Lex program to recognize a valid arithmetic expression.

//Lex program to recognize a valid arithmetic expression.

%{

#include<stdio.h>

int p=0,q=0,r=0,s=0,ob=0,cb=0;

int flagp=0,flagq=0,flagr=0,flags=0;

%}

%%

[a-zA-z]+ printf("\n %s is an identifier\n",yytext);

[+] {p++;flagp=1;}

[-] {q++;flagq=1;}

[*] {r++;flagr=1;}

[/] {s++;flags=1;}

[(] ob++;

[)] cb++;

%%

void main()

{

printf("Enter expression:");

yylex();

if(ob==cb)

printf("\nvalid expression\n");

else

printf("invalid expression\n");

printf("Addition=%d\tSubtract=%d\nMultiply=%d\tDivide=%d\n",p,q,r,s);

printf("\n Operators used:\n");

if(flagp==1)

printf("+\t");

if (flagq==1)

printf("-\t");

if(flagr==1)

printf("*\t");

if(flags==1)

printf("/\n");

}

//output of this code