C++ PointerArray

hier ein beispiel für vererbung mit jede menge unnötigem zeug ... (das scheinen lehrer zu mögen )

#include <iostream.h>
namespace nsp{
template <class T>
class CPoly{
protected:
T width, height;
public:
void set_values(T a, T b) { width=a; height=b;}
virtual T area(void) { return(0); }
};
template <class T>
class CRect: public CPoly<T>{
public:
T area() {return(width*height);}
};
template <class T>
class CTria: public CPoly<T>{
public:
T area() {return(width*height/2);}
};
}
void main () {
nsp::CPoly<int> poly;
nsp::CRect<double> rect;
nsp::CTria<float> trgl;
nsp::CRect<long> lrect;
nsp::CPoly<double> *ppoly1=&rect;
nsp::CPoly<float> *ppoly2=&trgl;
nsp::CPoly<int> *ppoly3=&poly;
nsp::CPoly<long> *ppoly4=&lrect;
ppoly1->set_values(1.15,2.6541);
ppoly2->set_values(2.5,3.4);
ppoly3->set_values(3,4),
ppoly4->set_values(100000,156);
cout << ppoly1->area() << endl;
cout << ppoly2->area() << endl;
cout << ppoly3->area() << endl;
cout << ppoly4->area() << endl;
}

oja, templates kann der uralte Turbo C++ Compiler doch (noch)