%{
/* anything between %{ and %} is copied directly into lex.yy.c */
/*#include <y.tab.h> only if yacc is used */
   int yylval;  
%}

/* definitions */
ws [ \n\t]*
%%
{ws} {}
a {yylval  = 1; printf("in rule1\n ");return('X');}
b {yylval = 2; printf("in rule2\n"); return('Y');}
%%

/* 2nd set of %%s must appear IMMEDIATELY following end of pattern */
/* anything following %% (functions) are copied into lex.yy.c */
/* yywrap must be defined.  says what to do at end of input */
int yywrap ()
 {
   printf("done\n");
 }