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   lex.1p    ( 1 )

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Примеры (Examples)

The following is an example of a lex program that implements a
       rudimentary scanner for a Pascal-like syntax:

           %{
           /* Need this for the call to atof() below. */
           #include <math.h>
           /* Need this for printf(), fopen(), and stdin below. */
           #include <stdio.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 white space. */

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

           %%

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

               yylex();
           }