Class with only virtual methods : virtual function « Class « C++ Tutorial

1. C++ Tutorial
2. Class
3. virtual function

#include <iostream>
 
 class Shape
 {
 public:
     Shape(){}
     virtual ~Shape(){}
     virtual long GetArea() = 0; 
     virtual long GetPerim()= 0;
     virtual void Draw() = 0;
 };
 
 class Circle : public Shape
 {
 public:
     Circle(int radius):itsRadius(radius){}
     ~Circle(){}
     long GetArea() { return 3 * itsRadius * itsRadius; }
     long GetPerim() { return 9 * itsRadius; }
     void Draw();
 private:
     int itsRadius;
     int itsCircumference;
 };
 
 void Circle::Draw()
 {
     std::cout << "Circle drawing \n";
 }
 
 
 class Rectangle : public Shape
 {
 public:
     Rectangle(int len, int width):
         itsLength(len), itsWidth(width){}
     virtual ~Rectangle(){}
     virtual long GetArea() { return itsLength * itsWidth; }
     virtual long GetPerim() {return 2*itsLength + 2*itsWidth; }
     virtual int GetLength() { return itsLength; }
     virtual int GetWidth() { return itsWidth; }
     virtual void Draw();
 private:
     int itsWidth;
     int itsLength;
 };
 
 void Rectangle::Draw()
 {
     for (int i = 0; i<itsLength; i++)
     {
         for (int j = 0; j<itsWidth; j++)
             std::cout << "x ";
 
         std::cout << "\n";
     }
 }
 
 class Square : public Rectangle
 {
 public:
     Square(int len);
     Square(int len, int width);
     ~Square(){}
     long GetPerim() {return 4 * GetLength();}
 };
 
 Square::Square(int len):Rectangle(len,len) {}
 
 Square::Square(int len, int width):Rectangle(len,width)
 {
     if (GetLength() != GetWidth())
         std::cout << "Error, not a square... a Rectangle??\n";
 }
 
 int main()
 {
     Shape * sp;
 
     sp = new Circle(5);
     sp->Draw();
     
     sp = new Rectangle(4,6);
     sp->Draw();
     
     sp = new Square(5);
     sp->Draw();
     return 0;
 }

Circle drawing
x x x x x x
x x x x x x
x x x x x x
x x x x x x
x x x x x
x x x x x
x x x x x
x x x x x
x x x x x