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Diffstat (limited to 'Build/source/texk/web2c/cwebdir/examples/extex.w')
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diff --git a/Build/source/texk/web2c/cwebdir/examples/extex.w b/Build/source/texk/web2c/cwebdir/examples/extex.w new file mode 100644 index 00000000000..b060d7431a6 --- /dev/null +++ b/Build/source/texk/web2c/cwebdir/examples/extex.w @@ -0,0 +1,366 @@ +\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. |