libstdc++-v3/include/std/tuple

   1 // <tuple> -*- C++ -*-
   2
   3 // Copyright (C) 2007-2014 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       template<typename _UHead, typename = typename
  65                enable_if<!is_convertible<_UHead,
  66                                          __uses_alloc_base>::value>::type>
  67         constexpr _Head_base(_UHead&& __h)
  68         : _Head(std::forward<_UHead>(__h)) { }
  69
  70       _Head_base(__uses_alloc0)
  71       : _Head() { }
  72
  73       template<typename _Alloc>
  74         _Head_base(__uses_alloc1<_Alloc> __a)
  75         : _Head(allocator_arg, *__a._M_a) { }
  76
  77       template<typename _Alloc>
  78         _Head_base(__uses_alloc2<_Alloc> __a)
  79         : _Head(*__a._M_a) { }
  80
  81       template<typename _UHead>
  82         _Head_base(__uses_alloc0, _UHead&& __uhead)
  83         : _Head(std::forward<_UHead>(__uhead)) { }
  84
  85       template<typename _Alloc, typename _UHead>
  86         _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
  87         : _Head(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead)) { }
  88
  89       template<typename _Alloc, typename _UHead>
  90         _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
  91         : _Head(std::forward<_UHead>(__uhead), *__a._M_a) { }
  92
  93       static constexpr _Head&
  94       _M_head(_Head_base& __b) noexcept { return __b; }
  95
  96       static constexpr const _Head&
  97       _M_head(const _Head_base& __b) noexcept { return __b; }
  98     };
  99
 100   template<std::size_t _Idx, typename _Head>
 101     struct _Head_base<_Idx, _Head, false>
 102     {
 103       constexpr _Head_base()
 104       : _M_head_impl() { }
 105
 106       constexpr _Head_base(const _Head& __h)
 107       : _M_head_impl(__h) { }
 108
 109       template<typename _UHead, typename = typename
 110                enable_if<!is_convertible<_UHead,
 111                                          __uses_alloc_base>::value>::type>
 112         constexpr _Head_base(_UHead&& __h)
 113         : _M_head_impl(std::forward<_UHead>(__h)) { }
 114
 115       _Head_base(__uses_alloc0)
 116       : _M_head_impl() { }
 117
 118       template<typename _Alloc>
 119         _Head_base(__uses_alloc1<_Alloc> __a)
 120         : _M_head_impl(allocator_arg, *__a._M_a) { }
 121
 122       template<typename _Alloc>
 123         _Head_base(__uses_alloc2<_Alloc> __a)
 124         : _M_head_impl(*__a._M_a) { }
 125
 126       template<typename _UHead>
 127         _Head_base(__uses_alloc0, _UHead&& __uhead)
 128         : _M_head_impl(std::forward<_UHead>(__uhead)) { }
 129
 130       template<typename _Alloc, typename _UHead>
 131         _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
 132         : _M_head_impl(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead))
 133         { }
 134
 135       template<typename _Alloc, typename _UHead>
 136         _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
 137         : _M_head_impl(std::forward<_UHead>(__uhead), *__a._M_a) { }
 138
 139       static constexpr _Head&
 140       _M_head(_Head_base& __b) noexcept { return __b._M_head_impl; }
 141
 142       static constexpr const _Head&
 143       _M_head(const _Head_base& __b) noexcept { return __b._M_head_impl; }
 144
 145       _Head _M_head_impl;
 146     };
 147
 148   /**
 149    * Contains the actual implementation of the @c tuple template, stored
 150    * as a recursive inheritance hierarchy from the first element (most
 151    * derived class) to the last (least derived class). The @c Idx
 152    * parameter gives the 0-based index of the element stored at this
 153    * point in the hierarchy; we use it to implement a constant-time
 154    * get() operation.
 155    */
 156   template<std::size_t _Idx, typename... _Elements>
 157     struct _Tuple_impl;
 158
 159   /**
 160    * Zero-element tuple implementation. This is the basis case for the
 161    * inheritance recursion.
 162    */
 163   template<std::size_t _Idx>
 164     struct _Tuple_impl<_Idx>
 165     {
 166       template<std::size_t, typename...> friend class _Tuple_impl;
 167
 168       _Tuple_impl() = default;
 169
 170       template<typename _Alloc>
 171         _Tuple_impl(allocator_arg_t, const _Alloc&) { }
 172
 173       template<typename _Alloc>
 174         _Tuple_impl(allocator_arg_t, const _Alloc&, const _Tuple_impl&) { }
 175
 176       template<typename _Alloc>
 177         _Tuple_impl(allocator_arg_t, const _Alloc&, _Tuple_impl&&) { }
 178
 179     protected:
 180       void _M_swap(_Tuple_impl&) noexcept { /* no-op */ }
 181     };
 182
 183   template<typename _Tp>
 184     struct __is_empty_non_tuple : is_empty<_Tp> { };
 185
 186   // Using EBO for elements that are tuples causes ambiguous base errors.
 187   template<typename _El0, typename... _El>
 188     struct __is_empty_non_tuple<tuple<_El0, _El...>> : false_type { };
 189
 190   // Use the Empty Base-class Optimization for empty, non-final types.
 191   template<typename _Tp>
 192     using __empty_not_final
 193     = typename conditional<__is_final(_Tp), false_type,
 194                            __is_empty_non_tuple<_Tp>>::type;
 195
 196   /**
 197    * Recursive tuple implementation. Here we store the @c Head element
 198    * and derive from a @c Tuple_impl containing the remaining elements
 199    * (which contains the @c Tail).
 200    */
 201   template<std::size_t _Idx, typename _Head, typename... _Tail>
 202     struct _Tuple_impl<_Idx, _Head, _Tail...>
 203     : public _Tuple_impl<_Idx + 1, _Tail...>,
 204       private _Head_base<_Idx, _Head, __empty_not_final<_Head>::value>
 205     {
 206       template<std::size_t, typename...> friend class _Tuple_impl;
 207
 208       typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
 209       typedef _Head_base<_Idx, _Head, __empty_not_final<_Head>::value> _Base;
 210
 211       static constexpr _Head&
 212       _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 213
 214       static constexpr const _Head&
 215       _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 216
 217       static constexpr _Inherited&
 218       _M_tail(_Tuple_impl& __t) noexcept { return __t; }
 219
 220       static constexpr const _Inherited&
 221       _M_tail(const _Tuple_impl& __t) noexcept { return __t; }
 222
 223       constexpr _Tuple_impl()
 224       : _Inherited(), _Base() { }
 225
 226       explicit
 227       constexpr _Tuple_impl(const _Head& __head, const _Tail&... __tail)
 228       : _Inherited(__tail...), _Base(__head) { }
 229
 230       template<typename _UHead, typename... _UTail, typename = typename
 231                enable_if<sizeof...(_Tail) == sizeof...(_UTail)>::type>
 232         explicit
 233         constexpr _Tuple_impl(_UHead&& __head, _UTail&&... __tail)
 234         : _Inherited(std::forward<_UTail>(__tail)...),
 235           _Base(std::forward<_UHead>(__head)) { }
 236
 237       constexpr _Tuple_impl(const _Tuple_impl&) = default;
 238
 239       constexpr
 240       _Tuple_impl(_Tuple_impl&& __in)
 241       noexcept(__and_<is_nothrow_move_constructible<_Head>,
 242                       is_nothrow_move_constructible<_Inherited>>::value)
 243       : _Inherited(std::move(_M_tail(__in))),
 244         _Base(std::forward<_Head>(_M_head(__in))) { }
 245
 246       template<typename... _UElements>
 247         constexpr _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
 248         : _Inherited(_Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
 249           _Base(_Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
 250
 251       template<typename _UHead, typename... _UTails>
 252         constexpr _Tuple_impl(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 253         : _Inherited(std::move
 254                      (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
 255           _Base(std::forward<_UHead>
 256                 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
 257
 258       template<typename _Alloc>
 259         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)
 260         : _Inherited(__tag, __a),
 261           _Base(__use_alloc<_Head>(__a)) { }
 262
 263       template<typename _Alloc>
 264         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 265                     const _Head& __head, const _Tail&... __tail)
 266         : _Inherited(__tag, __a, __tail...),
 267           _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head) { }
 268
 269       template<typename _Alloc, typename _UHead, typename... _UTail,
 270                typename = typename enable_if<sizeof...(_Tail)
 271                                              == sizeof...(_UTail)>::type>
 272         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 273                     _UHead&& __head, _UTail&&... __tail)
 274         : _Inherited(__tag, __a, std::forward<_UTail>(__tail)...),
 275           _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 276                 std::forward<_UHead>(__head)) { }
 277
 278       template<typename _Alloc>
 279         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 280                     const _Tuple_impl& __in)
 281         : _Inherited(__tag, __a, _M_tail(__in)),
 282           _Base(__use_alloc<_Head, _Alloc, _Head>(__a), _M_head(__in)) { }
 283
 284       template<typename _Alloc>
 285         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 286                     _Tuple_impl&& __in)
 287         : _Inherited(__tag, __a, std::move(_M_tail(__in))),
 288           _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 289                 std::forward<_Head>(_M_head(__in))) { }
 290
 291       template<typename _Alloc, typename... _UElements>
 292         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 293                     const _Tuple_impl<_Idx, _UElements...>& __in)
 294         : _Inherited(__tag, __a,
 295                      _Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
 296           _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 297                 _Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
 298
 299       template<typename _Alloc, typename _UHead, typename... _UTails>
 300         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 301                     _Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 302         : _Inherited(__tag, __a, std::move
 303                      (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
 304           _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 305                 std::forward<_UHead>
 306                 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
 307
 308       _Tuple_impl&
 309       operator=(const _Tuple_impl& __in)
 310       {
 311         _M_head(*this) = _M_head(__in);
 312         _M_tail(*this) = _M_tail(__in);
 313         return *this;
 314       }
 315
 316       _Tuple_impl&
 317       operator=(_Tuple_impl&& __in)
 318       noexcept(__and_<is_nothrow_move_assignable<_Head>,
 319                       is_nothrow_move_assignable<_Inherited>>::value)
 320       {
 321         _M_head(*this) = std::forward<_Head>(_M_head(__in));
 322         _M_tail(*this) = std::move(_M_tail(__in));
 323         return *this;
 324       }
 325
 326       template<typename... _UElements>
 327         _Tuple_impl&
 328         operator=(const _Tuple_impl<_Idx, _UElements...>& __in)
 329         {
 330           _M_head(*this) = _Tuple_impl<_Idx, _UElements...>::_M_head(__in);
 331           _M_tail(*this) = _Tuple_impl<_Idx, _UElements...>::_M_tail(__in);
 332           return *this;
 333         }
 334
 335       template<typename _UHead, typename... _UTails>
 336         _Tuple_impl&
 337         operator=(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 338         {
 339           _M_head(*this) = std::forward<_UHead>
 340             (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in));
 341           _M_tail(*this) = std::move
 342             (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in));
 343           return *this;
 344         }
 345
 346     protected:
 347       void
 348       _M_swap(_Tuple_impl& __in)
 349       noexcept(noexcept(swap(std::declval<_Head&>(),
 350                              std::declval<_Head&>()))
 351                && noexcept(_M_tail(__in)._M_swap(_M_tail(__in))))
 352       {
 353         using std::swap;
 354         swap(_M_head(*this), _M_head(__in));
 355         _Inherited::_M_swap(_M_tail(__in));
 356       }
 357     };
 358
 359   /// Primary class template, tuple
 360   template<typename... _Elements>
 361     class tuple : public _Tuple_impl<0, _Elements...>
 362     {
 363       typedef _Tuple_impl<0, _Elements...> _Inherited;
 364
 365     public:
 366       constexpr tuple()
 367       : _Inherited() { }
 368
 369       explicit
 370       constexpr tuple(const _Elements&... __elements)
 371       : _Inherited(__elements...) { }
 372
 373       template<typename... _UElements, typename = typename
 374         enable_if<__and_<is_convertible<_UElements,
 375                                         _Elements>...>::value>::type>
 376         explicit
 377         constexpr tuple(_UElements&&... __elements)
 378         : _Inherited(std::forward<_UElements>(__elements)...) { }
 379
 380       constexpr tuple(const tuple&) = default;
 381
 382       constexpr tuple(tuple&&) = default;
 383
 384       template<typename... _UElements, typename = typename
 385         enable_if<__and_<is_convertible<const _UElements&,
 386                                         _Elements>...>::value>::type>
 387         constexpr tuple(const tuple<_UElements...>& __in)
 388         : _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 389         { }
 390
 391       template<typename... _UElements, typename = typename
 392         enable_if<__and_<is_convertible<_UElements,
 393                                         _Elements>...>::value>::type>
 394         constexpr tuple(tuple<_UElements...>&& __in)
 395         : _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
 396
 397       // Allocator-extended constructors.
 398
 399       template<typename _Alloc>
 400         tuple(allocator_arg_t __tag, const _Alloc& __a)
 401         : _Inherited(__tag, __a) { }
 402
 403       template<typename _Alloc>
 404         tuple(allocator_arg_t __tag, const _Alloc& __a,
 405               const _Elements&... __elements)
 406         : _Inherited(__tag, __a, __elements...) { }
 407
 408       template<typename _Alloc, typename... _UElements, typename = typename
 409                enable_if<sizeof...(_UElements)
 410                          == sizeof...(_Elements)>::type>
 411         tuple(allocator_arg_t __tag, const _Alloc& __a,
 412               _UElements&&... __elements)
 413         : _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)
 414         { }
 415
 416       template<typename _Alloc>
 417         tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
 418         : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
 419
 420       template<typename _Alloc>
 421         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
 422         : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
 423
 424       template<typename _Alloc, typename... _UElements, typename = typename
 425                enable_if<sizeof...(_UElements)
 426                          == sizeof...(_Elements)>::type>
 427         tuple(allocator_arg_t __tag, const _Alloc& __a,
 428               const tuple<_UElements...>& __in)
 429         : _Inherited(__tag, __a,
 430                      static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 431         { }
 432
 433       template<typename _Alloc, typename... _UElements, typename = typename
 434                enable_if<sizeof...(_UElements)
 435                          == sizeof...(_Elements)>::type>
 436         tuple(allocator_arg_t __tag, const _Alloc& __a,
 437               tuple<_UElements...>&& __in)
 438         : _Inherited(__tag, __a,
 439                      static_cast<_Tuple_impl<0, _UElements...>&&>(__in))
 440         { }
 441
 442       tuple&
 443       operator=(const tuple& __in)
 444       {
 445         static_cast<_Inherited&>(*this) = __in;
 446         return *this;
 447       }
 448
 449       tuple&
 450       operator=(tuple&& __in)
 451       noexcept(is_nothrow_move_assignable<_Inherited>::value)
 452       {
 453         static_cast<_Inherited&>(*this) = std::move(__in);
 454         return *this;
 455       }
 456
 457       template<typename... _UElements, typename = typename
 458                enable_if<sizeof...(_UElements)
 459                          == sizeof...(_Elements)>::type>
 460         tuple&
 461         operator=(const tuple<_UElements...>& __in)
 462         {
 463           static_cast<_Inherited&>(*this) = __in;
 464           return *this;
 465         }
 466
 467       template<typename... _UElements, typename = typename
 468                enable_if<sizeof...(_UElements)
 469                          == sizeof...(_Elements)>::type>
 470         tuple&
 471         operator=(tuple<_UElements...>&& __in)
 472         {
 473           static_cast<_Inherited&>(*this) = std::move(__in);
 474           return *this;
 475         }
 476
 477       void
 478       swap(tuple& __in)
 479       noexcept(noexcept(__in._M_swap(__in)))
 480       { _Inherited::_M_swap(__in); }
 481     };
 482
 483   // Explicit specialization, zero-element tuple.
 484   template<>
 485     class tuple<>
 486     {
 487     public:
 488       void swap(tuple&) noexcept { /* no-op */ }
 489     };
 490
 491   /// Partial specialization, 2-element tuple.
 492   /// Includes construction and assignment from a pair.
 493   template<typename _T1, typename _T2>
 494     class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
 495     {
 496       typedef _Tuple_impl<0, _T1, _T2> _Inherited;
 497
 498     public:
 499       constexpr tuple()
 500       : _Inherited() { }
 501
 502       explicit
 503       constexpr tuple(const _T1& __a1, const _T2& __a2)
 504       : _Inherited(__a1, __a2) { }
 505
 506       template<typename _U1, typename _U2, typename = typename
 507                enable_if<__and_<is_convertible<_U1, _T1>,
 508                                 is_convertible<_U2, _T2>>::value>::type>
 509         explicit
 510         constexpr tuple(_U1&& __a1, _U2&& __a2)
 511         : _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
 512
 513       constexpr tuple(const tuple&) = default;
 514
 515       constexpr tuple(tuple&&) = default;
 516
 517       template<typename _U1, typename _U2, typename = typename
 518         enable_if<__and_<is_convertible<const _U1&, _T1>,
 519                          is_convertible<const _U2&, _T2>>::value>::type>
 520         constexpr tuple(const tuple<_U1, _U2>& __in)
 521         : _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
 522
 523       template<typename _U1, typename _U2, typename = typename
 524                enable_if<__and_<is_convertible<_U1, _T1>,
 525                                 is_convertible<_U2, _T2>>::value>::type>
 526         constexpr tuple(tuple<_U1, _U2>&& __in)
 527         : _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
 528
 529       template<typename _U1, typename _U2, typename = typename
 530         enable_if<__and_<is_convertible<const _U1&, _T1>,
 531                          is_convertible<const _U2&, _T2>>::value>::type>
 532         constexpr tuple(const pair<_U1, _U2>& __in)
 533         : _Inherited(__in.first, __in.second) { }
 534
 535       template<typename _U1, typename _U2, typename = typename
 536                enable_if<__and_<is_convertible<_U1, _T1>,
 537                                 is_convertible<_U2, _T2>>::value>::type>
 538         constexpr tuple(pair<_U1, _U2>&& __in)
 539         : _Inherited(std::forward<_U1>(__in.first),
 540                      std::forward<_U2>(__in.second)) { }
 541
 542       // Allocator-extended constructors.
 543
 544       template<typename _Alloc>
 545         tuple(allocator_arg_t __tag, const _Alloc& __a)
 546         : _Inherited(__tag, __a) { }
 547
 548       template<typename _Alloc>
 549         tuple(allocator_arg_t __tag, const _Alloc& __a,
 550               const _T1& __a1, const _T2& __a2)
 551         : _Inherited(__tag, __a, __a1, __a2) { }
 552
 553       template<typename _Alloc, typename _U1, typename _U2>
 554         tuple(allocator_arg_t __tag, const _Alloc& __a, _U1&& __a1, _U2&& __a2)
 555         : _Inherited(__tag, __a, std::forward<_U1>(__a1),
 556                      std::forward<_U2>(__a2)) { }
 557
 558       template<typename _Alloc>
 559         tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
 560         : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
 561
 562       template<typename _Alloc>
 563         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
 564         : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
 565
 566       template<typename _Alloc, typename _U1, typename _U2>
 567         tuple(allocator_arg_t __tag, const _Alloc& __a,
 568               const tuple<_U1, _U2>& __in)
 569         : _Inherited(__tag, __a,
 570                      static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in))
 571         { }
 572
 573       template<typename _Alloc, typename _U1, typename _U2>
 574         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple<_U1, _U2>&& __in)
 575         : _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))
 576         { }
 577
 578       template<typename _Alloc, typename _U1, typename _U2>
 579         tuple(allocator_arg_t __tag, const _Alloc& __a,
 580               const pair<_U1, _U2>& __in)
 581         : _Inherited(__tag, __a, __in.first, __in.second) { }
 582
 583       template<typename _Alloc, typename _U1, typename _U2>
 584         tuple(allocator_arg_t __tag, const _Alloc& __a, pair<_U1, _U2>&& __in)
 585         : _Inherited(__tag, __a, std::forward<_U1>(__in.first),
 586                      std::forward<_U2>(__in.second)) { }
 587
 588       tuple&
 589       operator=(const tuple& __in)
 590       {
 591         static_cast<_Inherited&>(*this) = __in;
 592         return *this;
 593       }
 594
 595       tuple&
 596       operator=(tuple&& __in)
 597       noexcept(is_nothrow_move_assignable<_Inherited>::value)
 598       {
 599         static_cast<_Inherited&>(*this) = std::move(__in);
 600         return *this;
 601       }
 602
 603       template<typename _U1, typename _U2>
 604         tuple&
 605         operator=(const tuple<_U1, _U2>& __in)
 606         {
 607           static_cast<_Inherited&>(*this) = __in;
 608           return *this;
 609         }
 610
 611       template<typename _U1, typename _U2>
 612         tuple&
 613         operator=(tuple<_U1, _U2>&& __in)
 614         {
 615           static_cast<_Inherited&>(*this) = std::move(__in);
 616           return *this;
 617         }
 618
 619       template<typename _U1, typename _U2>
 620         tuple&
 621         operator=(const pair<_U1, _U2>& __in)
 622         {
 623           this->_M_head(*this) = __in.first;
 624           this->_M_tail(*this)._M_head(*this) = __in.second;
 625           return *this;
 626         }
 627
 628       template<typename _U1, typename _U2>
 629         tuple&
 630         operator=(pair<_U1, _U2>&& __in)
 631         {
 632           this->_M_head(*this) = std::forward<_U1>(__in.first);
 633           this->_M_tail(*this)._M_head(*this) = std::forward<_U2>(__in.second);
 634           return *this;
 635         }
 636
 637       void
 638       swap(tuple& __in)
 639       noexcept(noexcept(__in._M_swap(__in)))
 640       { _Inherited::_M_swap(__in); }
 641     };
 642
 643
 644   /// Gives the type of the ith element of a given tuple type.
 645   template<std::size_t __i, typename _Tp>
 646     struct tuple_element;
 647
 648   /**
 649    * Recursive case for tuple_element: strip off the first element in
 650    * the tuple and retrieve the (i-1)th element of the remaining tuple.
 651    */
 652   template<std::size_t __i, typename _Head, typename... _Tail>
 653     struct tuple_element<__i, tuple<_Head, _Tail...> >
 654     : tuple_element<__i - 1, tuple<_Tail...> > { };
 655
 656   /**
 657    * Basis case for tuple_element: The first element is the one we're seeking.
 658    */
 659   template<typename _Head, typename... _Tail>
 660     struct tuple_element<0, tuple<_Head, _Tail...> >
 661     {
 662       typedef _Head type;
 663     };
 664
 665   // Duplicate of C++14's tuple_element_t for internal use in C++11 mode
 666   template<std::size_t __i, typename _Tp>
 667     using __tuple_element_t = typename tuple_element<__i, _Tp>::type;
 668
 669   template<std::size_t __i, typename _Tp>
 670     struct tuple_element<__i, const _Tp>
 671     {
 672       typedef typename add_const<__tuple_element_t<__i, _Tp>>::type type;
 673     };
 674
 675   template<std::size_t __i, typename _Tp>
 676     struct tuple_element<__i, volatile _Tp>
 677     {
 678       typedef typename add_volatile<__tuple_element_t<__i, _Tp>>::type type;
 679     };
 680
 681   template<std::size_t __i, typename _Tp>
 682     struct tuple_element<__i, const volatile _Tp>
 683     {
 684       typedef typename add_cv<__tuple_element_t<__i, _Tp>>::type type;
 685     };
 686
 687 #if __cplusplus > 201103L
 688   template<std::size_t __i, typename _Tp>
 689     using tuple_element_t = typename tuple_element<__i, _Tp>::type;
 690 #endif
 691
 692   /// Finds the size of a given tuple type.
 693   template<typename _Tp>
 694     struct tuple_size;
 695
 696   template<typename _Tp, typename _Ts = tuple_size<_Tp>>
 697     using __cv_tuple_size = integral_constant<
 698              typename remove_cv<decltype(_Ts::value)>::type, _Ts::value>;
 699
 700   template<typename _Tp>
 701     struct tuple_size<const _Tp> : __cv_tuple_size<_Tp> { };
 702
 703   template<typename _Tp>
 704     struct tuple_size<volatile _Tp> : __cv_tuple_size<_Tp> { };
 705
 706   template<typename _Tp>
 707     struct tuple_size<const volatile _Tp> : __cv_tuple_size<_Tp> { };
 708
 709   /// class tuple_size
 710   template<typename... _Elements>
 711     struct tuple_size<tuple<_Elements...>>
 712     : public integral_constant<std::size_t, sizeof...(_Elements)> { };
 713
 714   template<std::size_t __i, typename _Head, typename... _Tail>
 715     constexpr _Head&
 716     __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 717     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 718
 719   template<std::size_t __i, typename _Head, typename... _Tail>
 720     constexpr const _Head&
 721     __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 722     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 723
 724   /// Return a reference to the ith element of a tuple.
 725   template<std::size_t __i, typename... _Elements>
 726     constexpr __tuple_element_t<__i, tuple<_Elements...>>&
 727     get(tuple<_Elements...>& __t) noexcept
 728     { return std::__get_helper<__i>(__t); }
 729
 730   /// Return a const reference to the ith element of a const tuple.
 731   template<std::size_t __i, typename... _Elements>
 732     constexpr const __tuple_element_t<__i, tuple<_Elements...>>&
 733     get(const tuple<_Elements...>& __t) noexcept
 734     { return std::__get_helper<__i>(__t); }
 735
 736   /// Return an rvalue reference to the ith element of a tuple rvalue.
 737   template<std::size_t __i, typename... _Elements>
 738     constexpr __tuple_element_t<__i, tuple<_Elements...>>&&
 739     get(tuple<_Elements...>&& __t) noexcept
 740     {
 741       typedef __tuple_element_t<__i, tuple<_Elements...>> __element_type;
 742       return std::forward<__element_type&&>(std::get<__i>(__t));
 743     }
 744
 745 #if __cplusplus > 201103L
 746   template<typename _Head, size_t __i, typename... _Tail>
 747     constexpr _Head&
 748     __get_helper2(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 749     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 750
 751   template<typename _Head, size_t __i, typename... _Tail>
 752     constexpr const _Head&
 753     __get_helper2(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 754     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 755
 756   /// Return a reference to the unique element of type _Tp of a tuple.
 757   template <typename _Tp, typename... _Types>
 758     constexpr _Tp&
 759     get(tuple<_Types...>& __t) noexcept
 760     { return std::__get_helper2<_Tp>(__t); }
 761
 762   /// Return a reference to the unique element of type _Tp of a tuple rvalue.
 763   template <typename _Tp, typename... _Types>
 764     constexpr _Tp&&
 765     get(tuple<_Types...>&& __t) noexcept
 766     { return std::forward<_Tp&&>(std::__get_helper2<_Tp>(__t)); }
 767
 768   /// Return a const reference to the unique element of type _Tp of a tuple.
 769   template <typename _Tp, typename... _Types>
 770     constexpr const _Tp&
 771     get(const tuple<_Types...>& __t) noexcept
 772     { return std::__get_helper2<_Tp>(__t); }
 773 #endif
 774
 775   // This class performs the comparison operations on tuples
 776   template<typename _Tp, typename _Up, size_t __i, size_t __size>
 777     struct __tuple_compare
 778     {
 779       static constexpr bool
 780       __eq(const _Tp& __t, const _Up& __u)
 781       {
 782         return bool(std::get<__i>(__t) == std::get<__i>(__u))
 783           && __tuple_compare<_Tp, _Up, __i + 1, __size>::__eq(__t, __u);
 784       }
 785
 786       static constexpr bool
 787       __less(const _Tp& __t, const _Up& __u)
 788       {
 789         return bool(std::get<__i>(__t) < std::get<__i>(__u))
 790           || (!bool(std::get<__i>(__u) < std::get<__i>(__t))
 791               && __tuple_compare<_Tp, _Up, __i + 1, __size>::__less(__t, __u));
 792       }
 793     };
 794
 795   template<typename _Tp, typename _Up, size_t __size>
 796     struct __tuple_compare<_Tp, _Up, __size, __size>
 797     {
 798       static constexpr bool
 799       __eq(const _Tp&, const _Up&) { return true; }
 800
 801       static constexpr bool
 802       __less(const _Tp&, const _Up&) { return false; }
 803     };
 804
 805   template<typename... _TElements, typename... _UElements>
 806     constexpr bool
 807     operator==(const tuple<_TElements...>& __t,
 808                const tuple<_UElements...>& __u)
 809     {
 810       static_assert(sizeof...(_TElements) == sizeof...(_UElements),
 811           "tuple objects can only be compared if they have equal sizes.");
 812       using __compare = __tuple_compare<tuple<_TElements...>,
 813                                         tuple<_UElements...>,
 814                                         0, sizeof...(_TElements)>;
 815       return __compare::__eq(__t, __u);
 816     }
 817
 818   template<typename... _TElements, typename... _UElements>
 819     constexpr bool
 820     operator<(const tuple<_TElements...>& __t,
 821               const tuple<_UElements...>& __u)
 822     {
 823       static_assert(sizeof...(_TElements) == sizeof...(_UElements),
 824           "tuple objects can only be compared if they have equal sizes.");
 825       using __compare = __tuple_compare<tuple<_TElements...>,
 826                                         tuple<_UElements...>,
 827                                         0, sizeof...(_TElements)>;
 828       return __compare::__less(__t, __u);
 829     }
 830
 831   template<typename... _TElements, typename... _UElements>
 832     constexpr bool
 833     operator!=(const tuple<_TElements...>& __t,
 834                const tuple<_UElements...>& __u)
 835     { return !(__t == __u); }
 836
 837   template<typename... _TElements, typename... _UElements>
 838     constexpr bool
 839     operator>(const tuple<_TElements...>& __t,
 840               const tuple<_UElements...>& __u)
 841     { return __u < __t; }
 842
 843   template<typename... _TElements, typename... _UElements>
 844     constexpr bool
 845     operator<=(const tuple<_TElements...>& __t,
 846                const tuple<_UElements...>& __u)
 847     { return !(__u < __t); }
 848
 849   template<typename... _TElements, typename... _UElements>
 850     constexpr bool
 851     operator>=(const tuple<_TElements...>& __t,
 852                const tuple<_UElements...>& __u)
 853     { return !(__t < __u); }
 854
 855   // NB: DR 705.
 856   template<typename... _Elements>
 857     constexpr tuple<typename __decay_and_strip<_Elements>::__type...>
 858     make_tuple(_Elements&&... __args)
 859     {
 860       typedef tuple<typename __decay_and_strip<_Elements>::__type...>
 861         __result_type;
 862       return __result_type(std::forward<_Elements>(__args)...);
 863     }
 864
 865   template<typename... _Elements>
 866     tuple<_Elements&&...>
 867     forward_as_tuple(_Elements&&... __args) noexcept
 868     { return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
 869
 870   template<typename>
 871     struct __is_tuple_like_impl : false_type
 872     { };
 873
 874   template<typename... _Tps>
 875     struct __is_tuple_like_impl<tuple<_Tps...>> : true_type
 876     { };
 877
 878   template<typename _T1, typename _T2>
 879     struct __is_tuple_like_impl<pair<_T1, _T2>> : true_type
 880     { };
 881
 882   template<typename _Tp, std::size_t _Nm>
 883     struct __is_tuple_like_impl<array<_Tp, _Nm>> : true_type
 884     { };
 885
 886   // Internal type trait that allows us to sfinae-protect tuple_cat.
 887   template<typename _Tp>
 888     struct __is_tuple_like
 889     : public __is_tuple_like_impl<typename std::remove_cv
 890             <typename std::remove_reference<_Tp>::type>::type>::type
 891     { };
 892
 893   template<size_t, typename, typename, size_t>
 894     struct __make_tuple_impl;
 895
 896   template<size_t _Idx, typename _Tuple, typename... _Tp, size_t _Nm>
 897     struct __make_tuple_impl<_Idx, tuple<_Tp...>, _Tuple, _Nm>
 898     : __make_tuple_impl<_Idx + 1,
 899                         tuple<_Tp..., __tuple_element_t<_Idx, _Tuple>>,
 900                         _Tuple, _Nm>
 901     { };
 902
 903   template<std::size_t _Nm, typename _Tuple, typename... _Tp>
 904     struct __make_tuple_impl<_Nm, tuple<_Tp...>, _Tuple, _Nm>
 905     {
 906       typedef tuple<_Tp...> __type;
 907     };
 908
 909   template<typename _Tuple>
 910     struct __do_make_tuple
 911     : __make_tuple_impl<0, tuple<>, _Tuple, std::tuple_size<_Tuple>::value>
 912     { };
 913
 914   // Returns the std::tuple equivalent of a tuple-like type.
 915   template<typename _Tuple>
 916     struct __make_tuple
 917     : public __do_make_tuple<typename std::remove_cv
 918             <typename std::remove_reference<_Tuple>::type>::type>
 919     { };
 920
 921   // Combines several std::tuple's into a single one.
 922   template<typename...>
 923     struct __combine_tuples;
 924
 925   template<>
 926     struct __combine_tuples<>
 927     {
 928       typedef tuple<> __type;
 929     };
 930
 931   template<typename... _Ts>
 932     struct __combine_tuples<tuple<_Ts...>>
 933     {
 934       typedef tuple<_Ts...> __type;
 935     };
 936
 937   template<typename... _T1s, typename... _T2s, typename... _Rem>
 938     struct __combine_tuples<tuple<_T1s...>, tuple<_T2s...>, _Rem...>
 939     {
 940       typedef typename __combine_tuples<tuple<_T1s..., _T2s...>,
 941                                         _Rem...>::__type __type;
 942     };
 943
 944   // Computes the result type of tuple_cat given a set of tuple-like types.
 945   template<typename... _Tpls>
 946     struct __tuple_cat_result
 947     {
 948       typedef typename __combine_tuples
 949         <typename __make_tuple<_Tpls>::__type...>::__type __type;
 950     };
 951
 952   // Helper to determine the index set for the first tuple-like
 953   // type of a given set.
 954   template<typename...>
 955     struct __make_1st_indices;
 956
 957   template<>
 958     struct __make_1st_indices<>
 959     {
 960       typedef std::_Index_tuple<> __type;
 961     };
 962
 963   template<typename _Tp, typename... _Tpls>
 964     struct __make_1st_indices<_Tp, _Tpls...>
 965     {
 966       typedef typename std::_Build_index_tuple<std::tuple_size<
 967         typename std::remove_reference<_Tp>::type>::value>::__type __type;
 968     };
 969
 970   // Performs the actual concatenation by step-wise expanding tuple-like
 971   // objects into the elements,  which are finally forwarded into the
 972   // result tuple.
 973   template<typename _Ret, typename _Indices, typename... _Tpls>
 974     struct __tuple_concater;
 975
 976   template<typename _Ret, std::size_t... _Is, typename _Tp, typename... _Tpls>
 977     struct __tuple_concater<_Ret, std::_Index_tuple<_Is...>, _Tp, _Tpls...>
 978     {
 979       template<typename... _Us>
 980         static constexpr _Ret
 981         _S_do(_Tp&& __tp, _Tpls&&... __tps, _Us&&... __us)
 982         {
 983           typedef typename __make_1st_indices<_Tpls...>::__type __idx;
 984           typedef __tuple_concater<_Ret, __idx, _Tpls...>      __next;
 985           return __next::_S_do(std::forward<_Tpls>(__tps)...,
 986                                std::forward<_Us>(__us)...,
 987                                std::get<_Is>(std::forward<_Tp>(__tp))...);
 988         }
 989     };
 990
 991   template<typename _Ret>
 992     struct __tuple_concater<_Ret, std::_Index_tuple<>>
 993     {
 994       template<typename... _Us>
 995         static constexpr _Ret
 996         _S_do(_Us&&... __us)
 997         {
 998           return _Ret(std::forward<_Us>(__us)...);
 999         }
1000     };
1001
1002   /// tuple_cat
1003   template<typename... _Tpls, typename = typename
1004            enable_if<__and_<__is_tuple_like<_Tpls>...>::value>::type>
1005     constexpr auto
1006     tuple_cat(_Tpls&&... __tpls)
1007     -> typename __tuple_cat_result<_Tpls...>::__type
1008     {
1009       typedef typename __tuple_cat_result<_Tpls...>::__type __ret;
1010       typedef typename __make_1st_indices<_Tpls...>::__type __idx;
1011       typedef __tuple_concater<__ret, __idx, _Tpls...> __concater;
1012       return __concater::_S_do(std::forward<_Tpls>(__tpls)...);
1013     }
1014
1015   /// tie
1016   template<typename... _Elements>
1017     inline tuple<_Elements&...>
1018     tie(_Elements&... __args) noexcept
1019     { return tuple<_Elements&...>(__args...); }
1020
1021   /// swap
1022   template<typename... _Elements>
1023     inline void
1024     swap(tuple<_Elements...>& __x, tuple<_Elements...>& __y)
1025     noexcept(noexcept(__x.swap(__y)))
1026     { __x.swap(__y); }
1027
1028   // A class (and instance) which can be used in 'tie' when an element
1029   // of a tuple is not required
1030   struct _Swallow_assign
1031   {
1032     template<class _Tp>
1033       const _Swallow_assign&
1034       operator=(const _Tp&) const
1035       { return *this; }
1036   };
1037
1038   const _Swallow_assign ignore{};
1039
1040   /// Partial specialization for tuples
1041   template<typename... _Types, typename _Alloc>
1042     struct uses_allocator<tuple<_Types...>, _Alloc> : true_type { };
1043
1044   // See stl_pair.h...
1045   template<class _T1, class _T2>
1046     template<typename... _Args1, typename... _Args2>
1047       inline
1048       pair<_T1, _T2>::
1049       pair(piecewise_construct_t,
1050            tuple<_Args1...> __first, tuple<_Args2...> __second)
1051       : pair(__first, __second,
1052              typename _Build_index_tuple<sizeof...(_Args1)>::__type(),
1053              typename _Build_index_tuple<sizeof...(_Args2)>::__type())
1054       { }
1055
1056   template<class _T1, class _T2>
1057     template<typename... _Args1, std::size_t... _Indexes1,
1058              typename... _Args2, std::size_t... _Indexes2>
1059       inline
1060       pair<_T1, _T2>::
1061       pair(tuple<_Args1...>& __tuple1, tuple<_Args2...>& __tuple2,
1062            _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>)
1063       : first(std::forward<_Args1>(std::get<_Indexes1>(__tuple1))...),
1064         second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)
1065       { }
1066
1067   /// @}
1068
1069 _GLIBCXX_END_NAMESPACE_VERSION
1070 } // namespace std
1071
1072 #endif // C++11
1073
1074 #endif // _GLIBCXX_TUPLE