// test_swap.cpp   demonstrate pass parameter by reference         

void swap(int &v1, int &v2)
{
  int tmp = v2;
  v2 = v1;
  v1 = tmp;
} // end swap


#include <iostream>
using namespace std;

int main()                            // C++ test swap
{
  int i=10;
  int j=20;
  cout << "before swap  i= " << i << "  j= " << j << endl;
  
  swap(i,j);
  
  cout << "after  swap  i= " << i << "  j= " << j << endl;
  
  return 0;
} // end main