darmstadt.de    [130.83.55.75] *)
+        directory pub/tex/documentation/nts-l
+ 
+Each file in this directory is named yymm, where (guess :-) yy is the
+year and mm is the month when the mail arrived. (I.e., all postings
+of one month are bundled in one file.)
+*) Avoid using the number above ... it is subject to changes.
+ 
+Related stuff which is very worth reading you can find on the CTAN archives
+under tex/info/tex-implementors. In addition, I recommend reading the list
+of TeX bugs (tex-archive/systems/knuth/errata/tex82.bug).
+ 
+-1. Contents
+ 
+0. About NTS
+1. Proposed features of a New Typesetting system
+1.1. Improvement of Quality
+1.2. Internationality
+1.3. New Look and Feel
+1.4. Changing the ligaturing algorithm
+1.5. Writing more than one dvi-file
+1.6. Anchors
+1.7. dump/restore mechanism
+2. Proposed additions to TeX (concrete new primitives)
+2.1. \lastmark etc.
+2.2. \system
+2.3. \skylineskiplimit, \skylinehorizontallimit
+2.4. \directioncode
+2.5. \textcode
+2.6. \afterfi
+2.7. \interactionmode
+2.8. \mathspacing
+2.9. \inputescapechar
+2.10. \middle
+2.11. \outputunit
+2.12. \protected
+2.13. \scantokens
+2.14. \deferred
+2.15. \everyeof
+2.16. \readline
+2.17. \evaluate
+2.18. \ifevaluate
+2.19. \everyeof
+2.20. \fancyprompt
+3. Metaremarks
+3.1. TeX is not perfect
+3.2. In which language shall NTS be written
+3.3. The TeX language
+3.4. The TeX engine
+3.5. Extensions and Enhancements
+4. Deviations
+4.1. Automated Kerning
+4.2. About Lout
+5. Proposed changes to METAFONT
+5.1. Writing to auxiliary files
+6. Proposed changes to the tfm file format
+6.1. Vertical kerning
+6.2. Cross-font ligatures
+7. Proposed changes to the dvi file format
+7.1. Horizontal and Vertical Mirroring
+7.2. Rotation of a glphy by 180 degrees
+8. Additions to the TeX kit
+8.1. dvicopy
+8.2. dv2dp and dp2dv
+8.3. gftotxt
+8.4. qdtexvpl
+8.5. fontinst
+8.6. afmtotfm
+8.7. dvipaste
+8.8. METAPOST
+8.9. Tie
+8.10. dvi2dvi
+9. Existing extensions to TeX
+9.1. TeX-XeT
+9.2. TeX--XeT
+9.3. MLTeX
+9.4. SiSiSi
+9.5. Japanese TeX
+ 
+0. About NTS (Mar 93, see also Jul 92)
+ 
+  At DANTE '93, held at the Technical University Chemnitz last week, Joachim
+  Lammarsch, President of Dante, announced that the NTS project which had been
+  started under the aegis of DANTE, was to be re-formed under a new
+  co-ordinator, Philip Taylor. The old core group, announced at the previous
+  annual DANTE meeting, was to be dissolved, and a new core group established.
+  Membership of the new core group will not be restricted to DANTE members,
+  but will instead be offered to various well-known names (and some
+  lesser-known!) in the international TeX community.
+ 
+  see also:
+  F. Mittelbach: E-TeX Guidelines for future TeX, TUGboat v11n3 (1990)
+  P. Taylor: The future of TeX, EuroTeX'92 Prag (Proceedings); reprinted
+  in TUGboat v13n4, 433 (1992)
+ 
+  As of September 1994, there are two activities going on, the ETeX group
+  is working on a extension of TeX and is going to produce a first ETeX soon.
+  The NTS group takes the path to reimplement TeX in common LISP to get
+  a deeper understanding of how the modules of TeX are cooperating which
+  eachother.
+ 
+  Independently, the Omega project was launched to produce a typesetting system
+  which uses unicode as internal code and can handle arbitrarily encoded input
+  via filters.
+ 
+  The beforementioned projects were presented at the 1994 TUG meeting at Santa
+  Barbara and at the EuroTeX'94 conference at Gdansk. For more information,
+  consult the respective proceedings. For the Omega project exists a mailing
+  list, omega@ens.fr. To subscribe, send an e-mail to LISTSERV@ens.fr.
+ 
+  Omega is now announced to be presented at March 16, 1995 at CERN (Geneva).
+ 
+1. Proposed features of a New Typesetting system
+ 
+1.1. Improvement of Quality
+ 
+1.1.0 General:
+  Optimised page breaking, avoiding ``rivers'', letterspacing (see also 4.1),
+  Hyphenation (Haupt- und Nebentrennstellen), grid typesetting
+ 
+1.1.1 Skyline approach to line breaking (Mar 93)
+ 
+You can break paragraphs as usual with the current model, where all
+lines are simple rectangular boxes.  If there's no necessity to insert
+\lineskip, then you don't have to look at the skyline.  Only if two
+lines are too near (e.g. distance<\lineskiplimit), you have to look
+into the two rectangular boxes and to check if the boxes inside
+overlap at one or more places.
+For the worst case (i.e., you have to look at the skyline for all
+pairs of lines) processing the skyline model consumes a lot of process
+time, but this shouldn't hinder us to test this idea and look at the
+results.
+ 
+Btw, the skyline model seems to be easy to implement in the current
+TeX, because we need only some changes when the finally broken lines
+of the paragraph are put on the vertical list.  There are more changes
+needed in the code, if the line break should be changed for the cases
+where it is possible to avoid an overlap with other break points, but
+IMHO it's nonetheless a relatively small change.
+ 
+Additionally you have to introduce some new parameters.  I think of
+something like:
+        \skylineskiplimit    (b)
+                minimum vertical distance between two boxes
+        \skylinehorizontallimit   (a)
+                minimum horizontal distance
+ 
+ 
+line 1:       ------------
+        %     %
+        %     %             ----------
+        ------- <== (a) ==> %        %
+           ~                %        %
+          (b)               %        -------
+           v                %
+       ----------------------
+line 2:
+ 
+and other parameters, but the necessary parameter set, realization,
+etc. for "skylines" are subject of discussion.
+ 
+ 
+1.2. Internationality
+ 
+1.2.0 General:
+  Typesetting in arbitrary directions, unicode support (16bits), ISO10646
+  support (32bits), ligatures pointing to other fonts, vertical kerning,
+  better accent handling (\topaccent and \botaccent)
+ 
+  Remark: UTF-8 (UNICODE) can be handled with `TeX classic', LaTeX2e
+  support is provided by the CJK package written by Werner Lemberg.
+ 
+1.2.1 Supporting TeX--XeT primitives for right to left typesetting
+  TeX--XeT is an existing extension to TeX supporting right-to-left
+  typesetting an producing a usual dvi-file. TeX--XeT is written by
+  P. Breitenlohner and freely available. It is different from TeX-XeT
+  (one hyphen only). Allthough TeX will be frozen at version $\pi$,
+  this is not true for TeX--XeT. (see also 9.2)
+ 
+1.3. New Look and Feel
+ 
+1.3.0 General
+  Windows support, wysiwyg-like features
+ 
+1.3.1 Interaction with the operating system and other programmes
+  see 2.2. \system
+ 
+1.4. Changing the ligaturing algorithm
+  Replace the (IMHO over-)optimized ligature builder/kerning routines in
+  TeX by routines which separate between the building of ligatures and
+  the insertion of kerns between the characters/ligatures.
+ 
+  This can be realized in a simple way by using two passes: in the
+  first pass the ligatures are built and in the second pass the
+  resulting ligatures and remaining single characters are used to
+  determine the necessary kerns.
+ 
+  To ensure compatibility between e-TeX and TeX, it will be possible to
+  switch between the new and the current behaviour.
+ 
+  Additionally a flag in the TFM file of each font can be used to
+  specify which behaviour is to be used for the font.  This ensures that
+  "old" fonts with some tricky ligature/kerning programs depending on
+  the old behaviour can still be used with e-TeX.  (I don't know if this
+  font dependent switching is really necessary.  Comments, please!!)
+ 
+  Example:
+ 
+  A font contains the following ligatures and kerns:
+ 
+        o "             => ligature (o")  (= \"{o})
+        V o             => kern(-smallkern)
+        V lig(o")       => nothing
+ 
+  Input:        V o "
+  Output of current TeX:        V kern(-smallkern) ligature(o")
+  Output with change:           V                  ligature(o")
+ 
+  Status:
+ 
+  Bernd Raichle has written a simple, but running reimplementation of TeX's
+  ligature/kerning routine (in CommonLisp), which still waits to be
+  rewritten as a TeX.web change file.
+  The ligature builder/kerning routine is realized in one pass; kerns
+  are introduced in a delayed manner, i.e., after we are sure that
+  there's no possibility for a ligature.
+  Additionally there's a switch between the current TeX and the new
+  behaviour.  (The TRIP test fails with the new behaviour.)
+ 
+PS: IMHO the ligature/kerning routines should be further changed to
+  remove the `shelf{}ful' anomaly (see TeXbook, exercise 5.1), i.e.,
+  reinserting ligatures when words are hyphenated.
+  The change should allow ligatures for inputs like `f{}f' or
+  `f\relax f', which will simplify the macros in `german.sty',
+  Babel and changed macros for \", \', ... which are used to select
+  characters from DC fonts or other fonts with national characters.
+ 
+1.5. Writing more than one dvi-file (Nov 94)
+  I want to have TeX ready in the memory and avoid loading it anew and anew
+  for each run again which costs lots of startup time, if you have to load
+  every file via NFSS.
+  The idea I am toying with is to have something like
+       \level
+  which clones the current state of TeX and allows to start a new dvi-file.
+  Then you do anything you want (start even another \level) and at last you say
+       \exit
+  which performes like \end, except that it restores exactly the state before
+  the last cloning.
+  To communicate some information to the waiting lion, there may be one
+  exeption. You say
+       \exit{some_integer_number}
+  and this number can be read by using
+       \exitstatus.
+  Applications are many. If you have a format which usually requires several
+  runs, you can do all the runs within one job, and automatically decide,
+  whether a further run is necessary. Of course, you should device your format
+  to have a counter maxruns to avoid endless looping...
+ 
+1.6. Anchors (Nov 94)
+  Proposed by Jiri, an ``anchor point'' would be in some senses
+  be analogous to a mark, but rather than recording textual information it
+  would instead record the co-ordinates of itself, relative to the reference
+  point of the smallest surrounding box.  Additional new primitives would
+  be required to return the co-ordinates of a specified anchor point.
+ 
+1.7. dump/restore mechanism
+  I'd suggest something much simpler, but also more general:  Include \dump in
+  all versions of TeX.  The initex/virtex distinction is simply not worth the
+  bother of retaining any more - the memory differences are trivial in modern
+  terms.  \dump should ideally also be extended to allow dumping from inside of
+  a group.
+  Once you do this, it becomes possible to write programs to analyze format
+  files.  Since the analysis programs would not be part of TeX proper, they can
+  be as elaborate as anyone might want to make them.  Sorting would be no
+  problem, for example.
+  None of this would cost anything in TeX itself, and except for the ability
+  to \dump inside a group, if added, would not even have an effect on whether
+  the resulting E-TeX is properly "TeX", since it would be invisible to any
+  possible trip test.
+ 
+2. Proposed additions to TeX (concrete new primitives)
+ 
+2.0. General (Jun 92, Jul 92, Aug 93, Nov 94)
+  A rather long list of proposed primitives (more or less worked out) was
+  posted by Karl Berry on 10-Jun-1992. It contains suggestions like:
+  \elseif (selfexplaining), \format{foo} (allow the author to select a format),
+  \host{name} \host{os} \host{type} \getenv to extract host information
+  \TeXversion, \usertime, \everyeof, and others.
+ 
+  It is currently not possible to get some information about the current
+  mode of TeX and make conditionals dependent on it and/or restore it after
+  some action (see 2.7. \interactionmode). More of this kind are a
+  conditional or primitive to signal, when TeX is in "expand only" mode
+  (\edef, \mark, \write, ...), when TeX is scanning numbers (here I'm
+  thinking---and hating---german.sty's active doublequote, which can also
+  be used as a marker for hexadecimal numbers), when TeX is peeking for
+  some special tokens (first column in an \halign), etc...
+ 
+  A list of new primitives, enhancements and extensions has been prepared
+  on the NTS meeting at Lindau in October 1994. It was posted to this list in
+  November 1994 and provoked plenty of discussions and additional suggestions.
+  Under the discussed primitves were \bind, \contents<box#>, \futuredef,
+  \ifdefined, \ifcsname ... \endcsname, \unless, \OSname, \defaultextension.
+ 
+2.1. \lastmark etc. (Jun 92, Jul 92)
+  Currently you cannot remove a \write or \mark or
+  \insert or rule from any list at all. If we allow them to removed, how
+  will the commands appear to the user? If we have \lastmark like
+  \lastbox, then perhaps we need a mark data type so that we can say something
+  like \setmark0=\lastmark. It will probably be difficult
+  in the case of \insert's to think of a good command syntax.
+ 
+  Perhaps \lastpenalty, \lastkern, \lastskip should
+  remove the penalty, kern, skip, ... so that they are consistent with
+  \lastbox. Then \unpenalty, \unkern, and \unskip would be unnecessary.
+  (Of course most macro packages would probably want to reimplement them,
+  as macros: \def\unpenalty{\count@\lastpenalty},
+  \def\unkern{\dimen@\lastkern}, \def\unskip{\skip@\lastskip}.)
+ 
+2.2. \system (Mar 93)
+ 
+2.2.0 General
+  Oops, this got rather longish, but this topic has caused plenty of traffic.
+  I decided to quote directly the positions of both sides. The subpoints are
+  1. Pro 2. Contra 3. Syntax
+ 
+2.2.1 Pro
+  First comes the proposal as formulated by Phil Taylor:
+ 
+  There has been much discussion on how a \system primitive might interact
+  with different operating systems, each with different functionality and a
+  different syntax.  My idea was to extend the concept of a `TeX
+  implementation', which at the moment implies the creation and application
+  of a change-file to the master TeX source, to include an implementation-
+  specific macro library.  Thus each implementor, as well as creating and
+  applying a change file, would also be responsible for mapping a well-defined
+  set of macros, through the \system primitive, to the syntax and
+  functionality of the operating system for which he or she has assumed
+  responsibility.  To cite a specific example:
+ 
+  Assume that in e-Lib (a hypothetical macro library to accompany e-TeX),
+  a macro \sys$delete_file {<parameters>} is partially defined; then each
+  implementor would be responsible for mapping \sys$delete_file {<parameters}>
+  to his or her own implementation of \system.  e-Lib would define the effect
+  and the result(s), \system would provide the interface, and the implementor
+  would be responsible for providing the mapping.
+ 
+  The question has been asked: ``Why via \system and macros?  Why not via
+  explicit primitives to carry out the various functions that are envisaged?''
+ 
+  To which I would suggest that the answer is ``Because `the various functions
+  which are envisaged' is both enormous (requiring many new primitives), and
+  yet not large enough (because no matter what functionality we posit, someone
+  will come up with an idea that has not been considered).''  By implementing
+  just one \system primitive, and an extensible e-Lib macro library, one can
+  create a robust and well-tested e-TeX whilst allowing new system interactions
+  to be added at the simplest points: through the implementation-independent
+  and implementation-specific components of e-Lib.
+ 
+2.2.2 Contra
+  And here's from the ``Minority Report'' (Tim Murphy and J"org Knappen)
+ 
+  May I recall the immortal words of Ken Thompson,
+  "A program should do one thing, and do it well." (TM)
+ 
+  I don't like the hackers to decide, making eTeX yet another programme from
+  which I can send e-mail and read news :-) Maybe people will tell me eTeX is
+  a fine operating system, but TeX version $\pi$ is the better typesetter :-)
+ 
+  But there is another side of \system, I want to call it the monstrosity
+  side. Many people are thinking now, that TeX is a monster and difficult to
+  tame. \system will add to this monstrosity. It will create a new paradise
+  for hackers creating system hacks. And it will make people turn away from
+  eTeX and use other products, even if they are far less secure. (JK)
+ 
+2.2.3 Syntax
+  If a \system command is required, should it not have a similar syntax
+  and semantics to the a similar TeX command.  I can't think of anything
+  else in TeX (prepares to be shown wrong) that expands in the mouth and
+  has side-effects.  Should it not be like \read, \write etc. that is it
+  generates a whatsit that is obeyed at shipout, unless preceded by an
+  \immediate, in which case it is done immediately by the stomach.
+  There seem to be two obvious syntaxes, one like \write:
+     \system{foo}  or  \immediate\system{foo}
+  and one like \read:
+     \system{foo} to \baz  or  \immediate\system{foo} to \baz
+  The latter one would produce the exit code into \baz.  Should this be
+  done with catcode 12 characters, or should it be done like \read, with
+  the current catcodes?
+ 
+2.3. \skylineskiplimit, \skylinehorizontallimit
+  see section 1.1.1
+ 
+2.4. \directioncode (May 1993)
+ A \directioncode (with syntax analogous to \uccode, \lccode, sfcode) to be
+ assigned to each input character. The basic ones are
+  0 -- transparent (space, full stop...)
+  1 -- left-to-right (latin letters, digits...)
+  2 -- right-to-left (hebrew letters, arab letters...),
+ a truly international NTS will also have codes for vertical typesetting
+ and some special cases.
+ 
+ The question is how to use this idea consistently. One could extend the
+ notion of TeX's modes. Horizontal mode is in fact left-to-right mode, a
+ right-to-left mode is missing. To be complete, this mode will be equipped
+ with boxen and all the stuff TeX's left-to-right (aka horizontal) mode has.
+ 
+ At the beginning of a paragraph NTS decides which mode to choose by the
+ \directioncode of the first input character. Sometimes the first character
+ will have the wrong code, in this case the insertion of an explicit
+ control sequence (like \lrbox{}) is necessary. If a character with another
+ directioncode occurs, NTS starts a \rlbox and finishes it as soon as a
+ character with the original \directioncode appears or at the end of the
+ paragraph.
+ 
+  For the building of right-to-left tables a \rlalign is needed.
+ 
+2.5. \textcode (Sep 93, Nov 93)
+ Some of the character coding discussions in the Technical Working
+ Group on Multiple Language Coordination and some experiences I've made
+ with `german.sty' (specially the problems with an active doublequote
+ and hex integer constants!) lead to this _incomplete_ proposal/idea
+ for the following addition:
+   Introduce something like
+        \textcode       (and \textchar & \textchardef)
+ which are the text (hmode) equivalent of TeX's \mathcode (and
+ \mathchar/\mathchardef) primitives.
+ 
+ With an equivalent and appropriate implemented \textcode primitive
+ (with the choice to define a character as "pseudo-active"), it would
+ be possible to
+        * relate characters to different fonts
+          (using a generalized `fam' of \mathcode)
+ 
+        * suppress expansion of active characters (it will only be
+          expanded, if it is read to form the hlist)
+          (using an equivalent \mathcode="8000 value)
+          [This point allows the use of e.g. a pseudo-active "
+          which expands to non-expandable tokens and it removes
+          the special construct \relax\ifmmode... for active
+          characters, too.]
+ 
+2.6. \afterfi (August 1993)
+ In the answer to an exercise of the ``Around the Bend'' series, Michael Downes
+ realised the non-existence of an \afterfi primitive (Note: He did not
+ demand it nor really miss it). Perhaps an \afterfi can
+ simplify some obscure mouth-only macros with nested conditionals???
+ \afterfi should be expandable, because \if...\fi is expandable.
+ 
+2.7. \interactionmode   (Nov 93, was: \currentinteractionmode)
+  Add a new count register \interactionmode, which reflects the user
+  interaction level with the following values:
+        <= 0    batch_mode
+         = 1    nonstop_mode
+         = 2    scroll_mode
+        >= 3    error_stop_mode
+ 
+  The commands \batchmode...\errorstopmode, the "options" 'Q', 'R', 'S'
+  in the interactive error routine and all other TeX internal
+  interaction level changes (e.g. after an interruption) access this new
+  register.  The level changes in the interactive error routine and the
+  old commands should always work, even if the symbol \interactionmode is
+  redefined (this means that the user can redefine \interactionmode, but the
+  commands \batchmode...\errorstopmode still work).
+ 
+  Examples:
+ 
+   \ifnum\interactionmode<1 \AskUser \else \UseDefault \fi
+ 
+  {\interactionmode=0            % switch to \batchmode
+   \global\font\test=xyz10   % try to load font
+  }%                         % restore former interaction level
+  % ... now test if font has been loaded
+  %      without error (i.e. != nullfont)
+ 
+2.8. \mathspacing (Nov 93)
+  Add a new count register array \mathspacing with 64 entries (we really
+  need only 64-8=56 entries, because some of them are never used, but to
+  simplify things 64 are used) with the following syntax:
+ 
+   \mathspacing <num1>=<num2>           %  0 <= <num1> <= 63
+ 
+  The spacing specified in number <num2> is inserted between the two
+  math atom types specified in number <num1>.  The two numbers are coded
+  as
+ 
+  <num1> = <left_atom_type> * 8 + <right_atom_type>
+  <num2> = ( (<display_spacing> * 256 + <text_spacing>) * 256
+                 + <script_spacing> ) * 256 + <scriptscript_spacing>
+ 
+  This means that <num1> is easily expressed in octal and <num2> in
+  hexadecimal notation.
+ 
+  <..._atom_type> is one of the following seven types:
+ 
+  0 ordinary            1 large operator
+  2 binary operation    3 relation
+  4 opening             5 closing
+  6 punctuation         7 delimited subformula
+ 
+  <..._spacing> can be specified separately for each of the four math
+  styles (display, text, script and scriptscript) with the following
+  values:
+ 
+        0       no space
+        1       thin space      (specified by \thinmuskip)
+        2       medium space    ( -- " -- \medmuskip)
+        3       thick space     ( -- " -- \thickmuskip)
+ 
+        4-255   reserved for other things
+                (e.g. other spacings and/or additional penalties,
+                like \relpenalty, \binoppenalty, ...)
+ 
+  For more information see TeXbook, pp. 170f & Appendix G and TeX--The
+  Program, \S 764ff.
+ 
+  Examples:  (using TeX's standard spacing)
+ 
+  Between an `ordinary' (= 0) and a `relation' (= 3) atom a thick
+  space (= 3) is inserted, but not in script or scriptscript style.
+ 
+        \mathspacing '03 = "0033
+ 
+  Between a large operator (= 1) and an ordinary (= 0) atom a thin
+  space (= 1) is inserted:
+ 
+        \mathspacing '10 = "1111
+ 
+  Necessary changes for the sketched proposal are very simple to
+  implement.
+  The syntax of \mathspacing is awful, but this is true for \mathcode,
+  \delimitercode, etc.etc., too.
+ 
+2.9. \inputescapechar (Nov 93, alternative names were proposed during
+  discussion)
+  Use two new internal count registers \inputescapechar and
+  \outputescapechar to specify the "escape" character to be used for
+  unprintable characters.
+  If \inputescapechar is not in [0..255], TeX's behaviour is used,
+  i.e., two equal characters with category 7 are used as a prefix for a
+  ~~x notated character, otherwise two characters with code
+  \inputescapechar are used for this prefix.
+  If \outputescapechar is not in [0..255], the character `~' is used
+  when an unprintable character has to be written.
+ 
+  The default values of these two registers are
+    \inputescapechar  = -1
+    \outputescapechar = `~
+  to be compatible with TeX's standard behaviour.
+ 
+2.10. \middle (Jan 94)
+  Generalize the syntax of \left<delimiter>  <formula> \right<delimiter>
+  to allow one or more optional \middle delimiters,
+  \left<delimiter> <formula> \middle<delimiter> <formula> \right<delimiter>.
+ 
+  The middle delimiter grows to the same height as the left and right ones.
+  Constructions of this kind are used throughout quantum mechanics (Dirac
+  notation), e.g.
+  $$
+  \left\langle A  \middle% \hat{O} \middle% B \right\rangle
+  $$
+  By default, the \middle element is \mathrel, you can make it
+  \mathord by embracing it {\middle %}.
+ 
+ 
+2.11. \outputunit (Dec 93)
+  \outputunit       unit to be used when e-TeX shows some dimen or glue
+                    value
+  Usage: \outputunit=<unit of measure>       (s. TeXbook p. 270)
+  Rationale:
+ 
+  Currently TeX forces the user to think in points when it outputs any
+  dimen or glue value (e.g. when issueing an overfull hbox warning).
+  But a program should adapt to the conventions of the user instead the
+  other way round. The addition of \outputunit whould make TeX much
+  more user-friendly, since only a few people are thinking in points.
+ 
+2.12. \protected (new prefix for macro definitions) (Nov 94)
+  Analogous to \long, \outer, etc., causes the associated macro to be
+  non-expanding in contexts where such behaviour is likely to be undesirable
+  (in particular in \writes and \edefs); an explicit \expandafter \empty
+  may be used to force expansion in these circumstances.
+ 
+2.13. \scantokens (Nov 94)
+  Allows an existing token-list to be re-input under a different catcode regime
+  from that under which it was created; as it uses all of TeX's present \input
+  mechanism, even %%ff notation will be interpreted as if \input.  Causes an
+  `empty filename' to be input, resulting in `( )' appearing in the log file
+  if \tracingscantokens (q.v.) is strictly greater than zero.  If the token
+  list represents more than one line of input, and if an error occurs, then
+  \inputlinenumber will reflect the logical input line from the token list
+  rather than the current input line number from the current file.
+ 
+2.14. \deferred (Nov 94)
+  At the moment, only \writes are deferred; there are cases when it would
+  be desirable for other things, too, to be expanded only during \shipout,
+  and \specials are one of these. (See also 2.2.3)
+ 
+2.15.  \everyeof {<balanced text>}
+  Provides a hook whereby the contents of a token list register may be
+  inserted into TeX's reading orifice when end-of-file is encountered
+  during file reading.  Would not be invoked of the file indicated
+  logical e-o-f through the medium of \endinput.  Proposed by Phil
+  to allow clean processing of file-handling code which requires
+  a (sequence of characters yielding) \else or fi to be found in a
+  file, where no such sequence can be guaranteed.
+ 
+2.16. \readline <integer> to <cs> (Nov 94)
+  Allows a single line to be read from an input file as if each character
+  therein had catcode 12.  Intended to be used for verbatim copying
+  operations, in conjunction with \scantokens, or to allow error-free parsing
+  of `foreign' (non-TeX) files.
+ 
+2.17. \evaluate {<arithmetic expression>} (Nov 94)
+  Intended for use on the r-h-s of \count, \dimen and \skip assignments,
+  it would allow the use of infix arithmetic operators such as +, -, * and /;
+  the type of the result would, in general, be the type of the simplest operand
+  forming a part of the expression, and the normal semantics of TeX would allow
+  this to be further coerced where necessary.  Parenthesised sub-expressions
+  would be allowed.
+ 
+  Additional operations were proposed: trigonometric functions, square
+  root, pythagorean addition (METAFONT's `++'), angle{<delta_x, delta_y>}.
+ 
+2.18. \ifevaluate{<boolean expression>}....\else....\fi  (Nov 94)
+  The boolean expression should allow for the usual operators like
+  .not., .and., .or., .xor., =, >, <, <=, etc., if feasable it should also
+  allow the evaluation of arithmetic expressions. Some functions are needed
+  to get information old TeX \if's know now, I propose the name
+  \query<whatever> to these functions.
+ 
+  At the moment I see need for the following \query<whatever> functions:
+  \queryeof    returns `1' if eof, `0' else
+  \querymode   returns `0' in the infamous `no mode' (do we need to
+                             differentiate finer here?
+                       `1' in vertical mode
+                       `2' in restricted vertical mode
+                       `3' in horizontal mode
+                       `4' in restricted horizontal mode
+                       `5' in math mode
+                       `6' in restricted math mode
+    With \querymode \ifmmode, \ifhmode, \ifvmode, and \ifinner can be emulated.
+  \querydefined{\cs}   `1' if defined, `0' else
+  \querycsname...\endcsname  (ditto)
+ 
+2.19. \everyeof {<balanced text>}
+  Provides a hook whereby the contents of a token list register may be
+  inserted into TeX's reading orifice when end-of-file is encountered
+  during file reading.  Would not be invoked of the file indicated
+  logical e-o-f through the medium of \endinput.  Proposed by Phil
+  to allow clean processing of file-handling code which requires
+  a (sequence of characters yielding) \else or fi to be found in a
+  file, where no such sequence can be guaranteed.
+ 
+2.20. \fancyprompt
+  allow configuration of the TeX prompt (default `*'), e.g.
+  *\fancyprompt{eTeX>}
+  eTeX>
+ 
+3. Metaremarks
+ 
+3.0. General
+  Remarks about group efforts vs. one person creating software (Mar 93),
+  ALGOL 68 as a warning example
+ 
+3.1. TeX is not perfect (Jun 92, Jul 92)
+  The discussion has taken place in June and July 1992. Several details were
+  worked out, where TeX could be improved. Another point of criticism was
+  the programming language of TeX in general, several participants prefer a
+  procedural language over a macro language.
+ 
+3.2. In which language shall NTS be written (Mar 93)
+  In 1992, there was much discussion, in which language an NTS should be
+  implemented (candidates were LISP, C, and WEB). This has settled in March
+  1993 (to PASCAL-WEB), because of the acceptance of the
+  idea that rather than wait for an ``all-singing, all dancing'' NTS, the
+  group should develop, in a stepwise manner, small but significant
+  enhancements to TeX. This implies that the enhancements are implemented as
+  change files in WEB.
+ 
+3.3. The TeX language (Oct/Nov 93)
+  The TeX language is a simple language in the sense, that it contains only
+  few concepts. It belongs to the Lisp family. In particular, it's a
+  list-based macro language with late binding. Actually, that's all one
+  needs to say to characterize it.
+  Its data constructs are simpler than in Common Lisp: `token list' is the
+  only first order type. Glue, boxes, numbers, etc., are engine
+  concepts; instances of them are described by token lists.
+  Its lexical analzsis is simpler than CL: One cannot program
+  it. One can only configure it.
+  Its control constructs are simpler than in CL: Only macros, no
+  functions. And the macros are only simple ones, one can't compute
+  in them.
+ 
+3.4. The TeX engine (Oct/Nov 93)
+  The TeX engine lies below the TeX language. Glue, boxes, numbers, etc.
+  belong to the TeX engine. The registers of the engine can be changed
+  by TeX's primitives. However, the latter seem to be quite unregular and
+  baroque.
+ 
+3.5. Extensions and Enhancements (Nov 94)
+  `Extensions' are basically new primitives which have no effect on the
+   semantics of existing TeX documents, except insofaras any document which
+   tests whether such a primitive is, in fact, undefined, will clearly obtain
+   opposite results under TeX and e-TeX; `enhancements' are more fundamental
+   changes to the TeX kernel which may affect the semantics of existing TeX
+   documents even if no new primitive is used or even tested.  Such changes
+   may be, for example, differences in the construction of TeX's internal
+   lists, or perhaps different hyphenation or ligaturing behaviour.
+ 
+4. Deviations
+ 
+4.0. General
+  (empty)
+ 
+4.1. Automated Kerning (Oct 92)
+  Kindersley's "optical kerning": for the purposes of
+  kerning, each character is replaced by a circle centred on the centre of
+  gravity of that character; the radius of the circle is determined by the
+  fourth moment of the character (that is, the fourth root of the sum over
+  all black pixels of the fourth power of their distance from the centre). On
+  the UKTUG trip to Kindersley's studio, I tried to extract the reason why
+  the fourth, as opposed to third or fifth or whatever, moment is used; the
+  reason is apparently that it "looks right".
+ 
+  We can construct elaborate schemes for kerning (Kindersley's fourth
+  moments, FontStudio's (convex?) envelopes, Calamus' eight widths, etc), but
+  the proof of the typographical pudding is in the eating of the resulting
+  words, so to speak.
+ 
+4.2 About Lout (June 1993)
+ In June 1993, the new system Basser Lout caused several questions and
+ suggestions on this list. The following is taken from a short review
+ of Lout by Bernd Raichle:
+ 
+ `Lout' is a (yet another) document formatting system, released under
+ the terms of the GNU General Public License and available on some ftp
+ servers.
+ 
+ IMHO it's more like a `troff' (with a better input language and some
+ newer concepts) than a `TeX'.
+ 
+ A few citations from the documentation of lout:
+ 
+   Lout is a high-level language for document formatting, designed and
+   implemented by the author.  The implementation, known as Basser
+   Lout, is a fully operational production version written in C for the
+   Unix operating system, which translates Lout source code into
+   PostScript, a device-independent graphics rendering language
+   accepted by many high-resolution output devices, including most
+   laser printers.
+ [...]
+   When expert users can implement such applications quickly,
+   non-experts benefit.  Although Lout itself provides only a small
+   kernel of carefully chosen primitives,
+ 
+ Lout has 23 primitive operators... missing, for example, the simplest
+ arithmetical operators (there is only the operator "@Next" which
+ increases a number by one).
+ 
+   packages written in Lout and distributed with Basser Lout provide an
+   unprecedented array of advanced features in a form accessible to
+   non-expert users.  The features include rotation and scaling, fonts,
+ 
+ These features are mostly based on the output language... Postscript
+ (if you are looking inside a Lout package, you find large portions of
+ embedded Postscript code).
+ 
+   paragraph and page breaking,
+ 
+ TeX does a better job for these two items, because Lout is missing
+ most of TeX's paragraph/page breaking parameters.  (Note: Lout uses
+ TeX's hyphenation algorithm and the hyphenation patterns.)
+ 
+   displays and lists, floating figures and tables, footnotes, chapters
+   and sections (automatically numbered), running page headers and
+   footers, odd-even page layouts, automatically generated tables of
+   contents, sorted indexes and reference lists, bibliographic and
+   other databases (including databases of formats for printing
+   references), equations, tables, diagrams, formatting of Pascal
+   programs, and automatically maintained cross references.
+ 
+ TeX's math setting abilities are better.  Lout uses a package named
+ `eq' derived from the `eqn' preprocessor used with `troff'.  And there
+ are other packages named `tab' (for tabulars) and `fig' (drawing
+ figures).
+ 
+ [...]
+   Lout is organized around four key concepts -- objects, definitions,
+   galleys, and cross references -- [...]
+ 
+ The concept of `galleys' and the "expansion" of recursive defintions
+ are IMHO the only new concept in Lout:
+ 
+ `galleys' are a way to describe a page, dividing it in certain regions
+ which can be filled from different sources (e.g. a footnote galley is
+ filled with footnote text, etc.).
+ 
+ Recursive definitions are very simple, e.g.
+        def @Leaders { ..   @Leaders }
+ defines the command (Lout calls it `object') to "expand" to a `..' and
+ if there is place for another "expansion" it is called again.
+ 
+ For example
+        \hbox to 4in{Chapter 7 \dotfill 53}
+ is in Lout
+        4i @Wide { Chapter 7  @Leaders  53 }
+ 
+ With this recursive definitions, a whole document is defined as a
+ @PageList consisting of a @Page and a @PageList with an incremented
+ @PageNum.  A @Page is defined as a set of `galleys' (header, text
+ body, footnotes, footer), which are also defined as a list of
+ text/footnotes/... and so on.
+ 
+ Perhaps others can add more impressions, mine are based on the
+ documentation coming with the Lout package and some tests done in
+ 1-2 hours.
+ 
+5. Proposed changes to METAFONT
+ 
+5.O. General
+  Most of the General points in the discussion of TeX also apply to METAFONT.
+ 
+5.1. Writing to auxiliary files
+  METAFONT should be able to write to auxiliary files. Desparately needed
+  for packages which allow to draw figures in METAFONT and label them in TeX
+  (BoF session at EuroTeX '92, Prague).
+ 
+ 
+6. Proposed changes to the tfm file format
+ 
+6.1. Vertical kerning (Jun 92)
+   This may sound exotic to you, but the AFM format can do
+   it. And I desperately need it for non-Latin alphabets (everytime I need
+   a character in a ligature raised or lowered, I have to reserve a position
+   in the font for it).
+ 
+6.2. Cross-font ligatures (Jun 92)
+   Ligatures pointing to other fonts!! Yes, imagine for example that your
+   256 chars are full, you could still access characters by ligatures...but
+   they have to be in the same font.
+ 
+7. Proposed changes to the dvi file format
+ 
+7.0. General
+  A longer discussion about colour inclusion into the dvi-file occured in
+  Oct/Nov 93. The outcome was, that high-quality colour handling is a difficult
+  and device dependent task, better left to the printer driver. Colour can be
+  handled by the \special command which is sent directly to the driver.
+ 
+  On comp.text.tex I saw a remark, that specials may occur on places in the
+  dvi-file, where TeX can't put them. Maybe eTeX should take care of this
+  point.
+ 
+7.1. Horizontal and Vertical Mirroring (Nov 94)
+  Allow a glyph to be mirrored in a vertical axis, placed centrally;
+  mirrored in a horizontal axis, placed at half the x(?)-height.
+ 
+  It was noted, that the specification of the axes might cause problems.
+  It was also noted, that several drivers understand specials for the
+  requested action.
+ 
+7.2. Rotation of a glphy by 180 degrees (Nov 94)
+  This would greatly increase the power of vpl files (e.g. define schwa by
+  rotating e), and I hope that it would be possible for drivers to implement.
+ 
+  It was noted, that this is fine, but rotation by 90 degrees cannot be
+  device independent, because there are printers with rectangular (non-square)
+  pixels.
+ 
+8. Additions to the TeX kit
+ 
+8.0. General
+  The TeX kit, meaning the bundle of programmes building up a complete TeX
+  installation, contains besides the major programmes TeX and METAFONT
+  additional programmes, traditionally divided into several groups:
+ 
+  a) TeXware: dvitype, tftopl, pltotf, pooltype, pktype, patgen, vftovp,
+     vptovf, (outdated: pxtopk, pktopx)
+  b) MFware: mft, gftodvi, gftopk, gftype, (outdated: gftopxl)
+  c) webware: weave, tangle
+ 
+  And, of course, drivers for the screens and printers.
+ 
+  Other utility programmes more loosely associated with TeX are indexers
+  (makeindex, idxtex, glotex, ...) and bibliography tools (bibtex,
+  bibclean, ...). Makeindex and Bibtex are standard tools, because they
+  are described in the LaTeX manuals.
+ 
+  Another group includes drawing programmes (TeXCAD, xfig, gnuplot, ...) to
+  create graphics to be imported to TeX documents and graphics converters
+  (ghostscript, xv, bmt2font, ...).
+ 
+8.1. dvicopy
+  Written in WEB by Peter Breitenlohner
+  Available from CTAN
+  Resolves all references to virtual fonts in a dvi file. Can be used to
+  create a dvi file without virtual fonts (e.g. for drivers which cannot
+  handle vf's).
+ 
+8.2. dv2dp and dp2dv
+  Written in C by Geoffrey Tobin
+  Available on request from the author
+  dv2dp makes a human readable file from a dvi file. The companion
+  programme dp2dv makes a dvi file frome a dvi property list file.
+  It allows you to change dvi files with a text editor.
+ 
+8.3. gftotxt
+  Written in C by Yannis Haralambous
+  Available ?
+  Extracts a certain kind of specials from the gf file into a text file.
+  Workaround for the famous non-ability of METAFONT to write auxiliary
+  files.
+ 
+8.4. qdtexvpl
+  Written by Eberhard Mattes
+  Available from the CTAN archives
+  Generates a virtual font from TeX macros. qd = quick and dirty.
+ 
+8.5. fontinst
+  Written in TeX by Alan Jeffrey
+  Available form CTAN
+  Makes virtual fonts from afm files (PostScript fonts). Used by the LaTeX
+  team to create virtual fonts and fd files for LaTeX2e.
+ 
+8.6. afmtotfm
+  Written in C by Thomas Rokicki
+  Available from CTAN (part of dvips distribution)
+  Makes tfm files from afm files.
+ 
+8.7. dvipaste
+  Part of LAMSTeX (Michael Spivak)
+  Allows to paste a dvi-file into another one.
+ 
+8.8. METAPOST
+  Written in Web by John Hobby
+  Now freely available from the CTAN
+  A tool to build graphics to be included in TeX documents, uses a METAFONT
+  style language.
+ 
+8.9. Tie
+  Written by Klaus Gunthermann
+  Available from CTAN
+  Allows to process multiple change files to a given Web source. A tool
+  of this kind is needed to build any eTeX distribution, since one has
+  tex.web, etex.ch, tex.ch-system, and etex.ch-system files to deal with.
+ 
+8.10. dvi2dvi
+  Available from CTAN
+  Postprocessor for dvi files, allowing e.g. 2-up or 4-up layout of full
+  pages.
+ 
+9. Existing extensions to TeX
+ 
+9.0 General
+  Here I include short description of existing extensions to TeX. This section
+  does not include commercial TeX implementations because of lack of solid
+  enough information on them. It also does not yet include ETeX, NTS, nor
+  Omega.
+ 
+9.1. TeX-XeT (Don Knuth and Pierre MacKay)
+  CTAN: tex-archive/systems/knuth
+  Adds new primitives \beginR, \endR, \beginL, and \endL for right to left
+  typesetting. Despite their names, the new primitives are insensitive to
+  TeX's grouping mechanism. Outputs a special file in dvi-ivd format, which
+  need be resolved by another programme or requires special drivers.
+ 
+9.2. TeX--XeT (Peter Breitenlohner)
+  Available from CTAN  tex-archive/systems/knuth/tex--xet
+  Implements the same primitives as TeX-XeT, but outputs a normal dvi file.
+  Passes the trip test (as far as I know).
+ 
+9.3. MLTeX (Michael Ferguson)
+  Available from  aldebaran.ee.mcgill.ca in pub/mltex
+  Adds a primitive \charsubdef, which allows the following: input of 8-bit
+  characters, participation of accented characters not present in the output
+  encoding in hyphenation, ligatures and kerning with accented letters.
+  Especially popular in francophone countries.
+  emTeX supports MLTeX via the /ml option.
+ 
+9.4. SiSiSi (Wilhelm Barth, Heinrich Nirschl, Heini Hofstaedter und Harald
+               Mueller)
+  Available from CTAN: tex-archive/systems/vms (sic!)
+  Implements another hyphenation algorithm (the name means SIchere
+  SInnentsprechende SIlbentrennung, which is translated `secure sensitive
+  hyphenation') specific to the german language (with Haupt- und
+  Nebentrennstellen). Fails the trip test, therefore not a legitimate TeX.
+  In use at TU Wien (Austria).
+ 
+9.5. Japanese TeX
+  [in preparation]
+ 
+The End.