D-programming-unary-operators-overloading

単項演算子のオーバーロード

次の表に、単項演算子のリストとその目的を示します。

Function Name	Operator	Purpose
opUnary	-	Negative of (numeric complement of)
opUnary	+	The same value as (or, a copy of)
opUnary	~	Bitwise negation
opUnary	*	Access to what it points to
opUnary	++	Increment
opUnary	—	Decrement

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。

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 opUnary(string op)() {
         if(op == "++") {
            Box box = new Box();
            box.length = this.length + 1;
            box.breadth = this.breadth + 1 ;
            box.height = this.height + 1;
            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
   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);

  //volume of box 1
   volume = Box1.getVolume();
   writeln("Volume of Box1 : ", volume);

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

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

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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 : 336

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