Question

Can anybody explain why do you need to return a reference while overloading operators
e.g.

friend std::ostream& operator<< (std::ostream& out, const std::string& str)

Answer 1

It is to make “chaining” of the operator work, in examples like this:

std::cout << "hello," << " world";

If the first (leftmost) use of the operator<<() hadn’t returned a reference, there would not be an object to call for the second use of the operator.