[VC MFC C++ flex bison] flex example(Pascal-like language scanner)

//scanner.l

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

yylex();
}

以下方法生成:

fl scanner