// A8.cpp - accessing derived class extensions of base class protocol

#include <iostream>
namespace mt = std;

class X {
  public:
    virtual ~X() {}
    virtual void mf1() { mt::cout << "\n  X::mf1() called"; }
    virtual void mf2() { mt::cout << "\n  X::mf2() called"; }
};

class Y : public X {

  public:
    virtual ~Y() {}
    virtual void mf2() { mt::cout << "\n  Y::mf2() called"; }
    virtual void mf3() { mt::cout << "\n  Y::mf3() called"; }
};

void main() {

  X x;
  Y y;
  X *pX = &x;
  pX->mf1();
  pX->mf2();
  Y *pY = dynamic_cast<Y*>(pX);
  if(pY)
    pY->mf3();
  else
    mt::cout << "\n  dynamic cast fails";

  pX = &y;
  pX->mf1();
  pX->mf2();
//pX->mf3();  can't use extensions to base protocol 
//            with base pointer

  pY = dynamic_cast<Y*>(pX);
  if(pY)
    pY->mf3();
  else
    mt::cout << "\n  dynamic cast fails";

  mt::cout << "\n\n";
}