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//  -*- C++ -*-

// Copyright (C) 2007-2012 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library is free

// software; you can redistribute it and/or modify it under the

// terms of the GNU General Public License as published by the

// Free Software Foundation; either version 3, or (at your option)

// any later version.

// This library is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional

// permissions described in the GCC Runtime Library Exception, version

// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and

// a copy of the GCC Runtime Library Exception along with this program;

// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

// .

/** @file include/tuple

 *  This is a Standard C++ Library header.

 */

#ifndef _GLIBCXX_TUPLE

#define _GLIBCXX_TUPLE 1

#pragma GCC system_header

#if __cplusplus < 201103L

# include 

#else

#include 

#include 

#include 

namespace std _GLIBCXX_VISIBILITY(default)

{

_GLIBCXX_BEGIN_NAMESPACE_VERSION

  // Adds a const reference to a non-reference type.

  template

    struct __add_c_ref

    { typedef const _Tp& type; };

  template

    struct __add_c_ref<_Tp&>

    { typedef _Tp& type; };

  // Adds a reference to a non-reference type.

  template

    struct __add_ref

    { typedef _Tp& type; };

  template

    struct __add_ref<_Tp&>

    { typedef _Tp& type; };

  // Adds an rvalue reference to a non-reference type.

  template

    struct __add_r_ref

    { typedef _Tp&& type; };

  template

    struct __add_r_ref<_Tp&>

    { typedef _Tp& type; };

  template

    struct _Head_base;

  template

    struct _Head_base<_Idx, _Head, true>

    : public _Head

    {

      constexpr _Head_base()

      : _Head() { }

      constexpr _Head_base(const _Head& __h)

      : _Head(__h) { }

      template

               enable_if

                                         __uses_alloc_base>::value>::type>

        constexpr _Head_base(_UHead&& __h)

        : _Head(std::forward<_UHead>(__h)) { }

      _Head_base(__uses_alloc0)

      : _Head() { }

      template

        _Head_base(__uses_alloc1<_Alloc> __a)

        : _Head(allocator_arg, *__a._M_a) { }

      template

        _Head_base(__uses_alloc2<_Alloc> __a)

        : _Head(*__a._M_a) { }

      template

        _Head_base(__uses_alloc0, _UHead&& __uhead)

        : _Head(std::forward<_UHead>(__uhead)) { }

      template

        _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)

        : _Head(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead)) { }

      template

        _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)

        : _Head(std::forward<_UHead>(__uhead), *__a._M_a) { }

      static constexpr _Head&

      _M_head(_Head_base& __b) noexcept { return __b; }

      static constexpr const _Head&

      _M_head(const _Head_base& __b) noexcept { return __b; }

    };

  template

    struct _Head_base<_Idx, _Head, false>

    {

      constexpr _Head_base()

      : _M_head_impl() { }

      constexpr _Head_base(const _Head& __h)

      : _M_head_impl(__h) { }

      template

               enable_if

                                         __uses_alloc_base>::value>::type>

        constexpr _Head_base(_UHead&& __h)

        : _M_head_impl(std::forward<_UHead>(__h)) { }

      _Head_base(__uses_alloc0)

      : _M_head_impl() { }

      template

        _Head_base(__uses_alloc1<_Alloc> __a)

        : _M_head_impl(allocator_arg, *__a._M_a) { }

      template

        _Head_base(__uses_alloc2<_Alloc> __a)

        : _M_head_impl(*__a._M_a) { }

      template

        _Head_base(__uses_alloc0, _UHead&& __uhead)

        : _M_head_impl(std::forward<_UHead>(__uhead)) { }

      template

        _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)

        : _M_head_impl(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead))

        { }

      template

        _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)

        : _M_head_impl(std::forward<_UHead>(__uhead), *__a._M_a) { }

      static constexpr _Head&

      _M_head(_Head_base& __b) noexcept { return __b._M_head_impl; }

      static constexpr const _Head&

      _M_head(const _Head_base& __b) noexcept { return __b._M_head_impl; }

      _Head _M_head_impl;

    };

  /**

   * Contains the actual implementation of the @c tuple template, stored

   * as a recursive inheritance hierarchy from the first element (most

   * derived class) to the last (least derived class). The @c Idx

   * parameter gives the 0-based index of the element stored at this

   * point in the hierarchy; we use it to implement a constant-time

   * get() operation.

   */

  template

    struct _Tuple_impl;

  /**

   * Zero-element tuple implementation. This is the basis case for the

   * inheritance recursion.

   */

  template

    struct _Tuple_impl<_Idx>

    {

      template friend class _Tuple_impl;

      _Tuple_impl() = default;

      template

        _Tuple_impl(allocator_arg_t, const _Alloc&) { }

      template

        _Tuple_impl(allocator_arg_t, const _Alloc&, const _Tuple_impl&) { }

      template

        _Tuple_impl(allocator_arg_t, const _Alloc&, _Tuple_impl&&) { }

    protected:

      void _M_swap(_Tuple_impl&) noexcept { /* no-op */ }

    };

  template

    struct __is_empty_non_tuple : is_empty<_Tp> { };

  // Using EBO for elements that are tuples causes ambiguous base errors.

  template

    struct __is_empty_non_tuple> : false_type { };

  // Use the Empty Base-class Optimization for empty, non-final types.

  template

    using __empty_not_final

    = typename conditional<__is_final(_Tp), false_type,

                           __is_empty_non_tuple<_Tp>>::type;

  /**

   * Recursive tuple implementation. Here we store the @c Head element

   * and derive from a @c Tuple_impl containing the remaining elements

   * (which contains the @c Tail).

   */

  template

    struct _Tuple_impl<_Idx, _Head, _Tail...>

    : public _Tuple_impl<_Idx + 1, _Tail...>,

      private _Head_base<_Idx, _Head, __empty_not_final<_Head>::value>

    {

      template friend class _Tuple_impl;

      typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;

      typedef _Head_base<_Idx, _Head, __empty_not_final<_Head>::value> _Base;

      static constexpr _Head&

      _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }

      static constexpr const _Head&

      _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }

      static constexpr _Inherited&

      _M_tail(_Tuple_impl& __t) noexcept { return __t; }

      static constexpr const _Inherited&

      _M_tail(const _Tuple_impl& __t) noexcept { return __t; }

      constexpr _Tuple_impl()

      : _Inherited(), _Base() { }

      explicit

      constexpr _Tuple_impl(const _Head& __head, const _Tail&... __tail)

      : _Inherited(__tail...), _Base(__head) { }

      template

               enable_if::type>

        explicit

        constexpr _Tuple_impl(_UHead&& __head, _UTail&&... __tail)

        : _Inherited(std::forward<_UTail>(__tail)...),

          _Base(std::forward<_UHead>(__head)) { }

      constexpr _Tuple_impl(const _Tuple_impl&) = default;

      constexpr

      _Tuple_impl(_Tuple_impl&& __in)

      noexcept(__and_,

                      is_nothrow_move_constructible<_Inherited>>::value)

      : _Inherited(std::move(_M_tail(__in))),

        _Base(std::forward<_Head>(_M_head(__in))) { }

      template

        constexpr _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)

        : _Inherited(_Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),

          _Base(_Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }

      template

        constexpr _Tuple_impl(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)

        : _Inherited(std::move

                     (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),

          _Base(std::forward<_UHead>

                (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }

      template

        _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)

        : _Inherited(__tag, __a),

          _Base(__use_alloc<_Head>(__a)) { }

      template

        _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,

                    const _Head& __head, const _Tail&... __tail)

        : _Inherited(__tag, __a, __tail...),

          _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head) { }

      template

               typename = typename enable_if

                                             == sizeof...(_UTail)>::type>

        _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,

                    _UHead&& __head, _UTail&&... __tail)

        : _Inherited(__tag, __a, std::forward<_UTail>(__tail)...),

          _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),

                std::forward<_UHead>(__head)) { }

      template

        _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,

                    const _Tuple_impl& __in)

        : _Inherited(__tag, __a, _M_tail(__in)),

          _Base(__use_alloc<_Head, _Alloc, _Head>(__a), _M_head(__in)) { }

      template

        _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,

                    _Tuple_impl&& __in)

        : _Inherited(__tag, __a, std::move(_M_tail(__in))),

          _Base(__use_alloc<_Head, _Alloc, _Head>(__a),

                std::forward<_Head>(_M_head(__in))) { }

      template

        _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,

                    const _Tuple_impl<_Idx, _UElements...>& __in)

        : _Inherited(__tag, __a,

                     _Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),

          _Base(__use_alloc<_Head, _Alloc, _Head>(__a),

                _Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }

      template

        _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,

                    _Tuple_impl<_Idx, _UHead, _UTails...>&& __in)

        : _Inherited(__tag, __a, std::move

                     (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),

          _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),

                std::forward<_UHead>

                (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }

      _Tuple_impl&

      operator=(const _Tuple_impl& __in)

      {

        _M_head(*this) = _M_head(__in);

        _M_tail(*this) = _M_tail(__in);

        return *this;

      }

      _Tuple_impl&

      operator=(_Tuple_impl&& __in)

      noexcept(__and_,

                      is_nothrow_move_assignable<_Inherited>>::value)

      {

        _M_head(*this) = std::forward<_Head>(_M_head(__in));

        _M_tail(*this) = std::move(_M_tail(__in));

        return *this;

      }

      template

        _Tuple_impl&

        operator=(const _Tuple_impl<_Idx, _UElements...>& __in)

        {

          _M_head(*this) = _Tuple_impl<_Idx, _UElements...>::_M_head(__in);

          _M_tail(*this) = _Tuple_impl<_Idx, _UElements...>::_M_tail(__in);

          return *this;

        }

      template

        _Tuple_impl&

        operator=(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)

        {

          _M_head(*this) = std::forward<_UHead>

            (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in));

          _M_tail(*this) = std::move

            (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in));

          return *this;

        }

    protected:

      void

      _M_swap(_Tuple_impl& __in)

      noexcept(noexcept(swap(std::declval<_Head&>(),

                             std::declval<_Head&>()))

               && noexcept(_M_tail(__in)._M_swap(_M_tail(__in))))

      {

        using std::swap;

        swap(_M_head(*this), _M_head(__in));

        _Inherited::_M_swap(_M_tail(__in));

      }

    };

  /// Primary class template, tuple

  template

    class tuple : public _Tuple_impl<0, _Elements...>

    {

      typedef _Tuple_impl<0, _Elements...> _Inherited;

    public:

      constexpr tuple()

      : _Inherited() { }

      explicit

      constexpr tuple(const _Elements&... __elements)

      : _Inherited(__elements...) { }

      template

        enable_if<__and_

                                        _Elements>...>::value>::type>

        explicit

        constexpr tuple(_UElements&&... __elements)

        : _Inherited(std::forward<_UElements>(__elements)...) {     }

      constexpr tuple(const tuple&) = default;

      constexpr tuple(tuple&&) = default;

      template

        enable_if<__and_

                                        _Elements>...>::value>::type>

        constexpr tuple(const tuple<_UElements...>& __in)

        : _Inherited(static_cast&>(__in))

        { }

      template

        enable_if<__and_

                                        _Elements>...>::value>::type>

        constexpr tuple(tuple<_UElements...>&& __in)

        : _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }

      // Allocator-extended constructors.

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a)

        : _Inherited(__tag, __a) { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a,

              const _Elements&... __elements)

        : _Inherited(__tag, __a, __elements...) { }

      template

               enable_if

                         == sizeof...(_Elements)>::type>

        tuple(allocator_arg_t __tag, const _Alloc& __a,

              _UElements&&... __elements)

        : _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)

        { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)

        : _Inherited(__tag, __a, static_cast(__in)) { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)

        : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }

      template

               enable_if

                         == sizeof...(_Elements)>::type>

        tuple(allocator_arg_t __tag, const _Alloc& __a,

              const tuple<_UElements...>& __in)

        : _Inherited(__tag, __a,

                     static_cast&>(__in))

        { }

      template

               enable_if

                         == sizeof...(_Elements)>::type>

        tuple(allocator_arg_t __tag, const _Alloc& __a,

              tuple<_UElements...>&& __in)

        : _Inherited(__tag, __a,

                     static_cast<_Tuple_impl<0, _UElements...>&&>(__in))

        { }

      tuple&

      operator=(const tuple& __in)

      {

        static_cast<_Inherited&>(*this) = __in;

        return *this;

      }

      tuple&

      operator=(tuple&& __in)

      noexcept(is_nothrow_move_assignable<_Inherited>::value)

      {

        static_cast<_Inherited&>(*this) = std::move(__in);

        return *this;

      }

      template

               enable_if

                         == sizeof...(_Elements)>::type>

        tuple&

        operator=(const tuple<_UElements...>& __in)

        {

          static_cast<_Inherited&>(*this) = __in;

          return *this;

        }

      template

               enable_if

                         == sizeof...(_Elements)>::type>

        tuple&

        operator=(tuple<_UElements...>&& __in)

        {

          static_cast<_Inherited&>(*this) = std::move(__in);

          return *this;

        }

      void

      swap(tuple& __in)

      noexcept(noexcept(__in._M_swap(__in)))

      { _Inherited::_M_swap(__in); }

    };

  // Explicit specialization, zero-element tuple.

  template<>

    class tuple<>

    {

    public:

      void swap(tuple&) noexcept { /* no-op */ }

    };

  /// Partial specialization, 2-element tuple.

  /// Includes construction and assignment from a pair.

  template

    class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>

    {

      typedef _Tuple_impl<0, _T1, _T2> _Inherited;

    public:

      constexpr tuple()

      : _Inherited() { }

      explicit

      constexpr tuple(const _T1& __a1, const _T2& __a2)

      : _Inherited(__a1, __a2) { }

      template

               enable_if<__and_,

                                is_convertible<_U2, _T2>>::value>::type>

        explicit

        constexpr tuple(_U1&& __a1, _U2&& __a2)

        : _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }

      constexpr tuple(const tuple&) = default;

      constexpr tuple(tuple&&) = default;

      template

        enable_if<__and_,

                         is_convertible>::value>::type>

        constexpr tuple(const tuple<_U1, _U2>& __in)

        : _Inherited(static_cast&>(__in)) { }

      template

               enable_if<__and_,

                                is_convertible<_U2, _T2>>::value>::type>

        constexpr tuple(tuple<_U1, _U2>&& __in)

        : _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }

      template

        enable_if<__and_,

                         is_convertible>::value>::type>

        constexpr tuple(const pair<_U1, _U2>& __in)

        : _Inherited(__in.first, __in.second) { }

      template

               enable_if<__and_,

                                is_convertible<_U2, _T2>>::value>::type>

        constexpr tuple(pair<_U1, _U2>&& __in)

        : _Inherited(std::forward<_U1>(__in.first),

                     std::forward<_U2>(__in.second)) { }

      // Allocator-extended constructors.

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a)

        : _Inherited(__tag, __a) { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a,

              const _T1& __a1, const _T2& __a2)

        : _Inherited(__tag, __a, __a1, __a2) { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a, _U1&& __a1, _U2&& __a2)

        : _Inherited(__tag, __a, std::forward<_U1>(__a1),

                     std::forward<_U2>(__a2)) { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)

        : _Inherited(__tag, __a, static_cast(__in)) { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)

        : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a,

              const tuple<_U1, _U2>& __in)

        : _Inherited(__tag, __a,

                     static_cast&>(__in))

        { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a, tuple<_U1, _U2>&& __in)

        : _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))

        { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a,

              const pair<_U1, _U2>& __in)

        : _Inherited(__tag, __a, __in.first, __in.second) { }

      template

        tuple(allocator_arg_t __tag, const _Alloc& __a, pair<_U1, _U2>&& __in)

        : _Inherited(__tag, __a, std::forward<_U1>(__in.first),

                     std::forward<_U2>(__in.second)) { }

      tuple&

      operator=(const tuple& __in)

      {

        static_cast<_Inherited&>(*this) = __in;

        return *this;

      }

      tuple&

      operator=(tuple&& __in)

      noexcept(is_nothrow_move_assignable<_Inherited>::value)

      {

        static_cast<_Inherited&>(*this) = std::move(__in);

        return *this;

      }

      template

        tuple&

        operator=(const tuple<_U1, _U2>& __in)

        {

          static_cast<_Inherited&>(*this) = __in;

          return *this;

        }

      template

        tuple&

        operator=(tuple<_U1, _U2>&& __in)

        {

          static_cast<_Inherited&>(*this) = std::move(__in);

          return *this;

        }

      template

        tuple&

        operator=(const pair<_U1, _U2>& __in)

        {

          this->_M_head(*this) = __in.first;

          this->_M_tail(*this)._M_head(*this) = __in.second;

          return *this;

        }

      template

        tuple&

        operator=(pair<_U1, _U2>&& __in)

        {

          this->_M_head(*this) = std::forward<_U1>(__in.first);

          this->_M_tail(*this)._M_head(*this) = std::forward<_U2>(__in.second);

          return *this;

        }

      void

      swap(tuple& __in)

      noexcept(noexcept(__in._M_swap(__in)))

      { _Inherited::_M_swap(__in); }

    };

  /// Gives the type of the ith element of a given tuple type.

  template

    struct tuple_element;

  /**

   * Recursive case for tuple_element: strip off the first element in

   * the tuple and retrieve the (i-1)th element of the remaining tuple.

   */

  template

    struct tuple_element<__i, tuple<_Head, _Tail...> >

    : tuple_element<__i - 1, tuple<_Tail...> > { };

  /**

   * Basis case for tuple_element: The first element is the one we're seeking.

   */

  template

    struct tuple_element<0, tuple<_Head, _Tail...> >

    {

      typedef _Head type;

    };

  template

    struct tuple_element<__i, const _Tp>

    {

      typedef typename

      add_const::type>::type type;

    };

  template

    struct tuple_element<__i, volatile _Tp>

    {

      typedef typename

      add_volatile::type>::type type;

    };

  template

    struct tuple_element<__i, const volatile _Tp>

    {

      typedef typename

      add_cv::type>::type type;

    };

  /// Finds the size of a given tuple type.

  template

    struct tuple_size;

  template

    struct tuple_size

    : public integral_constant<

             typename remove_cv::value)>::type,

             tuple_size<_Tp>::value> { };

  template

    struct tuple_size

    : public integral_constant<

             typename remove_cv::value)>::type,

             tuple_size<_Tp>::value> { };

  template

    struct tuple_size

    : public integral_constant<

             typename remove_cv::value)>::type,

             tuple_size<_Tp>::value> { };

  /// class tuple_size

  template

    struct tuple_size>

    : public integral_constant { };

  template

    constexpr typename __add_ref<_Head>::type

    __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept

    { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }

  template

    constexpr typename __add_c_ref<_Head>::type

    __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept

    { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }

  // Return a reference (const reference, rvalue reference) to the ith element

  // of a tuple.  Any const or non-const ref elements are returned with their

  // original type.

  template

    constexpr typename __add_ref<

                      typename tuple_element<__i, tuple<_Elements...>>::type

                    >::type

    get(tuple<_Elements...>& __t) noexcept

    { return __get_helper<__i>(__t); }

  template

    constexpr typename __add_c_ref<

                      typename tuple_element<__i, tuple<_Elements...>>::type

                    >::type

    get(const tuple<_Elements...>& __t) noexcept

    { return __get_helper<__i>(__t); }

  template

    constexpr typename __add_r_ref<

                      typename tuple_element<__i, tuple<_Elements...>>::type

                    >::type

    get(tuple<_Elements...>&& __t) noexcept

    { return std::forward

        tuple<_Elements...>>::type&&>(get<__i>(__t)); }

  // This class helps construct the various comparison operations on tuples

  template

           typename _Tp, typename _Up>

    struct __tuple_compare;

  template

    struct __tuple_compare<0, __i, __j, _Tp, _Up>

    {

      static constexpr bool

      __eq(const _Tp& __t, const _Up& __u)

      {

        return (get<__i>(__t) == get<__i>(__u) &&

                __tuple_compare<0, __i + 1, __j, _Tp, _Up>::__eq(__t, __u));

      }

      static constexpr bool

      __less(const _Tp& __t, const _Up& __u)

      {

        return ((get<__i>(__t) < get<__i>(__u))

                || !(get<__i>(__u) < get<__i>(__t)) &&

                __tuple_compare<0, __i + 1, __j, _Tp, _Up>::__less(__t, __u));

      }

    };

  template

    struct __tuple_compare<0, __i, __i, _Tp, _Up>

    {

      static constexpr bool

      __eq(const _Tp&, const _Up&) { return true; }

      static constexpr bool

      __less(const _Tp&, const _Up&) { return false; }

    };

  template

    constexpr bool

    operator==(const tuple<_TElements...>& __t,

               const tuple<_UElements...>& __u)

    {

      typedef tuple<_TElements...> _Tp;

      typedef tuple<_UElements...> _Up;

      return bool(__tuple_compare::value - tuple_size<_Up>::value,

              0, tuple_size<_Tp>::value, _Tp, _Up>::__eq(__t, __u));

    }

  template

    constexpr bool

    operator<(const tuple<_TElements...>& __t,

              const tuple<_UElements...>& __u)

    {

      typedef tuple<_TElements...> _Tp;

      typedef tuple<_UElements...> _Up;

      return bool(__tuple_compare::value - tuple_size<_Up>::value,

              0, tuple_size<_Tp>::value, _Tp, _Up>::__less(__t, __u));

    }

  template

    inline constexpr bool

    operator!=(const tuple<_TElements...>& __t,

               const tuple<_UElements...>& __u)

    { return !(__t == __u); }

  template

    inline constexpr bool

    operator>(const tuple<_TElements...>& __t,

              const tuple<_UElements...>& __u)

    { return __u < __t; }

  template

    inline constexpr bool

    operator<=(const tuple<_TElements...>& __t,

               const tuple<_UElements...>& __u)

    { return !(__u < __t); }

  template

    inline constexpr bool

    operator>=(const tuple<_TElements...>& __t,

               const tuple<_UElements...>& __u)

    { return !(__t < __u); }

  // NB: DR 705.

  template

    constexpr tuple::__type...>

    make_tuple(_Elements&&... __args)

    {

      typedef tuple::__type...>

        __result_type;

      return __result_type(std::forward<_Elements>(__args)...);

    }

  template

    tuple<_Elements&&...>

    forward_as_tuple(_Elements&&... __args) noexcept

    { return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }

  template

    struct __is_tuple_like_impl : false_type

    { };

  template

    struct __is_tuple_like_impl> : true_type

    { };

  template

    struct __is_tuple_like_impl> : true_type

    { };

  template

    struct __is_tuple_like_impl> : true_type

    { };

  // Internal type trait that allows us to sfinae-protect tuple_cat.

  template

    struct __is_tuple_like

    : public __is_tuple_like_impl

            ::type>::type>::type

    { };

  // Stores a tuple of indices.  Also used by bind() to extract the elements

  // in a tuple.

  template

    struct _Index_tuple

    {

      typedef _Index_tuple<_Indexes..., sizeof...(_Indexes)> __next;

    };

  // Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.

  template

    struct _Build_index_tuple

    {

      typedef typename _Build_index_tuple<_Num - 1>::__type::__next __type;

    };

  template<>

    struct _Build_index_tuple<0>

    {

      typedef _Index_tuple<> __type;

    };

  template

    struct __make_tuple_impl;

  template

           std::size_t _Nm>

    struct __make_tuple_impl<_Idx, tuple<_Tp...>, _Tuple, _Nm>

    {

      typedef typename __make_tuple_impl<_Idx + 1, tuple<_Tp...,