二元運算子過載

下表顯示了二元運算子，其目的列表。

一個例子如下，解釋如何過載一個二元運算子。

import std.stdio;

class Box
{
   public:

      double getVolume()
      {
         return length * breadth * height;
      }
      void setLength( double len )
      {
         length = len;
      }

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

      void setHeight( double hei )
      {
         height = hei;
      }
      Box opBinary(string op)(Box b)
      {
         if(op == "+")
         {
            Box box = new Box();
            box.length = this.length + b.length;
            box.breadth = this.breadth + b.breadth;
            box.height = this.height + b.height;
            return box;
          }
      }
   private:
      double length;      // Length of a box
      double breadth;     // Breadth of a box
      double height;      // Height of a box
};
// Main function for the program
void main( )
{
   Box box1 = new Box();    // Declare Box1 of type Box
   Box box2 = new Box();    // Declare Box2 of type Box
   Box box3 = new Box();    // 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();
   writeln("Volume of Box1 : ", volume);

   // volume of box 2
   volume = box2.getVolume();
   writeln("Volume of Box2 : ", volume);

   // Add two object as follows:
   box3 = box1 + box2;

   // volume of box 3
   volume = box3.getVolume();
   writeln("Volume of Box3 : ", volume);

}

讓我們編譯和執行上面的程式，這將產生以下結果：

Volume of Box1 : 210
Volume of Box2 : 1560
Volume of Box3 : 5400