namespace Upp
{
	namespace nil
	{
		class null
		{
			// Cannot make another instance, copy or assign.
			null(null const &);
			null &operator=(null const &);

		protected:
			null() {}

		public:
			// null may be implicitly converted to any pointer type.
			template<typename T>
			operator T*() const { return 0; }
		
			// null is always false.
			bool operator!() const { return true; }
		
			// The address or reference of null is null.
			null const &operator&() const { return *this; }
			null const &operator*() const { return *this; }
		};
		
		struct nullptr : null {
			static nullptr const instance;
		private:
			nullptr() {}
		};
	}

	// Constant reference to constant singular nullptr instance.
	static nil::null const &null = nil::nullptr::instance;
}

// Replace any NULL macro for null
#ifdef NULL
#undef NULL
#endif
#define NULL ::Upp::null

nil::nullptr const nil::nullptr::instance;