How does comma operator work during assignment?

Question

int a = 1;
int b = (1,2,3);
cout << a+b << endl; // this prints 4

1. Is (1,2,3) some sort of structure in c++ (some pri

Answer 1

The second line is using the comma operator. An expression like

a, b

evaluates both a and b and returns b.

In this case, the second line is parsed like:

int b = ((1, 2), 3);

so (1, 2) is evaluated (to 2) then thrown away, and the end result is simply 3.