C - Comma Operator

The C comma , operator evaluates each of its operands (from left to right) and returns the value of the last operand. This facilitates to create a compound expression in which multiple expressions are evaluated, with the compound expression's final value being the value of the rightmost of its member expressions.

The comma operator has left-to-right associativity. Two expressions separated by a comma are evaluated left to right.

Example:

In the example below, the comma , operator is used to evaluate multiple expressions and returns the value of the last operand.

#include <stdio.h>
 
int main () {
  int x = 10;
  int y = 10;

  //using comma operator
  int A = (x++, x);
  int B = (y+=5, y*=2, y);

  //displaying the result
  printf("(x++, x) : %i\n", A); 
  printf("(y+=5, y*=2, y) : %i\n", B); 

  return 0;
}

The output of the above code will be:

(x++, x) : 11
(y+=5, y*=2, y) : 30