example31.cpp

来自「Advanced Internet Programming Lecture 2 」· C++ 代码 · 共 82 行

#include <iostream>
using namespace std;

class loc {
  int longitude, latitude;
public:
  loc() {} // needed to construct temporaries
  loc(int lg, int lt) {
    longitude = lg;
    latitude = lt;
  }

  void show() {
    cout << longitude << " ";
    cout << latitude << "\n";
  }

  loc operator+(loc op2);
  loc operator-(loc op2);
  loc operator=(loc op2);
  loc operator++();
};
// Overload + for loc.
loc loc::operator+(loc op2)
{
  loc temp;

  temp.longitude = op2.longitude + longitude;
  temp.latitude = op2.latitude + latitude;

  return temp;
}

// Overload - for loc.
loc loc::operator-(loc op2)
{
  loc temp;

  // notice order of operands
  temp.longitude = longitude - op2.longitude;
  temp.latitude = latitude - op2.latitude;

  return temp;
}
               loc loc::operator=(loc op2)
{
  longitude = op2.longitude;
  latitude = op2.latitude;

  return *this; // i.e., return object that generated call
}

// Overload prefix ++ for loc.
loc loc::operator++()
{
  longitude++;
  latitude++;

  return *this;
}
int main()
{
  loc ob1(10, 20), ob2( 5, 30), ob3(90, 90);

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

  ++ob1;
  ob1.show(); // displays 11 21

  ob2 = ++ob1;
  ob1.show(); // displays 12 22
  ob2.show(); // displays 12 22

  ob1 = ob2 = ob3; // multiple assignment
  ob1.show(); // displays 90 90
  ob2.show(); // displays 90 90

  return 0;
}