YACC program to evaluate an arithmetic expression involving +, - ,* , /

LEX program-
-> create a file named calci.l
and write following program in it.

%{
#include"y.tab.h"
#include<math.h>
extern yylval;
%}
%%
[0-9]+ {yylval=atoi(yytext);return NUM;}
[+] {return '+';}
[-] {return '-';}
[*] {return '*';}
[/] {return '/';}
[\t]+;
[\n] {return 0;}
.{return yytext[0];
}
%%

-----------------------------------------
YACC program-
-> create a file named calci.y
and write following program in it.

#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");
}
-----------------------------------------------------------
TO COMPILE & RUN-

write the following linux command & press enter:

lex calci.l
yacc -d calci.y
cc lex.yy.c y.tab.c
./a.out

Now it will print:
Enter the expression in terms of integers:
5*8+3
43
Success
-------------------------------------------------------------