From fe1ccca2776129541f1c4f645e4d1de89a22a031 Mon Sep 17 00:00:00 2001
From: patrick <patrick@openbsd.org>
Date: Sat, 3 Sep 2016 18:39:32 +0000
Subject: Import libc++ 3.9.0

---
 lib/libcxx/include/tuple | 1418 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1418 insertions(+)
 create mode 100644 lib/libcxx/include/tuple

(limited to 'lib/libcxx/include/tuple')

diff --git a/lib/libcxx/include/tuple b/lib/libcxx/include/tuple
new file mode 100644
index 00000000000..6805d8c7635
--- /dev/null
+++ b/lib/libcxx/include/tuple
@@ -0,0 +1,1418 @@
+// -*- 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; // constexpr in C++14
+template <class... T> tuple<T&...> tie(T&...) noexcept; // constexpr in C++14
+template <class... Tuples> tuple<CTypes...> tuple_cat(Tuples&&... tpls); // constexpr in C++14
+
+// [tuple.apply], calling a function with a tuple of arguments:
+template <class F, class Tuple>
+  constexpr decltype(auto) apply(F&& f, Tuple&& t); // C++17
+template <class T, class Tuple>
+  constexpr T make_from_tuple(Tuple&& t); // C++17
+
+// 20.4.1.4, tuple helper classes:
+template <class T> class tuple_size; // undefined
+template <class... T> class tuple_size<tuple<T...>>;
+template <class T>
+ constexpr size_t tuple_size_v = tuple_size<T>::value; // C++17
+template <size_t I, class T> class tuple_element; // undefined
+template <size_t I, class... T> class tuple_element<I, tuple<T...>>;
+template <size_t I, class T>
+  using tuple_element_t = typename tuple_element <I, T>::type; // C++14
+
+// 20.4.1.5, element access:
+template <size_t I, class... T>
+    typename tuple_element<I, tuple<T...>>::type&
+    get(tuple<T...>&) noexcept; // constexpr in C++14
+template <size_t I, class... T>
+    const typename tuple_element<I, tuple<T...>>::type&
+    get(const tuple<T...>&) noexcept; // constexpr in C++14
+template <size_t I, class... T>
+    typename tuple_element<I, tuple<T...>>::type&&
+    get(tuple<T...>&&) noexcept; // constexpr in C++14
+template <size_t I, class... T>
+    const typename tuple_element<I, tuple<T...>>::type&&
+    get(const 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 const T1& get(const tuple<T...>&) noexcept;   // C++14
+template <class T1, class... T>
+    constexpr T1&& get(tuple<T...>&&) noexcept;   // C++14
+template <class T1, class... T>
+    constexpr const T1&& get(const 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
+
+#ifndef _LIBCPP_HAS_NO_VARIADICS
+
+// tuple_size
+
+template <class ..._Tp>
+class _LIBCPP_TYPE_VIS_ONLY tuple_size<tuple<_Tp...> >
+    : public integral_constant<size_t, sizeof...(_Tp)>
+{
+};
+
+// tuple_element
+
+template <size_t _Ip, class ..._Tp>
+class _LIBCPP_TYPE_VIS_ONLY tuple_element<_Ip, tuple<_Tp...> >
+{
+public:
+    typedef typename tuple_element<_Ip, __tuple_types<_Tp...> >::type type;
+};
+
+#if _LIBCPP_STD_VER > 11
+template <size_t _Ip, class ..._Tp>
+using tuple_element_t = typename tuple_element <_Ip, _Tp...>::type;
+#endif
+
+// __tuple_leaf
+
+template <size_t _Ip, class _Hp,
+          bool=is_empty<_Hp>::value && !__libcpp_is_final<_Hp>::value
+         >
+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<
+                  __lazy_and<
+                      __lazy_not<is_same<typename decay<_Tp>::type, __tuple_leaf>>
+                    , 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");}
+
+    __tuple_leaf(const __tuple_leaf& __t) = default;
+    __tuple_leaf(__tuple_leaf&& __t) = default;
+
+    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<
+                  __lazy_and<
+                        __lazy_not<is_same<typename decay<_Tp>::type, __tuple_leaf>>
+                      , 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) {}
+
+    __tuple_leaf(__tuple_leaf const &) = default;
+    __tuple_leaf(__tuple_leaf &&) = default;
+
+    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 <class ..._Tp>
+struct __lazy_all : __all<_Tp::value...> {};
+
+template <class _Tp>
+struct __all_default_constructible;
+
+template <class ..._Tp>
+struct __all_default_constructible<__tuple_types<_Tp...>>
+    : __all<is_default_constructible<_Tp>::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_constructible<_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;
+        }
+
+    __tuple_impl(const __tuple_impl&) = default;
+    __tuple_impl(__tuple_impl&&) = default;
+
+    _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
+    __tuple_impl&
+    operator=(__tuple_impl&& __t) _NOEXCEPT_((__all<is_nothrow_move_assignable<_Tp>::value...>::value))
+    {
+        __swallow(__tuple_leaf<_Indx, _Tp>::operator=(_VSTD::forward<_Tp>(static_cast<__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 <bool _IsTuple, class _SizeTrait, size_t _Expected>
+struct __tuple_like_with_size_imp : false_type {};
+
+template <class _SizeTrait, size_t _Expected>
+struct __tuple_like_with_size_imp<true, _SizeTrait, _Expected>
+    : integral_constant<bool, _SizeTrait::value == _Expected> {};
+
+template <class _Tuple, size_t _ExpectedSize,
+          class _RawTuple = typename __uncvref<_Tuple>::type>
+using __tuple_like_with_size = __tuple_like_with_size_imp<
+                                   __tuple_like<_RawTuple>::value,
+                                   tuple_size<_RawTuple>, _ExpectedSize
+                              >;
+
+
+struct _LIBCPP_TYPE_VIS __check_tuple_constructor_fail {
+    template <class ...>
+    static constexpr bool __enable_explicit() { return false; }
+    template <class ...>
+    static constexpr bool __enable_implicit() { return false; }
+};
+
+template <class ..._Tp>
+class _LIBCPP_TYPE_VIS_ONLY tuple
+{
+    typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> base;
+
+    base base_;
+
+    template <class ..._Args>
+    struct _PackExpandsToThisTuple : false_type {};
+
+    template <class _Arg>
+    struct _PackExpandsToThisTuple<_Arg>
+        : is_same<typename __uncvref<_Arg>::type, tuple> {};
+
+    template <bool _MaybeEnable, class _Dummy = void>
+    struct _CheckArgsConstructor : __check_tuple_constructor_fail {};
+
+    template <class _Dummy>
+    struct _CheckArgsConstructor<true, _Dummy>
+    {
+        template <class ..._Args>
+        static constexpr bool __enable_explicit() {
+            return
+                __tuple_constructible<
+                    tuple<_Args...>,
+                    typename __make_tuple_types<tuple,
+                             sizeof...(_Args) < sizeof...(_Tp) ?
+                                 sizeof...(_Args) :
+                                 sizeof...(_Tp)>::type
+                >::value &&
+                !__tuple_convertible<
+                    tuple<_Args...>,
+                    typename __make_tuple_types<tuple,
+                             sizeof...(_Args) < sizeof...(_Tp) ?
+                                 sizeof...(_Args) :
+                                 sizeof...(_Tp)>::type
+                >::value &&
+                __all_default_constructible<
+                    typename __make_tuple_types<tuple, sizeof...(_Tp),
+                             sizeof...(_Args) < sizeof...(_Tp) ?
+                                 sizeof...(_Args) :
+                                 sizeof...(_Tp)>::type
+                >::value;
+        }
+
+        template <class ..._Args>
+        static constexpr bool __enable_implicit() {
+            return
+                __tuple_convertible<
+                    tuple<_Args...>,
+                    typename __make_tuple_types<tuple,
+                             sizeof...(_Args) < sizeof...(_Tp) ?
+                                 sizeof...(_Args) :
+                                 sizeof...(_Tp)>::type
+                >::value &&
+                __all_default_constructible<
+                    typename __make_tuple_types<tuple, sizeof...(_Tp),
+                             sizeof...(_Args) < sizeof...(_Tp) ?
+                                 sizeof...(_Args) :
+                                 sizeof...(_Tp)>::type
+                >::value;
+        }
+    };
+
+    template <bool _MaybeEnable,
+              bool = sizeof...(_Tp) == 1,
+              class _Dummy = void>
+    struct _CheckTupleLikeConstructor : __check_tuple_constructor_fail {};
+
+    template <class _Dummy>
+    struct _CheckTupleLikeConstructor<true, false, _Dummy>
+    {
+        template <class _Tuple>
+        static constexpr bool __enable_implicit() {
+            return __tuple_convertible<_Tuple, tuple>::value;
+        }
+
+        template <class _Tuple>
+        static constexpr bool __enable_explicit() {
+            return __tuple_constructible<_Tuple, tuple>::value
+               && !__tuple_convertible<_Tuple, tuple>::value;
+        }
+    };
+
+    template <class _Dummy>
+    struct _CheckTupleLikeConstructor<true, true, _Dummy>
+    {
+        // This trait is used to disable the tuple-like constructor when
+        // the UTypes... constructor should be selected instead.
+        // See LWG issue #2549.
+        template <class _Tuple>
+        using _PreferTupleLikeConstructor = __lazy_or<
+            // Don't attempt the two checks below if the tuple we are given
+            // has the same type as this tuple.
+            is_same<typename __uncvref<_Tuple>::type, tuple>,
+            __lazy_and<
+                __lazy_not<is_constructible<_Tp..., _Tuple>>,
+                __lazy_not<is_convertible<_Tuple, _Tp...>>
+            >
+        >;
+
+        template <class _Tuple>
+        static constexpr bool __enable_implicit() {
+            return __lazy_and<
+                __tuple_convertible<_Tuple, tuple>,
+                _PreferTupleLikeConstructor<_Tuple>
+            >::value;
+        }
+
+        template <class _Tuple>
+        static constexpr bool __enable_explicit() {
+            return __lazy_and<
+                __tuple_constructible<_Tuple, tuple>,
+                _PreferTupleLikeConstructor<_Tuple>,
+                __lazy_not<__tuple_convertible<_Tuple, tuple>>
+            >::value;
+        }
+    };
+
+    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;
+    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
+        const typename tuple_element<_Jp, tuple<_Up...> >::type&& get(const tuple<_Up...>&&) _NOEXCEPT;
+public:
+
+    template <bool _Dummy = true, class = typename enable_if<
+        __all<__dependent_type<is_default_constructible<_Tp>, _Dummy>::value...>::value
+    >::type>
+    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_CONSTEXPR tuple()
+        _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
+
+    template <class _AllocArgT, class _Alloc, bool _Dummy = true, class = typename enable_if<
+        __lazy_and<
+            is_same<allocator_arg_t, _AllocArgT>,
+            __lazy_all<__dependent_type<is_default_constructible<_Tp>, _Dummy>...>
+       >::value
+    >::type>
+    _LIBCPP_INLINE_VISIBILITY
+    tuple(_AllocArgT, _Alloc const& __a)
+      : base_(allocator_arg_t(), __a,
+                    __tuple_indices<>(), __tuple_types<>(),
+                    typename __make_tuple_indices<sizeof...(_Tp), 0>::type(),
+                    __tuple_types<_Tp...>()) {}
+
+    template <bool _Dummy = true,
+              typename enable_if
+                      <
+                         _CheckArgsConstructor<
+                            _Dummy
+                         >::template __enable_implicit<_Tp...>(),
+                         bool
+                      >::type = false
+        >
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    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 <bool _Dummy = true,
+              typename enable_if
+                      <
+                         _CheckArgsConstructor<
+                            _Dummy
+                         >::template __enable_explicit<_Tp...>(),
+                         bool
+                      >::type = false
+        >
+    _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, bool _Dummy = true,
+              typename enable_if
+                      <
+                         _CheckArgsConstructor<
+                            _Dummy
+                         >::template __enable_implicit<_Tp...>(),
+                         bool
+                      >::type = false
+        >
+      _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 _Alloc, bool _Dummy = true,
+              typename enable_if
+                      <
+                         _CheckArgsConstructor<
+                            _Dummy
+                         >::template __enable_explicit<_Tp...>(),
+                         bool
+                      >::type = false
+        >
+      _LIBCPP_INLINE_VISIBILITY
+      explicit
+      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
+                      <
+                         _CheckArgsConstructor<
+                             sizeof...(_Up) <= sizeof...(_Tp)
+                             && !_PackExpandsToThisTuple<_Up...>::value
+                         >::template __enable_implicit<_Up...>(),
+                         bool
+                      >::type = false
+             >
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+        tuple(_Up&&... __u)
+            _NOEXCEPT_((
+                is_nothrow_constructible<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,
+                    _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
+                      <
+                         _CheckArgsConstructor<
+                             sizeof...(_Up) <= sizeof...(_Tp)
+                             && !_PackExpandsToThisTuple<_Up...>::value
+                         >::template __enable_explicit<_Up...>(),
+                         bool
+                      >::type = false
+             >
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+        explicit
+        tuple(_Up&&... __u)
+            _NOEXCEPT_((
+                is_nothrow_constructible<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,
+                    _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,
+              typename enable_if
+                      <
+                         _CheckArgsConstructor<
+                             sizeof...(_Up) == sizeof...(_Tp) &&
+                             !_PackExpandsToThisTuple<_Up...>::value
+                         >::template __enable_implicit<_Up...>(),
+                         bool
+                      >::type = false
+             >
+        _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 _Alloc, class ..._Up,
+              typename enable_if
+                      <
+                         _CheckArgsConstructor<
+                             sizeof...(_Up) == sizeof...(_Tp) &&
+                             !_PackExpandsToThisTuple<_Up...>::value
+                         >::template __enable_explicit<_Up...>(),
+                         bool
+                      >::type = false
+             >
+        _LIBCPP_INLINE_VISIBILITY
+        explicit
+        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
+                      <
+                         _CheckTupleLikeConstructor<
+                             __tuple_like_with_size<_Tuple, sizeof...(_Tp)>::value
+                             && !_PackExpandsToThisTuple<_Tuple>::value
+                         >::template __enable_implicit<_Tuple>(),
+                         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
+                      <
+                         _CheckTupleLikeConstructor<
+                             __tuple_like_with_size<_Tuple, sizeof...(_Tp)>::value
+                             && !_PackExpandsToThisTuple<_Tuple>::value
+                         >::template __enable_explicit<_Tuple>(),
+                         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,
+              typename enable_if
+                      <
+                         _CheckTupleLikeConstructor<
+                             __tuple_like_with_size<_Tuple, sizeof...(_Tp)>::value
+                         >::template __enable_implicit<_Tuple>(),
+                         bool
+                      >::type = false
+             >
+        _LIBCPP_INLINE_VISIBILITY
+        tuple(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
+            : base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
+
+    template <class _Alloc, class _Tuple,
+              typename enable_if
+                      <
+                         _CheckTupleLikeConstructor<
+                             __tuple_like_with_size<_Tuple, sizeof...(_Tp)>::value
+                         >::template __enable_explicit<_Tuple>(),
+                         bool
+                      >::type = false
+             >
+        _LIBCPP_INLINE_VISIBILITY
+        explicit
+        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_ONLY 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());
+}
+
+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 type&&>(
+             static_cast<const __tuple_leaf<_Ip, type>&&>(__t.base_).get());
+}
+
+#if _LIBCPP_STD_VER > 11
+
+namespace __find_detail {
+
+static constexpr size_t __not_found = -1;
+static constexpr size_t __ambiguous = __not_found - 1;
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr size_t __find_idx_return(size_t __curr_i, size_t __res, bool __matches) {
+    return !__matches ? __res :
+        (__res == __not_found ? __curr_i : __ambiguous);
+}
+
+template <size_t _Nx>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr size_t __find_idx(size_t __i, const bool (&__matches)[_Nx]) {
+  return __i == _Nx ? __not_found :
+      __find_idx_return(__i, __find_idx(__i + 1, __matches), __matches[__i]);
+}
+
+template <class _T1, class ..._Args>
+struct __find_exactly_one_checked {
+  static constexpr bool __matches[] = {is_same<_T1, _Args>::value...};
+    static constexpr size_t value = __find_detail::__find_idx(0, __matches);
+    static_assert (value != __not_found, "type not found in type list" );
+    static_assert(value != __ambiguous,"type occurs more than once in type list");
+};
+
+template <class _T1>
+struct __find_exactly_one_checked<_T1> {
+    static_assert(!is_same<_T1, _T1>::value, "type not in empty type list");
+};
+
+} // namespace __find_detail;
+
+template <typename _T1, typename... _Args>
+struct __find_exactly_one_t
+    : public __find_detail::__find_exactly_one_checked<_T1, _Args...> {
+};
+
+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));
+}
+
+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>(_VSTD::move(__tup));
+}
+
+#endif
+
+// tie
+
+template <class ..._Tp>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+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>
+struct __make_tuple_return_impl
+{
+    typedef _Tp type;
+};
+
+template <class _Tp>
+struct __make_tuple_return_impl<reference_wrapper<_Tp> >
+{
+    typedef _Tp& type;
+};
+
+template <class _Tp>
+struct __make_tuple_return
+{
+    typedef typename __make_tuple_return_impl<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 <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) && _VSTD::get<_Ip-1>(__x) == _VSTD::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)
+    {
+        const size_t __idx = tuple_size<_Tp>::value - _Ip;
+        if (_VSTD::get<__idx>(__x) < _VSTD::get<__idx>(__y))
+            return true;
+        if (_VSTD::get<__idx>(__y) < _VSTD::get<__idx>(__x))
+            return false;
+        return __tuple_less<_Ip-1>()(__x, __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>(_VSTD::get<_I0>(__t))...,
+                                      _VSTD::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>(_VSTD::get<_I0>(__t))...,
+                              _VSTD::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_ONLY 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>(_VSTD::get<_I1>( __first_args))...),
+      second(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
+{
+}
+
+#endif  // _LIBCPP_HAS_NO_VARIADICS
+
+#if _LIBCPP_STD_VER > 14
+template <class _Tp>
+constexpr size_t tuple_size_v = tuple_size<_Tp>::value;
+
+#define _LIBCPP_NOEXCEPT_RETURN(...) noexcept(noexcept(__VA_ARGS__)) { return __VA_ARGS__; }
+
+template <class _Fn, class _Tuple, size_t ..._Id>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr decltype(auto) __apply_tuple_impl(_Fn && __f, _Tuple && __t,
+                                            __tuple_indices<_Id...>)
+_LIBCPP_NOEXCEPT_RETURN(
+    _VSTD::__invoke_constexpr(
+        _VSTD::forward<_Fn>(__f),
+        _VSTD::get<_Id>(_VSTD::forward<_Tuple>(__t))...)
+)
+
+template <class _Fn, class _Tuple>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr decltype(auto) apply(_Fn && __f, _Tuple && __t)
+_LIBCPP_NOEXCEPT_RETURN(
+    _VSTD::__apply_tuple_impl(
+        _VSTD::forward<_Fn>(__f), _VSTD::forward<_Tuple>(__t),
+        typename __make_tuple_indices<tuple_size_v<decay_t<_Tuple>>>::type{})
+)
+
+template <class _Tp, class _Tuple, size_t... _Idx>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Tp __make_from_tuple_impl(_Tuple&& __t, __tuple_indices<_Idx...>)
+_LIBCPP_NOEXCEPT_RETURN(
+    _Tp(_VSTD::get<_Idx>(_VSTD::forward<_Tuple>(__t))...)
+)
+
+template <class _Tp, class _Tuple>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Tp make_from_tuple(_Tuple&& __t)
+_LIBCPP_NOEXCEPT_RETURN(
+    _VSTD::__make_from_tuple_impl<_Tp>(_VSTD::forward<_Tuple>(__t),
+        typename __make_tuple_indices<tuple_size_v<decay_t<_Tuple>>>::type{})
+)
+
+#undef _LIBCPP_NOEXCEPT_RETURN
+
+#endif // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif  // _LIBCPP_TUPLE
-- 
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