System Software Lab Programs ( Lex and Yaac Programs ) 5b
// June 13th, 2009 // Educational, Engineering, Unix and System Software Lab // Written by sandeephegde
-->Subject : System Software Laboratory
Branch : Information Science & Engineering
Semester : 6
University : VTU
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PART – A
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5b. Program to recognize strings ‘aaab’, ‘abbb’, ‘ab’ and ‘a’ using the grammar (anbn, n>= 0).
5b.l
%{
#include<stdio.h>
#include “y.tab.h”
%}
%%
[a] return A;
[b] return B;
. return yytext[0];
\n return yytext[0];
%%
——————————————
5b.y
%{
#include<stdio.h>
%}
%token A B
%%
input:expr ‘\n’ {return 0;}
expr: X
X: A X B|;
%%
main()
{
printf(“\nEnter string: “);
if(!yyparse())
{
printf(“\nValid”);
exit(0);
}
}
int yyerror()
{
printf(“\nInvalid”);
return 1;
}
int yywrap()
{
return 1;
}
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