C++赋值运算符重载

#include <iostream>

using namespace std;

class distance {
   private:
      int feet;             // 0 to infinite
      int inches;           // 0 to 12

   public:
      // required constructors
      distance() {
         feet = 0;
         inches = 0;
      }
      distance(int f, int i) {
         feet = f;
         inches = i;
      }
      void operator = (const distance &D ) { 
         feet = D.feet;
         inches = D.inches;
      }

      // method to display distance
      void displaydistance() {
         cout << F:  << feet <<   I: <<  inches << endl;
      }
};

int main() {
   distance D1(11, 10), D2(5, 11);

   cout << First distance : ; 
   D1.displaydistance();
   cout << Second distance :; 
   D2.displaydistance();

   // use assignment operator
   D1 = D2;
   cout << First distance :; 
   D1.displaydistance();

   return 0;
}