#include <iostream>
using namespace std;

// void means no "return" statement;
// both parameters are pass-by-reference
void f( int & x, int & z )
{
    z = x * x;   // changes b in main() to 16
    x++;         // adds 1 to b in main() ==> 17
}

//int g( int x, int z )   // <== pass-by-value version
//int g( int & x, int z )   // <== version "two"
//int g( int x, int & z )   // <== version "three"
int g( int & x, int & z )   // <== pass-by-reference version
{
    x = z + 1;
    z = x + 2;
    return ( x + z );
}

int main()
{
    int a = 2, b = 4, c = 6;
    f( b, b );
    cout << a << " and " << b << " and " << c << endl;
      // OUTPUT: 2 and 17 and 6

    c = g( a, b );
    cout << a << " and " << b << " and " << c << endl;
      // OUTPUT: 18 and 20 and 38   <== pass-by-reference


      // OUTPUT: 2 and 20 and 38   <== version "three"


      // OUTPUT: 18 and 17 and 38   <== version "two"


      // OUTPUT: 2 and 17 and 38   // <== pass-by-value

    return 0;
}