include/tuple

// -*- C++ -*-
//===--------------------------- tuple ------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP_TUPLE
#define _LIBCPP_TUPLE

/*
 tuple synopsis

namespace std
{

template <class... T>
class tuple {
public:
 constexpr tuple();
 explicit tuple(const T&...); // constexpr in C++14
 template <class... U>
 explicit tuple(U&&...); // constexpr in C++14
 tuple(const tuple&) = default;
 tuple(tuple&&) = default;
 template <class... U>
 tuple(const tuple<U...>&); // constexpr in C++14
 template <class... U>
 tuple(tuple<U...>&&); // constexpr in C++14
 template <class U1, class U2>
 tuple(const pair<U1, U2>&); // iff sizeof...(T) == 2 // constexpr in C++14
 template <class U1, class U2>
 tuple(pair<U1, U2>&&); // iff sizeof...(T) == 2 // constexpr in C++14

 // allocator-extended constructors
 template <class Alloc>
 tuple(allocator_arg_t, const Alloc& a);
 template <class Alloc>
 tuple(allocator_arg_t, const Alloc& a, const T&...);
 template <class Alloc, class... U>
 tuple(allocator_arg_t, const Alloc& a, U&&...);
 template <class Alloc>
 tuple(allocator_arg_t, const Alloc& a, const tuple&);
 template <class Alloc>
 tuple(allocator_arg_t, const Alloc& a, tuple&&);
 template <class Alloc, class... U>
 tuple(allocator_arg_t, const Alloc& a, const tuple<U...>&);
 template <class Alloc, class... U>
 tuple(allocator_arg_t, const Alloc& a, tuple<U...>&&);
 template <class Alloc, class U1, class U2>
 tuple(allocator_arg_t, const Alloc& a, const pair<U1, U2>&);
 template <class Alloc, class U1, class U2>
 tuple(allocator_arg_t, const Alloc& a, pair<U1, U2>&&);

 tuple& operator=(const tuple&);
 tuple&
 operator=(tuple&&) noexcept(AND(is_nothrow_move_assignable<T>::value ...));
 template <class... U>
 tuple& operator=(const tuple<U...>&);
 template <class... U>
 tuple& operator=(tuple<U...>&&);
 template <class U1, class U2>
 tuple& operator=(const pair<U1, U2>&); // iff sizeof...(T) == 2
 template <class U1, class U2>
 tuple& operator=(pair<U1, U2>&&); //iffsizeof...(T) == 2

 void swap(tuple&) noexcept(AND(swap(declval<T&>(), declval<T&>())...));
};

const unspecified ignore;

template <class... T> tuple<V...> make_tuple(T&&...); // constexpr in C++14
template <class... T> tuple<ATypes...> forward_as_tuple(T&&...) noexcept;
template <class... T> tuple<T&...> tie(T&...) noexcept;
template <class... Tuples> tuple<CTypes...> tuple_cat(Tuples&&... tpls); // constexpr in C++14
 
// 20.4.1.4, tuple helper classes:
template <class T> class tuple_size; // undefined
template <class... T> class tuple_size<tuple<T...>>;
template <intsize_t I, class T> class tuple_element; // undefined
template <intsize_t I, class... T> class tuple_element<I, tuple<T...>>;

// 20.4.1.5, element access:
template <intsize_t I, class... T>
 typename tuple_element<I, tuple<T...>>::type&
 get(tuple<T...>&) noexcept; // constexpr in C++14
template <intsize_t I, class... T>
 typename tuple_element<I, tuple<T...>>::type const&
 get(const tuple<T...>&) noexcept; // constexpr in C++14
template <intsize_t I, class... T>
 typename tuple_element<I, tuple<T...>>::type&&
 get(tuple<T...>&&) noexcept; // constexpr in C++14

template <class T1, class... T>
 constexpr T1& get(tuple<T...>&) noexcept; // C++14
template <class T1, class... T>
 constexpr T1 const& get(const tuple<T...>&) noexcept; // C++14
template <class T1, class... T>
 constexpr T1&& get(tuple<T...>&&) noexcept; // C++14

// 20.4.1.6, relational operators:
template<class... T, class... U> bool operator==(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
template<class... T, class... U> bool operator<(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
template<class... T, class... U> bool operator!=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
template<class... T, class... U> bool operator>(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
template<class... T, class... U> bool operator<=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
template<class... T, class... U> bool operator>=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14

template <class... Types, class Alloc>
 struct uses_allocator<tuple<Types...>, Alloc>;

template <class... Types>
 void
 swap(tuple<Types...>& x, tuple<Types...>& y) noexcept(noexcept(x.swap(y)));

} // std

*/

#include <__config>
#include <__tuple>
#include <cstddef>
#include <type_traits>
#include <__functional_base>
#include <utility>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
#endif

_LIBCPP_BEGIN_NAMESPACE_STD

// allocator_arg_t

struct _LIBCPP_TYPE_VIS allocator_arg_t { };

#if defined(_LIBCPP_HAS_NO_CONSTEXPR) || defined(_LIBCPP_BUILDING_MEMORY)
extern const allocator_arg_t allocator_arg;
#else
constexpr allocator_arg_t allocator_arg = allocator_arg_t();
#endif

// uses_allocator

template <class _Tp>
struct __has_allocator_type
{
private:
 struct __two {char __lx; char __lxx;};
 template <class _Up> static __two __test(...);
 template <class _Up> static char __test(typename _Up::allocator_type* = 0);
public:
 static const bool value = sizeof(__test<_Tp>(0)) == 1;
};

template <class _Tp, class _Alloc, bool = __has_allocator_type<_Tp>::value>
struct __uses_allocator
 : public integral_constant<bool,
 is_convertible<_Alloc, typename _Tp::allocator_type>::value>
{
};

template <class _Tp, class _Alloc>
struct __uses_allocator<_Tp, _Alloc, false>
 : public false_type
{
};

template <class _Tp, class _Alloc>
struct _LIBCPP_TYPE_VIS uses_allocator
 : public __uses_allocator<_Tp, _Alloc>
{
};

#ifndef _LIBCPP_HAS_NO_VARIADICS

// uses-allocator construction

template <class _Tp, class _Alloc, class ..._Args>
struct __uses_alloc_ctor_imp
{
 static const bool __ua = uses_allocator<_Tp, _Alloc>::value;
 static const bool __ic =
 is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value;
 static const int value = __ua ? 2 - __ic : 0;
};

template <class _Tp, class _Alloc, class ..._Args>
struct __uses_alloc_ctor
 : integral_constant<int, __uses_alloc_ctor_imp<_Tp, _Alloc, _Args...>::value>
 {};

#endif // _LIBCPP_HAS_NO_VARIADICS

#ifndef _LIBCPP_HAS_NO_VARIADICS

// tuple_size

template <class ..._Tp>
class _LIBCPP_TYPE_VIS tuple_size<tuple<_Tp...> >
 : public integral_constant<size_t, sizeof...(_Tp)>
{
};

// tuple_element

template <size_t _Ip, class ..._Tp>
class _LIBCPP_TYPE_VIS tuple_element<_Ip, tuple<_Tp...> >
{
public:
 typedef typename tuple_element<_Ip, __tuple_types<_Tp...> >::type type;
};

// __tuple_leaf

template <size_t _Ip, class _Hp, bool=is_empty<_Hp>::value
#if __has_feature(is_final)
 && !__is_final(_Hp)
#endif
 >
class __tuple_leaf;

template <size_t _Ip, class _Hp, bool _Ep>
inline _LIBCPP_INLINE_VISIBILITY
void swap(__tuple_leaf<_Ip, _Hp, _Ep>& __x, __tuple_leaf<_Ip, _Hp, _Ep>& __y)
 _NOEXCEPT_(__is_nothrow_swappable<_Hp>::value)
{
 swap(__x.get(), __y.get());
}

template <size_t _Ip, class _Hp, bool>
class __tuple_leaf
{
 _Hp value;

 __tuple_leaf& operator=(const __tuple_leaf&);
public:
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __tuple_leaf()
 _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : value()
 {static_assert(!is_reference<_Hp>::value,
 "Attempted to default construct a reference element in a tuple");}

 template <class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 __tuple_leaf(integral_constant<int, 0>, const _Alloc&)
 : value()
 {static_assert(!is_reference<_Hp>::value,
 "Attempted to default construct a reference element in a tuple");}

 template <class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
 : value(allocator_arg_t(), __a)
 {static_assert(!is_reference<_Hp>::value,
 "Attempted to default construct a reference element in a tuple");}

 template <class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
 : value(__a)
 {static_assert(!is_reference<_Hp>::value,
 "Attempted to default construct a reference element in a tuple");}

 template <class _Tp,
 class = typename enable_if<is_constructible<_Hp, _Tp>::value>::type>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
 : value(_VSTD::forward<_Tp>(__t))
 {static_assert(!is_reference<_Hp>::value ||
 (is_lvalue_reference<_Hp>::value &&
 (is_lvalue_reference<_Tp>::value ||
 is_same<typename remove_reference<_Tp>::type,
 reference_wrapper<
 typename remove_reference<_Hp>::type
 >
 >::value)) ||
 (is_rvalue_reference<_Hp>::value &&
 !is_lvalue_reference<_Tp>::value),
 "Attempted to construct a reference element in a tuple with an rvalue");}

 template <class _Tp, class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
 : value(_VSTD::forward<_Tp>(__t))
 {static_assert(!is_lvalue_reference<_Hp>::value ||
 (is_lvalue_reference<_Hp>::value &&
 (is_lvalue_reference<_Tp>::value ||
 is_same<typename remove_reference<_Tp>::type,
 reference_wrapper<
 typename remove_reference<_Hp>::type
 >
 >::value)),
 "Attempted to construct a reference element in a tuple with an rvalue");}

 template <class _Tp, class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
 : value(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t))
 {static_assert(!is_lvalue_reference<_Hp>::value ||
 (is_lvalue_reference<_Hp>::value &&
 (is_lvalue_reference<_Tp>::value ||
 is_same<typename remove_reference<_Tp>::type,
 reference_wrapper<
 typename remove_reference<_Hp>::type
 >
 >::value)),
 "Attempted to construct a reference element in a tuple with an rvalue");}

 template <class _Tp, class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
 : value(_VSTD::forward<_Tp>(__t), __a)
 {static_assert(!is_lvalue_reference<_Hp>::value ||
 (is_lvalue_reference<_Hp>::value &&
 (is_lvalue_reference<_Tp>::value ||
 is_same<typename remove_reference<_Tp>::type,
 reference_wrapper<
 typename remove_reference<_Hp>::type
 >
 >::value)),
 "Attempted to construct a reference element in a tuple with an rvalue");}

 _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR_AFTER_CXX11
 __tuple_leaf(const __tuple_leaf& __t) _NOEXCEPT_(is_nothrow_copy_constructible<_Hp>::value)
 : value(__t.get())
 {static_assert(!is_rvalue_reference<_Hp>::value, "Can not copy a tuple with rvalue reference member");}

 _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR_AFTER_CXX11
 __tuple_leaf(__tuple_leaf&& __t) _NOEXCEPT_(is_nothrow_move_constructible<_Hp>::value)
 : value(_VSTD::move(__t.get()))
 {}

 template <class _Tp>
 _LIBCPP_INLINE_VISIBILITY
 __tuple_leaf&
 operator=(_Tp&& __t) _NOEXCEPT_((is_nothrow_assignable<_Hp&, _Tp>::value))
 {
 value = _VSTD::forward<_Tp>(__t);
 return *this;
 }

 _LIBCPP_INLINE_VISIBILITY
 int swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value)
 {
 _VSTD::swap(*this, __t);
 return 0;
 }

 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 _Hp& get() _NOEXCEPT {return value;}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return value;}
};

template <size_t _Ip, class _Hp>
class __tuple_leaf<_Ip, _Hp, true>
 : private _Hp
{

 __tuple_leaf& operator=(const __tuple_leaf&);
public:
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __tuple_leaf()
 _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) {}

 template <class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 __tuple_leaf(integral_constant<int, 0>, const _Alloc&) {}

 template <class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
 : _Hp(allocator_arg_t(), __a) {}

 template <class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
 : _Hp(__a) {}

 template <class _Tp,
 class = typename enable_if<is_constructible<_Hp, _Tp>::value>::type>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
 : _Hp(_VSTD::forward<_Tp>(__t)) {}

 template <class _Tp, class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
 : _Hp(_VSTD::forward<_Tp>(__t)) {}

 template <class _Tp, class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
 : _Hp(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t)) {}

 template <class _Tp, class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
 : _Hp(_VSTD::forward<_Tp>(__t), __a) {}

 template <class _Tp>
 _LIBCPP_INLINE_VISIBILITY
 __tuple_leaf&
 operator=(_Tp&& __t) _NOEXCEPT_((is_nothrow_assignable<_Hp&, _Tp>::value))
 {
 _Hp::operator=(_VSTD::forward<_Tp>(__t));
 return *this;
 }

 _LIBCPP_INLINE_VISIBILITY
 int
 swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value)
 {
 _VSTD::swap(*this, __t);
 return 0;
 }

 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 _Hp& get() _NOEXCEPT {return static_cast<_Hp&>(*this);}
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return static_cast<const _Hp&>(*this);}
};

template <class ..._Tp>
_LIBCPP_INLINE_VISIBILITY
void __swallow(_Tp&&...) _NOEXCEPT {}

template <bool ...> struct __all;

template <>
struct __all<>
{
 static const bool value = true;
};

template <bool _B0, bool ... _Bp>
struct __all<_B0, _Bp...>
{
 static const bool value = _B0 && __all<_Bp...>::value;
};

// __tuple_impl

template<class _Indx, class ..._Tp> struct __tuple_impl;

template<size_t ..._Indx, class ..._Tp>
struct __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
 : public __tuple_leaf<_Indx, _Tp>...
{
 _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR __tuple_impl()
 _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}

 template <size_t ..._Uf, class ..._Tf,
 size_t ..._Ul, class ..._Tl, class ..._Up>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 explicit
 __tuple_impl(__tuple_indices<_Uf...>, __tuple_types<_Tf...>,
 __tuple_indices<_Ul...>, __tuple_types<_Tl...>,
 _Up&&... __u)
 _NOEXCEPT_((__all<is_nothrow_constructible<_Tf, _Up>::value...>::value &&
 __all<is_nothrow_default_constructible<_Tl>::value...>::value)) :
 __tuple_leaf<_Uf, _Tf>(_VSTD::forward<_Up>(__u))...,
 __tuple_leaf<_Ul, _Tl>()...
 {}

 template <class _Alloc, size_t ..._Uf, class ..._Tf,
 size_t ..._Ul, class ..._Tl, class ..._Up>
 _LIBCPP_INLINE_VISIBILITY
 explicit
 __tuple_impl(allocator_arg_t, const _Alloc& __a,
 __tuple_indices<_Uf...>, __tuple_types<_Tf...>,
 __tuple_indices<_Ul...>, __tuple_types<_Tl...>,
 _Up&&... __u) :
 __tuple_leaf<_Uf, _Tf>(__uses_alloc_ctor<_Tf, _Alloc, _Up>(), __a,
 _VSTD::forward<_Up>(__u))...,
 __tuple_leaf<_Ul, _Tl>(__uses_alloc_ctor<_Tl, _Alloc>(), __a)...
 {}

 template <class _Tuple,
 class = typename enable_if
 <
 __tuple_constructible<_Tuple, tuple<_Tp...> >::value
 >::type
 >
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 __tuple_impl(_Tuple&& __t) _NOEXCEPT_((__all<is_nothrow_constructible<_Tp, typename tuple_element<_Indx,
 typename __make_tuple_types<_Tuple>::type>::type>::value...>::value))
 : __tuple_leaf<_Indx, _Tp>(_VSTD::forward<typename tuple_element<_Indx,
 typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...
 {}

 template <class _Alloc, class _Tuple,
 class = typename enable_if
 <
 __tuple_convertible<_Tuple, tuple<_Tp...> >::value
 >::type
 >
 _LIBCPP_INLINE_VISIBILITY
 __tuple_impl(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
 : __tuple_leaf<_Indx, _Tp>(__uses_alloc_ctor<_Tp, _Alloc, typename tuple_element<_Indx,
 typename __make_tuple_types<_Tuple>::type>::type>(), __a,
 _VSTD::forward<typename tuple_element<_Indx,
 typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...
 {}

 template <class _Tuple>
 _LIBCPP_INLINE_VISIBILITY
 typename enable_if
 <
 __tuple_assignable<_Tuple, tuple<_Tp...> >::value,
 __tuple_impl&
 >::type
 operator=(_Tuple&& __t) _NOEXCEPT_((__all<is_nothrow_assignable<_Tp&, typename tuple_element<_Indx,
 typename __make_tuple_types<_Tuple>::type>::type>::value...>::value))
 {
 __swallow(__tuple_leaf<_Indx, _Tp>::operator=(_VSTD::forward<typename tuple_element<_Indx,
 typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...);
 return *this;
 }

 _LIBCPP_INLINE_VISIBILITY
 __tuple_impl&
 operator=(const __tuple_impl& __t) _NOEXCEPT_((__all<is_nothrow_copy_assignable<_Tp>::value...>::value))
 {
 __swallow(__tuple_leaf<_Indx, _Tp>::operator=(static_cast<const __tuple_leaf<_Indx, _Tp>&>(__t).get())...);
 return *this;
 }

 _LIBCPP_INLINE_VISIBILITY
 void swap(__tuple_impl& __t)
 _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
 {
 __swallow(__tuple_leaf<_Indx, _Tp>::swap(static_cast<__tuple_leaf<_Indx, _Tp>&>(__t))...);
 }
};

template <class ..._Tp>
class _LIBCPP_TYPE_VIS tuple
{
 typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> base;

 base base_;

 template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Jp, tuple<_Up...> >::type& get(tuple<_Up...>&) _NOEXCEPT;
 template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
 const typename tuple_element<_Jp, tuple<_Up...> >::type& get(const tuple<_Up...>&) _NOEXCEPT;
 template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Jp, tuple<_Up...> >::type&& get(tuple<_Up...>&&) _NOEXCEPT;
public:

 _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR tuple()
 _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}

 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 explicit tuple(const _Tp& ... __t) _NOEXCEPT_((__all<is_nothrow_copy_constructible<_Tp>::value...>::value)) 
 : base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
 typename __make_tuple_indices<0>::type(),
 typename __make_tuple_types<tuple, 0>::type(),
 __t...
 ) {}

 template <class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t)
 : base_(allocator_arg_t(), __a,
 typename __make_tuple_indices<sizeof...(_Tp)>::type(),
 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
 typename __make_tuple_indices<0>::type(),
 typename __make_tuple_types<tuple, 0>::type(),
 __t...
 ) {}

 template <class ..._Up,
 typename enable_if
 <
 sizeof...(_Up) <= sizeof...(_Tp) &&
 __tuple_convertible
 <
 tuple<_Up...>,
 typename __make_tuple_types<tuple,
 sizeof...(_Up) < sizeof...(_Tp) ?
 sizeof...(_Up) :
 sizeof...(_Tp)>::type
 >::value,
 bool
 >::type = false
 >
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 tuple(_Up&&... __u)
 _NOEXCEPT_((
 is_nothrow_constructible<
 typename __make_tuple_indices<sizeof...(_Up)>::type,
 typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
 typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
 typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type,
 _Up...
 >::value
 ))
 : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
 typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
 typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
 typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
 _VSTD::forward<_Up>(__u)...) {}

 template <class ..._Up,
 typename enable_if
 <
 sizeof...(_Up) <= sizeof...(_Tp) &&
 __tuple_constructible
 <
 tuple<_Up...>,
 typename __make_tuple_types<tuple,
 sizeof...(_Up) < sizeof...(_Tp) ?
 sizeof...(_Up) :
 sizeof...(_Tp)>::type
 >::value &&
 !__tuple_convertible
 <
 tuple<_Up...>,
 typename __make_tuple_types<tuple,
 sizeof...(_Up) < sizeof...(_Tp) ?
 sizeof...(_Up) :
 sizeof...(_Tp)>::type
 >::value,
 bool
 >::type =false
 >
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 explicit
 tuple(_Up&&... __u)
 _NOEXCEPT_((
 is_nothrow_constructible<
 typename __make_tuple_indices<sizeof...(_Up)>::type,
 typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
 typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
 typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type,
 _Up...
 >::value
 ))
 : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
 typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
 typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
 typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
 _VSTD::forward<_Up>(__u)...) {}

 template <class _Alloc, class ..._Up,
 class = typename enable_if
 <
 sizeof...(_Up) <= sizeof...(_Tp) &&
 __tuple_convertible
 <
 tuple<_Up...>,
 typename __make_tuple_types<tuple,
 sizeof...(_Up) < sizeof...(_Tp) ?
 sizeof...(_Up) :
 sizeof...(_Tp)>::type
 >::value
 >::type
 >
 _LIBCPP_INLINE_VISIBILITY
 tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
 : base_(allocator_arg_t(), __a,
 typename __make_tuple_indices<sizeof...(_Up)>::type(),
 typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
 typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
 typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
 _VSTD::forward<_Up>(__u)...) {}

 template <class _Tuple,
 typename enable_if
 <
 __tuple_convertible<_Tuple, tuple>::value,
 bool
 >::type = false
 >
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
 : base_(_VSTD::forward<_Tuple>(__t)) {}

 template <class _Tuple,
 typename enable_if
 <
 __tuple_constructible<_Tuple, tuple>::value &&
 !__tuple_convertible<_Tuple, tuple>::value,
 bool
 >::type = false
 >
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 explicit
 tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
 : base_(_VSTD::forward<_Tuple>(__t)) {}

 template <class _Alloc, class _Tuple,
 class = typename enable_if
 <
 __tuple_convertible<_Tuple, tuple>::value
 >::type
 >
 _LIBCPP_INLINE_VISIBILITY
 tuple(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
 : base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}

 template <class _Tuple,
 class = typename enable_if
 <
 __tuple_assignable<_Tuple, tuple>::value
 >::type
 >
 _LIBCPP_INLINE_VISIBILITY
 tuple&
 operator=(_Tuple&& __t) _NOEXCEPT_((is_nothrow_assignable<base&, _Tuple>::value))
 {
 base_.operator=(_VSTD::forward<_Tuple>(__t));
 return *this;
 }

 _LIBCPP_INLINE_VISIBILITY
 void swap(tuple& __t) _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
 {base_.swap(__t.base_);}
};

template <>
class _LIBCPP_TYPE_VIS tuple<>
{
public:
 _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR tuple() _NOEXCEPT {}
 template <class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 tuple(allocator_arg_t, const _Alloc&) _NOEXCEPT {}
 template <class _Alloc>
 _LIBCPP_INLINE_VISIBILITY
 tuple(allocator_arg_t, const _Alloc&, const tuple&) _NOEXCEPT {}
 template <class _Up>
 _LIBCPP_INLINE_VISIBILITY
 tuple(array<_Up, 0>) _NOEXCEPT {}
 template <class _Alloc, class _Up>
 _LIBCPP_INLINE_VISIBILITY
 tuple(allocator_arg_t, const _Alloc&, array<_Up, 0>) _NOEXCEPT {}
 _LIBCPP_INLINE_VISIBILITY
 void swap(tuple&) _NOEXCEPT {}
};

template <class ..._Tp>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
<
 __all<__is_swappable<_Tp>::value...>::value,
 void
>::type
swap(tuple<_Tp...>& __t, tuple<_Tp...>& __u)
 _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
 {__t.swap(__u);}

// get

template <size_t _Ip, class ..._Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
typename tuple_element<_Ip, tuple<_Tp...> >::type&
get(tuple<_Tp...>& __t) _NOEXCEPT
{
 typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
 return static_cast<__tuple_leaf<_Ip, type>&>(__t.base_).get();
}

template <size_t _Ip, class ..._Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
const typename tuple_element<_Ip, tuple<_Tp...> >::type&
get(const tuple<_Tp...>& __t) _NOEXCEPT
{
 typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
 return static_cast<const __tuple_leaf<_Ip, type>&>(__t.base_).get();
}

template <size_t _Ip, class ..._Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
typename tuple_element<_Ip, tuple<_Tp...> >::type&&
get(tuple<_Tp...>&& __t) _NOEXCEPT
{
 typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
 return static_cast<type&&>(
 static_cast<__tuple_leaf<_Ip, type>&&>(__t.base_).get());
}

#if _LIBCPP_STD_VER > 11
// get by type
template <typename _T1, size_t _Idx, typename... _Args>
struct __find_exactly_one_t_helper;

// -- find exactly one
template <typename _T1, size_t _Idx, typename... _Args>
struct __find_exactly_one_t_checker {
 static constexpr size_t value = _Idx;
// Check the rest of the list to make sure there's only one
 static_assert ( __find_exactly_one_t_helper<_T1, 0, _Args...>::value == -1, "type can only occur once in type list" );
 };


template <typename _T1, size_t _Idx>
struct __find_exactly_one_t_helper <_T1, _Idx> {
 static constexpr size_t value = -1;
 };

template <typename _T1, size_t _Idx, typename _Head, typename... _Args>
struct __find_exactly_one_t_helper <_T1, _Idx, _Head, _Args...> {
 static constexpr size_t value =
 std::conditional<
 std::is_same<_T1, _Head>::value,
 __find_exactly_one_t_checker<_T1, _Idx,   _Args...>,
 __find_exactly_one_t_helper <_T1, _Idx+1, _Args...>
 >::type::value;
 };

template <typename _T1, typename... _Args>
struct __find_exactly_one_t {
 static constexpr size_t value = __find_exactly_one_t_helper<_T1, 0, _Args...>::value;
 static_assert ( value != -1, "type not found in type list" );
 };

template <class _T1, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
constexpr _T1& get(tuple<_Args...>& __tup) noexcept
{
 return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(__tup);
}

template <class _T1, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
constexpr _T1 const& get(tuple<_Args...> const& __tup) noexcept
{
 return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(__tup);
}

template <class _T1, class... _Args>
inline _LIBCPP_INLINE_VISIBILITY
constexpr _T1&& get(tuple<_Args...>&& __tup) noexcept
{
 return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(_VSTD::move(__tup));
}

#endif

// tie

template <class ..._Tp>
inline _LIBCPP_INLINE_VISIBILITY
tuple<_Tp&...>
tie(_Tp&... __t) _NOEXCEPT
{
 return tuple<_Tp&...>(__t...);
}

template <class _Up>
struct __ignore_t
{
 template <class _Tp>
 _LIBCPP_INLINE_VISIBILITY
 const __ignore_t& operator=(_Tp&&) const {return *this;}
};

namespace { const __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>(); }

template <class _Tp> class _LIBCPP_TYPE_VIS reference_wrapper;

template <class _Tp>
struct ___make_tuple_return
{
 typedef _Tp type;
};

template <class _Tp>
struct ___make_tuple_return<reference_wrapper<_Tp> >
{
 typedef _Tp& type;
};

template <class _Tp>
struct __make_tuple_return
{
 typedef typename ___make_tuple_return<typename decay<_Tp>::type>::type type;
};

template <class... _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
tuple<typename __make_tuple_return<_Tp>::type...>
make_tuple(_Tp&&... __t)
{
 return tuple<typename __make_tuple_return<_Tp>::type...>(_VSTD::forward<_Tp>(__t)...);
}

template <class... _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
tuple<_Tp&&...>
__forward_as_tuple(_Tp&&... __t) _NOEXCEPT
{
 return tuple<_Tp&&...>(_VSTD::forward<_Tp>(__t)...);
}

template <class... _Tp>
inline _LIBCPP_INLINE_VISIBILITY
tuple<_Tp&&...>
forward_as_tuple(_Tp&&... __t) _NOEXCEPT
{
 return tuple<_Tp&&...>(_VSTD::forward<_Tp>(__t)...);
}

template <size_t _Ip>
struct __tuple_equal
{
 template <class _Tp, class _Up>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool operator()(const _Tp& __x, const _Up& __y)
 {
 return __tuple_equal<_Ip - 1>()(__x, __y) && get<_Ip-1>(__x) == get<_Ip-1>(__y);
 }
};

template <>
struct __tuple_equal<0>
{
 template <class _Tp, class _Up>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool operator()(const _Tp&, const _Up&)
 {
 return true;
 }
};

template <class ..._Tp, class ..._Up>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator==(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
{
 return __tuple_equal<sizeof...(_Tp)>()(__x, __y);
}

template <class ..._Tp, class ..._Up>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator!=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
{
 return !(__x == __y);
}

template <size_t _Ip>
struct __tuple_less
{
 template <class _Tp, class _Up>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool operator()(const _Tp& __x, const _Up& __y)
 {
 return __tuple_less<_Ip-1>()(__x, __y) ||
 (!__tuple_less<_Ip-1>()(__y, __x) && get<_Ip-1>(__x) < get<_Ip-1>(__y));
 }
};

template <>
struct __tuple_less<0>
{
 template <class _Tp, class _Up>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool operator()(const _Tp&, const _Up&)
 {
 return false;
 }
};

template <class ..._Tp, class ..._Up>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator<(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
{
 return __tuple_less<sizeof...(_Tp)>()(__x, __y);
}

template <class ..._Tp, class ..._Up>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator>(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
{
 return __y < __x;
}

template <class ..._Tp, class ..._Up>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator>=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
{
 return !(__x < __y);
}

template <class ..._Tp, class ..._Up>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
bool
operator<=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
{
 return !(__y < __x);
}

// tuple_cat

template <class _Tp, class _Up> struct __tuple_cat_type;

template <class ..._Ttypes, class ..._Utypes>
struct __tuple_cat_type<tuple<_Ttypes...>, __tuple_types<_Utypes...> >
{
 typedef tuple<_Ttypes..., _Utypes...> type;
};

template <class _ResultTuple, bool _Is_Tuple0TupleLike, class ..._Tuples>
struct __tuple_cat_return_1
{
};

template <class ..._Types, class _Tuple0>
struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0>
{
 typedef typename __tuple_cat_type<tuple<_Types...>,
 typename __make_tuple_types<typename remove_reference<_Tuple0>::type>::type>::type
 type;
};

template <class ..._Types, class _Tuple0, class _Tuple1, class ..._Tuples>
struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0, _Tuple1, _Tuples...>
 : public __tuple_cat_return_1<
 typename __tuple_cat_type<
 tuple<_Types...>,
 typename __make_tuple_types<typename remove_reference<_Tuple0>::type>::type
 >::type,
 __tuple_like<typename remove_reference<_Tuple1>::type>::value,
 _Tuple1, _Tuples...>
{
};

template <class ..._Tuples> struct __tuple_cat_return;

template <class _Tuple0, class ..._Tuples>
struct __tuple_cat_return<_Tuple0, _Tuples...>
 : public __tuple_cat_return_1<tuple<>,
 __tuple_like<typename remove_reference<_Tuple0>::type>::value, _Tuple0,
 _Tuples...>
{
};

template <>
struct __tuple_cat_return<>
{
 typedef tuple<> type;
};

inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
tuple<>
tuple_cat()
{
 return tuple<>();
}

template <class _Rp, class _Indices, class _Tuple0, class ..._Tuples>
struct __tuple_cat_return_ref_imp;

template <class ..._Types, size_t ..._I0, class _Tuple0>
struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>, _Tuple0>
{
 typedef typename remove_reference<_Tuple0>::type _T0;
 typedef tuple<_Types..., typename __apply_cv<_Tuple0,
 typename tuple_element<_I0, _T0>::type>::type&&...> type;
};

template <class ..._Types, size_t ..._I0, class _Tuple0, class _Tuple1, class ..._Tuples>
struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>,
 _Tuple0, _Tuple1, _Tuples...>
 : public __tuple_cat_return_ref_imp<
 tuple<_Types..., typename __apply_cv<_Tuple0,
 typename tuple_element<_I0,
 typename remove_reference<_Tuple0>::type>::type>::type&&...>,
 typename __make_tuple_indices<tuple_size<typename
 remove_reference<_Tuple1>::type>::value>::type,
 _Tuple1, _Tuples...>
{
};

template <class _Tuple0, class ..._Tuples>
struct __tuple_cat_return_ref
 : public __tuple_cat_return_ref_imp<tuple<>,
 typename __make_tuple_indices<
 tuple_size<typename remove_reference<_Tuple0>::type>::value
 >::type, _Tuple0, _Tuples...>
{
};

template <class _Types, class _I0, class _J0>
struct __tuple_cat;

template <class ..._Types, size_t ..._I0, size_t ..._J0>
struct __tuple_cat<tuple<_Types...>, __tuple_indices<_I0...>, __tuple_indices<_J0...> >
{
 template <class _Tuple0>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&>::type
 operator()(tuple<_Types...> __t, _Tuple0&& __t0)
 {
 return __forward_as_tuple(_VSTD::forward<_Types>(get<_I0>(__t))...,
 get<_J0>(_VSTD::forward<_Tuple0>(__t0))...);
 }

 template <class _Tuple0, class _Tuple1, class ..._Tuples>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&, _Tuple1&&, _Tuples&&...>::type
 operator()(tuple<_Types...> __t, _Tuple0&& __t0, _Tuple1&& __t1, _Tuples&& ...__tpls)
 {
 typedef typename remove_reference<_Tuple0>::type _T0;
 typedef typename remove_reference<_Tuple1>::type _T1;
 return __tuple_cat<
 tuple<_Types..., typename __apply_cv<_Tuple0, typename tuple_element<_J0, _T0>::type>::type&&...>,
 typename __make_tuple_indices<sizeof ...(_Types) + tuple_size<_T0>::value>::type,
 typename __make_tuple_indices<tuple_size<_T1>::value>::type>()
 (__forward_as_tuple(
 _VSTD::forward<_Types>(get<_I0>(__t))...,
 get<_J0>(_VSTD::forward<_Tuple0>(__t0))...
 ),
 _VSTD::forward<_Tuple1>(__t1),
 _VSTD::forward<_Tuples>(__tpls)...);
 }
};

template <class _Tuple0, class... _Tuples>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
typename __tuple_cat_return<_Tuple0, _Tuples...>::type
tuple_cat(_Tuple0&& __t0, _Tuples&&... __tpls)
{
 typedef typename remove_reference<_Tuple0>::type _T0;
 return __tuple_cat<tuple<>, __tuple_indices<>,
 typename __make_tuple_indices<tuple_size<_T0>::value>::type>()
 (tuple<>(), _VSTD::forward<_Tuple0>(__t0),
 _VSTD::forward<_Tuples>(__tpls)...);
}

template <class ..._Tp, class _Alloc>
struct _LIBCPP_TYPE_VIS uses_allocator<tuple<_Tp...>, _Alloc>
 : true_type {};

template <class _T1, class _T2>
template <class... _Args1, class... _Args2, size_t ..._I1, size_t ..._I2>
inline _LIBCPP_INLINE_VISIBILITY
pair<_T1, _T2>::pair(piecewise_construct_t,
 tuple<_Args1...>& __first_args, tuple<_Args2...>& __second_args,
 __tuple_indices<_I1...>, __tuple_indices<_I2...>)
 : first(_VSTD::forward<_Args1>(get<_I1>( __first_args))...),
 second(_VSTD::forward<_Args2>(get<_I2>(__second_args))...)
{
}

#endif // _LIBCPP_HAS_NO_VARIADICS

_LIBCPP_END_NAMESPACE_STD

#endif // _LIBCPP_TUPLE