Write a Program to Implement a Calculator and Recognize a Valid Arithmetic Expression Using Lex and Yacc.

 

Examples:

Input: 4+5 
Output: Result=9
Entered arithmetic expression is Valid

Input: 10-5
Output: Result=5
Entered arithmetic expression is Valid

Input: 10+5-
Output: 
Entered arithmetic expression is Invalid

Input: 10/5
Output: Result=2
Entered arithmetic expression is Valid

Input: (2+5)*3
Output: Result=21
Entered arithmetic expression is Valid

Input: (2*4)+
Output: 
Entered arithmetic expression is Invalid

Input: 2%5
Output: Result=2
Entered arithmetic expression is Valid 

Lexical Analyzer Source Code:

%{ 

#include<stdio.h> 

#include "y.tab.h" 

extern int yylval; 

%} 

%% 

[0-9]+ { 

yylval=atoi(yytext); 

return NUMBER; 

} 

[\t] ; 

[\n] return 0; 

. return yytext[0]; 

%% 

int yywrap() 

{ 

return 1; 

} 

Parser Source Code :

%{ 

#include<stdio.h> 
int flag=0; 
%} 

%token NUMBER 

%left '+' '-'

%left '*' '/' '%'

%left '(' ')'


%% 

ArithmeticExpression: E{ 

		printf("\nResult=%d\n", $$); 

		return 0; 

		}; 
E:E'+'E {$$=$1+$3;} 

|E'-'E {$$=$1-$3;} 

|E'*'E {$$=$1*$3;} 

|E'/'E {$$=$1/$3;} 

|E'%'E {$$=$1%$3;} 

|'('E')' {$$=$2;} 
  
| NUMBER {$$=$1;} 
; 

%% 

 
void main() 
{ 
printf("\nEnter Any Arithmetic Expression which not contain any space in between:\n");
yyparse(); 
if(flag==0) 
printf("\nEntered arithmetic expression is Valid\n\n"); 
} 

yyerror(s)
char *s;
{
  printf("\nEntered arithmetic expression is Invalid\n\n"); 
  flag=1;
}

Output