// pointers to base class

// One of the key features of derived classes is that a pointer to a derived class
// is type-compatible with a pointer to its base class. Polymorphism is the art of
// taking advantage of this simple but powerful and versatile feature, that brings
// Object Oriented Methodologies to its full potential.

#include <iostream>
using namespace std;

class Polygon {
  protected:
    int width, height;
  public:
    void set_values (int a, int b)
      { width=a; height=b; }
  };

class Rectangle: public Polygon {
  public:
    int area ()
      { return (width * height); }
  };

class Triangle: public Polygon {
  public:
    int area ()
      { return (width * height / 2); }
  };

int main () {
  Rectangle rect;
  Triangle trgl;
  Polygon *poly1 = &rect;
  Polygon *poly2 = &trgl;
  poly1->set_values (4,5);
  poly2->set_values (4,5);
  cout << "The area of the rectangle is " << rect.area() << endl;
  cout << "The area of the triangle is " << trgl.area() << endl;
  getchar();
  
  return 0;
}