Polymorphism

// abstract base class
#include 
using namespace std;

class CPolygon {
protected:
int width, height;
public:
void set_values (int a, int b)
  { width=a; height=b; }
virtual int area (void) =0;
};

class CRectangle: public CPolygon {
public:
int area (void)
  { return (width * height); }
};

class CTriangle: public CPolygon {
public:
int area (void)
  { return (width * height / 2); }
};

int main () {
CRectangle rect;
CTriangle trgl;
CPolygon * ppoly1 = ▭
CPolygon * ppoly2 = &trgl;
ppoly1->set_values (4,5);
ppoly2->set_values (4,5);
ppoly1->area();
ppoly2->area();
return 0;
}