template <class T> struct tuple_size;
template <class... Types>
class tuple_size<tuple<Types...>> : public integral_constant<size_t, sizeof...(Types)> { };
template <size_t I, class... Types>
class tuple_element<I, tuple<Types...>> {
public:
using type = TI;
};
template <class T> class tuple_size<const T>;
template <class T> class tuple_size<volatile T>;
template <class T> class tuple_size<const volatile T>;
integral_constant<size_t, TS::value>
Otherwise, they shall have no member value.template <size_t I, class T> class tuple_element<I, const T>;
template <size_t I, class T> class tuple_element<I, volatile T>;
template <size_t I, class T> class tuple_element<I, const volatile T>;