Sandeep Hegde

System Software Lab Programs ( Lex and Yaac Programs ) 6a

// June 14th, 2009 // Educational, Engineering, Unix and System Software Lab

Subject : System Software Laboratory

Branch : Information Science & Engineering

Semester : 6

University : VTU

………………………………………………………………………………………………………………………….
PART – A

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6) Program to recognize the grammar (anb, n>= 10).

6.l

/* 6.l */
%{
#include<stdio.h>
#include “y.tab.h”
%}
%%
[aA] return A;
[bB] return B;
.|n return yytext[0];
%%

—————————————–

6.y

/* 6.y */
%{
#include<stdio.h>
%}
%token A B
%%
stmt: S ‘n’ {printf(“nValid expression”);exit(1);}
;
S: X B
X: X A | A A A A A A A A A A
%%
main()
{
printf(“nEnter the expression: “);
if(yyparse())
{
printf(“nValid expression”);
exit(0);
}
}
int yyerror()
{
printf(“nInvalid expressionn”);
return 1;
}

int yywrap()
{
return 1;
}