CODE:

template
class Validable{
	public:
		typedef T type;
		inline friend bool operator!(const type& t){return !( t.operator bool() );}//OK

		inline friend bool IsValid(const type& t){return ( t.operator bool() );}//ダメ
		inline friend bool IsInvalid(const type& t){return !( t.IsValid() );}//ダメ
};