Yacc Part :
%token NUMBER ID NL
%left ‘+’ ‘-‘
%left ‘*’ ‘/’
%%
stmt : exp NL { printf(“Valid Expression”); exit(0);}
;
exp : exp ‘+’ exp
| exp ‘-‘ exp
| exp ‘*’ exp
| exp ‘/’ exp
| ‘(‘ exp ‘)’
| ID
| NUMBER
;
%%
int yyerror(char *msg)
{
printf(“Invalid Expression\n”);
exit(0);
}
main ()
{
printf(“Enter the expression\n”);
yyparse();
}
Lex Part :
%{
#include “y.tab.h”
%}
%%
[0-9]+ { return DIGIT; }
[a-zA-Z][a-zA-Z0-9_]* { return ID; }
\n { return NL ;}
. { return yytext[0]; }
%%