D-programming-binary-operators-overloading

二項演算子のオーバーロード

次の表に、2項演算子のリストとその目的を示します。

Function Name	Operator	Purpose
opBinary	+	Add
opBinary	-	subtract
opBinary	*	multiply
opBinary	/	divide
opBinary	%	remainder of
opBinary	^^	to the power of
opBinary	&	bitwise and
opBinary
bitwise or	opBinary	^
bitwise xor	opBinary	<<
left-shift	opBinary	>>
right-shift	opBinary	>>>
logical right-shift	opBinary	~
concatenate	opBinary	in

以下に、バイナリ演算子をオーバーロードする方法を説明する例を示します。

例

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);
}

上記のコードをコンパイルして実行すると、次の結果が生成されます-

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