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-\datethis
-@* Introduction. This program is a simple filter that inputs \TEX/ or \.{CWEB}
-files and outputs its best guess at the ``words'' they contain. The word
-list can then be passed to a spelling check routine such as {\tt wordtest}.
-
-If this program is invoked with the name `{\tt excweb}', it will apply
-special rules based on the syntax of \.{CWEB} files. Otherwise it will
-use only the \TEX/ conventions. (Note that \UNIX/'s {\tt ln} command
-allows a program to be invoked with more than one name although it
-appears only once in the computer's memory.)
-
-The \TEX/ conventions adopted here say that words are what remain
-after you remove nonletters, control sequences,
-comments triggered by \.\% marks, and material enclosed
-within \.{\$...\$} or \.{\$\$...\$\$}. However, an apostrophe within
-a word will be retained. The plain \TEX/ control
-sequences for accented characters and special text characters, namely
-$$\vbox{\halign{&\.{\\#}\hfil\qquad\cr
-'&`&\relax\^&"&\relax\~&=&.&u&v\cr
-H&t&c&d&b&oe&OE&ae&AE\cr
-aa&AA&o&O&l&L&ss&i&j\cr}}$$
-will also be retained, so that users can treat them as parts of words.
-A blank space
-following any of the alphabetic control sequences in this list will be carried
-along too. If any of these control sequences is followed by \.\{, everything
-up to the next \.\} will also be retained. Thus, for example, the
-construction `\.{m\\=\{\\i\}n\\u\ us}' will be considered a single word,
-in spite of the control sequences and the space between the two u's.
-Discretionary hyphens `\.{\char`\\-}' are treated in the same way as accents.
-
-The \.{CWEB} conventions are essentially the same as the \TEX/ conventions,
-in the \TEX/ parts of a \.{CWEB} file. The \CEE/ parts of the file
-are blanked out.
-
-No attempt is made to reach a high level of artificial intelligence,
-which would be able to truly understand the input file. Tricky users can
- confuse us. But we claim that devious tricks are their problem, not ours.
-
-@ So here goes. The main idea is to keep a one-character lookahead
-buffer, called |c|, which is set to zero when the character has been
-processed. A giant switch to various cases, depending on the value of~|c|,
-keeps everything moving.
-
-If you don't like |goto| statements, don't read this. (And don't read
-any other programs that simulate finite-state automata.)
-
-@c
-#include <stdio.h>
-#include <ctype.h>
-#include <string.h>
-extern void exit(); /* system routine that terminates execution */
-@#
-@<Global variables@>@;
-@<Procedures@>@;
-@#
-int main(argc,argv)
- int argc; /* the number of arguments (should be 1, but this isn't checked) */
- char *argv[]; /* the arguments (|*argv| is the program name) */
-{
- @<Local variables@>;
- if (strlen(*argv)>=6 && strcmp(*argv+strlen(*argv)-6,"excweb")==0) {
- web=1;
- @<Adjust tables for \.{CWEB} mode@>;
- } else web=0;
- comment=skipping=c=0;
- main_cycle: if (c) goto big_switch;
- restart: c=get();
- big_switch: switch(c) {
- @<Special cases of the giant switch where we don't just discard |c|@>@;
- case EOF: exit(0);
- default: goto restart;
- }
- @<Labeled code segments, which exit by explicit |goto|@>;
-}
-
-@ @<Global variables@>=
-int c; /* one-character look-see buffer */
-
-@ @<Local variables@>=
-int web; /* are we looking for \.{CWEB} constructs? */
-int comment; /* are we inside a \CEE/ comment in a \.{CWEB} document? */
-int skipping; /* are we skipping \CEE/ code in a \.{CWEB} document? */
-int save_skipping; /* value of |skipping| outside current \CEE/ mode */
-register int cc; /* temporary buffer */
-
-@* Simple cases.
-Let's do some of the easiest things first, in order to get the hang of
-this program. Several special characters will cause us to ignore everything
-until the first appearance of something else.
-
-@d discard_to(x) {@+while (get()!=x) ;@+}
-@d discard_to_dol {@+for (cc=c,c=get();c!='$' || cc=='\\';cc=c,c=get())
- if (cc=='\\' && c==cc) c='\0';@+}
-
-@<Special cases...@>=
-case '%': discard_to('\n');@+goto restart;
-case '$': c=getchar();
- if (c!='$') discard_to_dol@;
- else { /* after \.{\$\$} we discard everything to the next \.{\$\$} */
- do discard_to_dol@;
- while (getchar()!='$');
- }
- goto restart;
-
-@ The `|get|' procedure in the code above is like \Cee's standard
-`|getchar|', except that it immediately terminates execution at the end of
-the input file. Otherwise malformed input files could lead to
-infinite loops.
-
-@<Procedures@>=
-int get()
-{@+register int x;
- x=getchar();
- if (x==EOF) exit(0);
- return x;
-}
-
-@ More complex behavior is handled by jumping out of the |switch| statement
-to one of the routines following it. None of the cases say |break|, so
-the code following the switch statement is accessible only via |goto|.
-
-@<Special cases...@>=
-case 'a': case 'A':
-case 'b': case 'B':
-case 'c': case 'C':
-case 'd': case 'D':
-case 'e': case 'E':
-case 'f': case 'F':
-case 'g': case 'G':
-case 'h': case 'H':
-case 'i': case 'I':
-case 'j': case 'J':
-case 'k': case 'K':
-case 'l': case 'L':
-case 'm': case 'M':
-case 'n': case 'N':
-case 'o': case 'O':
-case 'p': case 'P':
-case 'q': case 'Q':
-case 'r': case 'R':
-case 's': case 'S':
-case 't': case 'T':
-case 'u': case 'U':
-case 'v': case 'V':
-case 'w': case 'W':
-case 'x': case 'X':
-case 'y': case 'Y':
-case 'z': case 'Z':
-goto out_word;
-
-@ When letters appear in |stdin|, we pass them immediately through to |stdout|
-with little further ado.
-An apostrophe is rejected unless it is immediately followed by a letter.
-
-@<Labeled code...@>=
-out_word: putchar(c);
-continue_word: c=getchar();
-checkout_word:
-if (isalpha(c)) goto out_word;
-if (c=='\'') {
- c=getchar();
- if (isalpha(c)) {
- putchar('\'');@+goto out_word;
- }
- goto end_word;
-}
-if (c=='\\' && controlseq()) goto control_seq_in_word;
-end_word: putchar('\n');
- goto main_cycle;
-
-@* Control sequences. The |controlseq()| function is the only
-delicate part of this program. After a backslash has been scanned,
-|controlseq| looks to see if the next characters define one of the
-special plain \TEX/ macros listed above. If so, the control sequence
-and its immediately following argument (if any) are output and
-|controlseq| returns a nonzero value. If not, nothing is output and
-|controlseq| returns zero. In both cases the value of |c| will be
-nonzero if and only if |controlseq| has had to look ahead at a
-character it decided not to process.
-
-@ @<Labeled code...@>=
-control_seq_in_word: if (!c) goto continue_word;
-goto checkout_word;
-
-@ @<Special cases...@>=
-case '\\': if (controlseq()) goto control_seq_in_word;
-goto main_cycle;
-
-@ @<Procedures@>=
-int controlseq()
-{
- int l; /* number of letters in the control sequence */
- char a,b; /* the first two characters after `\.\\' */
- l=0;
- a=c=getchar();
- while (isalpha(c)) {
- l++;
- c=getchar();
- if (l==1) b=c;
- }
- if (l==0) c=getchar();
- @<Check for special plain \TEX/ control sequences;
- output them and |return 1| if found@>;
- return 0;
-}
-
-@ @d pair(x,y) (a==x && b==y)
-
-@<Check for special...@>=
-if ((a>='"' && a<='~' && ptab[a-'"']==l) ||
- (l==2 && (pair('a','e') || pair('A','E')@|
- || pair('o','e') || pair('O','E')@|
- || pair('a','a') || pair('A','A') || pair('s','s')))) {
- putchar('\\');
- putchar(a);
- if (l==2) putchar(b);
- if (l && c==' ') {
- putchar(' '); /* optional space after alphabetic control sequence */
- c=getchar();
- }
- if (c=='{') {
- do@+{putchar(c);
- c=get();
- }@+while (c!='}'); /* optional argument after special control sequence */
- putchar(c);
- c=0;
- }
- return 1;
-}
-
-@ The |ptab| entries for nonletters are 0 when the control sequence is
-special, otherwise~1; the conventions for letters are reversed.
-
-@<Global...@>=
-char ptab[]={0,1,1,1,1,0, /* \.{\\"} and \.{\\'} */
- 1,1,1,1,1,0,0,1, /* \.{\\-} and \.{\\.} */
- 1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1, /* \.{\\=} */
- 1,0,0,0,0,0,0,0,1,0,0,0,1,0,0,1, /* \.{\\H}, \.{\\L}, \.{\\O} */
- 0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,1, /* \.{\\\^} */
- 0,0,1,1,1,0,0,0, /* \.{\\`}, \.{\\b}, \.{\\c}, \.{\\d} */
- 0,1,1,0,1,0,0,1, /* \.{\\i}, \.{\\j}, \.{\\l}, \.{\\o} */
- 0,0,0,0,1,1,1,0, /* \.{\\t}, \.{\\u}, \.{\\v} */
- 0,0,0,1,1,1,0}; /* \.{\\\~} */
-
-@ In \.{CWEB} the \TEX/ control sequence `\.{\\.}' denotes the typewriter
-font used for strings, not the dot-over accent. We must modify
-|ptab| to reflect this unfortunate (but too-late-too-change) design decision.
-
-@<Adjust tables for \.{CWEB} mode@>=
-ptab[12]=1;
-
-@* CWEB considerations.
-We're finished now with all that would be needed if we only wanted to
-handle \TEX/. For \.{CWEB} a bit more should be done.
-
-The \.{CWEB} escape character is \.{@@}, and the character following
-it tells us what mode we should enter. In \TEX/ mode we should not
-only do what we normally do for \TEX/ files, we should also ignore
-material delimited by \.{\char"7C...\char"7C}, being careful to recognize when
-|'|'| is part of a string (as it just was). And we should stop \TEX/
-mode if we scan \.{*/} while in a \CEE/ comment.
-
-@<Special cases...@>=
-case '@@': if (web) goto do_web;
- goto restart;
-case '|': if (web>1) {
- save_skipping=skipping;
- goto skip_C_prime;
- }
- goto restart;
-case '*': if (!comment) goto restart;
- c=getchar();
- if (c=='/') {
- comment=0;
- goto skip_C;
- }
- goto big_switch;
-
-@ The characters that follow \.@@ in a \.{CWEB} file can be classified into
-a few types that have distinct implications for {\tt excweb}.
-
-@d nop 0 /* control code that doesn't matter to us */
-@d start_section 1 /* control code that begins a \.{CWEB} section */
-@d start_C 2 /* control code that begins \CEE/ code */
-@d start_name 3 /* control code that begins a section name */
-@d start_index 4 /* control code for \.{CWEB} index entry */
-@d start_insert 5 /* control code for \CEE/ material ended by `\.{@@>}' */
-@d end_item 6 /* `\.{@@>}' */
-@d ignore_line 7 /* `\.{@@i}' or `\.{@@l}' */
-
-@<Global...@>=
-char wtab[]={start_section,nop,nop,nop,nop,nop,nop,nop, /* \.{\ !"\#\$\%\&'} */
- start_name,nop,start_section,nop,nop,nop,start_index,nop, /* \.{()*+,-./} */
- nop,nop,nop,nop,nop,nop,nop,nop, /* \.{01234567} */
- nop,nop,start_index,nop,start_name,start_insert,end_item,nop,
- /* \.{89:;<=>?} */
- nop,nop,nop,start_C,start_C,nop,start_C,nop, /* \.{@@ABCDEFG} */
- nop,ignore_line,nop,nop,ignore_line,nop,nop,nop, /* \.{HIJKLMNO} */
- start_C,start_insert,nop,start_C,start_insert,nop,nop,nop, /* \.{PQRSTUVW} */
- nop,nop,nop,nop,nop,nop,start_index,nop, /* \.{XYZ[\\]\^\_} */
- nop,nop,nop,start_C,start_C,nop,start_C,nop, /* \.{`abcdefg} */
- nop,ignore_line,nop,nop,ignore_line,nop,nop,nop, /* \.{hijklmno} */
- start_C,start_insert,nop,start_C,start_insert}; /* \.{pqrst} */
-
-@ We do not leave \TEX/ mode until the first \.{WEB} section has begun.
-
-@<Labeled code...@>=
-do_web: c=getchar();
- if (c<' ' || c>'t') goto restart;
- switch(wtab[c-' ']){
- case nop: case start_index: goto restart;
- case start_section: web++; /* out of ``limbo'' */
- comment=skipping=0;@+goto restart;
- case start_C: if (web>1) goto skip_C;
- goto restart;
- case start_name: case start_insert: if (web>1) skipping=1;
- goto restart;
- case end_item: if (skipping) goto skip_C;
- goto restart;
- case ignore_line: discard_to('\n');
- goto restart;
- }
-
-@ The final piece of program we need is a sub-automaton to pass over
-the \CEE/ parts of a \.{CWEB} document. The main subtlety here is that
-we don't want to get out of synch while scanning over a supposed
-string constant or verbatim insert.
-
-@<Labeled code...@>=
-skip_C: save_skipping=2;
-skip_C_prime: skipping=1;
- while (1) {
- c=get();
- C_switch: switch(c) {
- case '/': c=get();
- if (c!='*') goto C_switch;
- comment=1; /* fall through to the next case, returning to \TEX/ mode */
- case '|': if (save_skipping==2) continue; /* |'|'| as \CEE/ operator */
- skipping=save_skipping;@+goto restart; /* |'|'| as \.{CWEB} delimiter */
- case '@@': c=getchar();
- inner_switch: if (c<' ' || c>'t') continue;
- switch(wtab[c-' ']) {
- case nop: case start_C: case end_item: continue;
- case start_section: web++;
- comment=skipping=0;@+goto restart;
- case start_name: case start_index: goto restart;
- case start_insert: do@+discard_to('@@')@;@+while ((c=getchar())=='@@');
- goto inner_switch; /* now |c| should equal |'>'| */
- case ignore_line: discard_to('\n');
- continue;
- }
- case '\'': case '"':
- while ((cc=get())!=c && cc!='\n')
- if (cc=='\\') getchar();
- else if (cc=='@@') {
- cc=getchar();
- if (cc!='@@') { /* syntax error, we try to recover */
- c=cc; goto inner_switch;
- }
- };
- continue; /* \.{CWEB} strings do not extend past one line */
- default: continue;
- }
- }
-
-@* Index.