What is Comma operator in C++?

The purpose of the comma operator is to string together several expressions. The value of a comma-separated list of expressions is the value of the rightmost expression. Essentially, the comma's effect is to cause a sequence of operations to be performed.

The values of the other expressions will be discarded. This means that the expression on the right side will become the value of the entire comma-separated expression. For example −

Example

The following program illustrates the working of comma operator −

#include <iostream>
using namespace std;

int main() {
   int i, j;
   j = 10;
   i = (j++, j+100, 999+j);
   cout << i;
   return 0;
}

Output

This gives the output −

1010

Here is the procedure how the value of i gets calculated: j starts with the value 10. j is then incremented to 11. Next, j is added to 100. Finally, j (still containing 11) is added to 999, which yields the result 1010.