template<class T>
class O
{
public:
	typedef O<T> CLASSNAME;
	O(const T & _t) : t(_t) {}
	O() {}

	operator T & () { return t; }
	operator const T & () const { return t; }

	T t;
};

template<class T>
class O1 : public O<T> {};

template<class T1, class T2>
class O2 : public O<T1>, public O<T2> {};

template<class T1, class T2, class T3>
class O3 : public O<T1>, public O<T2>, public O<T3> {};

template<class T1, class T2, class T3, class T4>
class O4 : public O<T1>, public O<T2> , public O<T3> , public O<T4> {};

	O2<int, float> o2;
	
	o2.O<int>::t = 123;
	o2.O<float>::t = 23.10f;