4A PROGRAM TO RECOGNIZE A VALID ARITHMETIC EXPRESSION THAT USESOPERATOR +, - , * AND / USING YACC

Ex. No: 4 A

Date:

4A.  PROGRAM TO RECOGNIZE A VALID ARITHMETIC EXPRESSION THAT USESOPERATOR +, - , * AND / USING YACC

AIM:

  To write a Yacc program to valid arithmetic expression using Yacc

ALGORITHM:

Step-1:Reading an expression 

Step-2: Checking the validating of the given expression according to the rule using yacc. 

Step-3:Using expression rule print the result of the given values 

PROGRAM

vae.l

%{ 

#include"y.tab.h" 

#include<math.h> 

extern yylval; 

%} 

%% 

[0-9]+ {yylval=atoi(yytext);return NUM;} 

[+] {return '+';} 

[-] {return '-';} 

[*] {return '*';} 

[/] {return '/';} 

[\t]+;

[\n] {return 0;} 

%%

vae.y

%{

#include<stdio.h> 

%} 

%token NUM 

%left '-''+' 

%right '*''/' 

%% 

start: exp {printf("%d\n",$$);} 

exp:exp'+'exp {$$=$1+$3;} 

|exp'-'exp {$$=$1-$3;} 

|exp'*'exp {$$=$1*$3;} 

|exp'/'exp 

{ 

if($3==0) 

yyerror("error"); 

else 

{ 

$$=$1/$3; 

} 

} 

|'('exp')' {$$=$2;} 

|NUM {$$=$1;} 

; 

%% 

main() 

{ 

printf("Enter the Expr. in terms of integers\n"); 

if(yyparse()==0) 

printf("Success\n"); 

} 

yywrap(){} 

yyerror() 

{ 

printf("Error\n"); 

}

OUTPUT:

D:\MOHANRAJ\CS6612 COMPILER LAB\lex_yacc\YACC\CD4A>lex vae.l

D: \MOHANRAJ\\CS6612 COMPILER LAB\lex_yacc\YACC\CD4A>yacc -d vae.y

D: \MOHANRAJ\\CS6612 COMPILER LAB\lex_yacc\YACC\CD4A>cc lex.yy.c y.tab.c

D: \MOHANRAJ\\CS6612 COMPILER LAB\lex_yacc\YACC\CD4A>a.exe

Enter the Expr. in terms of integers

1+2*3-4/2

5

Success

D: \MOHANRAJ\\CS6612 COMPILER LAB\lex_yacc\YACC\CD4A>a.exe

Enter the Expr. in terms of integers

m+3-4

mError

RESULT:

Thus the program for validating arithmetic expression was done.