//Listing 9.6 Demonstrates passing by reference
#include <iostream>
  
using namespace std;
void swap(int *x, int *y);
  
int main()
{
    int x = 5, y = 10;
  
    cout << "Main. Before swap, x: " << x << " y: " << y << endl;
    swap(&x,&y);
    cout << "Main. After swap, x: " << x << " y: " << y << endl;
    return 0;
}
  
void swap (int *px, int *py)
{
    int temp;
  
    cout << "Swap. Before swap, *px: " << *px <<
       " *py: " << *py << endl;
  
    temp = *px;
    *px = *py;
    *py = temp;
  
    cout << "Swap. After swap, *px: " << *px << 
       " *py: " << *py << endl;
  
}