23 General utilities library [utilities]
namespace std {
template <class... Types>
class tuple;
inline constexpr unspecified ignore;
template <class... TTypes>
constexpr tuple<VTypes...> make_tuple(TTypes&&...);
template <class... TTypes>
constexpr tuple<TTypes&&...> forward_as_tuple(TTypes&&...) noexcept;
template<class... TTypes>
constexpr tuple<TTypes&...> tie(TTypes&...) noexcept;
template <class... Tuples>
constexpr tuple<CTypes...> tuple_cat(Tuples&&...);
template <class F, class Tuple>
constexpr decltype(auto) apply(F&& f, Tuple&& t);
template <class T, class Tuple>
constexpr T make_from_tuple(Tuple&& t);
template <class T> class tuple_size; 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>;
template <class... Types> class tuple_size<tuple<Types...>>;
template <size_t I, class T> class tuple_element; 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>;
template <size_t I, class... Types>
class tuple_element<I, tuple<Types...>>;
template <size_t I, class T>
using tuple_element_t = typename tuple_element<I, T>::type;
template <size_t I, class... Types>
constexpr tuple_element_t<I, tuple<Types...>>& get(tuple<Types...>&) noexcept;
template <size_t I, class... Types>
constexpr tuple_element_t<I, tuple<Types...>>&& get(tuple<Types...>&&) noexcept;
template <size_t I, class... Types>
constexpr const tuple_element_t<I, tuple<Types...>>& get(const tuple<Types...>&) noexcept;
template <size_t I, class... Types>
constexpr const tuple_element_t<I, tuple<Types...>>&& get(const tuple<Types...>&&) noexcept;
template <class T, class... Types>
constexpr T& get(tuple<Types...>& t) noexcept;
template <class T, class... Types>
constexpr T&& get(tuple<Types...>&& t) noexcept;
template <class T, class... Types>
constexpr const T& get(const tuple<Types...>& t) noexcept;
template <class T, class... Types>
constexpr const T&& get(const tuple<Types...>&& t) noexcept;
template<class... TTypes, class... UTypes>
constexpr bool operator==(const tuple<TTypes...>&, const tuple<UTypes...>&);
template<class... TTypes, class... UTypes>
constexpr bool operator<(const tuple<TTypes...>&, const tuple<UTypes...>&);
template<class... TTypes, class... UTypes>
constexpr bool operator!=(const tuple<TTypes...>&, const tuple<UTypes...>&);
template<class... TTypes, class... UTypes>
constexpr bool operator>(const tuple<TTypes...>&, const tuple<UTypes...>&);
template<class... TTypes, class... UTypes>
constexpr bool operator<=(const tuple<TTypes...>&, const tuple<UTypes...>&);
template<class... TTypes, class... UTypes>
constexpr bool operator>=(const tuple<TTypes...>&, const tuple<UTypes...>&);
template <class... Types, class Alloc>
struct uses_allocator<tuple<Types...>, Alloc>;
template <class... Types>
void swap(tuple<Types...>& x, tuple<Types...>& y) noexcept(see below);
template <class T>
inline constexpr size_t tuple_size_v = tuple_size<T>::value;
}