Using a Friend to Overload ++ or – – : overload unary operator « Operator Overloading « C++ Tutorial

1. C++ Tutorial
2. Operator Overloading
3. overload unary operator

#include <iostream>
using namespace std;
   
class loc {
  int longitude, latitude;
public:
  loc() {}
  loc(int lg, int lt) {
    longitude = lg;
    latitude = lt;
  }
   
  void show() {
    cout << longitude << " ";
    cout << latitude << "\n";
  }
   
  loc operator=(loc op2);
  friend loc operator++(loc &op);
  friend loc operator--(loc &op);
};
   
// Overload assignment for loc.
loc loc::operator=(loc op2)
{
  longitude = op2.longitude;
  latitude = op2.latitude;
   
  return *this; // i.e., return object that generated call
}
   
// Now a friend; use a reference parameter.
loc operator++(loc &op)
{
  op.longitude++;
  op.latitude++;
   
  return op;
}
   
// Make op-- a friend; use reference.
loc operator--(loc &op)
{
  op.longitude--;
  op.latitude--;
   
  return op;
}
   
int main()
{
  loc ob1(10, 20), ob2;
   
  ob1.show();
  ++ob1;
  ob1.show(); 
   
  ob2 =  ++ob1;
  ob2.show(); 
   
  --ob2;
  ob2.show(); 
   
  return 0;
}