KTU
2019 Scheme
Compiler Design
Valid Identifier

YACC specification to recognize valid identifier

Aim

Generate a YACC specification to recognize a valid identifier which starts with a letter followed by any number of letters or digits.

Program

yacc

%{
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int flag=0;
%}

%token LETTER
%token DIGIT

%%
E:LETTER S
S:LETTER S
|DIGIT S
|
;
%%

void main()
{
	printf("Enter the identifier.\n");
	yyparse();
	if(flag==0)
	{
		printf("Valid Identifier.\n");
	}
}

void yyerror()
{
	flag=1;
	printf("Invalid identifier.\n");
}

lex

%{
#include"y.tab.h"
%}

%%
[a-zA-Z_] {return LETTER;}
[0-9] {return DIGIT;}
%%

int yywrap()
{
return 1;
}
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