#ifndef THREE_H
#define THREE_H

namespace three
{

	struct Strategy1
	{
		void f()
		{
			std::cout << "strategy 1" <<  std::endl;
		}
	};
	struct Strategy2
	{
		void g()
		{
			std::cout << "strategy 2" <<  std::endl;
		}
	};
	
	template <class T>
	void adapt( T* t)
	{
		t->f();
	}
	template <>
	void adapt<Strategy2>( Strategy2* t)
	{
		t->g();
	}
	
	struct IStrategy
	{
	template<class T>
	IStrategy(T* x) : x_(x), fun_(vTable_<T>::f)
	{}

	void f() const 
	{
		fun_(x_);
	}
	private:
	typedef void (*FUN)(void*);
	template <class TT>
	struct vTable_
	{
		static void f(void* x)
		{
			adapt(static_cast<TT*>(x));
		}
	};
	private:	
	FUN fun_;
	void* x_;
	};

	struct Context
	{
		Context(const IStrategy& strategy) : strategy_(strategy)
		{}
		void f() const 
		{
		 strategy_.f();
		}
	private:
		const IStrategy& strategy_;
	};

	void test()
	{
		Strategy1 s1;
		Strategy2 s2;
		IStrategy i(&s1);
		Context c(i);
		c.f();
		i = &s2;
		c.f();
	}

}

#endif