#include <iostream>
#include <map>

#define CALLBACK __stdcall

using namespace std;

typedef int UNIT;
typedef int HWND;
typedef int WPARAM;
typedef int LPARAM;
typedef int LRESULT;
typedef LRESULT (*WNDPROC)(HWND,UNIT,WPARAM,LPARAM);

class A{
public:
	
	A():proc(NULL){};
	
	operator WNDPROC()
	{
		return proc;
	};

	virtual LRESULT fn2(HWND z,UNIT y,WPARAM x,LPARAM w) {
		cout << "Class A " << "fn2 "<<(int)this << endl;
		return 0;
	};


	template<int T> void Init(void)
	{
		proc = WndProc<T>;
		disp[proc] = this;
	};



private:

	template <int T> static LRESULT WndProc(HWND z,UNIT y,WPARAM x,LPARAM w)
	{
		A * a = disp[WndProc<T>];
		return a->fn2(z,y,x,w);	
	};


private:
	WNDPROC proc;
	static map<WNDPROC,A *> disp;
};

map<WNDPROC,A *> A::disp;


class C : public A
{
public:
	virtual LRESULT fn2(HWND z,UNIT y,WPARAM x,LPARAM w) {
		cout << "Class C " << "fn2 "<<(int)this << endl;
		return 0;
	};
};

#define Init() Init<__COUNTER__>()

int main(int argc, char* argv[])
{
	A a;
	a.Init();
	C b;
	b.Init();

	A * d = &b;

	WNDPROC c = a;
	c(0,0,0,0);
	c = b;
	c(0,0,0,0);
	c = *d;
	c(0,0,0,0);
	return 0;
}