D语言基类和派生类

import std.stdio;

// Base class 
class Shape { 
   public: 
      void setWidth(int w) { 
         width = w; 
      }

      void setHeight(int h) { 
         height = h; 
      }

   protected: 
      int width; 
      int height; 
}

// Derived class 
class Rectangle: Shape { 
   public: 
      int getArea() { 
         return (width * height); 
      } 
}

void main() { 
   Rectangle Rect = new Rectangle();

   Rect.setWidth(5); 
   Rect.setHeight(7); 

   // Print the area of the object. 
   writeln("Total area: ", Rect.getArea()); 
}