What is the output of "cout << (a, b)" and why?

Question

It is possible to combine boolean expressions with a comma separator. I have seen it in a code and i am not sure what this resolves to. I wrote some sample code.

int BoolStatement(void)
{
    using std::cout;
    using std::endl;

    cout << "(0, 0) => " << (0, 0) << endl;
    cout << "(0, 1) => " << (0, 1) << endl;
    cout << "(1, 0) => " << (1, 0) << endl;
    cout << "(1, 1) => " << (1, 1) << endl;
    cout << "(0, 0) => " << (0, 0) << endl;
    cout << "(0, 3) => " << (0, 3) << endl;
    cout << "(5, 0) => " << (5, 0) << endl;
    cout << "(7, 1) => " << (7, 1) << endl;

    cout << endl;
    return 0;
}

The output of this is:

(0, 0) => 0
(0, 1) => 1
(1, 0) => 0
(1, 1) => 1
(0, 0) => 0
(0, 3) => 3
(5, 0) => 0
(7, 1) => 1

I am not sure if that is only true for my system and if this call is actually the same as a boolean combination of statements.

What is the output, is it the same on all systems? Why is that statement possible and is there documentation on it?

Answer 1

The comma operator returns the righthand side.

Wikipedia:

In the C and C++ programming languages, the comma operator (represented by the token ,) is a binary operator that evaluates its first operand and discards the result, and then evaluates the second operand and returns this value (and type).