Comma operator should be used carefully | GeeksforGeeks

In C and C++, comma is the last operator in precedence table. So comma should be carefully used on right side of an assignment expression. For example, one might expect the output as b = 10 in below program. But program prints b = 20 as assignment has higher precedence over comma and the statement “b = 20, a” becomes equivalent to “(b = 20), a”.

#include<stdio.h> int main() {   int a = 10, b;   b = 20, a;   // b = 20   printf(" b = %d ", b);   getchar();   return 0; }

Putting a bracket with comma makes b = a (or 10).

#include<stdio.h> int main() {   int a = 10, b;   b = (20, a); // b = a   printf(" b = %d ", b);   getchar();   return 0; }

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