YACC PROGRAM to recognize a valid variable, which starts with a letter followed by any number of letters or digits

program to recognize a valid variable, which starts with a letter followed by any number of letters or digits

4b.l file

%{

#include "y.tab.h"

%}

%%

[0-9]+ {return DIGIT;}

[a-zA-Z]+ {return LETTER;}

[ \t] {;}

\n { return 0;}

. {return yytext[0];}

%%

4b.y file

%{

#include<stdio.h>

%}

%token DIGIT LETTER

%%

stmt:A

     ;

A: LETTER B

 ;

B: LETTER B

 | DIGIT B

 | LETTER

 | DIGIT

 ;

%%

void main(){

printf("enter string \n");

yyparse();

printf("valid");

exit(0);

}

void yyerror()

{

printf("invalid");

exit(0);

}