+ is overloaded for Point + int : overload object and primitive data type « Operator Overloading « C++ Tutorial

1. C++ Tutorial
2. Operator Overloading
3. overload object and primitive data type

#include <iostream>
using namespace std;

class Point {
  int x, y;
public:
  Point() {}
  Point(int px, int py) {
    x = px;
    y = py;
  }

  void show() {
    cout << x << " ";
    cout << y << "\n";
  }

  friend Point operator+(Point op1, int op2);
  friend Point operator+(int op1, Point op2);
};

// + is overloaded for Point + int.
Point operator+(Point op1, int op2)
{
  Point temp;

  temp.x = op1.x + op2;
  temp.y = op1.y + op2;

  return temp;
}
// + is overloaded for int + Point.
Point operator+(int op1, Point op2)
{
  Point temp;

  temp.x = op1 + op2.x;
  temp.y = op1 + op2.y;

  return temp;
}

int main()
{
  Point ob1(10, 20), ob2( 5, 30), ob3(7, 14);

  ob1.show();
  ob2.show();
  ob3.show();

  ob1 = ob2 + 10; // both of these
  ob3 = 10 + ob2; // are valid

  ob1.show();
  ob3.show();

  return 0;
}

10 20
5 30
7 14
15 40
15 40