C++符号重载

#include <iostream>
using namespace std;

class 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;
      }
      Box operator*(const Box& c) {
      	Box box;
      	box.length = this->length + c.length;
      	box.breadth = this->breadth + c.breadth;
      	box.height = this->height + c.height;
      	return box;
      }
      int operator&(const Box& b) {
         int volume;
         Box box;
         box.length = this->length + b.length;
         box.breadth = this->breadth + b.breadth;
         box.height = this->height + b.height;
         volume = box.length * box.breadth * box.height;
         return volume;
      }
      
   private:
      double length;      // Length of a box
      double breadth;     // Breadth of a box
      double height;      // Height of a box
};

// Main function for the program
int main() {
   Box Box1;                // Declare Box1 of type Box
   Box Box2;                // Declare Box2 of type Box
   Box Box3, Box4;                // Declare Box3 of type Box
   int avol;
   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;
   Box4 = Box1*Box2;
   avol = Box1&Box2;

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

   // volume of box 4
   volume = Box4.getVolume();
   cout << "Volume of Box4: " << volume << endl;

   // volume of box1 + box2
   cout << avol << endl;

   return 0;
}

例子中有3个符号被重载，*，+，&

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;
      }
      Box operator*(const Box& c) {
      	Box box;
      	box.length = this->length + c.length;
      	box.breadth = this->breadth + c.breadth;
      	box.height = this->height + c.height;
      	return box;
      }
      int operator&(const Box& b) {
         int volume;
         Box box;
         box.length = this->length + b.length;
         box.breadth = this->breadth + b.breadth;
         box.height = this->height + b.height;
         volume = box.length * box.breadth * box.height;
         return volume;
      }

重载后可以返回不同类型的数据，例子中*和+重载后，返回类型依然是Box类，但&重载符的返回类型是int。