The following code example is taken from the book
Object-Oriented Programming in C++
by Nicolai M. Josuttis, Wiley, 2002
© Copyright Nicolai M. Josuttis 2002
#include <iostream>
#include "swap.hpp"
int main()
{
int x = 7;
int y = 13;
std::cout << "x: " << x // x: 7, y: 13
<< " y: " << y << std::endl;
swap (x, y); // swaps values of x and y
std::cout << "x: " << x // x: 13, y: 7
<< " y: " << y << std::endl;
}