libstdc++-v3/include/std/tuple

   1 // <tuple> -*- C++ -*-
   2
   3 // Copyright (C) 2007-2016 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 /** @file include/tuple
  26  *  This is a Standard C++ Library header.
  27  */
  28
  29 #ifndef _GLIBCXX_TUPLE
  30 #define _GLIBCXX_TUPLE 1
  31
  32 #pragma GCC system_header
  33
  34 #if __cplusplus < 201103L
  35 # include <bits/c++0x_warning.h>
  36 #else
  37
  38 #include <utility>
  39 #include <array>
  40 #include <bits/uses_allocator.h>
  41
  42 namespace std _GLIBCXX_VISIBILITY(default)
  43 {
  44 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  45
  46   /**
  47    *  @addtogroup utilities
  48    *  @{
  49    */
  50
  51   template<std::size_t _Idx, typename _Head, bool _IsEmptyNotFinal>
  52     struct _Head_base;
  53
  54   template<std::size_t _Idx, typename _Head>
  55     struct _Head_base<_Idx, _Head, true>
  56     : public _Head
  57     {
  58       constexpr _Head_base()
  59       : _Head() { }
  60
  61       constexpr _Head_base(const _Head& __h)
  62       : _Head(__h) { }
  63
  64       constexpr _Head_base(const _Head_base&) = default;
  65       constexpr _Head_base(_Head_base&&) = default;
  66
  67       template<typename _UHead>
  68         constexpr _Head_base(_UHead&& __h)
  69         : _Head(std::forward<_UHead>(__h)) { }
  70
  71       _Head_base(allocator_arg_t, __uses_alloc0)
  72       : _Head() { }
  73
  74       template<typename _Alloc>
  75         _Head_base(allocator_arg_t, __uses_alloc1<_Alloc> __a)
  76         : _Head(allocator_arg, *__a._M_a) { }
  77
  78       template<typename _Alloc>
  79         _Head_base(allocator_arg_t, __uses_alloc2<_Alloc> __a)
  80         : _Head(*__a._M_a) { }
  81
  82       template<typename _UHead>
  83         _Head_base(__uses_alloc0, _UHead&& __uhead)
  84         : _Head(std::forward<_UHead>(__uhead)) { }
  85
  86       template<typename _Alloc, typename _UHead>
  87         _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
  88         : _Head(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead)) { }
  89
  90       template<typename _Alloc, typename _UHead>
  91         _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
  92         : _Head(std::forward<_UHead>(__uhead), *__a._M_a) { }
  93
  94       static constexpr _Head&
  95       _M_head(_Head_base& __b) noexcept { return __b; }
  96
  97       static constexpr const _Head&
  98       _M_head(const _Head_base& __b) noexcept { return __b; }
  99     };
 100
 101   template<std::size_t _Idx, typename _Head>
 102     struct _Head_base<_Idx, _Head, false>
 103     {
 104       constexpr _Head_base()
 105       : _M_head_impl() { }
 106
 107       constexpr _Head_base(const _Head& __h)
 108       : _M_head_impl(__h) { }
 109
 110       constexpr _Head_base(const _Head_base&) = default;
 111       constexpr _Head_base(_Head_base&&) = default;
 112
 113       template<typename _UHead>
 114         constexpr _Head_base(_UHead&& __h)
 115         : _M_head_impl(std::forward<_UHead>(__h)) { }
 116
 117       _Head_base(allocator_arg_t, __uses_alloc0)
 118       : _M_head_impl() { }
 119
 120       template<typename _Alloc>
 121         _Head_base(allocator_arg_t, __uses_alloc1<_Alloc> __a)
 122         : _M_head_impl(allocator_arg, *__a._M_a) { }
 123
 124       template<typename _Alloc>
 125         _Head_base(allocator_arg_t, __uses_alloc2<_Alloc> __a)
 126         : _M_head_impl(*__a._M_a) { }
 127
 128       template<typename _UHead>
 129         _Head_base(__uses_alloc0, _UHead&& __uhead)
 130         : _M_head_impl(std::forward<_UHead>(__uhead)) { }
 131
 132       template<typename _Alloc, typename _UHead>
 133         _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
 134         : _M_head_impl(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead))
 135         { }
 136
 137       template<typename _Alloc, typename _UHead>
 138         _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
 139         : _M_head_impl(std::forward<_UHead>(__uhead), *__a._M_a) { }
 140
 141       static constexpr _Head&
 142       _M_head(_Head_base& __b) noexcept { return __b._M_head_impl; }
 143
 144       static constexpr const _Head&
 145       _M_head(const _Head_base& __b) noexcept { return __b._M_head_impl; }
 146
 147       _Head _M_head_impl;
 148     };
 149
 150   /**
 151    * Contains the actual implementation of the @c tuple template, stored
 152    * as a recursive inheritance hierarchy from the first element (most
 153    * derived class) to the last (least derived class). The @c Idx
 154    * parameter gives the 0-based index of the element stored at this
 155    * point in the hierarchy; we use it to implement a constant-time
 156    * get() operation.
 157    */
 158   template<std::size_t _Idx, typename... _Elements>
 159     struct _Tuple_impl;
 160
 161   template<typename _Tp>
 162     struct __is_empty_non_tuple : is_empty<_Tp> { };
 163
 164   // Using EBO for elements that are tuples causes ambiguous base errors.
 165   template<typename _El0, typename... _El>
 166     struct __is_empty_non_tuple<tuple<_El0, _El...>> : false_type { };
 167
 168   // Use the Empty Base-class Optimization for empty, non-final types.
 169   template<typename _Tp>
 170     using __empty_not_final
 171     = typename conditional<__is_final(_Tp), false_type,
 172                            __is_empty_non_tuple<_Tp>>::type;
 173
 174   /**
 175    * Recursive tuple implementation. Here we store the @c Head element
 176    * and derive from a @c Tuple_impl containing the remaining elements
 177    * (which contains the @c Tail).
 178    */
 179   template<std::size_t _Idx, typename _Head, typename... _Tail>
 180     struct _Tuple_impl<_Idx, _Head, _Tail...>
 181     : public _Tuple_impl<_Idx + 1, _Tail...>,
 182       private _Head_base<_Idx, _Head, __empty_not_final<_Head>::value>
 183     {
 184       template<std::size_t, typename...> friend class _Tuple_impl;
 185
 186       typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
 187       typedef _Head_base<_Idx, _Head, __empty_not_final<_Head>::value> _Base;
 188
 189       static constexpr _Head&
 190       _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 191
 192       static constexpr const _Head&
 193       _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 194
 195       static constexpr _Inherited&
 196       _M_tail(_Tuple_impl& __t) noexcept { return __t; }
 197
 198       static constexpr const _Inherited&
 199       _M_tail(const _Tuple_impl& __t) noexcept { return __t; }
 200
 201       constexpr _Tuple_impl()
 202       : _Inherited(), _Base() { }
 203
 204       explicit
 205       constexpr _Tuple_impl(const _Head& __head, const _Tail&... __tail)
 206       : _Inherited(__tail...), _Base(__head) { }
 207
 208       template<typename _UHead, typename... _UTail, typename = typename
 209                enable_if<sizeof...(_Tail) == sizeof...(_UTail)>::type>
 210         explicit
 211         constexpr _Tuple_impl(_UHead&& __head, _UTail&&... __tail)
 212         : _Inherited(std::forward<_UTail>(__tail)...),
 213           _Base(std::forward<_UHead>(__head)) { }
 214
 215       constexpr _Tuple_impl(const _Tuple_impl&) = default;
 216
 217       constexpr
 218       _Tuple_impl(_Tuple_impl&& __in)
 219       noexcept(__and_<is_nothrow_move_constructible<_Head>,
 220                       is_nothrow_move_constructible<_Inherited>>::value)
 221       : _Inherited(std::move(_M_tail(__in))),
 222         _Base(std::forward<_Head>(_M_head(__in))) { }
 223
 224       template<typename... _UElements>
 225         constexpr _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
 226         : _Inherited(_Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
 227           _Base(_Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
 228
 229       template<typename _UHead, typename... _UTails>
 230         constexpr _Tuple_impl(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 231         : _Inherited(std::move
 232                      (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
 233           _Base(std::forward<_UHead>
 234                 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
 235
 236       template<typename _Alloc>
 237         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)
 238         : _Inherited(__tag, __a),
 239           _Base(__tag, __use_alloc<_Head>(__a)) { }
 240
 241       template<typename _Alloc>
 242         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 243                     const _Head& __head, const _Tail&... __tail)
 244         : _Inherited(__tag, __a, __tail...),
 245           _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head) { }
 246
 247       template<typename _Alloc, typename _UHead, typename... _UTail,
 248                typename = typename enable_if<sizeof...(_Tail)
 249                                              == sizeof...(_UTail)>::type>
 250         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 251                     _UHead&& __head, _UTail&&... __tail)
 252         : _Inherited(__tag, __a, std::forward<_UTail>(__tail)...),
 253           _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 254                 std::forward<_UHead>(__head)) { }
 255
 256       template<typename _Alloc>
 257         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 258                     const _Tuple_impl& __in)
 259         : _Inherited(__tag, __a, _M_tail(__in)),
 260           _Base(__use_alloc<_Head, _Alloc, _Head>(__a), _M_head(__in)) { }
 261
 262       template<typename _Alloc>
 263         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 264                     _Tuple_impl&& __in)
 265         : _Inherited(__tag, __a, std::move(_M_tail(__in))),
 266           _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 267                 std::forward<_Head>(_M_head(__in))) { }
 268
 269       template<typename _Alloc, typename... _UElements>
 270         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 271                     const _Tuple_impl<_Idx, _UElements...>& __in)
 272         : _Inherited(__tag, __a,
 273                      _Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
 274           _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 275                 _Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
 276
 277       template<typename _Alloc, typename _UHead, typename... _UTails>
 278         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 279                     _Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 280         : _Inherited(__tag, __a, std::move
 281                      (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
 282           _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 283                 std::forward<_UHead>
 284                 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
 285
 286       _Tuple_impl&
 287       operator=(const _Tuple_impl& __in)
 288       {
 289         _M_head(*this) = _M_head(__in);
 290         _M_tail(*this) = _M_tail(__in);
 291         return *this;
 292       }
 293
 294       _Tuple_impl&
 295       operator=(_Tuple_impl&& __in)
 296       noexcept(__and_<is_nothrow_move_assignable<_Head>,
 297                       is_nothrow_move_assignable<_Inherited>>::value)
 298       {
 299         _M_head(*this) = std::forward<_Head>(_M_head(__in));
 300         _M_tail(*this) = std::move(_M_tail(__in));
 301         return *this;
 302       }
 303
 304       template<typename... _UElements>
 305         _Tuple_impl&
 306         operator=(const _Tuple_impl<_Idx, _UElements...>& __in)
 307         {
 308           _M_head(*this) = _Tuple_impl<_Idx, _UElements...>::_M_head(__in);
 309           _M_tail(*this) = _Tuple_impl<_Idx, _UElements...>::_M_tail(__in);
 310           return *this;
 311         }
 312
 313       template<typename _UHead, typename... _UTails>
 314         _Tuple_impl&
 315         operator=(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 316         {
 317           _M_head(*this) = std::forward<_UHead>
 318             (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in));
 319           _M_tail(*this) = std::move
 320             (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in));
 321           return *this;
 322         }
 323
 324     protected:
 325       void
 326       _M_swap(_Tuple_impl& __in)
 327       noexcept(__is_nothrow_swappable<_Head>::value
 328                && noexcept(_M_tail(__in)._M_swap(_M_tail(__in))))
 329       {
 330         using std::swap;
 331         swap(_M_head(*this), _M_head(__in));
 332         _Inherited::_M_swap(_M_tail(__in));
 333       }
 334     };
 335
 336   // Basis case of inheritance recursion.
 337   template<std::size_t _Idx, typename _Head>
 338     struct _Tuple_impl<_Idx, _Head>
 339     : private _Head_base<_Idx, _Head, __empty_not_final<_Head>::value>
 340     {
 341       template<std::size_t, typename...> friend class _Tuple_impl;
 342
 343       typedef _Head_base<_Idx, _Head, __empty_not_final<_Head>::value> _Base;
 344
 345       static constexpr _Head&
 346       _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 347
 348       static constexpr const _Head&
 349       _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 350
 351       constexpr _Tuple_impl()
 352       : _Base() { }
 353
 354       explicit
 355       constexpr _Tuple_impl(const _Head& __head)
 356       : _Base(__head) { }
 357
 358       template<typename _UHead>
 359         explicit
 360         constexpr _Tuple_impl(_UHead&& __head)
 361         : _Base(std::forward<_UHead>(__head)) { }
 362
 363       constexpr _Tuple_impl(const _Tuple_impl&) = default;
 364
 365       constexpr
 366       _Tuple_impl(_Tuple_impl&& __in)
 367       noexcept(is_nothrow_move_constructible<_Head>::value)
 368       : _Base(std::forward<_Head>(_M_head(__in))) { }
 369
 370       template<typename _UHead>
 371         constexpr _Tuple_impl(const _Tuple_impl<_Idx, _UHead>& __in)
 372         : _Base(_Tuple_impl<_Idx, _UHead>::_M_head(__in)) { }
 373
 374       template<typename _UHead>
 375         constexpr _Tuple_impl(_Tuple_impl<_Idx, _UHead>&& __in)
 376         : _Base(std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in)))
 377         { }
 378
 379       template<typename _Alloc>
 380         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)
 381         : _Base(__tag, __use_alloc<_Head>(__a)) { }
 382
 383       template<typename _Alloc>
 384         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 385                     const _Head& __head)
 386         : _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head) { }
 387
 388       template<typename _Alloc, typename _UHead>
 389         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 390                     _UHead&& __head)
 391         : _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 392                 std::forward<_UHead>(__head)) { }
 393
 394       template<typename _Alloc>
 395         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 396                     const _Tuple_impl& __in)
 397         : _Base(__use_alloc<_Head, _Alloc, _Head>(__a), _M_head(__in)) { }
 398
 399       template<typename _Alloc>
 400         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 401                     _Tuple_impl&& __in)
 402         : _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 403                 std::forward<_Head>(_M_head(__in))) { }
 404
 405       template<typename _Alloc, typename _UHead>
 406         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 407                     const _Tuple_impl<_Idx, _UHead>& __in)
 408         : _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 409                 _Tuple_impl<_Idx, _UHead>::_M_head(__in)) { }
 410
 411       template<typename _Alloc, typename _UHead>
 412         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 413                     _Tuple_impl<_Idx, _UHead>&& __in)
 414         : _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 415                 std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in)))
 416         { }
 417
 418       _Tuple_impl&
 419       operator=(const _Tuple_impl& __in)
 420       {
 421         _M_head(*this) = _M_head(__in);
 422         return *this;
 423       }
 424
 425       _Tuple_impl&
 426       operator=(_Tuple_impl&& __in)
 427       noexcept(is_nothrow_move_assignable<_Head>::value)
 428       {
 429         _M_head(*this) = std::forward<_Head>(_M_head(__in));
 430         return *this;
 431       }
 432
 433       template<typename _UHead>
 434         _Tuple_impl&
 435         operator=(const _Tuple_impl<_Idx, _UHead>& __in)
 436         {
 437           _M_head(*this) = _Tuple_impl<_Idx, _UHead>::_M_head(__in);
 438           return *this;
 439         }
 440
 441       template<typename _UHead>
 442         _Tuple_impl&
 443         operator=(_Tuple_impl<_Idx, _UHead>&& __in)
 444         {
 445           _M_head(*this)
 446             = std::forward<_UHead>(_Tuple_impl<_Idx, _UHead>::_M_head(__in));
 447           return *this;
 448         }
 449
 450     protected:
 451       void
 452       _M_swap(_Tuple_impl& __in)
 453       noexcept(__is_nothrow_swappable<_Head>::value)
 454       {
 455         using std::swap;
 456         swap(_M_head(*this), _M_head(__in));
 457       }
 458     };
 459
 460   template<typename... _Elements>
 461     class tuple;
 462
 463   // Concept utility functions, reused in conditionally-explicit
 464   // constructors.
 465   template<bool, typename... _Elements>
 466   struct _TC
 467   {
 468     template<typename... _UElements>
 469     static constexpr bool _ConstructibleTuple()
 470     {
 471       return __and_<is_constructible<_Elements, const _UElements&>...>::value;
 472     }
 473
 474     template<typename... _UElements>
 475     static constexpr bool _ImplicitlyConvertibleTuple()
 476     {
 477       return __and_<is_convertible<const _UElements&, _Elements>...>::value;
 478     }
 479
 480     template<typename... _UElements>
 481     static constexpr bool _MoveConstructibleTuple()
 482     {
 483       return __and_<is_constructible<_Elements, _UElements&&>...>::value;
 484     }
 485
 486     template<typename... _UElements>
 487     static constexpr bool _ImplicitlyMoveConvertibleTuple()
 488     {
 489       return __and_<is_convertible<_UElements&&, _Elements>...>::value;
 490     }
 491
 492     template<typename _SrcTuple>
 493     static constexpr bool _NonNestedTuple()
 494     {
 495       return  __and_<__not_<is_same<tuple<_Elements...>,
 496                                    typename remove_cv<
 497                                      typename remove_reference<_SrcTuple>::type
 498                                    >::type>>,
 499                      __not_<is_convertible<_SrcTuple, _Elements...>>,
 500                      __not_<is_constructible<_Elements..., _SrcTuple>>
 501               >::value;
 502     }
 503     template<typename... _UElements>
 504     static constexpr bool _NotSameTuple()
 505     {
 506       return  __not_<is_same<tuple<_Elements...>,
 507                              typename remove_const<
 508                                typename remove_reference<_UElements...>::type
 509                                >::type>>::value;
 510     }
 511   };
 512
 513   template<typename... _Elements>
 514   struct _TC<false, _Elements...>
 515   {
 516     template<typename... _UElements>
 517     static constexpr bool _ConstructibleTuple()
 518     {
 519       return false;
 520     }
 521
 522     template<typename... _UElements>
 523     static constexpr bool _ImplicitlyConvertibleTuple()
 524     {
 525       return false;
 526     }
 527
 528     template<typename... _UElements>
 529     static constexpr bool _MoveConstructibleTuple()
 530     {
 531       return false;
 532     }
 533
 534     template<typename... _UElements>
 535     static constexpr bool _ImplicitlyMoveConvertibleTuple()
 536     {
 537       return false;
 538     }
 539
 540     template<typename... _UElements>
 541     static constexpr bool _NonNestedTuple()
 542     {
 543       return true;
 544     }
 545     template<typename... _UElements>
 546     static constexpr bool _NotSameTuple()
 547     {
 548       return  true;
 549     }
 550   };
 551
 552   /// Primary class template, tuple
 553   template<typename... _Elements>
 554     class tuple : public _Tuple_impl<0, _Elements...>
 555     {
 556       typedef _Tuple_impl<0, _Elements...> _Inherited;
 557
 558       // Used for constraining the default constructor so
 559       // that it becomes dependent on the constraints.
 560       template<typename _Dummy>
 561       struct _TC2
 562       {
 563         static constexpr bool _DefaultConstructibleTuple()
 564         {
 565           return __and_<is_default_constructible<_Elements>...>::value;
 566         }
 567         static constexpr bool _ImplicitlyDefaultConstructibleTuple()
 568         {
 569           return __and_<__is_implicitly_default_constructible<_Elements>...>
 570             ::value;
 571         }
 572       };
 573
 574     public:
 575       template<typename _Dummy = void,
 576                typename enable_if<_TC2<_Dummy>::
 577                                     _ImplicitlyDefaultConstructibleTuple(),
 578                                   bool>::type = true>
 579       constexpr tuple()
 580       : _Inherited() { }
 581
 582       template<typename _Dummy = void,
 583                typename enable_if<_TC2<_Dummy>::
 584                                     _DefaultConstructibleTuple()
 585                                   &&
 586                                   !_TC2<_Dummy>::
 587                                     _ImplicitlyDefaultConstructibleTuple(),
 588                                   bool>::type = false>
 589       explicit constexpr tuple()
 590       : _Inherited() { }
 591
 592       // Shortcut for the cases where constructors taking _Elements...
 593       // need to be constrained.
 594       template<typename _Dummy> using _TCC =
 595         _TC<is_same<_Dummy, void>::value,
 596             _Elements...>;
 597
 598       template<typename _Dummy = void,
 599                typename enable_if<
 600                  _TCC<_Dummy>::template
 601                    _ConstructibleTuple<_Elements...>()
 602                  && _TCC<_Dummy>::template
 603                    _ImplicitlyConvertibleTuple<_Elements...>()
 604                  && (sizeof...(_Elements) >= 1),
 605                bool>::type=true>
 606         constexpr tuple(const _Elements&... __elements)
 607       : _Inherited(__elements...) { }
 608
 609       template<typename _Dummy = void,
 610                typename enable_if<
 611                  _TCC<_Dummy>::template
 612                    _ConstructibleTuple<_Elements...>()
 613                  && !_TCC<_Dummy>::template
 614                    _ImplicitlyConvertibleTuple<_Elements...>()
 615                  && (sizeof...(_Elements) >= 1),
 616                bool>::type=false>
 617       explicit constexpr tuple(const _Elements&... __elements)
 618       : _Inherited(__elements...) { }
 619
 620       // Shortcut for the cases where constructors taking _UElements...
 621       // need to be constrained.
 622       template<typename... _UElements> using _TMC =
 623                   _TC<(sizeof...(_Elements) == sizeof...(_UElements))
 624                       && (_TC<(sizeof...(_UElements)==1), _Elements...>::
 625                           template _NotSameTuple<_UElements...>()),
 626                       _Elements...>;
 627
 628       // Shortcut for the cases where constructors taking tuple<_UElements...>
 629       // need to be constrained.
 630       template<typename... _UElements> using _TMCT =
 631                   _TC<(sizeof...(_Elements) == sizeof...(_UElements))
 632                       && !is_same<tuple<_Elements...>,
 633                                   tuple<_UElements...>>::value,
 634                       _Elements...>;
 635
 636       template<typename... _UElements, typename
 637                enable_if<
 638                   _TMC<_UElements...>::template
 639                     _MoveConstructibleTuple<_UElements...>()
 640                   && _TMC<_UElements...>::template
 641                     _ImplicitlyMoveConvertibleTuple<_UElements...>()
 642                   && (sizeof...(_Elements) >= 1),
 643         bool>::type=true>
 644         constexpr tuple(_UElements&&... __elements)
 645         : _Inherited(std::forward<_UElements>(__elements)...) { }
 646
 647       template<typename... _UElements, typename
 648         enable_if<
 649                   _TMC<_UElements...>::template
 650                     _MoveConstructibleTuple<_UElements...>()
 651                   && !_TMC<_UElements...>::template
 652                     _ImplicitlyMoveConvertibleTuple<_UElements...>()
 653                   && (sizeof...(_Elements) >= 1),
 654         bool>::type=false>
 655         explicit constexpr tuple(_UElements&&... __elements)
 656         : _Inherited(std::forward<_UElements>(__elements)...) { }
 657
 658       constexpr tuple(const tuple&) = default;
 659
 660       constexpr tuple(tuple&&) = default;
 661
 662       // Shortcut for the cases where constructors taking tuples
 663       // must avoid creating temporaries.
 664       template<typename _Dummy> using _TNTC =
 665         _TC<is_same<_Dummy, void>::value && sizeof...(_Elements) == 1,
 666             _Elements...>;
 667
 668       template<typename... _UElements, typename _Dummy = void, typename
 669         enable_if<_TMCT<_UElements...>::template
 670                     _ConstructibleTuple<_UElements...>()
 671                   && _TMCT<_UElements...>::template
 672                     _ImplicitlyConvertibleTuple<_UElements...>()
 673                   && _TNTC<_Dummy>::template
 674                     _NonNestedTuple<const tuple<_UElements...>&>(),
 675         bool>::type=true>
 676         constexpr tuple(const tuple<_UElements...>& __in)
 677         : _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 678         { }
 679
 680       template<typename... _UElements, typename _Dummy = void, typename
 681         enable_if<_TMCT<_UElements...>::template
 682                     _ConstructibleTuple<_UElements...>()
 683                   && !_TMCT<_UElements...>::template
 684                     _ImplicitlyConvertibleTuple<_UElements...>()
 685                   && _TNTC<_Dummy>::template
 686                     _NonNestedTuple<const tuple<_UElements...>&>(),
 687         bool>::type=false>
 688         explicit constexpr tuple(const tuple<_UElements...>& __in)
 689         : _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 690         { }
 691
 692       template<typename... _UElements, typename _Dummy = void, typename
 693         enable_if<_TMCT<_UElements...>::template
 694                     _MoveConstructibleTuple<_UElements...>()
 695                   && _TMCT<_UElements...>::template
 696                     _ImplicitlyMoveConvertibleTuple<_UElements...>()
 697                   && _TNTC<_Dummy>::template
 698                     _NonNestedTuple<tuple<_UElements...>&&>(),
 699         bool>::type=true>
 700         constexpr tuple(tuple<_UElements...>&& __in)
 701         : _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
 702
 703       template<typename... _UElements, typename _Dummy = void, typename
 704         enable_if<_TMCT<_UElements...>::template
 705                     _MoveConstructibleTuple<_UElements...>()
 706                   && !_TMCT<_UElements...>::template
 707                     _ImplicitlyMoveConvertibleTuple<_UElements...>()
 708                   && _TNTC<_Dummy>::template
 709                     _NonNestedTuple<tuple<_UElements...>&&>(),
 710         bool>::type=false>
 711         explicit constexpr tuple(tuple<_UElements...>&& __in)
 712         : _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
 713
 714       // Allocator-extended constructors.
 715
 716       template<typename _Alloc>
 717         tuple(allocator_arg_t __tag, const _Alloc& __a)
 718         : _Inherited(__tag, __a) { }
 719
 720       template<typename _Alloc, typename _Dummy = void,
 721                typename enable_if<
 722                  _TCC<_Dummy>::template
 723                    _ConstructibleTuple<_Elements...>()
 724                  && _TCC<_Dummy>::template
 725                    _ImplicitlyConvertibleTuple<_Elements...>(),
 726                bool>::type=true>
 727         tuple(allocator_arg_t __tag, const _Alloc& __a,
 728               const _Elements&... __elements)
 729         : _Inherited(__tag, __a, __elements...) { }
 730
 731       template<typename _Alloc, typename _Dummy = void,
 732                typename enable_if<
 733                  _TCC<_Dummy>::template
 734                    _ConstructibleTuple<_Elements...>()
 735                  && !_TCC<_Dummy>::template
 736                    _ImplicitlyConvertibleTuple<_Elements...>(),
 737                bool>::type=false>
 738         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
 739                        const _Elements&... __elements)
 740         : _Inherited(__tag, __a, __elements...) { }
 741
 742       template<typename _Alloc, typename... _UElements, typename
 743         enable_if<_TMC<_UElements...>::template
 744                     _MoveConstructibleTuple<_UElements...>()
 745                   && _TMC<_UElements...>::template
 746                     _ImplicitlyMoveConvertibleTuple<_UElements...>(),
 747         bool>::type=true>
 748         tuple(allocator_arg_t __tag, const _Alloc& __a,
 749               _UElements&&... __elements)
 750         : _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)
 751         { }
 752
 753       template<typename _Alloc, typename... _UElements, typename
 754         enable_if<_TMC<_UElements...>::template
 755                     _MoveConstructibleTuple<_UElements...>()
 756                   && !_TMC<_UElements...>::template
 757                     _ImplicitlyMoveConvertibleTuple<_UElements...>(),
 758         bool>::type=false>
 759         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
 760               _UElements&&... __elements)
 761         : _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)
 762         { }
 763
 764       template<typename _Alloc>
 765         tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
 766         : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
 767
 768       template<typename _Alloc>
 769         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
 770         : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
 771
 772       template<typename _Alloc, typename _Dummy = void,
 773                typename... _UElements, typename
 774         enable_if<_TMCT<_UElements...>::template
 775                     _ConstructibleTuple<_UElements...>()
 776                   && _TMCT<_UElements...>::template
 777                     _ImplicitlyConvertibleTuple<_UElements...>()
 778                   && _TNTC<_Dummy>::template
 779                     _NonNestedTuple<tuple<_UElements...>&&>(),
 780         bool>::type=true>
 781         tuple(allocator_arg_t __tag, const _Alloc& __a,
 782               const tuple<_UElements...>& __in)
 783         : _Inherited(__tag, __a,
 784                      static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 785         { }
 786
 787       template<typename _Alloc, typename _Dummy = void,
 788                typename... _UElements, typename
 789         enable_if<_TMCT<_UElements...>::template
 790                     _ConstructibleTuple<_UElements...>()
 791                   && !_TMCT<_UElements...>::template
 792                     _ImplicitlyConvertibleTuple<_UElements...>()
 793                   && _TNTC<_Dummy>::template
 794                     _NonNestedTuple<tuple<_UElements...>&&>(),
 795         bool>::type=false>
 796         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
 797               const tuple<_UElements...>& __in)
 798         : _Inherited(__tag, __a,
 799                      static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 800         { }
 801
 802       template<typename _Alloc, typename _Dummy = void,
 803                typename... _UElements, typename
 804         enable_if<_TMCT<_UElements...>::template
 805                     _MoveConstructibleTuple<_UElements...>()
 806                   && _TMCT<_UElements...>::template
 807                     _ImplicitlyMoveConvertibleTuple<_UElements...>()
 808                   && _TNTC<_Dummy>::template
 809                     _NonNestedTuple<tuple<_UElements...>&&>(),
 810         bool>::type=true>
 811         tuple(allocator_arg_t __tag, const _Alloc& __a,
 812               tuple<_UElements...>&& __in)
 813         : _Inherited(__tag, __a,
 814                      static_cast<_Tuple_impl<0, _UElements...>&&>(__in))
 815         { }
 816
 817       template<typename _Alloc, typename _Dummy = void,
 818                typename... _UElements, typename
 819         enable_if<_TMCT<_UElements...>::template
 820                     _MoveConstructibleTuple<_UElements...>()
 821                   && !_TMCT<_UElements...>::template
 822                     _ImplicitlyMoveConvertibleTuple<_UElements...>()
 823                   && _TNTC<_Dummy>::template
 824                     _NonNestedTuple<tuple<_UElements...>&&>(),
 825         bool>::type=false>
 826         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
 827               tuple<_UElements...>&& __in)
 828         : _Inherited(__tag, __a,
 829                      static_cast<_Tuple_impl<0, _UElements...>&&>(__in))
 830         { }
 831
 832       tuple&
 833       operator=(const tuple& __in)
 834       {
 835         static_cast<_Inherited&>(*this) = __in;
 836         return *this;
 837       }
 838
 839       tuple&
 840       operator=(tuple&& __in)
 841       noexcept(is_nothrow_move_assignable<_Inherited>::value)
 842       {
 843         static_cast<_Inherited&>(*this) = std::move(__in);
 844         return *this;
 845       }
 846
 847       template<typename... _UElements, typename = typename
 848                enable_if<sizeof...(_UElements)
 849                          == sizeof...(_Elements)>::type>
 850         tuple&
 851         operator=(const tuple<_UElements...>& __in)
 852         {
 853           static_cast<_Inherited&>(*this) = __in;
 854           return *this;
 855         }
 856
 857       template<typename... _UElements, typename = typename
 858                enable_if<sizeof...(_UElements)
 859                          == sizeof...(_Elements)>::type>
 860         tuple&
 861         operator=(tuple<_UElements...>&& __in)
 862         {
 863           static_cast<_Inherited&>(*this) = std::move(__in);
 864           return *this;
 865         }
 866
 867       void
 868       swap(tuple& __in)
 869       noexcept(noexcept(__in._M_swap(__in)))
 870       { _Inherited::_M_swap(__in); }
 871     };
 872
 873   // Explicit specialization, zero-element tuple.
 874   template<>
 875     class tuple<>
 876     {
 877     public:
 878       void swap(tuple&) noexcept { /* no-op */ }
 879       // We need the default since we're going to define no-op
 880       // allocator constructors.
 881       tuple() = default;
 882       // No-op allocator constructors.
 883       template<typename _Alloc>
 884         tuple(allocator_arg_t, const _Alloc&) { }
 885       template<typename _Alloc>
 886         tuple(allocator_arg_t, const _Alloc&, const tuple&) { }
 887     };
 888
 889   /// Partial specialization, 2-element tuple.
 890   /// Includes construction and assignment from a pair.
 891   template<typename _T1, typename _T2>
 892     class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
 893     {
 894       typedef _Tuple_impl<0, _T1, _T2> _Inherited;
 895
 896     public:
 897       template <typename _U1 = _T1,
 898                 typename _U2 = _T2,
 899                 typename enable_if<__and_<
 900                                      __is_implicitly_default_constructible<_U1>,
 901                                      __is_implicitly_default_constructible<_U2>>
 902                                    ::value, bool>::type = true>
 903
 904       constexpr tuple()
 905       : _Inherited() { }
 906
 907       template <typename _U1 = _T1,
 908                 typename _U2 = _T2,
 909                 typename enable_if<
 910                   __and_<
 911                     is_default_constructible<_U1>,
 912                     is_default_constructible<_U2>,
 913                     __not_<
 914                       __and_<__is_implicitly_default_constructible<_U1>,
 915                              __is_implicitly_default_constructible<_U2>>>>
 916                   ::value, bool>::type = false>
 917
 918       explicit constexpr tuple()
 919       : _Inherited() { }
 920
 921       // Shortcut for the cases where constructors taking _T1, _T2
 922       // need to be constrained.
 923       template<typename _Dummy> using _TCC =
 924         _TC<is_same<_Dummy, void>::value, _T1, _T2>;
 925
 926       template<typename _Dummy = void, typename
 927                enable_if<_TCC<_Dummy>::template
 928                            _ConstructibleTuple<_T1, _T2>()
 929                          && _TCC<_Dummy>::template
 930                            _ImplicitlyConvertibleTuple<_T1, _T2>(),
 931         bool>::type = true>
 932         constexpr tuple(const _T1& __a1, const _T2& __a2)
 933         : _Inherited(__a1, __a2) { }
 934
 935       template<typename _Dummy = void, typename
 936                enable_if<_TCC<_Dummy>::template
 937                            _ConstructibleTuple<_T1, _T2>()
 938                          && !_TCC<_Dummy>::template
 939                            _ImplicitlyConvertibleTuple<_T1, _T2>(),
 940         bool>::type = false>
 941         explicit constexpr tuple(const _T1& __a1, const _T2& __a2)
 942         : _Inherited(__a1, __a2) { }
 943
 944       // Shortcut for the cases where constructors taking _U1, _U2
 945       // need to be constrained.
 946       using _TMC = _TC<true, _T1, _T2>;
 947
 948       template<typename _U1, typename _U2, typename
 949         enable_if<_TMC::template
 950                     _MoveConstructibleTuple<_U1, _U2>()
 951                   && _TMC::template
 952                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
 953         bool>::type = true>
 954         constexpr tuple(_U1&& __a1, _U2&& __a2)
 955         : _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
 956
 957       template<typename _U1, typename _U2, typename
 958         enable_if<_TMC::template
 959                     _MoveConstructibleTuple<_U1, _U2>()
 960                   && !_TMC::template
 961                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
 962         bool>::type = false>
 963         explicit constexpr tuple(_U1&& __a1, _U2&& __a2)
 964         : _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
 965
 966       constexpr tuple(const tuple&) = default;
 967
 968       constexpr tuple(tuple&&) = default;
 969
 970       template<typename _U1, typename _U2, typename
 971         enable_if<_TMC::template
 972                     _ConstructibleTuple<_U1, _U2>()
 973                   && _TMC::template
 974                     _ImplicitlyConvertibleTuple<_U1, _U2>(),
 975         bool>::type = true>
 976         constexpr tuple(const tuple<_U1, _U2>& __in)
 977         : _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
 978
 979       template<typename _U1, typename _U2, typename
 980         enable_if<_TMC::template
 981                     _ConstructibleTuple<_U1, _U2>()
 982                   && !_TMC::template
 983                     _ImplicitlyConvertibleTuple<_U1, _U2>(),
 984         bool>::type = false>
 985         explicit constexpr tuple(const tuple<_U1, _U2>& __in)
 986         : _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
 987
 988       template<typename _U1, typename _U2, typename
 989         enable_if<_TMC::template
 990                     _MoveConstructibleTuple<_U1, _U2>()
 991                   && _TMC::template
 992                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
 993         bool>::type = true>
 994         constexpr tuple(tuple<_U1, _U2>&& __in)
 995         : _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
 996
 997       template<typename _U1, typename _U2, typename
 998         enable_if<_TMC::template
 999                     _MoveConstructibleTuple<_U1, _U2>()
1000                   && !_TMC::template
1001                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
1002         bool>::type = false>
1003         explicit constexpr tuple(tuple<_U1, _U2>&& __in)
1004         : _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
1005
1006       template<typename _U1, typename _U2, typename
1007         enable_if<_TMC::template
1008                     _ConstructibleTuple<_U1, _U2>()
1009                   && _TMC::template
1010                     _ImplicitlyConvertibleTuple<_U1, _U2>(),
1011         bool>::type = true>
1012         constexpr tuple(const pair<_U1, _U2>& __in)
1013         : _Inherited(__in.first, __in.second) { }
1014
1015       template<typename _U1, typename _U2, typename
1016         enable_if<_TMC::template
1017                     _ConstructibleTuple<_U1, _U2>()
1018                   && !_TMC::template
1019                     _ImplicitlyConvertibleTuple<_U1, _U2>(),
1020         bool>::type = false>
1021         explicit constexpr tuple(const pair<_U1, _U2>& __in)
1022         : _Inherited(__in.first, __in.second) { }
1023
1024       template<typename _U1, typename _U2, typename
1025         enable_if<_TMC::template
1026                     _MoveConstructibleTuple<_U1, _U2>()
1027                   && _TMC::template
1028                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
1029         bool>::type = true>
1030         constexpr tuple(pair<_U1, _U2>&& __in)
1031         : _Inherited(std::forward<_U1>(__in.first),
1032                      std::forward<_U2>(__in.second)) { }
1033
1034       template<typename _U1, typename _U2, typename
1035         enable_if<_TMC::template
1036                     _MoveConstructibleTuple<_U1, _U2>()
1037                   && !_TMC::template
1038                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
1039         bool>::type = false>
1040         explicit constexpr tuple(pair<_U1, _U2>&& __in)
1041         : _Inherited(std::forward<_U1>(__in.first),
1042                      std::forward<_U2>(__in.second)) { }
1043
1044       // Allocator-extended constructors.
1045
1046       template<typename _Alloc>
1047         tuple(allocator_arg_t __tag, const _Alloc& __a)
1048         : _Inherited(__tag, __a) { }
1049
1050       template<typename _Alloc, typename _Dummy = void,
1051                typename enable_if<
1052                  _TCC<_Dummy>::template
1053                    _ConstructibleTuple<_T1, _T2>()
1054                  && _TCC<_Dummy>::template
1055                    _ImplicitlyConvertibleTuple<_T1, _T2>(),
1056                bool>::type=true>
1057
1058         tuple(allocator_arg_t __tag, const _Alloc& __a,
1059               const _T1& __a1, const _T2& __a2)
1060         : _Inherited(__tag, __a, __a1, __a2) { }
1061
1062       template<typename _Alloc, typename _Dummy = void,
1063                typename enable_if<
1064                  _TCC<_Dummy>::template
1065                    _ConstructibleTuple<_T1, _T2>()
1066                  && !_TCC<_Dummy>::template
1067                    _ImplicitlyConvertibleTuple<_T1, _T2>(),
1068                bool>::type=false>
1069
1070         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
1071               const _T1& __a1, const _T2& __a2)
1072         : _Inherited(__tag, __a, __a1, __a2) { }
1073
1074       template<typename _Alloc, typename _U1, typename _U2, typename
1075         enable_if<_TMC::template
1076                     _MoveConstructibleTuple<_U1, _U2>()
1077                   && _TMC::template
1078                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
1079         bool>::type = true>
1080         tuple(allocator_arg_t __tag, const _Alloc& __a, _U1&& __a1, _U2&& __a2)
1081         : _Inherited(__tag, __a, std::forward<_U1>(__a1),
1082                      std::forward<_U2>(__a2)) { }
1083
1084       template<typename _Alloc, typename _U1, typename _U2, typename
1085         enable_if<_TMC::template
1086                     _MoveConstructibleTuple<_U1, _U2>()
1087                   && !_TMC::template
1088                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
1089         bool>::type = false>
1090         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
1091                        _U1&& __a1, _U2&& __a2)
1092         : _Inherited(__tag, __a, std::forward<_U1>(__a1),
1093                      std::forward<_U2>(__a2)) { }
1094
1095       template<typename _Alloc>
1096         tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
1097         : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
1098
1099       template<typename _Alloc>
1100         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
1101         : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
1102
1103       template<typename _Alloc, typename _U1, typename _U2, typename
1104         enable_if<_TMC::template
1105                     _ConstructibleTuple<_U1, _U2>()
1106                   && _TMC::template
1107                     _ImplicitlyConvertibleTuple<_U1, _U2>(),
1108         bool>::type = true>
1109         tuple(allocator_arg_t __tag, const _Alloc& __a,
1110               const tuple<_U1, _U2>& __in)
1111         : _Inherited(__tag, __a,
1112                      static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in))
1113         { }
1114
1115       template<typename _Alloc, typename _U1, typename _U2, typename
1116         enable_if<_TMC::template
1117                     _ConstructibleTuple<_U1, _U2>()
1118                   && !_TMC::template
1119                     _ImplicitlyConvertibleTuple<_U1, _U2>(),
1120         bool>::type = false>
1121         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
1122               const tuple<_U1, _U2>& __in)
1123         : _Inherited(__tag, __a,
1124                      static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in))
1125         { }
1126
1127       template<typename _Alloc, typename _U1, typename _U2, typename
1128         enable_if<_TMC::template
1129                     _MoveConstructibleTuple<_U1, _U2>()
1130                   && _TMC::template
1131                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
1132         bool>::type = true>
1133         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple<_U1, _U2>&& __in)
1134         : _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))
1135         { }
1136
1137       template<typename _Alloc, typename _U1, typename _U2, typename
1138         enable_if<_TMC::template
1139                     _MoveConstructibleTuple<_U1, _U2>()
1140                   && !_TMC::template
1141                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
1142         bool>::type = false>
1143         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
1144                        tuple<_U1, _U2>&& __in)
1145         : _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))
1146         { }
1147
1148       template<typename _Alloc, typename _U1, typename _U2, typename
1149         enable_if<_TMC::template
1150                     _ConstructibleTuple<_U1, _U2>()
1151                   && _TMC::template
1152                     _ImplicitlyConvertibleTuple<_U1, _U2>(),
1153         bool>::type = true>
1154         tuple(allocator_arg_t __tag, const _Alloc& __a,
1155               const pair<_U1, _U2>& __in)
1156         : _Inherited(__tag, __a, __in.first, __in.second) { }
1157
1158       template<typename _Alloc, typename _U1, typename _U2, typename
1159         enable_if<_TMC::template
1160                     _ConstructibleTuple<_U1, _U2>()
1161                   && !_TMC::template
1162                     _ImplicitlyConvertibleTuple<_U1, _U2>(),
1163         bool>::type = false>
1164         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
1165               const pair<_U1, _U2>& __in)
1166         : _Inherited(__tag, __a, __in.first, __in.second) { }
1167
1168       template<typename _Alloc, typename _U1, typename _U2, typename
1169         enable_if<_TMC::template
1170                     _MoveConstructibleTuple<_U1, _U2>()
1171                   && _TMC::template
1172                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
1173         bool>::type = true>
1174         tuple(allocator_arg_t __tag, const _Alloc& __a, pair<_U1, _U2>&& __in)
1175         : _Inherited(__tag, __a, std::forward<_U1>(__in.first),
1176                      std::forward<_U2>(__in.second)) { }
1177
1178       template<typename _Alloc, typename _U1, typename _U2, typename
1179         enable_if<_TMC::template
1180                     _MoveConstructibleTuple<_U1, _U2>()
1181                   && !_TMC::template
1182                     _ImplicitlyMoveConvertibleTuple<_U1, _U2>(),
1183         bool>::type = false>
1184         explicit tuple(allocator_arg_t __tag, const _Alloc& __a,
1185                        pair<_U1, _U2>&& __in)
1186         : _Inherited(__tag, __a, std::forward<_U1>(__in.first),
1187                      std::forward<_U2>(__in.second)) { }
1188
1189       tuple&
1190       operator=(const tuple& __in)
1191       {
1192         static_cast<_Inherited&>(*this) = __in;
1193         return *this;
1194       }
1195
1196       tuple&
1197       operator=(tuple&& __in)
1198       noexcept(is_nothrow_move_assignable<_Inherited>::value)
1199       {
1200         static_cast<_Inherited&>(*this) = std::move(__in);
1201         return *this;
1202       }
1203
1204       template<typename _U1, typename _U2>
1205         tuple&
1206         operator=(const tuple<_U1, _U2>& __in)
1207         {
1208           static_cast<_Inherited&>(*this) = __in;
1209           return *this;
1210         }
1211
1212       template<typename _U1, typename _U2>
1213         tuple&
1214         operator=(tuple<_U1, _U2>&& __in)
1215         {
1216           static_cast<_Inherited&>(*this) = std::move(__in);
1217           return *this;
1218         }
1219
1220       template<typename _U1, typename _U2>
1221         tuple&
1222         operator=(const pair<_U1, _U2>& __in)
1223         {
1224           this->_M_head(*this) = __in.first;
1225           this->_M_tail(*this)._M_head(*this) = __in.second;
1226           return *this;
1227         }
1228
1229       template<typename _U1, typename _U2>
1230         tuple&
1231         operator=(pair<_U1, _U2>&& __in)
1232         {
1233           this->_M_head(*this) = std::forward<_U1>(__in.first);
1234           this->_M_tail(*this)._M_head(*this) = std::forward<_U2>(__in.second);
1235           return *this;
1236         }
1237
1238       void
1239       swap(tuple& __in)
1240       noexcept(noexcept(__in._M_swap(__in)))
1241       { _Inherited::_M_swap(__in); }
1242     };
1243
1244
1245   /**
1246    * Recursive case for tuple_element: strip off the first element in
1247    * the tuple and retrieve the (i-1)th element of the remaining tuple.
1248    */
1249   template<std::size_t __i, typename _Head, typename... _Tail>
1250     struct tuple_element<__i, tuple<_Head, _Tail...> >
1251     : tuple_element<__i - 1, tuple<_Tail...> > { };
1252
1253   /**
1254    * Basis case for tuple_element: The first element is the one we're seeking.
1255    */
1256   template<typename _Head, typename... _Tail>
1257     struct tuple_element<0, tuple<_Head, _Tail...> >
1258     {
1259       typedef _Head type;
1260     };
1261
1262   /// class tuple_size
1263   template<typename... _Elements>
1264     struct tuple_size<tuple<_Elements...>>
1265     : public integral_constant<std::size_t, sizeof...(_Elements)> { };
1266
1267   template<std::size_t __i, typename _Head, typename... _Tail>
1268     constexpr _Head&
1269     __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
1270     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
1271
1272   template<std::size_t __i, typename _Head, typename... _Tail>
1273     constexpr const _Head&
1274     __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
1275     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
1276
1277   /// Return a reference to the ith element of a tuple.
1278   template<std::size_t __i, typename... _Elements>
1279     constexpr __tuple_element_t<__i, tuple<_Elements...>>&
1280     get(tuple<_Elements...>& __t) noexcept
1281     { return std::__get_helper<__i>(__t); }
1282
1283   /// Return a const reference to the ith element of a const tuple.
1284   template<std::size_t __i, typename... _Elements>
1285     constexpr const __tuple_element_t<__i, tuple<_Elements...>>&
1286     get(const tuple<_Elements...>& __t) noexcept
1287     { return std::__get_helper<__i>(__t); }
1288
1289   /// Return an rvalue reference to the ith element of a tuple rvalue.
1290   template<std::size_t __i, typename... _Elements>
1291     constexpr __tuple_element_t<__i, tuple<_Elements...>>&&
1292     get(tuple<_Elements...>&& __t) noexcept
1293     {
1294       typedef __tuple_element_t<__i, tuple<_Elements...>> __element_type;
1295       return std::forward<__element_type&&>(std::get<__i>(__t));
1296     }
1297
1298 #if __cplusplus > 201103L
1299
1300 #define __cpp_lib_tuples_by_type 201304
1301
1302   template<typename _Head, size_t __i, typename... _Tail>
1303     constexpr _Head&
1304     __get_helper2(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
1305     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
1306
1307   template<typename _Head, size_t __i, typename... _Tail>
1308     constexpr const _Head&
1309     __get_helper2(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
1310     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
1311
1312   /// Return a reference to the unique element of type _Tp of a tuple.
1313   template <typename _Tp, typename... _Types>
1314     constexpr _Tp&
1315     get(tuple<_Types...>& __t) noexcept
1316     { return std::__get_helper2<_Tp>(__t); }
1317
1318   /// Return a reference to the unique element of type _Tp of a tuple rvalue.
1319   template <typename _Tp, typename... _Types>
1320     constexpr _Tp&&
1321     get(tuple<_Types...>&& __t) noexcept
1322     { return std::forward<_Tp&&>(std::__get_helper2<_Tp>(__t)); }
1323
1324   /// Return a const reference to the unique element of type _Tp of a tuple.
1325   template <typename _Tp, typename... _Types>
1326     constexpr const _Tp&
1327     get(const tuple<_Types...>& __t) noexcept
1328     { return std::__get_helper2<_Tp>(__t); }
1329 #endif
1330
1331   // This class performs the comparison operations on tuples
1332   template<typename _Tp, typename _Up, size_t __i, size_t __size>
1333     struct __tuple_compare
1334     {
1335       static constexpr bool
1336       __eq(const _Tp& __t, const _Up& __u)
1337       {
1338         return bool(std::get<__i>(__t) == std::get<__i>(__u))
1339           && __tuple_compare<_Tp, _Up, __i + 1, __size>::__eq(__t, __u);
1340       }
1341
1342       static constexpr bool
1343       __less(const _Tp& __t, const _Up& __u)
1344       {
1345         return bool(std::get<__i>(__t) < std::get<__i>(__u))
1346           || (!bool(std::get<__i>(__u) < std::get<__i>(__t))
1347               && __tuple_compare<_Tp, _Up, __i + 1, __size>::__less(__t, __u));
1348       }
1349     };
1350
1351   template<typename _Tp, typename _Up, size_t __size>
1352     struct __tuple_compare<_Tp, _Up, __size, __size>
1353     {
1354       static constexpr bool
1355       __eq(const _Tp&, const _Up&) { return true; }
1356
1357       static constexpr bool
1358       __less(const _Tp&, const _Up&) { return false; }
1359     };
1360
1361   template<typename... _TElements, typename... _UElements>
1362     constexpr bool
1363     operator==(const tuple<_TElements...>& __t,
1364                const tuple<_UElements...>& __u)
1365     {
1366       static_assert(sizeof...(_TElements) == sizeof...(_UElements),
1367           "tuple objects can only be compared if they have equal sizes.");
1368       using __compare = __tuple_compare<tuple<_TElements...>,
1369                                         tuple<_UElements...>,
1370                                         0, sizeof...(_TElements)>;
1371       return __compare::__eq(__t, __u);
1372     }
1373
1374   template<typename... _TElements, typename... _UElements>
1375     constexpr bool
1376     operator<(const tuple<_TElements...>& __t,
1377               const tuple<_UElements...>& __u)
1378     {
1379       static_assert(sizeof...(_TElements) == sizeof...(_UElements),
1380           "tuple objects can only be compared if they have equal sizes.");
1381       using __compare = __tuple_compare<tuple<_TElements...>,
1382                                         tuple<_UElements...>,
1383                                         0, sizeof...(_TElements)>;
1384       return __compare::__less(__t, __u);
1385     }
1386
1387   template<typename... _TElements, typename... _UElements>
1388     constexpr bool
1389     operator!=(const tuple<_TElements...>& __t,
1390                const tuple<_UElements...>& __u)
1391     { return !(__t == __u); }
1392
1393   template<typename... _TElements, typename... _UElements>
1394     constexpr bool
1395     operator>(const tuple<_TElements...>& __t,
1396               const tuple<_UElements...>& __u)
1397     { return __u < __t; }
1398
1399   template<typename... _TElements, typename... _UElements>
1400     constexpr bool
1401     operator<=(const tuple<_TElements...>& __t,
1402                const tuple<_UElements...>& __u)
1403     { return !(__u < __t); }
1404
1405   template<typename... _TElements, typename... _UElements>
1406     constexpr bool
1407     operator>=(const tuple<_TElements...>& __t,
1408                const tuple<_UElements...>& __u)
1409     { return !(__t < __u); }
1410
1411   // NB: DR 705.
1412   template<typename... _Elements>
1413     constexpr tuple<typename __decay_and_strip<_Elements>::__type...>
1414     make_tuple(_Elements&&... __args)
1415     {
1416       typedef tuple<typename __decay_and_strip<_Elements>::__type...>
1417         __result_type;
1418       return __result_type(std::forward<_Elements>(__args)...);
1419     }
1420
1421   // _GLIBCXX_RESOLVE_LIB_DEFECTS
1422   // 2275. Why is forward_as_tuple not constexpr?
1423   template<typename... _Elements>
1424     constexpr tuple<_Elements&&...>
1425     forward_as_tuple(_Elements&&... __args) noexcept
1426     { return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
1427
1428   template<typename... _Tps>
1429     struct __is_tuple_like_impl<tuple<_Tps...>> : true_type
1430     { };
1431
1432   // Internal type trait that allows us to sfinae-protect tuple_cat.
1433   template<typename _Tp>
1434     struct __is_tuple_like
1435     : public __is_tuple_like_impl<typename std::remove_cv
1436             <typename std::remove_reference<_Tp>::type>::type>::type
1437     { };
1438
1439   template<size_t, typename, typename, size_t>
1440     struct __make_tuple_impl;
1441
1442   template<size_t _Idx, typename _Tuple, typename... _Tp, size_t _Nm>
1443     struct __make_tuple_impl<_Idx, tuple<_Tp...>, _Tuple, _Nm>
1444     : __make_tuple_impl<_Idx + 1,
1445                         tuple<_Tp..., __tuple_element_t<_Idx, _Tuple>>,
1446                         _Tuple, _Nm>
1447     { };
1448
1449   template<std::size_t _Nm, typename _Tuple, typename... _Tp>
1450     struct __make_tuple_impl<_Nm, tuple<_Tp...>, _Tuple, _Nm>
1451     {
1452       typedef tuple<_Tp...> __type;
1453     };
1454
1455   template<typename _Tuple>
1456     struct __do_make_tuple
1457     : __make_tuple_impl<0, tuple<>, _Tuple, std::tuple_size<_Tuple>::value>
1458     { };
1459
1460   // Returns the std::tuple equivalent of a tuple-like type.
1461   template<typename _Tuple>
1462     struct __make_tuple
1463     : public __do_make_tuple<typename std::remove_cv
1464             <typename std::remove_reference<_Tuple>::type>::type>
1465     { };
1466
1467   // Combines several std::tuple's into a single one.
1468   template<typename...>
1469     struct __combine_tuples;
1470
1471   template<>
1472     struct __combine_tuples<>
1473     {
1474       typedef tuple<> __type;
1475     };
1476
1477   template<typename... _Ts>
1478     struct __combine_tuples<tuple<_Ts...>>
1479     {
1480       typedef tuple<_Ts...> __type;
1481     };
1482
1483   template<typename... _T1s, typename... _T2s, typename... _Rem>
1484     struct __combine_tuples<tuple<_T1s...>, tuple<_T2s...>, _Rem...>
1485     {
1486       typedef typename __combine_tuples<tuple<_T1s..., _T2s...>,
1487                                         _Rem...>::__type __type;
1488     };
1489
1490   // Computes the result type of tuple_cat given a set of tuple-like types.
1491   template<typename... _Tpls>
1492     struct __tuple_cat_result
1493     {
1494       typedef typename __combine_tuples
1495         <typename __make_tuple<_Tpls>::__type...>::__type __type;
1496     };
1497
1498   // Helper to determine the index set for the first tuple-like
1499   // type of a given set.
1500   template<typename...>
1501     struct __make_1st_indices;
1502
1503   template<>
1504     struct __make_1st_indices<>
1505     {
1506       typedef std::_Index_tuple<> __type;
1507     };
1508
1509   template<typename _Tp, typename... _Tpls>
1510     struct __make_1st_indices<_Tp, _Tpls...>
1511     {
1512       typedef typename std::_Build_index_tuple<std::tuple_size<
1513         typename std::remove_reference<_Tp>::type>::value>::__type __type;
1514     };
1515
1516   // Performs the actual concatenation by step-wise expanding tuple-like
1517   // objects into the elements,  which are finally forwarded into the
1518   // result tuple.
1519   template<typename _Ret, typename _Indices, typename... _Tpls>
1520     struct __tuple_concater;
1521
1522   template<typename _Ret, std::size_t... _Is, typename _Tp, typename... _Tpls>
1523     struct __tuple_concater<_Ret, std::_Index_tuple<_Is...>, _Tp, _Tpls...>
1524     {
1525       template<typename... _Us>
1526         static constexpr _Ret
1527         _S_do(_Tp&& __tp, _Tpls&&... __tps, _Us&&... __us)
1528         {
1529           typedef typename __make_1st_indices<_Tpls...>::__type __idx;
1530           typedef __tuple_concater<_Ret, __idx, _Tpls...>      __next;
1531           return __next::_S_do(std::forward<_Tpls>(__tps)...,
1532                                std::forward<_Us>(__us)...,
1533                                std::get<_Is>(std::forward<_Tp>(__tp))...);
1534         }
1535     };
1536
1537   template<typename _Ret>
1538     struct __tuple_concater<_Ret, std::_Index_tuple<>>
1539     {
1540       template<typename... _Us>
1541         static constexpr _Ret
1542         _S_do(_Us&&... __us)
1543         {
1544           return _Ret(std::forward<_Us>(__us)...);
1545         }
1546     };
1547
1548   /// tuple_cat
1549   template<typename... _Tpls, typename = typename
1550            enable_if<__and_<__is_tuple_like<_Tpls>...>::value>::type>
1551     constexpr auto
1552     tuple_cat(_Tpls&&... __tpls)
1553     -> typename __tuple_cat_result<_Tpls...>::__type
1554     {
1555       typedef typename __tuple_cat_result<_Tpls...>::__type __ret;
1556       typedef typename __make_1st_indices<_Tpls...>::__type __idx;
1557       typedef __tuple_concater<__ret, __idx, _Tpls...> __concater;
1558       return __concater::_S_do(std::forward<_Tpls>(__tpls)...);
1559     }
1560
1561   // _GLIBCXX_RESOLVE_LIB_DEFECTS
1562   // 2301. Why is tie not constexpr?
1563   /// tie
1564   template<typename... _Elements>
1565     constexpr tuple<_Elements&...>
1566     tie(_Elements&... __args) noexcept
1567     { return tuple<_Elements&...>(__args...); }
1568
1569   /// swap
1570   template<typename... _Elements>
1571     inline void
1572     swap(tuple<_Elements...>& __x, tuple<_Elements...>& __y)
1573     noexcept(noexcept(__x.swap(__y)))
1574     { __x.swap(__y); }
1575
1576   // A class (and instance) which can be used in 'tie' when an element
1577   // of a tuple is not required
1578   struct _Swallow_assign
1579   {
1580     template<class _Tp>
1581       const _Swallow_assign&
1582       operator=(const _Tp&) const
1583       { return *this; }
1584   };
1585
1586   const _Swallow_assign ignore{};
1587
1588   /// Partial specialization for tuples
1589   template<typename... _Types, typename _Alloc>
1590     struct uses_allocator<tuple<_Types...>, _Alloc> : true_type { };
1591
1592   // See stl_pair.h...
1593   template<class _T1, class _T2>
1594     template<typename... _Args1, typename... _Args2>
1595       inline
1596       pair<_T1, _T2>::
1597       pair(piecewise_construct_t,
1598            tuple<_Args1...> __first, tuple<_Args2...> __second)
1599       : pair(__first, __second,
1600              typename _Build_index_tuple<sizeof...(_Args1)>::__type(),
1601              typename _Build_index_tuple<sizeof...(_Args2)>::__type())
1602       { }
1603
1604   template<class _T1, class _T2>
1605     template<typename... _Args1, std::size_t... _Indexes1,
1606              typename... _Args2, std::size_t... _Indexes2>
1607       inline
1608       pair<_T1, _T2>::
1609       pair(tuple<_Args1...>& __tuple1, tuple<_Args2...>& __tuple2,
1610            _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>)
1611       : first(std::forward<_Args1>(std::get<_Indexes1>(__tuple1))...),
1612         second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)
1613       { }
1614
1615   /// @}
1616
1617 _GLIBCXX_END_NAMESPACE_VERSION
1618 } // namespace std
1619
1620 #endif // C++11
1621
1622 #endif // _GLIBCXX_TUPLE