C++二进制运算符重载

#include <iostream>

using namespace std;

class Box {
   double length;      // Length of a Box
   double breadth;     // Breadth of a Box
   double height;      // Height of a Box

   public:
   double getVolume(void) {
      return length * breadth * height;
   }

   void setLength( double len ) {
      length = len;
   }

   void setBreadth( double bre ) {
      breadth = bre;
   }

   void setHeight( double hei ) {
      height = hei;
   }

   // Overload + operator to add two Box objects.
   Box operator+(const Box& b) {
      Box Box;
      Box.length = this->length + b.length;
      Box.breadth = this->breadth + b.breadth;
      Box.height = this->height + b.height;
      return Box;
   }
};

// Main function for the program
int main() {
   Box Box1;                // Declare Box1 of type Box
   Box Box2;                // Declare Box2 of type Box
   Box Box3;                // Declare Box3 of type Box
   double volume = 0.0;     // Store the volume of a Box here

   // Box 1 specification
   Box1.setLength(6.0); 
   Box1.setBreadth(7.0); 
   Box1.setHeight(5.0);

   // Box 2 specification
   Box2.setLength(12.0); 
   Box2.setBreadth(13.0); 
   Box2.setHeight(10.0);

   // volume of Box 1
   volume = Box1.getVolume();
   cout << Volume of Box1 :  << volume <<endl;

   // volume of Box 2
   volume = Box2.getVolume();
   cout << Volume of Box2 :  << volume <<endl;

   // Add two object as follows:
   Box3 = Box1 + Box2;

   // volume of Box 3
   volume = Box3.getVolume();
   cout << Volume of Box3 :  << volume <<endl;

   return 0;
}