cosmopolitan/third_party/lex
Justine Tunney c91b3c5006 Initial import 2020-06-15 07:18:57 -07:00
..
COPYING Initial import 2020-06-15 07:18:57 -07:00
ChangeLog Initial import 2020-06-15 07:18:57 -07:00
FlexLexer.h Initial import 2020-06-15 07:18:57 -07:00
NEWS Initial import 2020-06-15 07:18:57 -07:00
NOTES Initial import 2020-06-15 07:18:57 -07:00
ONEWS Initial import 2020-06-15 07:18:57 -07:00
README.txt Initial import 2020-06-15 07:18:57 -07:00
buf.c Initial import 2020-06-15 07:18:57 -07:00
ccl.c Initial import 2020-06-15 07:18:57 -07:00
config.h Initial import 2020-06-15 07:18:57 -07:00
dfa.c Initial import 2020-06-15 07:18:57 -07:00
ecs.c Initial import 2020-06-15 07:18:57 -07:00
filter.c Initial import 2020-06-15 07:18:57 -07:00
flex.1 Initial import 2020-06-15 07:18:57 -07:00
flex.skl Initial import 2020-06-15 07:18:57 -07:00
flexdef.h Initial import 2020-06-15 07:18:57 -07:00
flexint.h Initial import 2020-06-15 07:18:57 -07:00
gen.c Initial import 2020-06-15 07:18:57 -07:00
lex.mk Initial import 2020-06-15 07:18:57 -07:00
lex.ms Initial import 2020-06-15 07:18:57 -07:00
libmain.c Initial import 2020-06-15 07:18:57 -07:00
libyywrap.c Initial import 2020-06-15 07:18:57 -07:00
main.c Initial import 2020-06-15 07:18:57 -07:00
misc.c Initial import 2020-06-15 07:18:57 -07:00
mkskel.sh Initial import 2020-06-15 07:18:57 -07:00
nfa.c Initial import 2020-06-15 07:18:57 -07:00
options.c Initial import 2020-06-15 07:18:57 -07:00
options.h Initial import 2020-06-15 07:18:57 -07:00
parse.c Initial import 2020-06-15 07:18:57 -07:00
parse.h Initial import 2020-06-15 07:18:57 -07:00
parse.y Initial import 2020-06-15 07:18:57 -07:00
regex.c Initial import 2020-06-15 07:18:57 -07:00
scan.c Initial import 2020-06-15 07:18:57 -07:00
scan.l Initial import 2020-06-15 07:18:57 -07:00
scanflags.c Initial import 2020-06-15 07:18:57 -07:00
scanopt.c Initial import 2020-06-15 07:18:57 -07:00
scanopt.h Initial import 2020-06-15 07:18:57 -07:00
skel.c Initial import 2020-06-15 07:18:57 -07:00
sym.c Initial import 2020-06-15 07:18:57 -07:00
tables.c Initial import 2020-06-15 07:18:57 -07:00
tables.h Initial import 2020-06-15 07:18:57 -07:00
tables_shared.c Initial import 2020-06-15 07:18:57 -07:00
tables_shared.h Initial import 2020-06-15 07:18:57 -07:00
tblcmp.c Initial import 2020-06-15 07:18:57 -07:00
version.h Initial import 2020-06-15 07:18:57 -07:00
yylex.c Initial import 2020-06-15 07:18:57 -07:00

README.txt

This file contains ambiguous Unicode characters!

This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.

FLEX(1)             Cosmopolitan General Commands Manual              -*-text-*-

๐๐€๐Œ๐„
     ๐—ณ๐—น๐—ฒ๐˜…, ๐—ณ๐—น๐—ฒ๐˜…++, ๐—น๐—ฒ๐˜… โ€” fast lexical analyzer generator

๐’๐˜๐๐Ž๐๐’๐ˆ๐’
     ๐—ณ๐—น๐—ฒ๐˜… [-๐Ÿณ๐Ÿด๐๐—ฏ๐—ฑ๐…๐—ณ๐—ต๐ˆ๐—ถ๐‹๐—น๐—ป๐—ฝ๐˜€๐“๐˜๐•๐˜ƒ๐˜„+?] [-๐‚[๐—ฎ๐—ฒ๐…๐—ณ๐—บ๐—ฟ]] [--๐—ต๐—ฒ๐—น๐—ฝ] [--๐˜ƒ๐—ฒ๐—ฟ๐˜€๐—ถ๐—ผ๐—ป]
          [-๐—ผoฬฒuฬฒtฬฒpฬฒuฬฒtฬฒ] [-๐pฬฒrฬฒeฬฒfฬฒiฬฒxฬฒ] [-๐’sฬฒkฬฒeฬฒlฬฒeฬฒtฬฒoฬฒnฬฒ] [fฬฒiฬฒlฬฒeฬฒ .ฬฒ.ฬฒ.ฬฒ]

๐ƒ๐„๐’๐‚๐‘๐ˆ๐๐“๐ˆ๐Ž๐
     ๐—ณ๐—น๐—ฒ๐˜… is a tool for generating sฬฒcฬฒaฬฒnฬฒnฬฒeฬฒrฬฒsฬฒ: programs which recognize
     lexical patterns in text.  ๐—ณ๐—น๐—ฒ๐˜… reads the given input files, or its
     standard input if no file names are given, for a description of a
     scanner to generate.  The description is in the form of pairs of
     regular expressions and C code, called rฬฒuฬฒlฬฒeฬฒsฬฒ.  ๐—ณ๐—น๐—ฒ๐˜… generates as
     output a C source file, lฬฒeฬฒxฬฒ.ฬฒyฬฒyฬฒ.ฬฒcฬฒ, which defines a routine ๐˜†๐˜†๐—น๐—ฒ๐˜…().
     This file is compiled and linked with the -๐—น๐—ณ๐—น library to produce
     an executable.  When the executable is run, it analyzes its input
     for occurrences of the regular expressions.  Whenever it finds one,
     it executes the corresponding C code.

     ๐—น๐—ฒ๐˜… is a synonym for ๐—ณ๐—น๐—ฒ๐˜….  ๐—ณ๐—น๐—ฒ๐˜…++ is a synonym for ๐—ณ๐—น๐—ฒ๐˜… -+.

     The manual includes both tutorial and reference sections:

     ๐’๐—ผ๐—บ๐—ฒ ๐’๐—ถ๐—บ๐—ฝ๐—น๐—ฒ ๐„๐˜…๐—ฎ๐—บ๐—ฝ๐—น๐—ฒ๐˜€

     ๐…๐—ผ๐—ฟ๐—บ๐—ฎ๐˜ ๐—ผ๐—ณ ๐˜๐—ต๐—ฒ ๐ˆ๐—ป๐—ฝ๐˜‚๐˜ ๐…๐—ถ๐—น๐—ฒ

     ๐๐—ฎ๐˜๐˜๐—ฒ๐—ฟ๐—ป๐˜€
     The extended regular expressions used by ๐—ณ๐—น๐—ฒ๐˜….

     ๐‡๐—ผ๐˜„ ๐˜๐—ต๐—ฒ ๐ˆ๐—ป๐—ฝ๐˜‚๐˜ ๐—ถ๐˜€ ๐Œ๐—ฎ๐˜๐—ฐ๐—ต๐—ฒ๐—ฑ
     The rules for determining what has been matched.

     ๐€๐—ฐ๐˜๐—ถ๐—ผ๐—ป๐˜€
     How to specify what to do when a pattern is matched.

     ๐“๐—ต๐—ฒ ๐†๐—ฒ๐—ป๐—ฒ๐—ฟ๐—ฎ๐˜๐—ฒ๐—ฑ ๐’๐—ฐ๐—ฎ๐—ป๐—ป๐—ฒ๐—ฟ
     Details regarding the scanner that ๐—ณ๐—น๐—ฒ๐˜… produces; how to control
     the input source.

     ๐’๐˜๐—ฎ๐—ฟ๐˜ ๐‚๐—ผ๐—ป๐—ฑ๐—ถ๐˜๐—ถ๐—ผ๐—ป๐˜€
     Introducing context into scanners, and managing "mini-scanners".

     ๐Œ๐˜‚๐—น๐˜๐—ถ๐—ฝ๐—น๐—ฒ ๐ˆ๐—ป๐—ฝ๐˜‚๐˜ ๐๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ๐˜€
     How to manipulate multiple input sources; how to scan from strings
     instead of files.

     ๐„๐—ป๐—ฑ-๐—ผ๐—ณ-๐…๐—ถ๐—น๐—ฒ ๐‘๐˜‚๐—น๐—ฒ๐˜€
     Special rules for matching the end of the input.

     ๐Œ๐—ถ๐˜€๐—ฐ๐—ฒ๐—น๐—น๐—ฎ๐—ป๐—ฒ๐—ผ๐˜‚๐˜€ ๐Œ๐—ฎ๐—ฐ๐—ฟ๐—ผ๐˜€
     A summary of macros available to the actions.

     ๐•๐—ฎ๐—น๐˜‚๐—ฒ๐˜€ ๐€๐˜ƒ๐—ฎ๐—ถ๐—น๐—ฎ๐—ฏ๐—น๐—ฒ ๐˜๐—ผ ๐˜๐—ต๐—ฒ ๐”๐˜€๐—ฒ๐—ฟ
     A summary of values available to the actions.

     ๐ˆ๐—ป๐˜๐—ฒ๐—ฟ๐—ณ๐—ฎ๐—ฐ๐—ถ๐—ป๐—ด ๐˜„๐—ถ๐˜๐—ต ๐˜๐—ฎ๐—ฐ๐—ฐ
     Connecting flex scanners together with yacc(1) parsers.

     ๐Ž๐—ฝ๐˜๐—ถ๐—ผ๐—ป๐˜€
     ๐—ณ๐—น๐—ฒ๐˜… command-line options, and the โ€œ%optionโ€ directive.

     ๐๐—ฒ๐—ฟ๐—ณ๐—ผ๐—ฟ๐—บ๐—ฎ๐—ป๐—ฐ๐—ฒ ๐‚๐—ผ๐—ป๐˜€๐—ถ๐—ฑ๐—ฒ๐—ฟ๐—ฎ๐˜๐—ถ๐—ผ๐—ป๐˜€
     How to make scanners go as fast as possible.

     ๐†๐—ฒ๐—ป๐—ฒ๐—ฟ๐—ฎ๐˜๐—ถ๐—ป๐—ด ๐‚++ ๐’๐—ฐ๐—ฎ๐—ป๐—ป๐—ฒ๐—ฟ๐˜€
     The (experimental) facility for generating C++ scanner classes.

     ๐ˆ๐—ป๐—ฐ๐—ผ๐—บ๐—ฝ๐—ฎ๐˜๐—ถ๐—ฏ๐—ถ๐—น๐—ถ๐˜๐—ถ๐—ฒ๐˜€ ๐˜„๐—ถ๐˜๐—ต ๐‹๐—ฒ๐˜… ๐—ฎ๐—ป๐—ฑ ๐๐Ž๐’๐ˆ๐—
     How ๐—ณ๐—น๐—ฒ๐˜… differs from AT&T UNIX ๐—น๐—ฒ๐˜… and the POSIX ๐—น๐—ฒ๐˜… standard.

     ๐…๐—ถ๐—น๐—ฒ๐˜€
     Files used by ๐—ณ๐—น๐—ฒ๐˜….

     ๐ƒ๐—ถ๐—ฎ๐—ด๐—ป๐—ผ๐˜€๐˜๐—ถ๐—ฐ๐˜€
     Those error messages produced by ๐—ณ๐—น๐—ฒ๐˜… (or scanners it generates)
     whose meanings might not be apparent.

     ๐’๐—ฒ๐—ฒ ๐€๐—น๐˜€๐—ผ
     Other documentation, related tools.

     ๐€๐˜‚๐˜๐—ต๐—ผ๐—ฟ๐˜€
     Includes contact information.

     ๐๐˜‚๐—ด๐˜€
     Known problems with ๐—ณ๐—น๐—ฒ๐˜….

๐’๐Ž๐Œ๐„ ๐’๐ˆ๐Œ๐๐‹๐„ ๐„๐—๐€๐Œ๐๐‹๐„๐’
     First some simple examples to get the flavor of how one uses ๐—ณ๐—น๐—ฒ๐˜….
     The following ๐—ณ๐—น๐—ฒ๐˜… input specifies a scanner which whenever it
     encounters the string "username" will replace it with the user's
     login name:

           %%
           username    printf("%s", getlogin());

     By default, any text not matched by a ๐—ณ๐—น๐—ฒ๐˜… scanner is copied to the
     output, so the net effect of this scanner is to copy its input file
     to its output with each occurrence of "username" expanded.  In this
     input, there is just one rule.  "username" is the pฬฒaฬฒtฬฒtฬฒeฬฒrฬฒnฬฒ and the
     "printf" is the aฬฒcฬฒtฬฒiฬฒoฬฒnฬฒ.  The "%%" marks the beginning of the rules.

     Here's another simple example:

           %{
           int num_lines = 0, num_chars = 0;
           %}

           %%
           \n      ++num_lines; ++num_chars;
           .       ++num_chars;

           %%
           main()
           {
                   yylex();
                   printf("# of lines = %d, # of chars = %d\n",
                       num_lines, num_chars);
           }

     This scanner counts the number of characters and the number of
     lines in its input (it produces no output other than the final
     report on the counts).  The first line declares two globals,
     "num_lines" and "num_chars", which are accessible both inside
     ๐˜†๐˜†๐—น๐—ฒ๐˜…() and in the ๐—บ๐—ฎ๐—ถ๐—ป() routine declared after the second "%%".
     There are two rules, one which matches a newline ("\n") and increโ€
     ments both the line count and the character count, and one which
     matches any character other than a newline (indicated by the "."
     regular expression).

     A somewhat more complicated example:

           /* scanner for a toy Pascal-like language */

           %{
           /* need this for the call to atof() below */
           #include <math.h>
           %}

           DIGIT    [0-9]
           ID       [a-z][a-z0-9]*

           %%

           {DIGIT}+ {
                   printf("An integer: %s (%d)\n", yytext,
                       atoi(yytext));
           }

           {DIGIT}+"."{DIGIT}* {
                   printf("A float: %s (%g)\n", yytext,
                       atof(yytext));
           }

           if|then|begin|end|procedure|function {
                   printf("A keyword: %s\n", yytext);
           }

           {ID}    printf("An identifier: %s\n", yytext);

           "+"|"-"|"*"|"/"   printf("An operator: %s\n", yytext);

           "{"[^}\n]*"}"     /* eat up one-line comments */

           [ \t\n]+          /* eat up whitespace */

           .       printf("Unrecognized character: %s\n", yytext);

           %%

           main(int argc, char *argv[])
           {
                   ++argv; --argc;  /* skip over program name */
                   if (argc > 0)
                           yyin = fopen(argv[0], "r");
                   else
                           yyin = stdin;

                   yylex();
           }

     This is the beginnings of a simple scanner for a language like Pasโ€
     cal.  It identifies different types of tฬฒoฬฒkฬฒeฬฒnฬฒsฬฒ and reports on what
     it has seen.

     The details of this example will be explained in the following secโ€
     tions.

๐…๐Ž๐‘๐Œ๐€๐“ ๐Ž๐… ๐“๐‡๐„ ๐ˆ๐๐๐”๐“ ๐…๐ˆ๐‹๐„
     The ๐—ณ๐—น๐—ฒ๐˜… input file consists of three sections, separated by a line
     with just "%%" in it:

           definitions
           %%
           rules
           %%
           user code

     The dฬฒeฬฒfฬฒiฬฒnฬฒiฬฒtฬฒiฬฒoฬฒnฬฒsฬฒ section contains declarations of simple nฬฒaฬฒmฬฒeฬฒ defiโ€
     nitions to simplify the scanner specification, and declarations of
     sฬฒtฬฒaฬฒrฬฒtฬฒ cฬฒoฬฒnฬฒdฬฒiฬฒtฬฒiฬฒoฬฒnฬฒsฬฒ, which are explained in a later section.

     Name definitions have the form:

           name definition

     The "name" is a word beginning with a letter or an underscore (โ€˜_โ€™)
     followed by zero or more letters, digits, โ€˜_โ€™, or โ€˜-โ€™ (dash).  The
     definition is taken to begin at the first non-whitespace character
     following the name and continuing to the end of the line.  The defโ€
     inition can subsequently be referred to using "{name}", which will
     expand to "(definition)".  For example:

           DIGIT    [0-9]
           ID       [a-z][a-z0-9]*

     This defines "DIGIT" to be a regular expression which matches a
     single digit, and "ID" to be a regular expression which matches a
     letter followed by zero-or-more letters-or-digits.  A subsequent
     reference to

           {DIGIT}+"."{DIGIT}*

     is identical to

           ([0-9])+"."([0-9])*

     and matches one-or-more digits followed by a โ€˜.โ€™ followed by zero-
     or-more digits.

     The rฬฒuฬฒlฬฒeฬฒsฬฒ section of the ๐—ณ๐—น๐—ฒ๐˜… input contains a series of rules of
     the form:

           pattern   action

     The pattern must be unindented and the action must begin on the
     same line.

     See below for a further description of patterns and actions.

     Finally, the user code section is simply copied to lฬฒeฬฒxฬฒ.ฬฒyฬฒyฬฒ.ฬฒcฬฒ verbaโ€
     tim.  It is used for companion routines which call or are called by
     the scanner.  The presence of this section is optional; if it is
     missing, the second "%%" in the input file may be skipped too.

     In the definitions and rules sections, any indented text or text
     enclosed in โ€˜%{โ€™ and โ€˜%}โ€™ is copied verbatim to the output (with
     the %{}'s removed).  The %{}'s must appear unindented on lines by
     themselves.

     In the rules section, any indented or %{} text appearing before the
     first rule may be used to declare variables which are local to the
     scanning routine and (after the declarations) code which is to be
     executed whenever the scanning routine is entered.  Other indented
     or %{} text in the rule section is still copied to the output, but
     its meaning is not well-defined and it may well cause compile-time
     errors (this feature is present for POSIX compliance; see below for
     other such features).

     In the definitions section (but not in the rules section), an uninโ€
     dented comment (i.e., a line beginning with "/*") is also copied
     verbatim to the output up to the next "*/".

๐๐€๐“๐“๐„๐‘๐๐’
     The patterns in the input are written using an extended set of regโ€
     ular expressions.  These are:

     x         Match the character โ€˜xโ€™.

     .         Any character (byte) except newline.

     [xyz]     A "character class"; in this case, the pattern matches
               either an โ€˜xโ€™, a โ€˜yโ€™, or a โ€˜zโ€™.

     [abj-oZ]  A "character class" with a range in it; matches an โ€˜aโ€™, a
               โ€˜bโ€™, any letter from โ€˜jโ€™ through โ€˜oโ€™, or a โ€˜Zโ€™.

     [^A-Z]    A "negated character class", i.e., any character but
               those in the class.  In this case, any character EXCEPT
               an uppercase letter.

     [^A-Z\n]  Any character EXCEPT an uppercase letter or a newline.

     r*        Zero or more r's, where โ€˜rโ€™ is any regular expression.

     r+        One or more r's.

     r?        Zero or one r's (that is, "an optional r").

     r{2,5}    Anywhere from two to five r's.

     r{2,}     Two or more r's.

     r{4}      Exactly 4 r's.

     {name}    The expansion of the "name" definition (see above).

     "[xyz]\"foo"
               The literal string: [xyz]"foo.

     \X        If โ€˜Xโ€™ is an โ€˜aโ€™, โ€˜bโ€™, โ€˜fโ€™, โ€˜nโ€™, โ€˜rโ€™, โ€˜tโ€™, or โ€˜vโ€™, then
               the ANSI-C interpretation of โ€˜\Xโ€™.  Otherwise, a literal
               โ€˜Xโ€™ (used to escape operators such as โ€˜*โ€™).

     \0        A NUL character (ASCII code 0).

     \123      The character with octal value 123.

     \x2a      The character with hexadecimal value 2a.

     (r)       Match an โ€˜rโ€™; parentheses are used to override precedence
               (see below).

     rs        The regular expression โ€˜rโ€™ followed by the regular
               expression โ€˜sโ€™; called "concatenation".

     r|s       Either an โ€˜rโ€™ or an โ€˜sโ€™.

     r/s       An โ€˜rโ€™, but only if it is followed by an โ€˜sโ€™.  The text
               matched by โ€˜sโ€™ is included when determining whether this
               rule is the "longest match", but is then returned to the
               input before the action is executed.  So the action only
               sees the text matched by โ€˜rโ€™.  This type of pattern is
               called "trailing context".  (There are some combinations
               of r/s that ๐—ณ๐—น๐—ฒ๐˜… cannot match correctly; see notes in the
               BฬฒUฬฒGฬฒSฬฒ section below regarding "dangerous trailing
               context".)

     ^r        An โ€˜rโ€™, but only at the beginning of a line (i.e., just
               starting to scan, or right after a newline has been
               scanned).

     r$        An โ€˜rโ€™, but only at the end of a line (i.e., just before
               a newline).  Equivalent to "r/\n".

               Note that ๐—ณ๐—น๐—ฒ๐˜…'s notion of "newline" is exactly whatever
               the C compiler used to compile ๐—ณ๐—น๐—ฒ๐˜… interprets โ€˜\nโ€™ as.

     <s>r      An โ€˜rโ€™, but only in start condition โ€˜sโ€™ (see below for
               discussion of start conditions).

     <s1,s2,s3>r
               The same, but in any of start conditions s1, s2, or s3.

     <*>r      An โ€˜rโ€™ in any start condition, even an exclusive one.

     <<EOF>>   An end-of-file.

     <s1,s2><<EOF>>
               An end-of-file when in start condition s1 or s2.

     Note that inside of a character class, all regular expression operโ€
     ators lose their special meaning except escape (โ€˜\โ€™) and the charโ€
     acter class operators, โ€˜-โ€™, โ€˜]โ€™, and, at the beginning of the
     class, โ€˜^โ€™.

     The regular expressions listed above are grouped according to
     precedence, from highest precedence at the top to lowest at the
     bottom.  Those grouped together have equal precedence.  For examโ€
     ple,

           foo|bar*

     is the same as

           (foo)|(ba(r*))

     since the โ€˜*โ€™ operator has higher precedence than concatenation,
     and concatenation higher than alternation (โ€˜|โ€™).  This pattern
     therefore matches eฬฒiฬฒtฬฒhฬฒeฬฒrฬฒ the string "foo" oฬฒrฬฒ the string "ba" folโ€
     lowed by zero-or-more r's.  To match "foo" or zero-or-more "bar"'s,
     use:

           foo|(bar)*

     and to match zero-or-more "foo"'s-or-"bar"'s:

           (foo|bar)*

     In addition to characters and ranges of characters, character
     classes can also contain character class eฬฒxฬฒpฬฒrฬฒeฬฒsฬฒsฬฒiฬฒoฬฒnฬฒsฬฒ.  These are
     expressions enclosed inside โ€˜[:โ€™ and โ€˜:]โ€™ delimiters (which themโ€
     selves must appear between the โ€˜[โ€™ and โ€˜]โ€™ of the character class;
     other elements may occur inside the character class, too).  The
     valid expressions are:

           [:alnum:] [:alpha:] [:blank:]
           [:cntrl:] [:digit:] [:graph:]
           [:lower:] [:print:] [:punct:]
           [:space:] [:upper:] [:xdigit:]

     These expressions all designate a set of characters equivalent to
     the corresponding standard C ๐—ถ๐˜€๐—๐—๐—() function.  For example,
     [:alnum:] designates those characters for which isalnum(3) returns
     true - i.e., any alphabetic or numeric.  Some systems don't provide
     isblank(3), so ๐—ณ๐—น๐—ฒ๐˜… defines [:blank:] as a blank or a tab.

     For example, the following character classes are all equivalent:

           [[:alnum:]]
           [[:alpha:][:digit:]]
           [[:alpha:]0-9]
           [a-zA-Z0-9]

     If the scanner is case-insensitive (the -๐—ถ flag), then [:upper:]
     and [:lower:] are equivalent to [:alpha:].

     Some notes on patterns:

     -   A negated character class such as the example "[^A-Z]" above
         will match a newline unless "\n" (or an equivalent escape
         sequence) is one of the characters explicitly present in the
         negated character class (e.g., "[^A-Z\n]").  This is unlike how
         many other regular expression tools treat negated character
         classes, but unfortunately the inconsistency is historically
         entrenched.  Matching newlines means that a pattern like
         "[^"]*" can match the entire input unless there's another quote
         in the input.

     -   A rule can have at most one instance of trailing context (the
         โ€˜/โ€™ operator or the โ€˜$โ€™ operator).  The start condition, โ€˜^โ€™,
         and "<<EOF>>" patterns can only occur at the beginning of a
         pattern and, as well as with โ€˜/โ€™ and โ€˜$โ€™, cannot be grouped
         inside parentheses.  A โ€˜^โ€™ which does not occur at the beginโ€
         ning of a rule or a โ€˜$โ€™ which does not occur at the end of a
         rule loses its special properties and is treated as a normal
         character.

     -   The following are illegal:

               foo/bar$
               <sc1>foo<sc2>bar

         Note that the first of these, can be written "foo/bar\n".

     -   The following will result in โ€˜$โ€™ or โ€˜^โ€™ being treated as a norโ€
         mal character:

               foo|(bar$)
               foo|^bar

         If what's wanted is a "foo" or a bar-followed-by-a-newline, the
         following could be used (the special โ€˜|โ€™ action is explained
         below):

               foo      |
               bar$     /* action goes here */

         A similar trick will work for matching a foo or a bar-at-the-
         beginning-of-a-line.

๐‡๐Ž๐– ๐“๐‡๐„ ๐ˆ๐๐๐”๐“ ๐ˆ๐’ ๐Œ๐€๐“๐‚๐‡๐„๐ƒ
     When the generated scanner is run, it analyzes its input looking
     for strings which match any of its patterns.  If it finds more than
     one match, it takes the one matching the most text (for trailing
     context rules, this includes the length of the trailing part, even
     though it will then be returned to the input).  If it finds two or
     more matches of the same length, the rule listed first in the ๐—ณ๐—น๐—ฒ๐˜…
     input file is chosen.

     Once the match is determined, the text corresponding to the match
     (called the tฬฒoฬฒkฬฒeฬฒnฬฒ) is made available in the global character
     pointer yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ, and its length in the global integer yฬฒyฬฒlฬฒeฬฒnฬฒgฬฒ.  The
     aฬฒcฬฒtฬฒiฬฒoฬฒnฬฒ corresponding to the matched pattern is then executed (a
     more detailed description of actions follows), and then the remainโ€
     ing input is scanned for another match.

     If no match is found, then the default rule is executed: the next
     character in the input is considered matched and copied to the
     standard output.  Thus, the simplest legal ๐—ณ๐—น๐—ฒ๐˜… input is:

           %%

     which generates a scanner that simply copies its input (one
     character at a time) to its output.

     Note that yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ can be defined in two different ways: either as a
     character pointer or as a character array.  Which definition ๐—ณ๐—น๐—ฒ๐˜…
     uses can be controlled by including one of the special directives
     โ€œ%pointerโ€ or โ€œ%arrayโ€ in the first (definitions) section of flex
     input.  The default is โ€œ%pointerโ€, unless the -๐—น ๐—น๐—ฒ๐˜… compatibility
     option is used, in which case yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ will be an array.  The advanโ€
     tage of using โ€œ%pointerโ€ is substantially faster scanning and no
     buffer overflow when matching very large tokens (unless not enough
     dynamic memory is available).  The disadvantage is that actions are
     restricted in how they can modify yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ (see the next section),
     and calls to the ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() function destroy the present contents of
     yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ, which can be a considerable porting headache when moving
     between different ๐—น๐—ฒ๐˜… versions.

     The advantage of โ€œ%arrayโ€ is that yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ can be modified as much as
     wanted, and calls to ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() do not destroy yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ (see below).
     Furthermore, existing ๐—น๐—ฒ๐˜… programs sometimes access yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ exterโ€
     nally using declarations of the form:

           extern char yytext[];

     This definition is erroneous when used with โ€œ%pointerโ€, but correct
     for โ€œ%arrayโ€.

     โ€œ%arrayโ€ defines yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ to be an array of YYLMAX characters, which
     defaults to a fairly large value.  The size can be changed by simโ€
     ply #define'ing YYLMAX to a different value in the first section of
     ๐—ณ๐—น๐—ฒ๐˜… input.  As mentioned above, with โ€œ%pointerโ€ yytext grows
     dynamically to accommodate large tokens.  While this means a
     โ€œ%pointerโ€ scanner can accommodate very large tokens (such as
     matching entire blocks of comments), bear in mind that each time
     the scanner must resize yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ it also must rescan the entire token
     from the beginning, so matching such tokens can prove slow.  yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ
     presently does not dynamically grow if a call to ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() results in
     too much text being pushed back; instead, a run-time error results.

     Also note that โ€œ%arrayโ€ cannot be used with C++ scanner classes
     (the c++ option; see below).

๐€๐‚๐“๐ˆ๐Ž๐๐’
     Each pattern in a rule has a corresponding action, which can be any
     arbitrary C statement.  The pattern ends at the first non-escaped
     whitespace character; the remainder of the line is its action.  If
     the action is empty, then when the pattern is matched the input
     token is simply discarded.  For example, here is the specification
     for a program which deletes all occurrences of "zap me" from its
     input:

           %%
           "zap me"

     (It will copy all other characters in the input to the output since
     they will be matched by the default rule.)

     Here is a program which compresses multiple blanks and tabs down to
     a single blank, and throws away whitespace found at the end of a
     line:

           %%
           [ \t]+        putchar(' ');
           [ \t]+$       /* ignore this token */

     If the action contains a โ€˜{โ€™, then the action spans till the balโ€
     ancing โ€˜}โ€™ is found, and the action may cross multiple lines.  ๐—ณ๐—น๐—ฒ๐˜…
     knows about C strings and comments and won't be fooled by braces
     found within them, but also allows actions to begin with โ€˜%{โ€™ and
     will consider the action to be all the text up to the next โ€˜%}โ€™
     (regardless of ordinary braces inside the action).

     An action consisting solely of a vertical bar (โ€˜|โ€™) means "same as
     the action for the next rule".  See below for an illustration.

     Actions can include arbitrary C code, including return statements
     to return a value to whatever routine called ๐˜†๐˜†๐—น๐—ฒ๐˜…().  Each time
     ๐˜†๐˜†๐—น๐—ฒ๐˜…() is called, it continues processing tokens from where it
     last left off until it either reaches the end of the file or exeโ€
     cutes a return.

     Actions are free to modify yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ except for lengthening it (adding
     characters to its end - these will overwrite later characters in
     the input stream).  This, however, does not apply when using
     โ€œ%arrayโ€ (see above); in that case, yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ may be freely modified
     in any way.

     Actions are free to modify yฬฒyฬฒlฬฒeฬฒnฬฒgฬฒ except they should not do so if
     the action also includes use of ๐˜†๐˜†๐—บ๐—ผ๐—ฟ๐—ฒ() (see below).

     There are a number of special directives which can be included
     within an action:

     ECHO    Copies yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ to the scanner's output.

     BEGIN   Followed by the name of a start condition, places the scanโ€
             ner in the corresponding start condition (see below).

     REJECT  Directs the scanner to proceed on to the "second best" rule
             which matched the input (or a prefix of the input).  The
             rule is chosen as described above in HฬฒOฬฒWฬฒ TฬฒHฬฒEฬฒ IฬฒNฬฒPฬฒUฬฒTฬฒ IฬฒSฬฒ
             MฬฒAฬฒTฬฒCฬฒHฬฒEฬฒDฬฒ, and yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ and yฬฒyฬฒlฬฒeฬฒnฬฒgฬฒ set up appropriately.  It
             may either be one which matched as much text as the origiโ€
             nally chosen rule but came later in the ๐—ณ๐—น๐—ฒ๐˜… input file, or
             one which matched less text.  For example, the following
             will both count the words in the input and call the routine
             ๐˜€๐—ฝ๐—ฒ๐—ฐ๐—ถ๐—ฎ๐—น() whenever "frob" is seen:

                   int word_count = 0;
                   %%

                   frob        special(); REJECT;
                   [^ \t\n]+   ++word_count;

             Without the RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ, any "frob"'s in the input would not be
             counted as words, since the scanner normally executes only
             one action per token.  Multiple RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ's are allowed, each
             one finding the next best choice to the currently active
             rule.  For example, when the following scanner scans the
             token "abcd", it will write "abcdabcaba" to the output:

                   %%
                   a        |
                   ab       |
                   abc      |
                   abcd     ECHO; REJECT;
                   .|\n     /* eat up any unmatched character */

             (The first three rules share the fourth's action since they
             use the special โ€˜|โ€™ action.)  RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ is a particularly
             expensive feature in terms of scanner performance; if it is
             used in any of the scanner's actions it will slow down all
             of the scanner's matching.  Furthermore, RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ cannot be
             used with the -๐‚๐—ณ or -๐‚๐… options (see below).

             Note also that unlike the other special actions, RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ is
             a bฬฒrฬฒaฬฒnฬฒcฬฒhฬฒ; code immediately following it in the action will
             not be executed.

     yymore()
             Tells the scanner that the next time it matches a rule, the
             corresponding token should be appended onto the current
             value of yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ rather than replacing it.  For example,
             given the input "mega-kludge" the following will write
             "mega-mega-kludge" to the output:

                   %%
                   mega-    ECHO; yymore();
                   kludge   ECHO;

             First "mega-" is matched and echoed to the output.  Then
             "kludge" is matched, but the previous "mega-" is still
             hanging around at the beginning of yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ so the EฬฒCฬฒHฬฒOฬฒ for
             the "kludge" rule will actually write "mega-kludge".

             Two notes regarding use of ๐˜†๐˜†๐—บ๐—ผ๐—ฟ๐—ฒ(): First, ๐˜†๐˜†๐—บ๐—ผ๐—ฟ๐—ฒ()
             depends on the value of yฬฒyฬฒlฬฒeฬฒnฬฒgฬฒ correctly reflecting the
             size of the current token, so yฬฒyฬฒlฬฒeฬฒnฬฒgฬฒ must not be modified
             when using ๐˜†๐˜†๐—บ๐—ผ๐—ฟ๐—ฒ().  Second, the presence of ๐˜†๐˜†๐—บ๐—ผ๐—ฟ๐—ฒ() in
             the scanner's action entails a minor performance penalty in
             the scanner's matching speed.

     yyless(n)
             Returns all but the first nฬฒ characters of the current token
             back to the input stream, where they will be rescanned when
             the scanner looks for the next match.  yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ and yฬฒyฬฒlฬฒeฬฒnฬฒgฬฒ
             are adjusted appropriately (e.g., yฬฒyฬฒlฬฒeฬฒnฬฒgฬฒ will now be equal
             to nฬฒ).  For example, on the input "foobar" the following
             will write out "foobarbar":

                   %%
                   foobar    ECHO; yyless(3);
                   [a-z]+    ECHO;

             An argument of 0 to yฬฒyฬฒlฬฒeฬฒsฬฒsฬฒ will cause the entire current
             input string to be scanned again.  Unless how the scanner
             will subsequently process its input has been changed (using
             BฬฒEฬฒGฬฒIฬฒNฬฒ, for example), this will result in an endless loop.

             Note that yฬฒyฬฒlฬฒeฬฒsฬฒsฬฒ is a macro and can only be used in the
             ๐—ณ๐—น๐—ฒ๐˜… input file, not from other source files.

     unput(c)
             Puts the character cฬฒ back into the input stream.  It will
             be the next character scanned.  The following action will
             take the current token and cause it to be rescanned
             enclosed in parentheses.

                   {
                           int i;
                           char *yycopy;

                           /* Copy yytext because unput() trashes yytext */
                           if ((yycopy = strdup(yytext)) == NULL)
                                   err(1, NULL);
                           unput(')');
                           for (i = yyleng - 1; i >= 0; --i)
                                   unput(yycopy[i]);
                           unput('(');
                           free(yycopy);
                   }

             Note that since each ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() puts the given character back
             at the beginning of the input stream, pushing back strings
             must be done back-to-front.

             An important potential problem when using ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() is that
             if using โ€œ%pointerโ€ (the default), a call to ๐˜‚๐—ป๐—ฝ๐˜‚๐˜()
             destroys the contents of yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ, starting with its rightโ€
             most character and devouring one character to the left with
             each call.  If the value of yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ should be preserved
             after a call to ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() (as in the above example), it must
             either first be copied elsewhere, or the scanner must be
             built using โ€œ%arrayโ€ instead (see HฬฒOฬฒWฬฒ TฬฒHฬฒEฬฒ IฬฒNฬฒPฬฒUฬฒTฬฒ IฬฒSฬฒ
             MฬฒAฬฒTฬฒCฬฒHฬฒEฬฒDฬฒ).

             Finally, note that EOF cannot be put back to attempt to
             mark the input stream with an end-of-file.

     input()
             Reads the next character from the input stream.  For examโ€
             ple, the following is one way to eat up C comments:

                   %%
                   "/*" {
                           int c;

                           for (;;) {
                                   while ((c = input()) != '*' && c != EOF)
                                           ; /* eat up text of comment */

                                   if (c == '*') {
                                           while ((c = input()) == '*')
                                                   ;
                                           if (c == '/')
                                                   break; /* found the end */
                                   }

                                   if (c == EOF) {
                                           errx(1, "EOF in comment");
                                           break;
                                   }
                           }
                   }

             (Note that if the scanner is compiled using C++, then
             ๐—ถ๐—ป๐—ฝ๐˜‚๐˜() is instead referred to as ๐˜†๐˜†๐—ถ๐—ป๐—ฝ๐˜‚๐˜(), in order to
             avoid a name clash with the C++ stream by the name of
             input.)

     YY_FLUSH_BUFFER
             Flushes the scanner's internal buffer so that the next time
             the scanner attempts to match a token, it will first refill
             the buffer using YY_INPUT (see TฬฒHฬฒEฬฒ GฬฒEฬฒNฬฒEฬฒRฬฒAฬฒTฬฒEฬฒDฬฒ SฬฒCฬฒAฬฒNฬฒNฬฒEฬฒRฬฒ,
             below).  This action is a special case of the more general
             ๐˜†๐˜†_๐—ณ๐—น๐˜‚๐˜€๐—ต_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ() function, described below in the section
             MฬฒUฬฒLฬฒTฬฒIฬฒPฬฒLฬฒEฬฒ IฬฒNฬฒPฬฒUฬฒTฬฒ BฬฒUฬฒFฬฒFฬฒEฬฒRฬฒSฬฒ.

     yyterminate()
             Can be used in lieu of a return statement in an action.  It
             terminates the scanner and returns a 0 to the scanner's
             caller, indicating "all done".  By default, ๐˜†๐˜†๐˜๐—ฒ๐—ฟ๐—บ๐—ถ๐—ป๐—ฎ๐˜๐—ฒ()
             is also called when an end-of-file is encountered.  It is a
             macro and may be redefined.

๐“๐‡๐„ ๐†๐„๐๐„๐‘๐€๐“๐„๐ƒ ๐’๐‚๐€๐๐๐„๐‘
     The output of ๐—ณ๐—น๐—ฒ๐˜… is the file lฬฒeฬฒxฬฒ.ฬฒyฬฒyฬฒ.ฬฒcฬฒ, which contains the scanโ€
     ning routine ๐˜†๐˜†๐—น๐—ฒ๐˜…(), a number of tables used by it for matching
     tokens, and a number of auxiliary routines and macros.  By default,
     ๐˜†๐˜†๐—น๐—ฒ๐˜…() is declared as follows:

           int yylex()
           {
               ... various definitions and the actions in here ...
           }

     (If the environment supports function prototypes, then it will be
     "int yylex(void)".)  This definition may be changed by defining the
     YY_DECL macro.  For example:

           #define YY_DECL float lexscan(a, b) float a, b;

     would give the scanning routine the name lฬฒeฬฒxฬฒsฬฒcฬฒaฬฒnฬฒ, returning a
     float, and taking two floats as arguments.  Note that if arguments
     are given to the scanning routine using a K&R-style/non-prototyped
     function declaration, the definition must be terminated with a
     semi-colon (โ€˜;โ€™).

     Whenever ๐˜†๐˜†๐—น๐—ฒ๐˜…() is called, it scans tokens from the global input
     file yฬฒyฬฒiฬฒnฬฒ (which defaults to stdin).  It continues until it either
     reaches an end-of-file (at which point it returns the value 0) or
     one of its actions executes a rฬฒeฬฒtฬฒuฬฒrฬฒnฬฒ statement.

     If the scanner reaches an end-of-file, subsequent calls are undeโ€
     fined unless either yฬฒyฬฒiฬฒnฬฒ is pointed at a new input file (in which
     case scanning continues from that file), or ๐˜†๐˜†๐—ฟ๐—ฒ๐˜€๐˜๐—ฎ๐—ฟ๐˜() is called.
     ๐˜†๐˜†๐—ฟ๐—ฒ๐˜€๐˜๐—ฎ๐—ฟ๐˜() takes one argument, a FฬฒIฬฒLฬฒEฬฒ *ฬฒ pointer (which can be nil,
     if YY_INPUT has been set up to scan from a source other than yฬฒyฬฒiฬฒnฬฒ),
     and initializes yฬฒyฬฒiฬฒnฬฒ for scanning from that file.  Essentially
     there is no difference between just assigning yฬฒyฬฒiฬฒnฬฒ to a new input
     file or using ๐˜†๐˜†๐—ฟ๐—ฒ๐˜€๐˜๐—ฎ๐—ฟ๐˜() to do so; the latter is available for
     compatibility with previous versions of ๐—ณ๐—น๐—ฒ๐˜…, and because it can be
     used to switch input files in the middle of scanning.  It can also
     be used to throw away the current input buffer, by calling it with
     an argument of yฬฒyฬฒiฬฒnฬฒ; but better is to use YY_FLUSH_BUFFER (see
     above).  Note that ๐˜†๐˜†๐—ฟ๐—ฒ๐˜€๐˜๐—ฎ๐—ฟ๐˜() does not reset the start condition
     to IฬฒNฬฒIฬฒTฬฒIฬฒAฬฒLฬฒ (see SฬฒTฬฒAฬฒRฬฒTฬฒ CฬฒOฬฒNฬฒDฬฒIฬฒTฬฒIฬฒOฬฒNฬฒSฬฒ, below).

     If ๐˜†๐˜†๐—น๐—ฒ๐˜…() stops scanning due to executing a rฬฒeฬฒtฬฒuฬฒrฬฒnฬฒ statement in
     one of the actions, the scanner may then be called again and it
     will resume scanning where it left off.

     By default (and for purposes of efficiency), the scanner uses
     block-reads rather than simple getc(3) calls to read characters
     from yฬฒyฬฒiฬฒnฬฒ.  The nature of how it gets its input can be controlled
     by defining the YY_INPUT macro.  YY_INPUT's calling sequence is
     "YY_INPUT(buf,result,max_size)".  Its action is to place up to
     max_size characters in the character array bฬฒuฬฒfฬฒ and return in the
     integer variable rฬฒeฬฒsฬฒuฬฒlฬฒtฬฒ either the number of characters read or the
     constant YY_NULL (0 on UNIX systems) to indicate EOF.  The default
     YY_INPUT reads from the global file-pointer "yyin".

     A sample definition of YY_INPUT (in the definitions section of the
     input file):

           %{
           #define YY_INPUT(buf,result,max_size) \
           { \
                   int c = getchar(); \
                   result = (c == EOF) ? YY_NULL : (buf[0] = c, 1); \
           }
           %}

     This definition will change the input processing to occur one charโ€
     acter at a time.

     When the scanner receives an end-of-file indication from YY_INPUT,
     it then checks the ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ() function.  If ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ() returns false
     (zero), then it is assumed that the function has gone ahead and set
     up yฬฒyฬฒiฬฒnฬฒ to point to another input file, and scanning continues.  If
     it returns true (non-zero), then the scanner terminates, returning
     0 to its caller.  Note that in either case, the start condition
     remains unchanged; it does not revert to IฬฒNฬฒIฬฒTฬฒIฬฒAฬฒLฬฒ.

     If you do not supply your own version of ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ(), then you must
     either use โ€œ%option noyywrapโ€ (in which case the scanner behaves as
     though ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ() returned 1), or you must link with -๐—น๐—ณ๐—น to obtain
     the default version of the routine, which always returns 1.

     Three routines are available for scanning from in-memory buffers
     rather than files: ๐˜†๐˜†_๐˜€๐—ฐ๐—ฎ๐—ป_๐˜€๐˜๐—ฟ๐—ถ๐—ป๐—ด(), ๐˜†๐˜†_๐˜€๐—ฐ๐—ฎ๐—ป_๐—ฏ๐˜†๐˜๐—ฒ๐˜€(), and
     ๐˜†๐˜†_๐˜€๐—ฐ๐—ฎ๐—ป_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ().  See the discussion of them below in the section
     MฬฒUฬฒLฬฒTฬฒIฬฒPฬฒLฬฒEฬฒ IฬฒNฬฒPฬฒUฬฒTฬฒ BฬฒUฬฒFฬฒFฬฒEฬฒRฬฒSฬฒ.

     The scanner writes its EฬฒCฬฒHฬฒOฬฒ output to the yฬฒyฬฒoฬฒuฬฒtฬฒ global (default,
     stdout), which may be redefined by the user simply by assigning it
     to some other FฬฒIฬฒLฬฒEฬฒ pointer.

๐’๐“๐€๐‘๐“ ๐‚๐Ž๐๐ƒ๐ˆ๐“๐ˆ๐Ž๐๐’
     ๐—ณ๐—น๐—ฒ๐˜… provides a mechanism for conditionally activating rules.  Any
     rule whose pattern is prefixed with "โŸจscโŸฉ" will only be active when
     the scanner is in the start condition named "sc".  For example,

           <STRING>[^"]* { /* eat up the string body ... */
                   ...
           }

     will be active only when the scanner is in the "STRING" start conโ€
     dition, and

           <INITIAL,STRING,QUOTE>\. { /* handle an escape ... */
                   ...
           }

     will be active only when the current start condition is either
     "INITIAL", "STRING", or "QUOTE".

     Start conditions are declared in the definitions (first) section of
     the input using unindented lines beginning with either โ€˜%sโ€™ or โ€˜%xโ€™
     followed by a list of names.  The former declares iฬฒnฬฒcฬฒlฬฒuฬฒsฬฒiฬฒvฬฒeฬฒ start
     conditions, the latter eฬฒxฬฒcฬฒlฬฒuฬฒsฬฒiฬฒvฬฒeฬฒ start conditions.  A start condiโ€
     tion is activated using the BฬฒEฬฒGฬฒIฬฒNฬฒ action.  Until the next BฬฒEฬฒGฬฒIฬฒNฬฒ
     action is executed, rules with the given start condition will be
     active and rules with other start conditions will be inactive.  If
     the start condition is inclusive, then rules with no start condiโ€
     tions at all will also be active.  If it is exclusive, then only
     rules qualified with the start condition will be active.  A set of
     rules contingent on the same exclusive start condition describe a
     scanner which is independent of any of the other rules in the ๐—ณ๐—น๐—ฒ๐˜…
     input.  Because of this, exclusive start conditions make it easy to
     specify "mini-scanners" which scan portions of the input that are
     syntactically different from the rest (e.g., comments).

     If the distinction between inclusive and exclusive start conditions
     is still a little vague, here's a simple example illustrating the
     connection between the two.  The set of rules:

           %s example
           %%

           <example>foo   do_something();

           bar            something_else();

     is equivalent to

           %x example
           %%

           <example>foo   do_something();

           <INITIAL,example>bar    something_else();

     Without the โŸจINITIAL,exampleโŸฉ qualifier, the โ€œbarโ€ pattern in the
     second example wouldn't be active (i.e., couldn't match) when in
     start condition โ€œexampleโ€.  If we just used โŸจexampleโŸฉ to qualify
     โ€œbarโ€, though, then it would only be active in โ€œexampleโ€ and not in
     IฬฒNฬฒIฬฒTฬฒIฬฒAฬฒLฬฒ, while in the first example it's active in both, because in
     the first example the โ€œexampleโ€ start condition is an inclusive
     (โ€˜%sโ€™) start condition.

     Also note that the special start-condition specifier โ€˜โŸจ*โŸฉโ€™ matches
     every start condition.  Thus, the above example could also have
     been written:

           %x example
           %%

           <example>foo   do_something();

           <*>bar         something_else();

     The default rule (to EฬฒCฬฒHฬฒOฬฒ any unmatched character) remains active
     in start conditions.  It is equivalent to:

           <*>.|\n     ECHO;

     โ€œBEGIN(0)โ€ returns to the original state where only the rules with
     no start conditions are active.  This state can also be referred to
     as the start-condition IฬฒNฬฒIฬฒTฬฒIฬฒAฬฒLฬฒ, so โ€œBEGIN(INITIAL)โ€ is equivalent
     to โ€œBEGIN(0)โ€.  (The parentheses around the start condition name
     are not required but are considered good style.)

     BฬฒEฬฒGฬฒIฬฒNฬฒ actions can also be given as indented code at the beginning
     of the rules section.  For example, the following will cause the
     scanner to enter the "SPECIAL" start condition whenever ๐˜†๐˜†๐—น๐—ฒ๐˜…() is
     called and the global variable eฬฒnฬฒtฬฒeฬฒrฬฒ_sฬฒpฬฒeฬฒcฬฒiฬฒaฬฒlฬฒ is true:

           int enter_special;

           %x SPECIAL
           %%
                   if (enter_special)
                           BEGIN(SPECIAL);

           <SPECIAL>blahblahblah
           ...more rules follow...

     To illustrate the uses of start conditions, here is a scanner which
     provides two different interpretations of a string like "123.456".
     By default it will treat it as three tokens: the integer "123", a
     dot (โ€˜.โ€™), and the integer "456".  But if the string is preceded
     earlier in the line by the string "expect-floats" it will treat it
     as a single token, the floating-point number 123.456:

           %{
           #include <math.h>
           %}
           %s expect

           %%
           expect-floats        BEGIN(expect);

           <expect>[0-9]+"."[0-9]+ {
                   printf("found a float, = %f\n",
                       atof(yytext));
           }
           <expect>\n {
                   /*
                    * That's the end of the line, so
                    * we need another "expect-number"
                    * before we'll recognize any more
                    * numbers.
                    */
                   BEGIN(INITIAL);
           }

           [0-9]+ {
                   printf("found an integer, = %d\n",
                       atoi(yytext));
           }

           "."     printf("found a dot\n");

     Here is a scanner which recognizes (and discards) C comments while
     maintaining a count of the current input line:

           %x comment
           %%
           int line_num = 1;

           "/*"                    BEGIN(comment);

           <comment>[^*\n]*        /* eat anything that's not a '*' */
           <comment>"*"+[^*/\n]*   /* eat up '*'s not followed by '/'s */
           <comment>\n             ++line_num;
           <comment>"*"+"/"        BEGIN(INITIAL);

     This scanner goes to a bit of trouble to match as much text as posโ€
     sible with each rule.  In general, when attempting to write a high-
     speed scanner try to match as much as possible in each rule, as
     it's a big win.

     Note that start-condition names are really integer values and can
     be stored as such.  Thus, the above could be extended in the folโ€
     lowing fashion:

           %x comment foo
           %%
           int line_num = 1;
           int comment_caller;

           "/*" {
                   comment_caller = INITIAL;
                   BEGIN(comment);
           }

           ...

           <foo>"/*" {
                   comment_caller = foo;
                   BEGIN(comment);
           }

           <comment>[^*\n]*        /* eat anything that's not a '*' */
           <comment>"*"+[^*/\n]*   /* eat up '*'s not followed by '/'s */
           <comment>\n             ++line_num;
           <comment>"*"+"/"        BEGIN(comment_caller);

     Furthermore, the current start condition can be accessed by using
     the integer-valued YY_START macro.  For example, the above assignโ€
     ments to cฬฒoฬฒmฬฒmฬฒeฬฒnฬฒtฬฒ_cฬฒaฬฒlฬฒlฬฒeฬฒrฬฒ could instead be written

           comment_caller = YY_START;

     Flex provides YYSTATE as an alias for YY_START (since that is
     what's used by AT&T UNIX ๐—น๐—ฒ๐˜…).

     Note that start conditions do not have their own name-space; %s's
     and %x's declare names in the same fashion as #define's.

     Finally, here's an example of how to match C-style quoted strings
     using exclusive start conditions, including expanded escape
     sequences (but not including checking for a string that's too
     long):

           %x str

           %%
           #define MAX_STR_CONST 1024
           char string_buf[MAX_STR_CONST];
           char *string_buf_ptr;

           \"      string_buf_ptr = string_buf; BEGIN(str);

           <str>\" { /* saw closing quote - all done */
                   BEGIN(INITIAL);
                   *string_buf_ptr = '\0';
                   /*
                    * return string constant token type and
                    * value to parser
                    */
           }

           <str>\n {
                   /* error - unterminated string constant */
                   /* generate error message */
           }

           <str>\\[0-7]{1,3} {
                   /* octal escape sequence */
                   int result;

                   (void) sscanf(yytext + 1, "%o", &result);

                   if (result > 0xff) {
                           /* error, constant is out-of-bounds */
                   } else
                           *string_buf_ptr++ = result;
           }

           <str>\\[0-9]+ {
                   /*
                    * generate error - bad escape sequence; something
                    * like '\48' or '\0777777'
                    */
           }

           <str>\\n  *string_buf_ptr++ = '\n';
           <str>\\t  *string_buf_ptr++ = '\t';
           <str>\\r  *string_buf_ptr++ = '\r';
           <str>\\b  *string_buf_ptr++ = '\b';
           <str>\\f  *string_buf_ptr++ = '\f';

           <str>\\(.|\n)  *string_buf_ptr++ = yytext[1];

           <str>[^\\\n\"]+ {
                   char *yptr = yytext;

                   while (*yptr)
                           *string_buf_ptr++ = *yptr++;
           }

     Often, such as in some of the examples above, a whole bunch of
     rules are all preceded by the same start condition(s).  ๐—ณ๐—น๐—ฒ๐˜… makes
     this a little easier and cleaner by introducing a notion of start
     condition sฬฒcฬฒoฬฒpฬฒeฬฒ.  A start condition scope is begun with:

           <SCs>{

     where โ€œSCsโ€ is a list of one or more start conditions.  Inside the
     start condition scope, every rule automatically has the prefix
     โŸจSCsโŸฉ applied to it, until a โ€˜}โ€™ which matches the initial โ€˜{โ€™.
     So, for example,

           <ESC>{
               "\\n"   return '\n';
               "\\r"   return '\r';
               "\\f"   return '\f';
               "\\0"   return '\0';
           }

     is equivalent to:

           <ESC>"\\n"  return '\n';
           <ESC>"\\r"  return '\r';
           <ESC>"\\f"  return '\f';
           <ESC>"\\0"  return '\0';

     Start condition scopes may be nested.

     Three routines are available for manipulating stacks of start conโ€
     ditions:

     void yy_push_state(int new_state)
             Pushes the current start condition onto the top of the
             start condition stack and switches to nฬฒeฬฒwฬฒ_sฬฒtฬฒaฬฒtฬฒeฬฒ as though
             โ€œBEGIN new_stateโ€ had been used (recall that start
             condition names are also integers).

     void yy_pop_state()
             Pops the top of the stack and switches to it via BฬฒEฬฒGฬฒIฬฒNฬฒ.

     int yy_top_state()
             Returns the top of the stack without altering the stack's
             contents.

     The start condition stack grows dynamically and so has no built-in
     size limitation.  If memory is exhausted, program execution aborts.

     To use start condition stacks, scanners must include a โ€œ%option
     stackโ€ directive (see OฬฒPฬฒTฬฒIฬฒOฬฒNฬฒSฬฒ below).

๐Œ๐”๐‹๐“๐ˆ๐๐‹๐„ ๐ˆ๐๐๐”๐“ ๐๐”๐…๐…๐„๐‘๐’
     Some scanners (such as those which support "include" files) require
     reading from several input streams.  As ๐—ณ๐—น๐—ฒ๐˜… scanners do a large
     amount of buffering, one cannot control where the next input will
     be read from by simply writing a YY_INPUT which is sensitive to the
     scanning context.  YY_INPUT is only called when the scanner reaches
     the end of its buffer, which may be a long time after scanning a
     statement such as an "include" which requires switching the input
     source.

     To negotiate these sorts of problems, ๐—ณ๐—น๐—ฒ๐˜… provides a mechanism for
     creating and switching between multiple input buffers.  An input
     buffer is created by using:

           YY_BUFFER_STATE yy_create_buffer(FILE *file, int size)

     which takes a FฬฒIฬฒLฬฒEฬฒ pointer and a sฬฒiฬฒzฬฒeฬฒ and creates a buffer associโ€
     ated with the given file and large enough to hold sฬฒiฬฒzฬฒeฬฒ characters
     (when in doubt, use YY_BUF_SIZE for the size).  It returns a
     YY_BUFFER_STATE handle, which may then be passed to other routines
     (see below).  The YY_BUFFER_STATE type is a pointer to an opaque
     โ€œstruct yy_buffer_stateโ€ structure, so YY_BUFFER_STATE variables
     may be safely initialized to โ€œ((YY_BUFFER_STATE) 0)โ€ if desired,
     and the opaque structure can also be referred to in order to corโ€
     rectly declare input buffers in source files other than that of
     scanners.  Note that the FฬฒIฬฒLฬฒEฬฒ pointer in the call to
     ๐˜†๐˜†_๐—ฐ๐—ฟ๐—ฒ๐—ฎ๐˜๐—ฒ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ() is only used as the value of yฬฒyฬฒiฬฒnฬฒ seen by
     YY_INPUT; if YY_INPUT is redefined so that it no longer uses yฬฒyฬฒiฬฒnฬฒ,
     then a nil FฬฒIฬฒLฬฒEฬฒ pointer can safely be passed to ๐˜†๐˜†_๐—ฐ๐—ฟ๐—ฒ๐—ฎ๐˜๐—ฒ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ().
     To select a particular buffer to scan:

           void yy_switch_to_buffer(YY_BUFFER_STATE new_buffer)

     It switches the scanner's input buffer so subsequent tokens will
     come from nฬฒeฬฒwฬฒ_bฬฒuฬฒfฬฒfฬฒeฬฒrฬฒ.  Note that ๐˜†๐˜†_๐˜€๐˜„๐—ถ๐˜๐—ฐ๐—ต_๐˜๐—ผ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ() may be used
     by ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ() to set things up for continued scanning, instead of
     opening a new file and pointing yฬฒyฬฒiฬฒnฬฒ at it.  Note also that switchโ€
     ing input sources via either ๐˜†๐˜†_๐˜€๐˜„๐—ถ๐˜๐—ฐ๐—ต_๐˜๐—ผ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ() or ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ() does
     not change the start condition.

           void yy_delete_buffer(YY_BUFFER_STATE buffer)

     is used to reclaim the storage associated with a buffer.  (bฬฒuฬฒfฬฒfฬฒeฬฒrฬฒ
     can be nil, in which case the routine does nothing.)  To clear the
     current contents of a buffer:

           void yy_flush_buffer(YY_BUFFER_STATE buffer)

     This function discards the buffer's contents, so the next time the
     scanner attempts to match a token from the buffer, it will first
     fill the buffer anew using YY_INPUT.

     ๐˜†๐˜†_๐—ป๐—ฒ๐˜„_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ() is an alias for ๐˜†๐˜†_๐—ฐ๐—ฟ๐—ฒ๐—ฎ๐˜๐—ฒ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ(), provided for
     compatibility with the C++ use of nฬฒeฬฒwฬฒ and dฬฒeฬฒlฬฒeฬฒtฬฒeฬฒ for creating and
     destroying dynamic objects.

     Finally, the YY_CURRENT_BUFFER macro returns a YY_BUFFER_STATE hanโ€
     dle to the current buffer.

     Here is an example of using these features for writing a scanner
     which expands include files (the โŸจโŸจEOFโŸฉโŸฉ feature is discussed
     below):

           /*
            * the "incl" state is used for picking up the name
            * of an include file
            */
           %x incl

           %{
           #define MAX_INCLUDE_DEPTH 10
           YY_BUFFER_STATE include_stack[MAX_INCLUDE_DEPTH];
           int include_stack_ptr = 0;
           %}

           %%
           include             BEGIN(incl);

           [a-z]+              ECHO;
           [^a-z\n]*\n?        ECHO;

           <incl>[ \t]*        /* eat the whitespace */
           <incl>[^ \t\n]+ {   /* got the include file name */
                   if (include_stack_ptr >= MAX_INCLUDE_DEPTH)
                           errx(1, "Includes nested too deeply");

                   include_stack[include_stack_ptr++] =
                       YY_CURRENT_BUFFER;

                   yyin = fopen(yytext, "r");

                   if (yyin == NULL)
                           err(1, NULL);

                   yy_switch_to_buffer(
                       yy_create_buffer(yyin, YY_BUF_SIZE));

                   BEGIN(INITIAL);
           }

           <<EOF>> {
                   if (--include_stack_ptr < 0)
                           yyterminate();
                   else {
                           yy_delete_buffer(YY_CURRENT_BUFFER);
                           yy_switch_to_buffer(
                               include_stack[include_stack_ptr]);
                  }
           }

     Three routines are available for setting up input buffers for scanโ€
     ning in-memory strings instead of files.  All of them create a new
     input buffer for scanning the string, and return a corresponding
     YY_BUFFER_STATE handle (which should be deleted afterwards using
     ๐˜†๐˜†_๐—ฑ๐—ฒ๐—น๐—ฒ๐˜๐—ฒ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ()).  They also switch to the new buffer using
     ๐˜†๐˜†_๐˜€๐˜„๐—ถ๐˜๐—ฐ๐—ต_๐˜๐—ผ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ(), so the next call to ๐˜†๐˜†๐—น๐—ฒ๐˜…() will start scanโ€
     ning the string.

     yy_scan_string(const char *str)
             Scans a NUL-terminated string.

     yy_scan_bytes(const char *bytes, int len)
             Scans lฬฒeฬฒnฬฒ bytes (including possibly NUL's) starting at
             location bฬฒyฬฒtฬฒeฬฒsฬฒ.

     Note that both of these functions create and scan a copy of the
     string or bytes.  (This may be desirable, since ๐˜†๐˜†๐—น๐—ฒ๐˜…() modifies
     the contents of the buffer it is scanning.)  The copy can be
     avoided by using:

     yy_scan_buffer(char *base, yy_size_t size)
             Which scans the buffer starting at bฬฒaฬฒsฬฒeฬฒ, consisting of sฬฒiฬฒzฬฒeฬฒ
             bytes, the last two bytes of which must be
             YY_END_OF_BUFFER_CHAR (ASCII NUL).  These last two bytes
             are not scanned; thus, scanning consists of base[0] through
             base[size-2], inclusive.

             If bฬฒaฬฒsฬฒeฬฒ is not set up in this manner (i.e., forget the
             final two YY_END_OF_BUFFER_CHAR bytes), then
             ๐˜†๐˜†_๐˜€๐—ฐ๐—ฎ๐—ป_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ() returns a nil pointer instead of creating
             a new input buffer.

             The type yฬฒyฬฒ_sฬฒiฬฒzฬฒeฬฒ_tฬฒ is an integral type which can be cast to
             an integer expression reflecting the size of the buffer.

๐„๐๐ƒ-๐Ž๐…-๐…๐ˆ๐‹๐„ ๐‘๐”๐‹๐„๐’
     The special rule "โŸจโŸจEOFโŸฉโŸฉ" indicates actions which are to be taken
     when an end-of-file is encountered and ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ() returns non-zero
     (i.e., indicates no further files to process).  The action must
     finish by doing one of four things:

     -   Assigning yฬฒyฬฒiฬฒnฬฒ to a new input file (in previous versions of
         ๐—ณ๐—น๐—ฒ๐˜…, after doing the assignment, it was necessary to call the
         special action YY_NEW_FILE; this is no longer necessary).

     -   Executing a rฬฒeฬฒtฬฒuฬฒrฬฒnฬฒ statement.

     -   Executing the special ๐˜†๐˜†๐˜๐—ฒ๐—ฟ๐—บ๐—ถ๐—ป๐—ฎ๐˜๐—ฒ() action.

     -   Switching to a new buffer using ๐˜†๐˜†_๐˜€๐˜„๐—ถ๐˜๐—ฐ๐—ต_๐˜๐—ผ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ() as shown
         in the example above.

     โŸจโŸจEOFโŸฉโŸฉ rules may not be used with other patterns; they may only be
     qualified with a list of start conditions.  If an unqualified
     โŸจโŸจEOFโŸฉโŸฉ rule is given, it applies to all start conditions which do
     not already have โŸจโŸจEOFโŸฉโŸฉ actions.  To specify an โŸจโŸจEOFโŸฉโŸฉ rule for
     only the initial start condition, use

           <INITIAL><<EOF>>

     These rules are useful for catching things like unclosed comments.
     An example:

           %x quote
           %%

           ...other rules for dealing with quotes...

           <quote><<EOF>> {
                    error("unterminated quote");
                    yyterminate();
           }
           <<EOF>> {
                    if (*++filelist)
                            yyin = fopen(*filelist, "r");
                    else
                            yyterminate();
           }

๐Œ๐ˆ๐’๐‚๐„๐‹๐‹๐€๐๐„๐Ž๐”๐’ ๐Œ๐€๐‚๐‘๐Ž๐’
     The macro YY_USER_ACTION can be defined to provide an action which
     is always executed prior to the matched rule's action.  For examโ€
     ple, it could be #define'd to call a routine to convert yytext to
     lower-case.  When YY_USER_ACTION is invoked, the variable yฬฒyฬฒ_aฬฒcฬฒtฬฒ
     gives the number of the matched rule (rules are numbered starting
     with 1).  For example, to profile how often each rule is matched,
     the following would do the trick:

           #define YY_USER_ACTION ++ctr[yy_act]

     where cฬฒtฬฒrฬฒ is an array to hold the counts for the different rules.
     Note that the macro YY_NUM_RULES gives the total number of rules
     (including the default rule, even if -๐˜€ is used), so a correct decโ€
     laration for cฬฒtฬฒrฬฒ is:

           int ctr[YY_NUM_RULES];

     The macro YY_USER_INIT may be defined to provide an action which is
     always executed before the first scan (and before the scanner's
     internal initializations are done).  For example, it could be used
     to call a routine to read in a data table or open a logging file.

     The macro yy_set_interactive(is_interactive) can be used to control
     whether the current buffer is considered iฬฒnฬฒtฬฒeฬฒrฬฒaฬฒcฬฒtฬฒiฬฒvฬฒeฬฒ.  An interacโ€
     tive buffer is processed more slowly, but must be used when the
     scanner's input source is indeed interactive to avoid problems due
     to waiting to fill buffers (see the discussion of the -๐ˆ flag
     below).  A non-zero value in the macro invocation marks the buffer
     as interactive, a zero value as non-interactive.  Note that use of
     this macro overrides โ€œ%option always-interactiveโ€ or โ€œ%option
     never-interactiveโ€ (see OฬฒPฬฒTฬฒIฬฒOฬฒNฬฒSฬฒ below).  ๐˜†๐˜†_๐˜€๐—ฒ๐˜_๐—ถ๐—ป๐˜๐—ฒ๐—ฟ๐—ฎ๐—ฐ๐˜๐—ถ๐˜ƒ๐—ฒ() must
     be invoked prior to beginning to scan the buffer that is (or is
     not) to be considered interactive.

     The macro yy_set_bol(at_bol) can be used to control whether the
     current buffer's scanning context for the next token match is done
     as though at the beginning of a line.  A non-zero macro argument
     makes rules anchored with โ€˜^โ€™ active, while a zero argument makes
     โ€˜^โ€™ rules inactive.

     The macro YY_AT_BOL returns true if the next token scanned from the
     current buffer will have โ€˜^โ€™ rules active, false otherwise.

     In the generated scanner, the actions are all gathered in one large
     switch statement and separated using YY_BREAK, which may be redeโ€
     fined.  By default, it is simply a "break", to separate each rule's
     action from the following rules.  Redefining YY_BREAK allows, for
     example, C++ users to โ€œ#define YY_BREAKโ€ to do nothing (while being
     very careful that every rule ends with a "break" or a "return"!)
     to avoid suffering from unreachable statement warnings where
     because a rule's action ends with โ€œreturnโ€, the YY_BREAK is inacโ€
     cessible.

๐•๐€๐‹๐”๐„๐’ ๐€๐•๐€๐ˆ๐‹๐€๐๐‹๐„ ๐“๐Ž ๐“๐‡๐„ ๐”๐’๐„๐‘
     This section summarizes the various values available to the user in
     the rule actions.

     char *yytext
             Holds the text of the current token.  It may be modified
             but not lengthened (characters cannot be appended to the
             end).

             If the special directive โ€œ%arrayโ€ appears in the first secโ€
             tion of the scanner description, then yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ is instead
             declared โ€œchar yytext[YYLMAX]โ€, where YYLMAX is a macro
             definition that can be redefined in the first section to
             change the default value (generally 8KB).  Using โ€œ%arrayโ€
             results in somewhat slower scanners, but the value of
             yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ becomes immune to calls to ๐—ถ๐—ป๐—ฝ๐˜‚๐˜() and ๐˜‚๐—ป๐—ฝ๐˜‚๐˜(),
             which potentially destroy its value when yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ is a charโ€
             acter pointer.  The opposite of โ€œ%arrayโ€ is โ€œ%pointerโ€,
             which is the default.

             โ€œ%arrayโ€ cannot be used when generating C++ scanner classes
             (the -+ flag).

     int yyleng
             Holds the length of the current token.

     FILE *yyin
             Is the file which by default ๐—ณ๐—น๐—ฒ๐˜… reads from.  It may be
             redefined, but doing so only makes sense before scanning
             begins or after an EOF has been encountered.  Changing it
             in the midst of scanning will have unexpected results since
             ๐—ณ๐—น๐—ฒ๐˜… buffers its input; use ๐˜†๐˜†๐—ฟ๐—ฒ๐˜€๐˜๐—ฎ๐—ฟ๐˜() instead.  Once
             scanning terminates because an end-of-file has been seen,
             yฬฒyฬฒiฬฒnฬฒ can be assigned as the new input file and the scanner
             can be called again to continue scanning.

     void yyrestart(FILE *new_file)
             May be called to point yฬฒyฬฒiฬฒnฬฒ at the new input file.  The
             switch-over to the new file is immediate (any previously
             buffered-up input is lost).  Note that calling ๐˜†๐˜†๐—ฟ๐—ฒ๐˜€๐˜๐—ฎ๐—ฟ๐˜()
             with yฬฒyฬฒiฬฒnฬฒ as an argument thus throws away the current input
             buffer and continues scanning the same input file.

     FILE *yyout
             Is the file to which EฬฒCฬฒHฬฒOฬฒ actions are done.  It can be
             reassigned by the user.

     YY_CURRENT_BUFFER
             Returns a YY_BUFFER_STATE handle to the current buffer.

     YY_START
             Returns an integer value corresponding to the current start
             condition.  This value can subsequently be used with BฬฒEฬฒGฬฒIฬฒNฬฒ
             to return to that start condition.

๐ˆ๐๐“๐„๐‘๐…๐€๐‚๐ˆ๐๐† ๐–๐ˆ๐“๐‡ ๐˜๐€๐‚๐‚
     One of the main uses of ๐—ณ๐—น๐—ฒ๐˜… is as a companion to the yacc(1)
     parser-generator.  yacc parsers expect to call a routine named
     ๐˜†๐˜†๐—น๐—ฒ๐˜…() to find the next input token.  The routine is supposed to
     return the type of the next token as well as putting any associated
     value in the global yฬฒyฬฒlฬฒvฬฒaฬฒlฬฒ, which is defined externally, and can be
     a union or any other complex data structure.  To use ๐—ณ๐—น๐—ฒ๐˜… with
     yacc, one specifies the -๐—ฑ option to yacc to instruct it to generโ€
     ate the file yฬฒ.ฬฒtฬฒaฬฒbฬฒ.ฬฒhฬฒ containing definitions of all the โ€œ%tokensโ€
     appearing in the yacc input.  This file is then included in the
     ๐—ณ๐—น๐—ฒ๐˜… scanner.  For example, if one of the tokens is "TOK_NUMBER",
     part of the scanner might look like:

           %{
           #include "y.tab.h"
           %}

           %%

           [0-9]+        yylval = atoi(yytext); return TOK_NUMBER;

๐Ž๐๐“๐ˆ๐Ž๐๐’
     ๐—ณ๐—น๐—ฒ๐˜… has the following options:

     -๐Ÿณ      Instructs ๐—ณ๐—น๐—ฒ๐˜… to generate a 7-bit scanner, i.e., one which
             can only recognize 7-bit characters in its input.  The
             advantage of using -๐Ÿณ is that the scanner's tables can be
             up to half the size of those generated using the -๐Ÿด option
             (see below).  The disadvantage is that such scanners often
             hang or crash if their input contains an 8-bit character.

             Note, however, that unless generating a scanner using the
             -๐‚๐—ณ or -๐‚๐… table compression options, use of -๐Ÿณ will save
             only a small amount of table space, and make the scanner
             considerably less portable.  ๐—ณ๐—น๐—ฒ๐˜…'s default behavior is to
             generate an 8-bit scanner unless -๐‚๐—ณ or -๐‚๐… is specified,
             in which case ๐—ณ๐—น๐—ฒ๐˜… defaults to generating 7-bit scanners
             unless it was configured to generate 8-bit scanners (as
             will often be the case with non-USA sites).  It is possible
             tell whether ๐—ณ๐—น๐—ฒ๐˜… generated a 7-bit or an 8-bit scanner by
             inspecting the flag summary in the -๐˜ƒ output as described
             below.

             Note that if -๐‚๐—ณ๐—ฒ or -๐‚๐…๐—ฒ are used (the table compression
             options, but also using equivalence classes as discussed
             below), ๐—ณ๐—น๐—ฒ๐˜… still defaults to generating an 8-bit scanner,
             since usually with these compression options full 8-bit
             tables are not much more expensive than 7-bit tables.

     -๐Ÿด      Instructs ๐—ณ๐—น๐—ฒ๐˜… to generate an 8-bit scanner, i.e., one
             which can recognize 8-bit characters.  This flag is only
             needed for scanners generated using -๐‚๐—ณ or -๐‚๐…, as otherโ€
             wise ๐—ณ๐—น๐—ฒ๐˜… defaults to generating an 8-bit scanner anyway.

             See the discussion of -๐Ÿณ above for ๐—ณ๐—น๐—ฒ๐˜…'s default behavior
             and the tradeoffs between 7-bit and 8-bit scanners.

     -๐      Instructs ๐—ณ๐—น๐—ฒ๐˜… to generate a bฬฒaฬฒtฬฒcฬฒhฬฒ scanner, the opposite of
             iฬฒnฬฒtฬฒeฬฒrฬฒaฬฒcฬฒtฬฒiฬฒvฬฒeฬฒ scanners generated by -๐ˆ (see below).  In genโ€
             eral, -๐ is used when the scanner will never be used interโ€
             actively, and you want to squeeze a little more performance
             out of it.  If the aim is instead to squeeze out a lot more
             performance, use the -๐‚๐—ณ or -๐‚๐… options (discussed below),
             which turn on -๐ automatically anyway.

     -๐—ฏ      Generate backing-up information to lฬฒeฬฒxฬฒ.ฬฒbฬฒaฬฒcฬฒkฬฒuฬฒpฬฒ.  This is a
             list of scanner states which require backing up and the
             input characters on which they do so.  By adding rules one
             can remove backing-up states.  If all backing-up states are
             eliminated and -๐‚๐—ณ or -๐‚๐… is used, the generated scanner
             will run faster (see the -๐—ฝ flag).  Only users who wish to
             squeeze every last cycle out of their scanners need worry
             about this option.  (See the section on PฬฒEฬฒRฬฒFฬฒOฬฒRฬฒMฬฒAฬฒNฬฒCฬฒEฬฒ
             CฬฒOฬฒNฬฒSฬฒIฬฒDฬฒEฬฒRฬฒAฬฒTฬฒIฬฒOฬฒNฬฒSฬฒ below.)

     -๐‚[๐—ฎ๐—ฒ๐…๐—ณ๐—บ๐—ฟ]
             Controls the degree of table compression and, more generโ€
             ally, trade-offs between small scanners and fast scanners.

             -๐‚๐—ฎ     Instructs ๐—ณ๐—น๐—ฒ๐˜… to trade off larger tables in the
                     generated scanner for faster performance because
                     the elements of the tables are better aligned for
                     memory access and computation.  On some RISC archiโ€
                     tectures, fetching and manipulating longwords is
                     more efficient than with smaller-sized units such
                     as shortwords.  This option can double the size of
                     the tables used by the scanner.

             -๐‚๐—ฒ     Directs ๐—ณ๐—น๐—ฒ๐˜… to construct eฬฒqฬฒuฬฒiฬฒvฬฒaฬฒlฬฒeฬฒnฬฒcฬฒeฬฒ cฬฒlฬฒaฬฒsฬฒsฬฒeฬฒsฬฒ,
                     i.e., sets of characters which have identical lexiโ€
                     cal properties (for example, if the only appearance
                     of digits in the ๐—ณ๐—น๐—ฒ๐˜… input is in the character
                     class "[0-9]" then the digits โ€˜0โ€™, โ€˜1โ€™, โ€˜...โ€™, โ€˜9โ€™
                     will all be put in the same equivalence class).
                     Equivalence classes usually give dramatic reducโ€
                     tions in the final table/object file sizes
                     (typically a factor of 2-5) and are pretty cheap
                     performance-wise (one array look-up per character
                     scanned).

             -๐‚๐…     Specifies that the alternate fast scanner represenโ€
                     tation (described below under the -๐… option) should
                     be used.  This option cannot be used with -+.

             -๐‚๐—ณ     Specifies that the fฬฒuฬฒlฬฒlฬฒ scanner tables should be
                     generated - ๐—ณ๐—น๐—ฒ๐˜… should not compress the tables by
                     taking advantage of similar transition functions
                     for different states.

             -๐‚๐—บ     Directs ๐—ณ๐—น๐—ฒ๐˜… to construct mฬฒeฬฒtฬฒaฬฒ-ฬฒeฬฒqฬฒuฬฒiฬฒvฬฒaฬฒlฬฒeฬฒnฬฒcฬฒeฬฒ cฬฒlฬฒaฬฒsฬฒsฬฒeฬฒsฬฒ,
                     which are sets of equivalence classes (or characโ€
                     ters, if equivalence classes are not being used)
                     that are commonly used together.  Meta-equivalence
                     classes are often a big win when using compressed
                     tables, but they have a moderate performance impact
                     (one or two "if" tests and one array look-up per
                     character scanned).

             -๐‚๐—ฟ     Causes the generated scanner to bฬฒyฬฒpฬฒaฬฒsฬฒsฬฒ use of the
                     standard I/O library (stdio) for input.  Instead of
                     calling fread(3) or getc(3), the scanner will use
                     the read(2) system call, resulting in a performance
                     gain which varies from system to system, but in
                     general is probably negligible unless -๐‚๐—ณ or -๐‚๐…
                     are being used.  Using -๐‚๐—ฟ can cause strange behavโ€
                     ior if, for example, reading from yฬฒyฬฒiฬฒnฬฒ using stdio
                     prior to calling the scanner (because the scanner
                     will miss whatever text previous reads left in the
                     stdio input buffer).

                     -๐‚๐—ฟ has no effect if YY_INPUT is defined (see TฬฒHฬฒEฬฒ
                     GฬฒEฬฒNฬฒEฬฒRฬฒAฬฒTฬฒEฬฒDฬฒ SฬฒCฬฒAฬฒNฬฒNฬฒEฬฒRฬฒ above).

             A lone -๐‚ specifies that the scanner tables should be comโ€
             pressed but neither equivalence classes nor meta-equivaโ€
             lence classes should be used.

             The options -๐‚๐—ณ or -๐‚๐… and -๐‚๐—บ do not make sense together -
             there is no opportunity for meta-equivalence classes if the
             table is not being compressed.  Otherwise the options may
             be freely mixed, and are cumulative.

             The default setting is -๐‚๐—ฒ๐—บ which specifies that ๐—ณ๐—น๐—ฒ๐˜…
             should generate equivalence classes and meta-equivalence
             classes.  This setting provides the highest degree of table
             compression.  It is possible to trade off faster-executing
             scanners at the cost of larger tables with the following
             generally being true:

                   slowest & smallest
                         -Cem
                         -Cm
                         -Ce
                         -C
                         -C{f,F}e
                         -C{f,F}
                         -C{f,F}a
                   fastest & largest

             Note that scanners with the smallest tables are usually
             generated and compiled the quickest, so during development
             the default is usually best, maximal compression.

             -๐‚๐—ณ๐—ฒ is often a good compromise between speed and size for
             production scanners.

     -๐—ฑ      Makes the generated scanner run in debug mode.  Whenever a
             pattern is recognized and the global yฬฒyฬฒ_fฬฒlฬฒeฬฒxฬฒ_dฬฒeฬฒbฬฒuฬฒgฬฒ is non-
             zero (which is the default), the scanner will write to
             stderr a line of the form:

                   --accepting rule at line 53 ("the matched text")

             The line number refers to the location of the rule in the
             file defining the scanner (i.e., the file that was fed to
             ๐—ณ๐—น๐—ฒ๐˜…).  Messages are also generated when the scanner backs
             up, accepts the default rule, reaches the end of its input
             buffer (or encounters a NUL; at this point, the two look
             the same as far as the scanner's concerned), or reaches an
             end-of-file.

     -๐…      Specifies that the fast scanner table representation should
             be used (and stdio bypassed).  This representation is about
             as fast as the full table representation (-๐—ณ), and for some
             sets of patterns will be considerably smaller (and for
             others, larger).  In general, if the pattern set contains
             both "keywords" and a catch-all, "identifier" rule, such as
             in the set:

                   "case"    return TOK_CASE;
                   "switch"  return TOK_SWITCH;
                   ...
                   "default" return TOK_DEFAULT;
                   [a-z]+    return TOK_ID;

             then it's better to use the full table representation.  If
             only the "identifier" rule is present and a hash table or
             some such is used to detect the keywords, it's better to
             use -๐….

             This option is equivalent to -๐‚๐…๐—ฟ (see above).  It cannot
             be used with -+.

     -๐—ณ      Specifies fฬฒaฬฒsฬฒtฬฒ sฬฒcฬฒaฬฒnฬฒnฬฒeฬฒrฬฒ.  No table compression is done and
             stdio is bypassed.  The result is large but fast.  This
             option is equivalent to -๐‚๐—ณ๐—ฟ (see above).

     -๐—ต      Generates a help summary of ๐—ณ๐—น๐—ฒ๐˜…'s options to stdout and
             then exits.  -? and --๐—ต๐—ฒ๐—น๐—ฝ are synonyms for -๐—ต.

     -๐ˆ      Instructs ๐—ณ๐—น๐—ฒ๐˜… to generate an iฬฒnฬฒtฬฒeฬฒrฬฒaฬฒcฬฒtฬฒiฬฒvฬฒeฬฒ scanner.  An
             interactive scanner is one that only looks ahead to decide
             what token has been matched if it absolutely must.  It
             turns out that always looking one extra character ahead,
             even if the scanner has already seen enough text to disamโ€
             biguate the current token, is a bit faster than only lookโ€
             ing ahead when necessary.  But scanners that always look
             ahead give dreadful interactive performance; for example,
             when a user types a newline, it is not recognized as a newโ€
             line token until they enter aฬฒnฬฒoฬฒtฬฒhฬฒeฬฒrฬฒ token, which often
             means typing in another whole line.

             ๐—ณ๐—น๐—ฒ๐˜… scanners default to iฬฒnฬฒtฬฒeฬฒrฬฒaฬฒcฬฒtฬฒiฬฒvฬฒeฬฒ unless -๐‚๐—ณ or -๐‚๐… taโ€
             ble-compression options are specified (see above).  That's
             because if high-performance is most important, one of these
             options should be used, so if they weren't, ๐—ณ๐—น๐—ฒ๐˜… assumes it
             is preferable to trade off a bit of run-time performance
             for intuitive interactive behavior.  Note also that -๐ˆ canโ€
             not be used in conjunction with -๐‚๐—ณ or -๐‚๐….  Thus, this
             option is not really needed; it is on by default for all
             those cases in which it is allowed.

             A scanner can be forced to not be interactive by using -๐
             (see above).

     -๐—ถ      Instructs ๐—ณ๐—น๐—ฒ๐˜… to generate a case-insensitive scanner.  The
             case of letters given in the ๐—ณ๐—น๐—ฒ๐˜… input patterns will be
             ignored, and tokens in the input will be matched regardless
             of case.  The matched text given in yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ will have the
             preserved case (i.e., it will not be folded).

     -๐‹      Instructs ๐—ณ๐—น๐—ฒ๐˜… not to generate โ€œ#lineโ€ directives.  Without
             this option, ๐—ณ๐—น๐—ฒ๐˜… peppers the generated scanner with #line
             directives so error messages in the actions will be corโ€
             rectly located with respect to either the original ๐—ณ๐—น๐—ฒ๐˜…
             input file (if the errors are due to code in the input
             file), or lฬฒeฬฒxฬฒ.ฬฒyฬฒyฬฒ.ฬฒcฬฒ (if the errors are ๐—ณ๐—น๐—ฒ๐˜…'s fault - these
             sorts of errors should be reported to the email address
             given below).

     -๐—น      Turns on maximum compatibility with the original AT&T UNIX
             ๐—น๐—ฒ๐˜… implementation.  Note that this does not mean full comโ€
             patibility.  Use of this option costs a considerable amount
             of performance, and it cannot be used with the -+, -๐—ณ, -๐…,
             -๐‚๐—ณ, or -๐‚๐… options.  For details on the compatibilities it
             provides, see the section IฬฒNฬฒCฬฒOฬฒMฬฒPฬฒAฬฒTฬฒIฬฒBฬฒIฬฒLฬฒIฬฒTฬฒIฬฒEฬฒSฬฒ WฬฒIฬฒTฬฒHฬฒ LฬฒEฬฒXฬฒ AฬฒNฬฒDฬฒ
             PฬฒOฬฒSฬฒIฬฒXฬฒ below.  This option also results in the name
             YY_FLEX_LEX_COMPAT being #define'd in the generated scanโ€
             ner.

     -๐—ป      Another do-nothing, deprecated option included only for
             POSIX compliance.

     -๐—ผoฬฒuฬฒtฬฒpฬฒuฬฒtฬฒ
             Directs ๐—ณ๐—น๐—ฒ๐˜… to write the scanner to the file oฬฒuฬฒtฬฒpฬฒuฬฒtฬฒ
             instead of lฬฒeฬฒxฬฒ.ฬฒyฬฒyฬฒ.ฬฒcฬฒ.  If -๐—ผ is combined with the -๐˜ option,
             then the scanner is written to stdout but its โ€œ#lineโ€
             directives (see the -๐‹ option above) refer to the file
             oฬฒuฬฒtฬฒpฬฒuฬฒtฬฒ.

     -๐pฬฒrฬฒeฬฒfฬฒiฬฒxฬฒ
             Changes the default "yy" prefix used by ๐—ณ๐—น๐—ฒ๐˜… for all globโ€
             ally visible variable and function names to instead be
             pฬฒrฬฒeฬฒfฬฒiฬฒxฬฒ.  For example, -๐fฬฒoฬฒoฬฒ changes the name of yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ to
             fฬฒoฬฒoฬฒtฬฒeฬฒxฬฒtฬฒ.  It also changes the name of the default output
             file from lฬฒeฬฒxฬฒ.ฬฒyฬฒyฬฒ.ฬฒcฬฒ to lฬฒeฬฒxฬฒ.ฬฒfฬฒoฬฒoฬฒ.ฬฒcฬฒ.  Here are all of the names
             affected:

                   yy_create_buffer
                   yy_delete_buffer
                   yy_flex_debug
                   yy_init_buffer
                   yy_flush_buffer
                   yy_load_buffer_state
                   yy_switch_to_buffer
                   yyin
                   yyleng
                   yylex
                   yylineno
                   yyout
                   yyrestart
                   yytext
                   yywrap

             (If using a C++ scanner, then only yฬฒyฬฒwฬฒrฬฒaฬฒpฬฒ and yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ
             are affected.)  Within the scanner itself, it is still posโ€
             sible to refer to the global variables and functions using
             either version of their name; but externally, they have the
             modified name.

             This option allows multiple ๐—ณ๐—น๐—ฒ๐˜… programs to be easily
             linked together into the same executable.  Note, though,
             that using this option also renames ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ(), so now either
             an (appropriately named) version of the routine for the
             scanner must be supplied, or โ€œ%option noyywrapโ€ must be
             used, as linking with -๐—น๐—ณ๐—น no longer provides one by
             default.

     -๐—ฝ      Generates a performance report to stderr.  The report conโ€
             sists of comments regarding features of the ๐—ณ๐—น๐—ฒ๐˜… input file
             which will cause a serious loss of performance in the
             resulting scanner.  If the flag is specified twice, comโ€
             ments regarding features that lead to minor performance
             losses will also be reported>

             Note that the use of RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ, โ€œ%option yylinenoโ€, and variโ€
             able trailing context (see the BฬฒUฬฒGฬฒSฬฒ section below) entails
             a substantial performance penalty; use of ๐˜†๐˜†๐—บ๐—ผ๐—ฟ๐—ฒ(), the โ€˜^โ€™
             operator, and the -๐ˆ flag entail minor performance penalโ€
             ties.

     -๐’sฬฒkฬฒeฬฒlฬฒeฬฒtฬฒoฬฒnฬฒ
             Overrides the default skeleton file from which ๐—ณ๐—น๐—ฒ๐˜… conโ€
             structs its scanners.  This option is needed only for ๐—ณ๐—น๐—ฒ๐˜…
             maintenance or development.

     -๐˜€      Causes the default rule (that unmatched scanner input is
             echoed to stdout) to be suppressed.  If the scanner encounโ€
             ters input that does not match any of its rules, it aborts
             with an error.  This option is useful for finding holes in
             a scanner's rule set.

     -๐“      Makes ๐—ณ๐—น๐—ฒ๐˜… run in tฬฒrฬฒaฬฒcฬฒeฬฒ mode.  It will generate a lot of
             messages to stderr concerning the form of the input and the
             resultant non-deterministic and deterministic finite automโ€
             ata.  This option is mostly for use in maintaining ๐—ณ๐—น๐—ฒ๐˜….

     -๐˜      Instructs ๐—ณ๐—น๐—ฒ๐˜… to write the scanner it generates to stanโ€
             dard output instead of lฬฒeฬฒxฬฒ.ฬฒyฬฒyฬฒ.ฬฒcฬฒ.

     -๐•      Prints the version number to stdout and exits.  --๐˜ƒ๐—ฒ๐—ฟ๐˜€๐—ถ๐—ผ๐—ป
             is a synonym for -๐•.

     -๐˜ƒ      Specifies that ๐—ณ๐—น๐—ฒ๐˜… should write to stderr a summary of
             statistics regarding the scanner it generates.  Most of the
             statistics are meaningless to the casual ๐—ณ๐—น๐—ฒ๐˜… user, but the
             first line identifies the version of ๐—ณ๐—น๐—ฒ๐˜… (same as reported
             by -๐•), and the next line the flags used when generating
             the scanner, including those that are on by default.

     -๐˜„      Suppresses warning messages.

     -+      Specifies that ๐—ณ๐—น๐—ฒ๐˜… should generate a C++ scanner class.
             See the section on GฬฒEฬฒNฬฒEฬฒRฬฒAฬฒTฬฒIฬฒNฬฒGฬฒ Cฬฒ+ฬฒ+ฬฒ SฬฒCฬฒAฬฒNฬฒNฬฒEฬฒRฬฒSฬฒ below for
             details.

     ๐—ณ๐—น๐—ฒ๐˜… also provides a mechanism for controlling options within the
     scanner specification itself, rather than from the ๐—ณ๐—น๐—ฒ๐˜… command
     line.  This is done by including โ€œ%optionโ€ directives in the first
     section of the scanner specification.  Multiple options can be
     specified with a single โ€œ%optionโ€ directive, and multiple direcโ€
     tives in the first section of the ๐—ณ๐—น๐—ฒ๐˜… input file.

     Most options are given simply as names, optionally preceded by the
     word "no" (with no intervening whitespace) to negate their meaning.
     A number are equivalent to ๐—ณ๐—น๐—ฒ๐˜… flags or their negation:

           7bit            -7 option
           8bit            -8 option
           align           -Ca option
           backup          -b option
           batch           -B option
           c++             -+ option

           caseful or
           case-sensitive  opposite of -i (default)

           case-insensitive or
           caseless        -i option

           debug           -d option
           default         opposite of -s option
           ecs             -Ce option
           fast            -F option
           full            -f option
           interactive     -I option
           lex-compat      -l option
           meta-ecs        -Cm option
           perf-report     -p option
           read            -Cr option
           stdout          -t option
           verbose         -v option
           warn            opposite of -w option
                           (use "%option nowarn" for -w)

           array           equivalent to "%array"
           pointer         equivalent to "%pointer" (default)

     Some %option's provide features otherwise not available:

     always-interactive
             Instructs ๐—ณ๐—น๐—ฒ๐˜… to generate a scanner which always considers
             its input "interactive".  Normally, on each new input file
             the scanner calls ๐—ถ๐˜€๐—ฎ๐˜๐˜๐˜†() in an attempt to determine
             whether the scanner's input source is interactive and thus
             should be read a character at a time.  When this option is
             used, however, no such call is made.

     main    Directs ๐—ณ๐—น๐—ฒ๐˜… to provide a default ๐—บ๐—ฎ๐—ถ๐—ป() program for the
             scanner, which simply calls ๐˜†๐˜†๐—น๐—ฒ๐˜…().  This option implies
             โ€œnoyywrapโ€ (see below).

     never-interactive
             Instructs ๐—ณ๐—น๐—ฒ๐˜… to generate a scanner which never considers
             its input "interactive" (again, no call made to ๐—ถ๐˜€๐—ฎ๐˜๐˜๐˜†()).
             This is the opposite of โ€œalways-interactiveโ€.

     stack   Enables the use of start condition stacks (see SฬฒTฬฒAฬฒRฬฒTฬฒ
             CฬฒOฬฒNฬฒDฬฒIฬฒTฬฒIฬฒOฬฒNฬฒSฬฒ above).

     stdinit
             If set (i.e., โ€œ%option stdinitโ€), initializes yฬฒyฬฒiฬฒnฬฒ and
             yฬฒyฬฒoฬฒuฬฒtฬฒ to stdin and stdout, instead of the default of โ€œnilโ€.
             Some existing ๐—น๐—ฒ๐˜… programs depend on this behavior, even
             though it is not compliant with ANSI C, which does not
             require stdin and stdout to be compile-time constant.

     yylineno
             Directs ๐—ณ๐—น๐—ฒ๐˜… to generate a scanner that maintains the numโ€
             ber of the current line read from its input in the global
             variable yฬฒyฬฒlฬฒiฬฒnฬฒeฬฒnฬฒoฬฒ.  This option is implied by โ€œ%option
             lex-compatโ€.

     yywrap  If unset (i.e., โ€œ%option noyywrapโ€), makes the scanner not
             call ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ() upon an end-of-file, but simply assume that
             there are no more files to scan (until the user points yฬฒyฬฒiฬฒnฬฒ
             at a new file and calls ๐˜†๐˜†๐—น๐—ฒ๐˜…() again).

     ๐—ณ๐—น๐—ฒ๐˜… scans rule actions to determine whether the RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ or ๐˜†๐˜†๐—บ๐—ผ๐—ฟ๐—ฒ()
     features are being used.  The โ€œrejectโ€ and โ€œyymoreโ€ options are
     available to override its decision as to whether to use the
     options, either by setting them (e.g., โ€œ%option rejectโ€) to indiโ€
     cate the feature is indeed used, or unsetting them to indicate it
     actually is not used (e.g., โ€œ%option noyymoreโ€).

     Three options take string-delimited values, offset with โ€˜=โ€™:

           %option outfile="ABC"

     is equivalent to -๐—ผAฬฒBฬฒCฬฒ, and

           %option prefix="XYZ"

     is equivalent to -๐XฬฒYฬฒZฬฒ.  Finally,

           %option yyclass="foo"

     only applies when generating a C++ scanner (-+ option).  It informs
     ๐—ณ๐—น๐—ฒ๐˜… that โ€œfooโ€ has been derived as a subclass of yyFlexLexer, so
     ๐—ณ๐—น๐—ฒ๐˜… will place actions in the member function โ€œfoo::yylex()โ€
     instead of โ€œyyFlexLexer::yylex()โ€.  It also generates a
     โ€œyyFlexLexer::yylex()โ€ member function that emits a run-time error
     (by invoking โ€œyyFlexLexer::LexerError()โ€) if called.  See
     GฬฒEฬฒNฬฒEฬฒRฬฒAฬฒTฬฒIฬฒNฬฒGฬฒ Cฬฒ+ฬฒ+ฬฒ SฬฒCฬฒAฬฒNฬฒNฬฒEฬฒRฬฒSฬฒ, below, for additional information.

     A number of options are available for lint purists who want to supโ€
     press the appearance of unneeded routines in the generated scanner.
     Each of the following, if unset (e.g., โ€œ%option nounputโ€), results
     in the corresponding routine not appearing in the generated scanโ€
     ner:

           input, unput
           yy_push_state, yy_pop_state, yy_top_state
           yy_scan_buffer, yy_scan_bytes, yy_scan_string

     (though ๐˜†๐˜†_๐—ฝ๐˜‚๐˜€๐—ต_๐˜€๐˜๐—ฎ๐˜๐—ฒ() and friends won't appear anyway unless
     โ€œ%option stackโ€ is being used).

๐๐„๐‘๐…๐Ž๐‘๐Œ๐€๐๐‚๐„ ๐‚๐Ž๐๐’๐ˆ๐ƒ๐„๐‘๐€๐“๐ˆ๐Ž๐๐’
     The main design goal of ๐—ณ๐—น๐—ฒ๐˜… is that it generate high-performance
     scanners.  It has been optimized for dealing well with large sets
     of rules.  Aside from the effects on scanner speed of the table
     compression -๐‚ options outlined above, there are a number of
     options/actions which degrade performance.  These are, from most
     expensive to least:

           REJECT
           %option yylineno
           arbitrary trailing context

           pattern sets that require backing up
           %array
           %option interactive
           %option always-interactive

           '^' beginning-of-line operator
           yymore()

     with the first three all being quite expensive and the last two
     being quite cheap.  Note also that ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() is implemented as a rouโ€
     tine call that potentially does quite a bit of work, while ๐˜†๐˜†๐—น๐—ฒ๐˜€๐˜€()
     is a quite-cheap macro; so if just putting back some excess text,
     use ๐˜†๐˜†๐—น๐—ฒ๐˜€๐˜€().

     RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ should be avoided at all costs when performance is imporโ€
     tant.  It is a particularly expensive option.

     Getting rid of backing up is messy and often may be an enormous
     amount of work for a complicated scanner.  In principal, one begins
     by using the -๐—ฏ flag to generate a lฬฒeฬฒxฬฒ.ฬฒbฬฒaฬฒcฬฒkฬฒuฬฒpฬฒ file.  For example,
     on the input

           %%
           foo        return TOK_KEYWORD;
           foobar     return TOK_KEYWORD;

     the file looks like:

           State #6 is non-accepting -
            associated rule line numbers:
                  2       3
            out-transitions: [ o ]
            jam-transitions: EOF [ \001-n  p-\177 ]

           State #8 is non-accepting -
            associated rule line numbers:
                  3
            out-transitions: [ a ]
            jam-transitions: EOF [ \001-`  b-\177 ]

           State #9 is non-accepting -
            associated rule line numbers:
                  3
            out-transitions: [ r ]
            jam-transitions: EOF [ \001-q  s-\177 ]

           Compressed tables always back up.

     The first few lines tell us that there's a scanner state in which
     it can make a transition on an โ€˜oโ€™ but not on any other character,
     and that in that state the currently scanned text does not match
     any rule.  The state occurs when trying to match the rules found at
     lines 2 and 3 in the input file.  If the scanner is in that state
     and then reads something other than an โ€˜oโ€™, it will have to back up
     to find a rule which is matched.  With a bit of headscratching one
     can see that this must be the state it's in when it has seen โ€˜foโ€™.
     When this has happened, if anything other than another โ€˜oโ€™ is seen,
     the scanner will have to back up to simply match the โ€˜fโ€™ (by the
     default rule).

     The comment regarding State #8 indicates there's a problem when
     "foob" has been scanned.  Indeed, on any character other than an
     โ€˜aโ€™, the scanner will have to back up to accept "foo".  Similarly,
     the comment for State #9 concerns when "fooba" has been scanned and
     an โ€˜rโ€™ does not follow.

     The final comment reminds us that there's no point going to all the
     trouble of removing backing up from the rules unless we're using
     -๐‚๐—ณ or -๐‚๐…, since there's no performance gain doing so with comโ€
     pressed scanners.

     The way to remove the backing up is to add "error" rules:

           %%
           foo    return TOK_KEYWORD;
           foobar return TOK_KEYWORD;

           fooba  |
           foob   |
           fo {
                   /* false alarm, not really a keyword */
                   return TOK_ID;
           }

     Eliminating backing up among a list of keywords can also be done
     using a "catch-all" rule:

           %%
           foo    return TOK_KEYWORD;
           foobar return TOK_KEYWORD;

           [a-z]+ return TOK_ID;

     This is usually the best solution when appropriate.

     Backing up messages tend to cascade.  With a complicated set of
     rules it's not uncommon to get hundreds of messages.  If one can
     decipher them, though, it often only takes a dozen or so rules to
     eliminate the backing up (though it's easy to make a mistake and
     have an error rule accidentally match a valid token; a possible
     future ๐—ณ๐—น๐—ฒ๐˜… feature will be to automatically add rules to eliminate
     backing up).

     It's important to keep in mind that the benefits of eliminating
     backing up are gained only if eฬฒvฬฒeฬฒrฬฒyฬฒ instance of backing up is elimโ€
     inated.  Leaving just one gains nothing.

     Vฬฒaฬฒrฬฒiฬฒaฬฒbฬฒlฬฒeฬฒ trailing context (where both the leading and trailing
     parts do not have a fixed length) entails almost the same perforโ€
     mance loss as RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ (i.e., substantial).  So when possible a rule
     like:

           %%
           mouse|rat/(cat|dog)   run();

     is better written:

           %%
           mouse/cat|dog         run();
           rat/cat|dog           run();

     or as

           %%
           mouse|rat/cat         run();
           mouse|rat/dog         run();

     Note that here the special โ€˜|โ€™ action does not provide any savings,
     and can even make things worse (see BฬฒUฬฒGฬฒSฬฒ below).

     Another area where the user can increase a scanner's performance
     (and one that's easier to implement) arises from the fact that the
     longer the tokens matched, the faster the scanner will run.  This
     is because with long tokens the processing of most input characters
     takes place in the (short) inner scanning loop, and does not often
     have to go through the additional work of setting up the scanning
     environment (e.g., yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ) for the action.  Recall the scanner for
     C comments:

           %x comment
           %%
           int line_num = 1;

           "/*"                    BEGIN(comment);

           <comment>[^*\n]*
           <comment>"*"+[^*/\n]*
           <comment>\n             ++line_num;
           <comment>"*"+"/"        BEGIN(INITIAL);

     This could be sped up by writing it as:

           %x comment
           %%
           int line_num = 1;

           "/*"                    BEGIN(comment);

           <comment>[^*\n]*
           <comment>[^*\n]*\n      ++line_num;
           <comment>"*"+[^*/\n]*
           <comment>"*"+[^*/\n]*\n ++line_num;
           <comment>"*"+"/"        BEGIN(INITIAL);

     Now instead of each newline requiring the processing of another
     action, recognizing the newlines is "distributed" over the other
     rules to keep the matched text as long as possible.  Note that
     adding rules does nฬฒoฬฒtฬฒ slow down the scanner!  The speed of the
     scanner is independent of the number of rules or (modulo the conโ€
     siderations given at the beginning of this section) how complicated
     the rules are with regard to operators such as โ€˜*โ€™ and โ€˜|โ€™.

     A final example in speeding up a scanner: scan through a file conโ€
     taining identifiers and keywords, one per line and with no other
     extraneous characters, and recognize all the keywords.  A natural
     first approach is:

           %%
           asm      |
           auto     |
           break    |
           ... etc ...
           volatile |
           while    /* it's a keyword */

           .|\n     /* it's not a keyword */

     To eliminate the back-tracking, introduce a catch-all rule:

           %%
           asm      |
           auto     |
           break    |
           ... etc ...
           volatile |
           while    /* it's a keyword */

           [a-z]+   |
           .|\n     /* it's not a keyword */

     Now, if it's guaranteed that there's exactly one word per line,
     then we can reduce the total number of matches by a half by merging
     in the recognition of newlines with that of the other tokens:

           %%
           asm\n      |
           auto\n     |
           break\n    |
           ... etc ...
           volatile\n |
           while\n    /* it's a keyword */

           [a-z]+\n   |
           .|\n       /* it's not a keyword */

     One has to be careful here, as we have now reintroduced backing up
     into the scanner.  In particular, while we know that there will
     never be any characters in the input stream other than letters or
     newlines, ๐—ณ๐—น๐—ฒ๐˜… can't figure this out, and it will plan for possibly
     needing to back up when it has scanned a token like "auto" and then
     the next character is something other than a newline or a letter.
     Previously it would then just match the "auto" rule and be done,
     but now it has no "auto" rule, only an "auto\n" rule.  To eliminate
     the possibility of backing up, we could either duplicate all rules
     but without final newlines or, since we never expect to encounter
     such an input and therefore don't how it's classified, we can
     introduce one more catch-all rule, this one which doesn't include a
     newline:

           %%
           asm\n      |
           auto\n     |
           break\n    |
           ... etc ...
           volatile\n |
           while\n    /* it's a keyword */

           [a-z]+\n   |
           [a-z]+     |
           .|\n       /* it's not a keyword */

     Compiled with -๐‚๐—ณ, this is about as fast as one can get a ๐—ณ๐—น๐—ฒ๐˜…
     scanner to go for this particular problem.

     A final note: ๐—ณ๐—น๐—ฒ๐˜… is slow when matching NUL's, particularly when a
     token contains multiple NUL's.  It's best to write rules which
     match short amounts of text if it's anticipated that the text will
     often include NUL's.

     Another final note regarding performance: as mentioned above in the
     section HฬฒOฬฒWฬฒ TฬฒHฬฒEฬฒ IฬฒNฬฒPฬฒUฬฒTฬฒ IฬฒSฬฒ MฬฒAฬฒTฬฒCฬฒHฬฒEฬฒDฬฒ, dynamically resizing yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ to
     accommodate huge tokens is a slow process because it presently
     requires that the (huge) token be rescanned from the beginning.
     Thus if performance is vital, it is better to attempt to match
     "large" quantities of text but not "huge" quantities, where the
     cutoff between the two is at about 8K characters/token.

๐†๐„๐๐„๐‘๐€๐“๐ˆ๐๐† ๐‚++ ๐’๐‚๐€๐๐๐„๐‘๐’
     ๐—ณ๐—น๐—ฒ๐˜… provides two different ways to generate scanners for use with
     C++.  The first way is to simply compile a scanner generated by
     ๐—ณ๐—น๐—ฒ๐˜… using a C++ compiler instead of a C compiler.  This should not
     generate any compilation errors (please report any found to the
     email address given in the AฬฒUฬฒTฬฒHฬฒOฬฒRฬฒSฬฒ section below).  C++ code can
     then be used in rule actions instead of C code.  Note that the
     default input source for scanners remains yฬฒyฬฒiฬฒnฬฒ, and default echoing
     is still done to yฬฒyฬฒoฬฒuฬฒtฬฒ.  Both of these remain FฬฒIฬฒLฬฒEฬฒ *ฬฒ variables and
     not C++ streams.

     ๐—ณ๐—น๐—ฒ๐˜… can also be used to generate a C++ scanner class, using the -+
     option (or, equivalently, โ€œ%option c++โ€), which is automatically
     specified if the name of the flex executable ends in a โ€˜+โ€™, such as
     ๐—ณ๐—น๐—ฒ๐˜…++.  When using this option, ๐—ณ๐—น๐—ฒ๐˜… defaults to generating the
     scanner to the file lฬฒeฬฒxฬฒ.ฬฒyฬฒyฬฒ.ฬฒcฬฒcฬฒ instead of lฬฒeฬฒxฬฒ.ฬฒyฬฒyฬฒ.ฬฒcฬฒ.  The generated
     scanner includes the header file <gฬฒ+ฬฒ+ฬฒ/ฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ.ฬฒhฬฒ>, which defines
     the interface to two C++ classes.

     The first class, FฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ, provides an abstract base class definโ€
     ing the general scanner class interface.  It provides the following
     member functions:

     const char* YYText()
             Returns the text of the most recently matched token, the
             equivalent of yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ.

     int YYLeng()
             Returns the length of the most recently matched token, the
             equivalent of yฬฒyฬฒlฬฒeฬฒnฬฒgฬฒ.

     int lineno() const
             Returns the current input line number (see โ€œ%option
             yylinenoโ€), or 1 if โ€œ%option yylinenoโ€ was not used.

     void set_debug(int flag)
             Sets the debugging flag for the scanner, equivalent to
             assigning to yฬฒyฬฒ_fฬฒlฬฒeฬฒxฬฒ_dฬฒeฬฒbฬฒuฬฒgฬฒ (see the OฬฒPฬฒTฬฒIฬฒOฬฒNฬฒSฬฒ section above).
             Note that the scanner must be built using โ€œ%option debugโ€
             to include debugging information in it.

     int debug() const
             Returns the current setting of the debugging flag.

     Also provided are member functions equivalent to
     ๐˜†๐˜†_๐˜€๐˜„๐—ถ๐˜๐—ฐ๐—ต_๐˜๐—ผ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ(), ๐˜†๐˜†_๐—ฐ๐—ฟ๐—ฒ๐—ฎ๐˜๐—ฒ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ() (though the first arguโ€
     ment is an sฬฒtฬฒdฬฒ:ฬฒ:ฬฒiฬฒsฬฒtฬฒrฬฒeฬฒaฬฒmฬฒ*ฬฒ object pointer and not a FฬฒIฬฒLฬฒEฬฒ*ฬฒ),
     ๐˜†๐˜†_๐—ณ๐—น๐˜‚๐˜€๐—ต_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ(), ๐˜†๐˜†_๐—ฑ๐—ฒ๐—น๐—ฒ๐˜๐—ฒ_๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ(), and ๐˜†๐˜†๐—ฟ๐—ฒ๐˜€๐˜๐—ฎ๐—ฟ๐˜() (again, the
     first argument is an sฬฒtฬฒdฬฒ:ฬฒ:ฬฒiฬฒsฬฒtฬฒrฬฒeฬฒaฬฒmฬฒ*ฬฒ object pointer).

     The second class defined in <gฬฒ+ฬฒ+ฬฒ/ฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ.ฬฒhฬฒ> is yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ, which
     is derived from FฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ.  It defines the following additional
     member functions:

     yyFlexLexer(std::istream* arg_yyin = 0, std::ostream* arg_yyout =
             0)
             Constructs a yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ object using the given streams for
             input and output.  If not specified, the streams default to
             cฬฒiฬฒnฬฒ and cฬฒoฬฒuฬฒtฬฒ, respectively.

     virtual int yylex()
             Performs the same role as ๐˜†๐˜†๐—น๐—ฒ๐˜…() does for ordinary flex
             scanners: it scans the input stream, consuming tokens,
             until a rule's action returns a value.  If subclass โ€˜Sโ€™ is
             derived from yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ, in order to access the member
             functions and variables of โ€˜Sโ€™ inside ๐˜†๐˜†๐—น๐—ฒ๐˜…(), use โ€œ%option
             yyclass="S"โ€ to inform ๐—ณ๐—น๐—ฒ๐˜… that the โ€˜Sโ€™ subclass will be
             used instead of yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ.  In this case, rather than
             generating โ€œyyFlexLexer::yylex()โ€, ๐—ณ๐—น๐—ฒ๐˜… generates
             โ€œS::yylex()โ€ (and also generates a dummy
             โ€œyyFlexLexer::yylex()โ€ that calls
             โ€œyyFlexLexer::LexerError()โ€ if called).

     virtual void switch_streams(std::istream* new_in = 0, std::ostream*
             new_out = 0)
             Reassigns yฬฒyฬฒiฬฒnฬฒ to nฬฒeฬฒwฬฒ_iฬฒnฬฒ (if non-nil) and yฬฒyฬฒoฬฒuฬฒtฬฒ to nฬฒeฬฒwฬฒ_oฬฒuฬฒtฬฒ
             (ditto), deleting the previous input buffer if yฬฒyฬฒiฬฒnฬฒ is
             reassigned.

     int yylex(std::istream* new_in, std::ostream* new_out = 0)
             First switches the input streams via
             โ€œswitch_streams(new_in, new_out)โ€ and then returns the
             value of ๐˜†๐˜†๐—น๐—ฒ๐˜…().

     In addition, yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ defines the following protected virtual
     functions which can be redefined in derived classes to tailor the
     scanner:

     virtual int LexerInput(char* buf, int max_size)
             Reads up to mฬฒaฬฒxฬฒ_sฬฒiฬฒzฬฒeฬฒ characters into bฬฒuฬฒfฬฒ and returns the
             number of characters read.  To indicate end-of-input,
             return 0 characters.  Note that "interactive" scanners (see
             the -๐ and -๐ˆ flags) define the macro YY_INTERACTIVE.  If
             ๐‹๐—ฒ๐˜…๐—ฒ๐—ฟ๐ˆ๐—ป๐—ฝ๐˜‚๐˜() has been redefined, and it's necessary to take
             different actions depending on whether or not the scanner
             might be scanning an interactive input source, it's possiโ€
             ble to test for the presence of this name via โ€œ#ifdefโ€.

     virtual void LexerOutput(const char* buf, int size)
             Writes out sฬฒiฬฒzฬฒeฬฒ characters from the buffer bฬฒuฬฒfฬฒ, which,
             while NUL-terminated, may also contain "internal" NUL's if
             the scanner's rules can match text with NUL's in them.

     virtual void LexerError(const char* msg)
             Reports a fatal error message.  The default version of this
             function writes the message to the stream cฬฒeฬฒrฬฒrฬฒ and exits.

     Note that a yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ object contains its entire scanning state.
     Thus such objects can be used to create reentrant scanners.  Multiโ€
     ple instances of the same yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ class can be instantiated,
     and multiple C++ scanner classes can be combined in the same proโ€
     gram using the -๐ option discussed above.

     Finally, note that the โ€œ%arrayโ€ feature is not available to C++
     scanner classes; โ€œ%pointerโ€ must be used (the default).

     Here is an example of a simple C++ scanner:

           // An example of using the flex C++ scanner class.

           %{
           #include <errno.h>
           int mylineno = 0;
           %}

           string  \"[^\n"]+\"

           ws      [ \t]+

           alpha   [A-Za-z]
           dig     [0-9]
           name    ({alpha}|{dig}|\$)({alpha}|{dig}|[_.\-/$])*
           num1    [-+]?{dig}+\.?([eE][-+]?{dig}+)?
           num2    [-+]?{dig}*\.{dig}+([eE][-+]?{dig}+)?
           number  {num1}|{num2}

           %%

           {ws}    /* skip blanks and tabs */

           "/*" {
                   int c;

                   while ((c = yyinput()) != 0) {
                           if(c == '\n')
                               ++mylineno;
                           else if(c == '*') {
                               if ((c = yyinput()) == '/')
                                   break;
                               else
                                   unput(c);
                           }
                   }
           }

           {number}  cout << "number " << YYText() << '\n';

           \n        mylineno++;

           {name}    cout << "name " << YYText() << '\n';

           {string}  cout << "string " << YYText() << '\n';

           %%

           int main(int /* argc */, char** /* argv */)
           {
                   FlexLexer* lexer = new yyFlexLexer;
                   while(lexer->yylex() != 0)
                       ;
                   return 0;
           }

     To create multiple (different) lexer classes, use the -๐ flag (or
     the โ€œprefix=โ€ option) to rename each yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ to some other
     xฬฒxฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ.  <gฬฒ+ฬฒ+ฬฒ/ฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ.ฬฒhฬฒ> can then be included in other
     sources once per lexer class, first renaming yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ as folโ€
     lows:

           #undef yyFlexLexer
           #define yyFlexLexer xxFlexLexer
           #include <g++/FlexLexer.h>

           #undef yyFlexLexer
           #define yyFlexLexer zzFlexLexer
           #include <g++/FlexLexer.h>

     If, for example, โ€œ%option prefix="xx"โ€ is used for one scanner and
     โ€œ%option prefix="zz"โ€ is used for the other.

     ๐ˆ๐Œ๐๐Ž๐‘๐“๐€๐๐“: the present form of the scanning class is experimental
     and may change considerably between major releases.

๐ˆ๐๐‚๐Ž๐Œ๐๐€๐“๐ˆ๐๐ˆ๐‹๐ˆ๐“๐ˆ๐„๐’ ๐–๐ˆ๐“๐‡ ๐‹๐„๐— ๐€๐๐ƒ ๐๐Ž๐’๐ˆ๐—
     ๐—ณ๐—น๐—ฒ๐˜… is a rewrite of the AT&T UNIX ๐—น๐—ฒ๐˜… tool (the two implementaโ€
     tions do not share any code, though), with some extensions and
     incompatibilities, both of which are of concern to those who wish
     to write scanners acceptable to either implementation.  ๐—ณ๐—น๐—ฒ๐˜… is
     fully compliant with the POSIX ๐—น๐—ฒ๐˜… specification, except that when
     using โ€œ%pointerโ€ (the default), a call to ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() destroys the conโ€
     tents of yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ, which is counter to the POSIX specification.

     In this section we discuss all of the known areas of incompatibilโ€
     ity between ๐—ณ๐—น๐—ฒ๐˜…, AT&T UNIX ๐—น๐—ฒ๐˜…, and the POSIX specification.

     ๐—ณ๐—น๐—ฒ๐˜…'s -๐—น option turns on maximum compatibility with the original
     AT&T UNIX ๐—น๐—ฒ๐˜… implementation, at the cost of a major loss in the
     generated scanner's performance.  We note below which incompatibilโ€
     ities can be overcome using the -๐—น option.

     ๐—ณ๐—น๐—ฒ๐˜… is fully compatible with ๐—น๐—ฒ๐˜… with the following exceptions:

     -   The undocumented ๐—น๐—ฒ๐˜… scanner internal variable yฬฒyฬฒlฬฒiฬฒnฬฒeฬฒnฬฒoฬฒ is not
         supported unless -๐—น or โ€œ%option yylinenoโ€ is used.

         yฬฒyฬฒlฬฒiฬฒnฬฒeฬฒnฬฒoฬฒ should be maintained on a per-buffer basis, rather
         than a per-scanner (single global variable) basis.

         yฬฒyฬฒlฬฒiฬฒnฬฒeฬฒnฬฒoฬฒ is not part of the POSIX specification.

     -   The ๐—ถ๐—ป๐—ฝ๐˜‚๐˜() routine is not redefinable, though it may be called
         to read characters following whatever has been matched by a
         rule.  If ๐—ถ๐—ป๐—ฝ๐˜‚๐˜() encounters an end-of-file, the normal
         ๐˜†๐˜†๐˜„๐—ฟ๐—ฎ๐—ฝ() processing is done.  A โ€œrealโ€ end-of-file is returned
         by ๐—ถ๐—ป๐—ฝ๐˜‚๐˜() as EOF.

         Input is instead controlled by defining the YY_INPUT macro.

         The ๐—ณ๐—น๐—ฒ๐˜… restriction that ๐—ถ๐—ป๐—ฝ๐˜‚๐˜() cannot be redefined is in
         accordance with the POSIX specification, which simply does not
         specify any way of controlling the scanner's input other than
         by making an initial assignment to yฬฒyฬฒiฬฒnฬฒ.

     -   The ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() routine is not redefinable.  This restriction is in
         accordance with POSIX.

     -   ๐—ณ๐—น๐—ฒ๐˜… scanners are not as reentrant as ๐—น๐—ฒ๐˜… scanners.  In particโ€
         ular, if a scanner is interactive and an interrupt handler
         long-jumps out of the scanner, and the scanner is subsequently
         called again, the following error message may be displayed:

               fatal flex scanner internal error--end of buffer missed

         To reenter the scanner, first use

               yyrestart(yyin);

         Note that this call will throw away any buffered input; usually
         this isn't a problem with an interactive scanner.

         Also note that flex C++ scanner classes are reentrant, so if
         using C++ is an option , they should be used instead.  See
         GฬฒEฬฒNฬฒEฬฒRฬฒAฬฒTฬฒIฬฒNฬฒGฬฒ Cฬฒ+ฬฒ+ฬฒ SฬฒCฬฒAฬฒNฬฒNฬฒEฬฒRฬฒSฬฒ above for details.

     -   ๐—ผ๐˜‚๐˜๐—ฝ๐˜‚๐˜() is not supported.  Output from the EฬฒCฬฒHฬฒOฬฒ macro is done
         to the file-pointer yฬฒyฬฒoฬฒuฬฒtฬฒ (default stdout).

         ๐—ผ๐˜‚๐˜๐—ฝ๐˜‚๐˜() is not part of the POSIX specification.

     -   ๐—น๐—ฒ๐˜… does not support exclusive start conditions (%x), though
         they are in the POSIX specification.

     -   When definitions are expanded, ๐—ณ๐—น๐—ฒ๐˜… encloses them in parentheโ€
         ses.  With ๐—น๐—ฒ๐˜…, the following:

               NAME    [A-Z][A-Z0-9]*
               %%
               foo{NAME}?      printf("Found it\n");
               %%

         will not match the string "foo" because when the macro is
         expanded the rule is equivalent to "foo[A-Z][A-Z0-9]*?" and the
         precedence is such that the โ€˜?โ€™ is associated with "[A-Z0-9]*".
         With ๐—ณ๐—น๐—ฒ๐˜…, the rule will be expanded to "foo([A-Z][A-Z0-9]*)?"
         and so the string "foo" will match.

         Note that if the definition begins with โ€˜^โ€™ or ends with โ€˜$โ€™
         then it is not expanded with parentheses, to allow these operaโ€
         tors to appear in definitions without losing their special
         meanings.  But the โ€˜โŸจsโŸฉโ€™, โ€˜/โ€™, and โŸจโŸจEOFโŸฉโŸฉ operators cannot be
         used in a ๐—ณ๐—น๐—ฒ๐˜… definition.

         Using -๐—น results in the ๐—น๐—ฒ๐˜… behavior of no parentheses around
         the definition.

         The POSIX specification is that the definition be enclosed in
         parentheses.

     -   Some implementations of ๐—น๐—ฒ๐˜… allow a rule's action to begin on a
         separate line, if the rule's pattern has trailing whitespace:

               %%
               foo|bar<space here>
                 { foobar_action(); }

         ๐—ณ๐—น๐—ฒ๐˜… does not support this feature.

     -   The ๐—น๐—ฒ๐˜… โ€˜%rโ€™ (generate a Ratfor scanner) option is not supโ€
         ported.  It is not part of the POSIX specification.

     -   After a call to ๐˜‚๐—ป๐—ฝ๐˜‚๐˜(), yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ is undefined until the next
         token is matched, unless the scanner was built using โ€œ%arrayโ€.
         This is not the case with ๐—น๐—ฒ๐˜… or the POSIX specification.  The
         -๐—น option does away with this incompatibility.

     -   The precedence of the โ€˜{}โ€™ (numeric range) operator is differโ€
         ent.  ๐—น๐—ฒ๐˜… interprets "abc{1,3}" as match one, two, or three
         occurrences of โ€˜abcโ€™, whereas ๐—ณ๐—น๐—ฒ๐˜… interprets it as match โ€˜abโ€™
         followed by one, two, or three occurrences of โ€˜cโ€™.  The latter
         is in agreement with the POSIX specification.

     -   The precedence of the โ€˜^โ€™ operator is different.  ๐—น๐—ฒ๐˜… interโ€
         prets "^foo|bar" as match either โ€˜fooโ€™ at the beginning of a
         line, or โ€˜barโ€™ anywhere, whereas ๐—ณ๐—น๐—ฒ๐˜… interprets it as match
         either โ€˜fooโ€™ or โ€˜barโ€™ if they come at the beginning of a line.
         The latter is in agreement with the POSIX specification.

     -   The special table-size declarations such as โ€˜%aโ€™ supported by
         ๐—น๐—ฒ๐˜… are not required by ๐—ณ๐—น๐—ฒ๐˜… scanners; ๐—ณ๐—น๐—ฒ๐˜… ignores them.

     -   The name FLEX_SCANNER is #define'd so scanners may be written
         for use with either ๐—ณ๐—น๐—ฒ๐˜… or ๐—น๐—ฒ๐˜….  Scanners also include
         YY_FLEX_MAJOR_VERSION and YY_FLEX_MINOR_VERSION indicating
         which version of ๐—ณ๐—น๐—ฒ๐˜… generated the scanner (for example, for
         the 2.5 release, these defines would be 2 and 5, respectively).

     The following ๐—ณ๐—น๐—ฒ๐˜… features are not included in ๐—น๐—ฒ๐˜… or the POSIX
     specification:

           C++ scanners
           %option
           start condition scopes
           start condition stacks
           interactive/non-interactive scanners
           yy_scan_string() and friends
           yyterminate()
           yy_set_interactive()
           yy_set_bol()
           YY_AT_BOL()
           <<EOF>>
           <*>
           YY_DECL
           YY_START
           YY_USER_ACTION
           YY_USER_INIT
           #line directives
           %{}'s around actions
           multiple actions on a line

     plus almost all of the ๐—ณ๐—น๐—ฒ๐˜… flags.  The last feature in the list
     refers to the fact that with ๐—ณ๐—น๐—ฒ๐˜… multiple actions can be placed on
     the same line, separated with semi-colons, while with ๐—น๐—ฒ๐˜…, the folโ€
     lowing

           foo handle_foo(); ++num_foos_seen;

     is (rather surprisingly) truncated to

           foo handle_foo();

     ๐—ณ๐—น๐—ฒ๐˜… does not truncate the action.  Actions that are not enclosed
     in braces are simply terminated at the end of the line.

๐…๐ˆ๐‹๐„๐’
     flex.skl           Skeleton scanner.  This file is only used when
                        building flex, not when ๐—ณ๐—น๐—ฒ๐˜… executes.

     lex.backup         Backing-up information for the -๐—ฏ flag (called
                        lฬฒeฬฒxฬฒ.ฬฒbฬฒcฬฒkฬฒ on some systems).

     lex.yy.c           Generated scanner (called lฬฒeฬฒxฬฒyฬฒyฬฒ.ฬฒcฬฒ on some sysโ€
                        tems).

     lex.yy.cc          Generated C++ scanner class, when using -+.

     <g++/FlexLexer.h>  Header file defining the C++ scanner base class,
                        FฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ, and its derived class, yฬฒyฬฒFฬฒlฬฒeฬฒxฬฒLฬฒeฬฒxฬฒeฬฒrฬฒ.

     /usr/lib/libl.*    ๐—ณ๐—น๐—ฒ๐˜… libraries.  The /ฬฒuฬฒsฬฒrฬฒ/ฬฒlฬฒiฬฒbฬฒ/ฬฒlฬฒiฬฒbฬฒfฬฒlฬฒ.ฬฒ*ฬฒ libraries
                        are links to these.  Scanners must be linked
                        using either -๐—น๐—น or -๐—น๐—ณ๐—น.

๐„๐—๐ˆ๐“ ๐’๐“๐€๐“๐”๐’
     The ๐—ณ๐—น๐—ฒ๐˜… utility exits 0 on success, and >0 if an error occurs.

๐ƒ๐ˆ๐€๐†๐๐Ž๐’๐“๐ˆ๐‚๐’
     ๐˜„๐—ฎ๐—ฟ๐—ป๐—ถ๐—ป๐—ด, ๐—ฟ๐˜‚๐—น๐—ฒ ๐—ฐ๐—ฎ๐—ป๐—ป๐—ผ๐˜ ๐—ฏ๐—ฒ ๐—บ๐—ฎ๐˜๐—ฐ๐—ต๐—ฒ๐—ฑ  Indicates that the given rule canโ€
     not be matched because it follows other rules that will always
     match the same text as it.  For example, in the following โ€œfooโ€
     cannot be matched because it comes after an identifier "catch-all"
     rule:

           [a-z]+    got_identifier();
           foo       got_foo();

     Using RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ in a scanner suppresses this warning.

     ๐˜„๐—ฎ๐—ฟ๐—ป๐—ถ๐—ป๐—ด, -๐˜€ ๐—ผ๐—ฝ๐˜๐—ถ๐—ผ๐—ป ๐—ด๐—ถ๐˜ƒ๐—ฒ๐—ป ๐—ฏ๐˜‚๐˜ ๐—ฑ๐—ฒ๐—ณ๐—ฎ๐˜‚๐—น๐˜ ๐—ฟ๐˜‚๐—น๐—ฒ ๐—ฐ๐—ฎ๐—ป ๐—ฏ๐—ฒ ๐—บ๐—ฎ๐˜๐—ฐ๐—ต๐—ฒ๐—ฑ  Means
     that it is possible (perhaps only in a particular start condition)
     that the default rule (match any single character) is the only one
     that will match a particular input.  Since -๐˜€ was given, presumably
     this is not intended.

     ๐—ฟ๐—ฒ๐—ท๐—ฒ๐—ฐ๐˜_๐˜‚๐˜€๐—ฒ๐—ฑ_๐—ฏ๐˜‚๐˜_๐—ป๐—ผ๐˜_๐—ฑ๐—ฒ๐˜๐—ฒ๐—ฐ๐˜๐—ฒ๐—ฑ ๐˜‚๐—ป๐—ฑ๐—ฒ๐—ณ๐—ถ๐—ป๐—ฒ๐—ฑ
     ๐˜†๐˜†๐—บ๐—ผ๐—ฟ๐—ฒ_๐˜‚๐˜€๐—ฒ๐—ฑ_๐—ฏ๐˜‚๐˜_๐—ป๐—ผ๐˜_๐—ฑ๐—ฒ๐˜๐—ฒ๐—ฐ๐˜๐—ฒ๐—ฑ ๐˜‚๐—ป๐—ฑ๐—ฒ๐—ณ๐—ถ๐—ป๐—ฒ๐—ฑ  These errors can occur at
     compile time.  They indicate that the scanner uses RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ or
     ๐˜†๐˜†๐—บ๐—ผ๐—ฟ๐—ฒ() but that ๐—ณ๐—น๐—ฒ๐˜… failed to notice the fact, meaning that ๐—ณ๐—น๐—ฒ๐˜…
     scanned the first two sections looking for occurrences of these
     actions and failed to find any, but somehow they snuck in (via an
     #include file, for example).  Use โ€œ%option rejectโ€ or โ€œ%option
     yymoreโ€ to indicate to ๐—ณ๐—น๐—ฒ๐˜… that these features are really needed.

     ๐—ณ๐—น๐—ฒ๐˜… ๐˜€๐—ฐ๐—ฎ๐—ป๐—ป๐—ฒ๐—ฟ ๐—ท๐—ฎ๐—บ๐—บ๐—ฒ๐—ฑ  A scanner compiled with -๐˜€ has encountered an
     input string which wasn't matched by any of its rules.  This error
     can also occur due to internal problems.

     ๐˜๐—ผ๐—ธ๐—ฒ๐—ป ๐˜๐—ผ๐—ผ ๐—น๐—ฎ๐—ฟ๐—ด๐—ฒ, ๐—ฒ๐˜…๐—ฐ๐—ฒ๐—ฒ๐—ฑ๐˜€ ๐˜๐˜๐‹๐Œ๐€๐—  The scanner uses โ€œ%arrayโ€ and one
     of its rules matched a string longer than the YYLMAX constant (8K
     bytes by default).  The value can be increased by #define'ing
     YYLMAX in the definitions section of ๐—ณ๐—น๐—ฒ๐˜… input.

     ๐˜€๐—ฐ๐—ฎ๐—ป๐—ป๐—ฒ๐—ฟ ๐—ฟ๐—ฒ๐—พ๐˜‚๐—ถ๐—ฟ๐—ฒ๐˜€ -๐Ÿด ๐—ณ๐—น๐—ฎ๐—ด ๐˜๐—ผ ๐˜‚๐˜€๐—ฒ ๐˜๐—ต๐—ฒ ๐—ฐ๐—ต๐—ฎ๐—ฟ๐—ฎ๐—ฐ๐˜๐—ฒ๐—ฟ '๐˜…'  The scanner
     specification includes recognizing the 8-bit character โ€˜xโ€™ and the
     -๐Ÿด flag was not specified, and defaulted to 7-bit because the -๐‚๐—ณ
     or -๐‚๐… table compression options were used.  See the discussion of
     the -๐Ÿณ flag for details.

     ๐—ณ๐—น๐—ฒ๐˜… ๐˜€๐—ฐ๐—ฎ๐—ป๐—ป๐—ฒ๐—ฟ ๐—ฝ๐˜‚๐˜€๐—ต-๐—ฏ๐—ฎ๐—ฐ๐—ธ ๐—ผ๐˜ƒ๐—ฒ๐—ฟ๐—ณ๐—น๐—ผ๐˜„  unput() was used to push back so
     much text that the scanner's buffer could not hold both the pushed-
     back text and the current token in yฬฒyฬฒtฬฒeฬฒxฬฒtฬฒ.  Ideally the scanner
     should dynamically resize the buffer in this case, but at present
     it does not.

     ๐—ถ๐—ป๐—ฝ๐˜‚๐˜ ๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ ๐—ผ๐˜ƒ๐—ฒ๐—ฟ๐—ณ๐—น๐—ผ๐˜„, ๐—ฐ๐—ฎ๐—ป'๐˜ ๐—ฒ๐—ป๐—น๐—ฎ๐—ฟ๐—ด๐—ฒ ๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ ๐—ฏ๐—ฒ๐—ฐ๐—ฎ๐˜‚๐˜€๐—ฒ ๐˜€๐—ฐ๐—ฎ๐—ป๐—ป๐—ฒ๐—ฟ ๐˜‚๐˜€๐—ฒ๐˜€
     ๐‘๐„๐‰๐„๐‚๐“  The scanner was working on matching an extremely large
     token and needed to expand the input buffer.  This doesn't work
     with scanners that use RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ.

     ๐—ณ๐—ฎ๐˜๐—ฎ๐—น ๐—ณ๐—น๐—ฒ๐˜… ๐˜€๐—ฐ๐—ฎ๐—ป๐—ป๐—ฒ๐—ฟ ๐—ถ๐—ป๐˜๐—ฒ๐—ฟ๐—ป๐—ฎ๐—น ๐—ฒ๐—ฟ๐—ฟ๐—ผ๐—ฟ--๐—ฒ๐—ป๐—ฑ ๐—ผ๐—ณ ๐—ฏ๐˜‚๐—ณ๐—ณ๐—ฒ๐—ฟ ๐—บ๐—ถ๐˜€๐˜€๐—ฒ๐—ฑ  This can
     occur in an scanner which is reentered after a long-jump has jumped
     out (or over) the scanner's activation frame.  Before reentering
     the scanner, use:

           yyrestart(yyin);

     or, as noted above, switch to using the C++ scanner class.

     ๐˜๐—ผ๐—ผ ๐—บ๐—ฎ๐—ป๐˜† ๐˜€๐˜๐—ฎ๐—ฟ๐˜ ๐—ฐ๐—ผ๐—ป๐—ฑ๐—ถ๐˜๐—ถ๐—ผ๐—ป๐˜€ ๐—ถ๐—ป <> ๐—ฐ๐—ผ๐—ป๐˜€๐˜๐—ฟ๐˜‚๐—ฐ๐˜!  More start conditions
     than exist were listed in a <> construct (so at least one of them
     must have been listed twice).

๐’๐„๐„ ๐€๐‹๐’๐Ž
     awk(1), sed(1), yacc(1)

     John Levine, Tony Mason, and Doug Brown, Lฬฒeฬฒxฬฒ &ฬฒ Yฬฒaฬฒcฬฒcฬฒ, Oฬฒ'ฬฒRฬฒeฬฒiฬฒlฬฒlฬฒyฬฒ aฬฒnฬฒdฬฒ
     Aฬฒsฬฒsฬฒoฬฒcฬฒiฬฒaฬฒtฬฒeฬฒsฬฒ, 2nd edition.

     Alfred Aho, Ravi Sethi, and Jeffrey Ullman, Cฬฒoฬฒmฬฒpฬฒiฬฒlฬฒeฬฒrฬฒsฬฒ:ฬฒ Pฬฒrฬฒiฬฒnฬฒcฬฒiฬฒpฬฒlฬฒeฬฒsฬฒ,ฬฒ
     Tฬฒeฬฒcฬฒhฬฒnฬฒiฬฒqฬฒuฬฒeฬฒsฬฒ aฬฒnฬฒdฬฒ Tฬฒoฬฒoฬฒlฬฒsฬฒ, Aฬฒdฬฒdฬฒiฬฒsฬฒoฬฒnฬฒ-ฬฒWฬฒeฬฒsฬฒlฬฒeฬฒyฬฒ, 1986, Describes the pattern-
     matching techniques used by flex (deterministic finite automata).

๐’๐“๐€๐๐ƒ๐€๐‘๐ƒ๐’
     The ๐—น๐—ฒ๐˜… utility is compliant with the IEEE Std 1003.1-2008
     (โ€œPOSIX.1โ€) specification, though its presence is optional.

     The flags [-๐Ÿณ๐Ÿด๐๐—ฏ๐‚๐—ฑ๐…๐—ณ๐—ต๐ˆ๐—ถ๐‹๐—น๐—ผ๐๐—ฝ๐’๐˜€๐“๐•๐˜„+?], [--๐—ต๐—ฒ๐—น๐—ฝ], and [--๐˜ƒ๐—ฒ๐—ฟ๐˜€๐—ถ๐—ผ๐—ป] are
     extensions to that specification.

     See also the IฬฒNฬฒCฬฒOฬฒMฬฒPฬฒAฬฒTฬฒIฬฒBฬฒIฬฒLฬฒIฬฒTฬฒIฬฒEฬฒSฬฒ WฬฒIฬฒTฬฒHฬฒ LฬฒEฬฒXฬฒ AฬฒNฬฒDฬฒ PฬฒOฬฒSฬฒIฬฒXฬฒ section, above.

๐€๐”๐“๐‡๐Ž๐‘๐’
     Vern Paxson, with the help of many ideas and much inspiration from
     Van Jacobson.  Original version by Jef Poskanzer.  The fast table
     representation is a partial implementation of a design done by Van
     Jacobson.  The implementation was done by Kevin Gong and Vern Paxโ€
     son.

     Thanks to the many ๐—ณ๐—น๐—ฒ๐˜… beta-testers, feedbackers, and contribuโ€
     tors, especially Francois Pinard, Casey Leedom, Robert Abramovitz,
     Stan Adermann, Terry Allen, David Barker-Plummer, John Basrai, Neal
     Becker, Nelson H.F. Beebe, bฬฒeฬฒnฬฒsฬฒoฬฒnฬฒ@ฬฒoฬฒdฬฒiฬฒ.ฬฒcฬฒoฬฒmฬฒ, Karl Berry, Peter A.
     Bigot, Simon Blanchard, Keith Bostic, Frederic Brehm, Ian Brockโ€
     bank, Kin Cho, Nick Christopher, Brian Clapper, J.T. Conklin, Jason
     Coughlin, Bill Cox, Nick Cropper, Dave Curtis, Scott David Daniels,
     Chris G. Demetriou, Theo de Raadt, Mike Donahue, Chuck Doucette,
     Tom Epperly, Leo Eskin, Chris Faylor, Chris Flatters, Jon Forrest,
     Jeffrey Friedl, Joe Gayda, Kaveh R. Ghazi, Wolfgang Glunz, Eric
     Goldman, Christopher M. Gould, Ulrich Grepel, Peer Griebel, Jan
     Hajic, Charles Hemphill, NORO Hideo, Jarkko Hietaniemi, Scott Hofโ€
     mann, Jeff Honig, Dana Hudes, Eric Hughes, John Interrante, Ceriel
     Jacobs, Michal Jaegermann, Sakari Jalovaara, Jeffrey R. Jones,
     Henry Juengst, Klaus Kaempf, Jonathan I. Kamens, Terrence O Kane,
     Amir Katz, kฬฒeฬฒnฬฒ@ฬฒkฬฒeฬฒnฬฒ.ฬฒhฬฒiฬฒlฬฒcฬฒoฬฒ.ฬฒcฬฒoฬฒmฬฒ, Kevin B. Kenny, Steve Kirsch, Winโ€
     fried Koenig, Marq Kole, Ronald Lamprecht, Greg Lee, Rohan Lenard,
     Craig Leres, John Levine, Steve Liddle, David Loffredo, Mike Long,
     Mohamed el Lozy, Brian Madsen, Malte, Joe Marshall, Bengt Martensโ€
     son, Chris Metcalf, Luke Mewburn, Jim Meyering, R. Alexander
     Milowski, Erik Naggum, G.T. Nicol, Landon Noll, James Nordby, Marc
     Nozell, Richard Ohnemus, Karsten Pahnke, Sven Panne, Roland Pesch,
     Walter Pelissero, Gaumond Pierre, Esmond Pitt, Jef Poskanzer, Joe
     Rahmeh, Jarmo Raiha, Frederic Raimbault, Pat Rankin, Rick Richardโ€
     son, Kevin Rodgers, Kai Uwe Rommel, Jim Roskind, Alberto Santini,
     Andreas Scherer, Darrell Schiebel, Raf Schietekat, Doug Schmidt,
     Philippe Schnoebelen, Andreas Schwab, Larry Schwimmer, Alex Siegel,
     Eckehard Stolz, Jan-Erik Strvmquist, Mike Stump, Paul Stuart, Dave
     Tallman, Ian Lance Taylor, Chris Thewalt, Richard M. Timoney, Jodi
     Tsai, Paul Tuinenga, Gary Weik, Frank Whaley, Gerhard Wilhelms,
     Kent Williams, Ken Yap, Ron Zellar, Nathan Zelle, David Zuhn, and
     those whose names have slipped my marginal mail-archiving skills
     but whose contributions are appreciated all the same.

     Thanks to Keith Bostic, Jon Forrest, Noah Friedman, John Gilmore,
     Craig Leres, John Levine, Bob Mulcahy, G.T.  Nicol, Francois
     Pinard, Rich Salz, and Richard Stallman for help with various disโ€
     tribution headaches.

     Thanks to Esmond Pitt and Earle Horton for 8-bit character support;
     to Benson Margulies and Fred Burke for C++ support; to Kent
     Williams and Tom Epperly for C++ class support; to Ove Ewerlid for
     support of NUL's; and to Eric Hughes for support of multiple bufโ€
     fers.

     This work was primarily done when I was with the Real Time Systems
     Group at the Lawrence Berkeley Laboratory in Berkeley, CA.  Many
     thanks to all there for the support I received.

     Send comments to โŸจvฬฒeฬฒrฬฒnฬฒ@ฬฒeฬฒeฬฒ.ฬฒlฬฒbฬฒlฬฒ.ฬฒgฬฒoฬฒvฬฒโŸฉ.

๐๐”๐†๐’
     Some trailing context patterns cannot be properly matched and genโ€
     erate warning messages (dangerous trailing context).  These are
     patterns where the ending of the first part of the rule matches the
     beginning of the second part, such as "zx*/xy*", where the โ€˜x*โ€™
     matches the โ€˜xโ€™ at the beginning of the trailing context.  (Note
     that the POSIX draft states that the text matched by such patterns
     is undefined.)

     For some trailing context rules, parts which are actually fixed-
     length are not recognized as such, leading to the above mentioned
     performance loss.  In particular, parts using โ€˜|โ€™ or โ€˜{n}โ€™ (such as
     "foo{3}") are always considered variable-length.

     Combining trailing context with the special โ€˜|โ€™ action can result
     in fixed trailing context being turned into the more expensive
     variable trailing context.  For example, in the following:

           %%
           abc      |
           xyz/def

     Use of ๐˜‚๐—ป๐—ฝ๐˜‚๐˜() invalidates yytext and yyleng, unless the โ€œ%arrayโ€
     directive or the -๐—น option has been used.

     Pattern-matching of NUL's is substantially slower than matching
     other characters.

     Dynamic resizing of the input buffer is slow, as it entails rescanโ€
     ning all the text matched so far by the current (generally huge)
     token.

     Due to both buffering of input and read-ahead, it is not possible
     to intermix calls to <sฬฒtฬฒdฬฒiฬฒoฬฒ.ฬฒhฬฒ> routines, such as, for example,
     ๐—ด๐—ฒ๐˜๐—ฐ๐—ต๐—ฎ๐—ฟ(), with ๐—ณ๐—น๐—ฒ๐˜… rules and expect it to work.  Call ๐—ถ๐—ป๐—ฝ๐˜‚๐˜()
     instead.

     The total table entries listed by the -๐˜ƒ flag excludes the number
     of table entries needed to determine what rule has been matched.
     The number of entries is equal to the number of DFA states if the
     scanner does not use RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ, and somewhat greater than the number
     of states if it does.

     RฬฒEฬฒJฬฒEฬฒCฬฒTฬฒ cannot be used with the -๐—ณ or -๐… options.

     The ๐—ณ๐—น๐—ฒ๐˜… internal algorithms need documentation.

COSMOPOLITAN                September 21, 2015                          BSD