RECOGNITION OF THE GRAMMAR(anb where n>=10) USING YACC

To write a YACC program to recognize the grammar anb where n>=10.

1. Start the program.
2. Write a program in the vi editor and save it with .l extension.
3. In the lex program, write the translation rules for the variables a and b.
4. Write a program in the vi editor and save it with .y extension.
5. Compile the lex program with lex compiler to produce output file as lex.yy.c. eg $ lex filename.l
6. Compile the yacc program with yacc compiler to produce output file as y.tab.c. eg $ yacc –d arith_id.y
7. Compile these with the C compiler as gcc lex.yy.c y.tab.c
8. Enter a string as input and it is identified as valid or invalid.

%{
/* Definition section */
#include "y.tab.h"
%}
/* Rule Section */
%%
[aA] {return A;}
[bB] {return B;}
\n {return NL;}
. {return yytext[0];}
%%
int yywrap()
{
return 1;
}

%{
/* Definition section */
#include<stdio.h>
#include<stdlib.h>
%}
%token A B NL
/* Rule Section */
%%
stmt: S NL { printf("valid string\n");
exit(0); }
;
S: A S B |
;
%%
int yyerror(char *msg)
{
printf("invalid string\n");
exit(0);
}
//driver code
main()
{
printf("enter the string\n");
yyparse();
}

The YACC program to recognize the grammar anb where n>=10 is executed successfully and the output is verified.