// Project File reference.cpp

#include <iostream>
using namespace std;

int main()
{
    void f(int, int&);
    int& g(int&);
    int x = 3, y = 5;

    cout << x << " " << y << endl;
    f(x, y);
    cout << x << " " << y << endl;
    x = g(x);
    cout << x << " " << y << endl;

    return EXIT_SUCCESS;
}

void f(int a, int &b)
{
    a += 2;
    b += 2;
}

int& g(int &a)
{
    a += 9;
    return a;
}

// The preceding function avoids making a copy 
// of a when it is passed in and avoids making
// a copy of the value of a when it is returned.
// This is especially useful when an input file
// object (ostream) is passed in and returned.
// Because the copy constructor for ostream is
// private, a copy cannot be made, so references
// are the only possibility.

// Output:
// 3 5
// 13 13
// 13 7
// 22 7