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       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   /**
 162    * Zero-element tuple implementation. This is the basis case for the
 163    * inheritance recursion.
 164    */
 165   template<std::size_t _Idx>
 166     struct _Tuple_impl<_Idx>
 167     {
 168       template<std::size_t, typename...> friend class _Tuple_impl;
 169
 170       _Tuple_impl() = default;
 171
 172       template<typename _Alloc>
 173         _Tuple_impl(allocator_arg_t, const _Alloc&) { }
 174
 175       template<typename _Alloc>
 176         _Tuple_impl(allocator_arg_t, const _Alloc&, const _Tuple_impl&) { }
 177
 178       template<typename _Alloc>
 179         _Tuple_impl(allocator_arg_t, const _Alloc&, _Tuple_impl&&) { }
 180
 181     protected:
 182       void _M_swap(_Tuple_impl&) noexcept { /* no-op */ }
 183     };
 184
 185   template<typename _Tp>
 186     struct __is_empty_non_tuple : is_empty<_Tp> { };
 187
 188   // Using EBO for elements that are tuples causes ambiguous base errors.
 189   template<typename _El0, typename... _El>
 190     struct __is_empty_non_tuple<tuple<_El0, _El...>> : false_type { };
 191
 192   // Use the Empty Base-class Optimization for empty, non-final types.
 193   template<typename _Tp>
 194     using __empty_not_final
 195     = typename conditional<__is_final(_Tp), false_type,
 196                            __is_empty_non_tuple<_Tp>>::type;
 197
 198   /**
 199    * Recursive tuple implementation. Here we store the @c Head element
 200    * and derive from a @c Tuple_impl containing the remaining elements
 201    * (which contains the @c Tail).
 202    */
 203   template<std::size_t _Idx, typename _Head, typename... _Tail>
 204     struct _Tuple_impl<_Idx, _Head, _Tail...>
 205     : public _Tuple_impl<_Idx + 1, _Tail...>,
 206       private _Head_base<_Idx, _Head, __empty_not_final<_Head>::value>
 207     {
 208       template<std::size_t, typename...> friend class _Tuple_impl;
 209
 210       typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
 211       typedef _Head_base<_Idx, _Head, __empty_not_final<_Head>::value> _Base;
 212
 213       static constexpr _Head&
 214       _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 215
 216       static constexpr const _Head&
 217       _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 218
 219       static constexpr _Inherited&
 220       _M_tail(_Tuple_impl& __t) noexcept { return __t; }
 221
 222       static constexpr const _Inherited&
 223       _M_tail(const _Tuple_impl& __t) noexcept { return __t; }
 224
 225       constexpr _Tuple_impl()
 226       : _Inherited(), _Base() { }
 227
 228       explicit
 229       constexpr _Tuple_impl(const _Head& __head, const _Tail&... __tail)
 230       : _Inherited(__tail...), _Base(__head) { }
 231
 232       template<typename _UHead, typename... _UTail, typename = typename
 233                enable_if<sizeof...(_Tail) == sizeof...(_UTail)>::type>
 234         explicit
 235         constexpr _Tuple_impl(_UHead&& __head, _UTail&&... __tail)
 236         : _Inherited(std::forward<_UTail>(__tail)...),
 237           _Base(std::forward<_UHead>(__head)) { }
 238
 239       constexpr _Tuple_impl(const _Tuple_impl&) = default;
 240
 241       constexpr
 242       _Tuple_impl(_Tuple_impl&& __in)
 243       noexcept(__and_<is_nothrow_move_constructible<_Head>,
 244                       is_nothrow_move_constructible<_Inherited>>::value)
 245       : _Inherited(std::move(_M_tail(__in))),
 246         _Base(std::forward<_Head>(_M_head(__in))) { }
 247
 248       template<typename... _UElements>
 249         constexpr _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
 250         : _Inherited(_Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
 251           _Base(_Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
 252
 253       template<typename _UHead, typename... _UTails>
 254         constexpr _Tuple_impl(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 255         : _Inherited(std::move
 256                      (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
 257           _Base(std::forward<_UHead>
 258                 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
 259
 260       template<typename _Alloc>
 261         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)
 262         : _Inherited(__tag, __a),
 263           _Base(__tag, __use_alloc<_Head>(__a)) { }
 264
 265       template<typename _Alloc>
 266         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 267                     const _Head& __head, const _Tail&... __tail)
 268         : _Inherited(__tag, __a, __tail...),
 269           _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head) { }
 270
 271       template<typename _Alloc, typename _UHead, typename... _UTail,
 272                typename = typename enable_if<sizeof...(_Tail)
 273                                              == sizeof...(_UTail)>::type>
 274         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 275                     _UHead&& __head, _UTail&&... __tail)
 276         : _Inherited(__tag, __a, std::forward<_UTail>(__tail)...),
 277           _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 278                 std::forward<_UHead>(__head)) { }
 279
 280       template<typename _Alloc>
 281         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 282                     const _Tuple_impl& __in)
 283         : _Inherited(__tag, __a, _M_tail(__in)),
 284           _Base(__use_alloc<_Head, _Alloc, _Head>(__a), _M_head(__in)) { }
 285
 286       template<typename _Alloc>
 287         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 288                     _Tuple_impl&& __in)
 289         : _Inherited(__tag, __a, std::move(_M_tail(__in))),
 290           _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 291                 std::forward<_Head>(_M_head(__in))) { }
 292
 293       template<typename _Alloc, typename... _UElements>
 294         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 295                     const _Tuple_impl<_Idx, _UElements...>& __in)
 296         : _Inherited(__tag, __a,
 297                      _Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
 298           _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 299                 _Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
 300
 301       template<typename _Alloc, typename _UHead, typename... _UTails>
 302         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 303                     _Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 304         : _Inherited(__tag, __a, std::move
 305                      (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
 306           _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 307                 std::forward<_UHead>
 308                 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
 309
 310       _Tuple_impl&
 311       operator=(const _Tuple_impl& __in)
 312       {
 313         _M_head(*this) = _M_head(__in);
 314         _M_tail(*this) = _M_tail(__in);
 315         return *this;
 316       }
 317
 318       _Tuple_impl&
 319       operator=(_Tuple_impl&& __in)
 320       noexcept(__and_<is_nothrow_move_assignable<_Head>,
 321                       is_nothrow_move_assignable<_Inherited>>::value)
 322       {
 323         _M_head(*this) = std::forward<_Head>(_M_head(__in));
 324         _M_tail(*this) = std::move(_M_tail(__in));
 325         return *this;
 326       }
 327
 328       template<typename... _UElements>
 329         _Tuple_impl&
 330         operator=(const _Tuple_impl<_Idx, _UElements...>& __in)
 331         {
 332           _M_head(*this) = _Tuple_impl<_Idx, _UElements...>::_M_head(__in);
 333           _M_tail(*this) = _Tuple_impl<_Idx, _UElements...>::_M_tail(__in);
 334           return *this;
 335         }
 336
 337       template<typename _UHead, typename... _UTails>
 338         _Tuple_impl&
 339         operator=(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 340         {
 341           _M_head(*this) = std::forward<_UHead>
 342             (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in));
 343           _M_tail(*this) = std::move
 344             (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in));
 345           return *this;
 346         }
 347
 348     protected:
 349       void
 350       _M_swap(_Tuple_impl& __in)
 351       noexcept(noexcept(swap(std::declval<_Head&>(),
 352                              std::declval<_Head&>()))
 353                && noexcept(_M_tail(__in)._M_swap(_M_tail(__in))))
 354       {
 355         using std::swap;
 356         swap(_M_head(*this), _M_head(__in));
 357         _Inherited::_M_swap(_M_tail(__in));
 358       }
 359     };
 360
 361   /// Primary class template, tuple
 362   template<typename... _Elements>
 363     class tuple : public _Tuple_impl<0, _Elements...>
 364     {
 365       typedef _Tuple_impl<0, _Elements...> _Inherited;
 366
 367     public:
 368       constexpr tuple()
 369       : _Inherited() { }
 370
 371       explicit
 372       constexpr tuple(const _Elements&... __elements)
 373       : _Inherited(__elements...) { }
 374
 375       template<typename... _UElements, typename = typename
 376         enable_if<__and_<is_convertible<_UElements,
 377                                         _Elements>...>::value>::type>
 378         explicit
 379         constexpr tuple(_UElements&&... __elements)
 380         : _Inherited(std::forward<_UElements>(__elements)...) { }
 381
 382       constexpr tuple(const tuple&) = default;
 383
 384       constexpr tuple(tuple&&) = default;
 385
 386       template<typename... _UElements, typename = typename
 387         enable_if<__and_<is_convertible<const _UElements&,
 388                                         _Elements>...>::value>::type>
 389         constexpr tuple(const tuple<_UElements...>& __in)
 390         : _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 391         { }
 392
 393       template<typename... _UElements, typename = typename
 394         enable_if<__and_<is_convertible<_UElements,
 395                                         _Elements>...>::value>::type>
 396         constexpr tuple(tuple<_UElements...>&& __in)
 397         : _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
 398
 399       // Allocator-extended constructors.
 400
 401       template<typename _Alloc>
 402         tuple(allocator_arg_t __tag, const _Alloc& __a)
 403         : _Inherited(__tag, __a) { }
 404
 405       template<typename _Alloc>
 406         tuple(allocator_arg_t __tag, const _Alloc& __a,
 407               const _Elements&... __elements)
 408         : _Inherited(__tag, __a, __elements...) { }
 409
 410       template<typename _Alloc, typename... _UElements, typename = typename
 411                enable_if<sizeof...(_UElements)
 412                          == sizeof...(_Elements)>::type>
 413         tuple(allocator_arg_t __tag, const _Alloc& __a,
 414               _UElements&&... __elements)
 415         : _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)
 416         { }
 417
 418       template<typename _Alloc>
 419         tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
 420         : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
 421
 422       template<typename _Alloc>
 423         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
 424         : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
 425
 426       template<typename _Alloc, typename... _UElements, typename = typename
 427                enable_if<sizeof...(_UElements)
 428                          == sizeof...(_Elements)>::type>
 429         tuple(allocator_arg_t __tag, const _Alloc& __a,
 430               const tuple<_UElements...>& __in)
 431         : _Inherited(__tag, __a,
 432                      static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 433         { }
 434
 435       template<typename _Alloc, typename... _UElements, typename = typename
 436                enable_if<sizeof...(_UElements)
 437                          == sizeof...(_Elements)>::type>
 438         tuple(allocator_arg_t __tag, const _Alloc& __a,
 439               tuple<_UElements...>&& __in)
 440         : _Inherited(__tag, __a,
 441                      static_cast<_Tuple_impl<0, _UElements...>&&>(__in))
 442         { }
 443
 444       tuple&
 445       operator=(const tuple& __in)
 446       {
 447         static_cast<_Inherited&>(*this) = __in;
 448         return *this;
 449       }
 450
 451       tuple&
 452       operator=(tuple&& __in)
 453       noexcept(is_nothrow_move_assignable<_Inherited>::value)
 454       {
 455         static_cast<_Inherited&>(*this) = std::move(__in);
 456         return *this;
 457       }
 458
 459       template<typename... _UElements, typename = typename
 460                enable_if<sizeof...(_UElements)
 461                          == sizeof...(_Elements)>::type>
 462         tuple&
 463         operator=(const tuple<_UElements...>& __in)
 464         {
 465           static_cast<_Inherited&>(*this) = __in;
 466           return *this;
 467         }
 468
 469       template<typename... _UElements, typename = typename
 470                enable_if<sizeof...(_UElements)
 471                          == sizeof...(_Elements)>::type>
 472         tuple&
 473         operator=(tuple<_UElements...>&& __in)
 474         {
 475           static_cast<_Inherited&>(*this) = std::move(__in);
 476           return *this;
 477         }
 478
 479       void
 480       swap(tuple& __in)
 481       noexcept(noexcept(__in._M_swap(__in)))
 482       { _Inherited::_M_swap(__in); }
 483     };
 484
 485   // Explicit specialization, zero-element tuple.
 486   template<>
 487     class tuple<>
 488     {
 489     public:
 490       void swap(tuple&) noexcept { /* no-op */ }
 491     };
 492
 493   /// Partial specialization, 2-element tuple.
 494   /// Includes construction and assignment from a pair.
 495   template<typename _T1, typename _T2>
 496     class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
 497     {
 498       typedef _Tuple_impl<0, _T1, _T2> _Inherited;
 499
 500     public:
 501       constexpr tuple()
 502       : _Inherited() { }
 503
 504       explicit
 505       constexpr tuple(const _T1& __a1, const _T2& __a2)
 506       : _Inherited(__a1, __a2) { }
 507
 508       template<typename _U1, typename _U2, typename = typename
 509                enable_if<__and_<is_convertible<_U1, _T1>,
 510                                 is_convertible<_U2, _T2>>::value>::type>
 511         explicit
 512         constexpr tuple(_U1&& __a1, _U2&& __a2)
 513         : _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
 514
 515       constexpr tuple(const tuple&) = default;
 516
 517       constexpr tuple(tuple&&) = default;
 518
 519       template<typename _U1, typename _U2, typename = typename
 520         enable_if<__and_<is_convertible<const _U1&, _T1>,
 521                          is_convertible<const _U2&, _T2>>::value>::type>
 522         constexpr tuple(const tuple<_U1, _U2>& __in)
 523         : _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
 524
 525       template<typename _U1, typename _U2, typename = typename
 526                enable_if<__and_<is_convertible<_U1, _T1>,
 527                                 is_convertible<_U2, _T2>>::value>::type>
 528         constexpr tuple(tuple<_U1, _U2>&& __in)
 529         : _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
 530
 531       template<typename _U1, typename _U2, typename = typename
 532         enable_if<__and_<is_convertible<const _U1&, _T1>,
 533                          is_convertible<const _U2&, _T2>>::value>::type>
 534         constexpr tuple(const pair<_U1, _U2>& __in)
 535         : _Inherited(__in.first, __in.second) { }
 536
 537       template<typename _U1, typename _U2, typename = typename
 538                enable_if<__and_<is_convertible<_U1, _T1>,
 539                                 is_convertible<_U2, _T2>>::value>::type>
 540         constexpr tuple(pair<_U1, _U2>&& __in)
 541         : _Inherited(std::forward<_U1>(__in.first),
 542                      std::forward<_U2>(__in.second)) { }
 543
 544       // Allocator-extended constructors.
 545
 546       template<typename _Alloc>
 547         tuple(allocator_arg_t __tag, const _Alloc& __a)
 548         : _Inherited(__tag, __a) { }
 549
 550       template<typename _Alloc>
 551         tuple(allocator_arg_t __tag, const _Alloc& __a,
 552               const _T1& __a1, const _T2& __a2)
 553         : _Inherited(__tag, __a, __a1, __a2) { }
 554
 555       template<typename _Alloc, typename _U1, typename _U2>
 556         tuple(allocator_arg_t __tag, const _Alloc& __a, _U1&& __a1, _U2&& __a2)
 557         : _Inherited(__tag, __a, std::forward<_U1>(__a1),
 558                      std::forward<_U2>(__a2)) { }
 559
 560       template<typename _Alloc>
 561         tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
 562         : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
 563
 564       template<typename _Alloc>
 565         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
 566         : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
 567
 568       template<typename _Alloc, typename _U1, typename _U2>
 569         tuple(allocator_arg_t __tag, const _Alloc& __a,
 570               const tuple<_U1, _U2>& __in)
 571         : _Inherited(__tag, __a,
 572                      static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in))
 573         { }
 574
 575       template<typename _Alloc, typename _U1, typename _U2>
 576         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple<_U1, _U2>&& __in)
 577         : _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))
 578         { }
 579
 580       template<typename _Alloc, typename _U1, typename _U2>
 581         tuple(allocator_arg_t __tag, const _Alloc& __a,
 582               const pair<_U1, _U2>& __in)
 583         : _Inherited(__tag, __a, __in.first, __in.second) { }
 584
 585       template<typename _Alloc, typename _U1, typename _U2>
 586         tuple(allocator_arg_t __tag, const _Alloc& __a, pair<_U1, _U2>&& __in)
 587         : _Inherited(__tag, __a, std::forward<_U1>(__in.first),
 588                      std::forward<_U2>(__in.second)) { }
 589
 590       tuple&
 591       operator=(const tuple& __in)
 592       {
 593         static_cast<_Inherited&>(*this) = __in;
 594         return *this;
 595       }
 596
 597       tuple&
 598       operator=(tuple&& __in)
 599       noexcept(is_nothrow_move_assignable<_Inherited>::value)
 600       {
 601         static_cast<_Inherited&>(*this) = std::move(__in);
 602         return *this;
 603       }
 604
 605       template<typename _U1, typename _U2>
 606         tuple&
 607         operator=(const tuple<_U1, _U2>& __in)
 608         {
 609           static_cast<_Inherited&>(*this) = __in;
 610           return *this;
 611         }
 612
 613       template<typename _U1, typename _U2>
 614         tuple&
 615         operator=(tuple<_U1, _U2>&& __in)
 616         {
 617           static_cast<_Inherited&>(*this) = std::move(__in);
 618           return *this;
 619         }
 620
 621       template<typename _U1, typename _U2>
 622         tuple&
 623         operator=(const pair<_U1, _U2>& __in)
 624         {
 625           this->_M_head(*this) = __in.first;
 626           this->_M_tail(*this)._M_head(*this) = __in.second;
 627           return *this;
 628         }
 629
 630       template<typename _U1, typename _U2>
 631         tuple&
 632         operator=(pair<_U1, _U2>&& __in)
 633         {
 634           this->_M_head(*this) = std::forward<_U1>(__in.first);
 635           this->_M_tail(*this)._M_head(*this) = std::forward<_U2>(__in.second);
 636           return *this;
 637         }
 638
 639       void
 640       swap(tuple& __in)
 641       noexcept(noexcept(__in._M_swap(__in)))
 642       { _Inherited::_M_swap(__in); }
 643     };
 644
 645
 646   /// Gives the type of the ith element of a given tuple type.
 647   template<std::size_t __i, typename _Tp>
 648     struct tuple_element;
 649
 650   /**
 651    * Recursive case for tuple_element: strip off the first element in
 652    * the tuple and retrieve the (i-1)th element of the remaining tuple.
 653    */
 654   template<std::size_t __i, typename _Head, typename... _Tail>
 655     struct tuple_element<__i, tuple<_Head, _Tail...> >
 656     : tuple_element<__i - 1, tuple<_Tail...> > { };
 657
 658   /**
 659    * Basis case for tuple_element: The first element is the one we're seeking.
 660    */
 661   template<typename _Head, typename... _Tail>
 662     struct tuple_element<0, tuple<_Head, _Tail...> >
 663     {
 664       typedef _Head type;
 665     };
 666
 667   // Duplicate of C++14's tuple_element_t for internal use in C++11 mode
 668   template<std::size_t __i, typename _Tp>
 669     using __tuple_element_t = typename tuple_element<__i, _Tp>::type;
 670
 671   template<std::size_t __i, typename _Tp>
 672     struct tuple_element<__i, const _Tp>
 673     {
 674       typedef typename add_const<__tuple_element_t<__i, _Tp>>::type type;
 675     };
 676
 677   template<std::size_t __i, typename _Tp>
 678     struct tuple_element<__i, volatile _Tp>
 679     {
 680       typedef typename add_volatile<__tuple_element_t<__i, _Tp>>::type type;
 681     };
 682
 683   template<std::size_t __i, typename _Tp>
 684     struct tuple_element<__i, const volatile _Tp>
 685     {
 686       typedef typename add_cv<__tuple_element_t<__i, _Tp>>::type type;
 687     };
 688
 689 #if __cplusplus > 201103L
 690   template<std::size_t __i, typename _Tp>
 691     using tuple_element_t = typename tuple_element<__i, _Tp>::type;
 692 #endif
 693
 694   /// Finds the size of a given tuple type.
 695   template<typename _Tp>
 696     struct tuple_size;
 697
 698   // _GLIBCXX_RESOLVE_LIB_DEFECTS
 699   // 2313. tuple_size should always derive from integral_constant<size_t, N>
 700   template<typename _Tp>
 701     struct tuple_size<const _Tp>
 702     : integral_constant<size_t, tuple_size<_Tp>::value> { };
 703
 704   template<typename _Tp>
 705     struct tuple_size<volatile _Tp>
 706     : integral_constant<size_t, tuple_size<_Tp>::value> { };
 707
 708   template<typename _Tp>
 709     struct tuple_size<const volatile _Tp>
 710     : integral_constant<size_t, tuple_size<_Tp>::value> { };
 711
 712   /// class tuple_size
 713   template<typename... _Elements>
 714     struct tuple_size<tuple<_Elements...>>
 715     : public integral_constant<std::size_t, sizeof...(_Elements)> { };
 716
 717   template<std::size_t __i, typename _Head, typename... _Tail>
 718     constexpr _Head&
 719     __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 720     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 721
 722   template<std::size_t __i, typename _Head, typename... _Tail>
 723     constexpr const _Head&
 724     __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 725     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 726
 727   /// Return a reference to the ith element of a tuple.
 728   template<std::size_t __i, typename... _Elements>
 729     constexpr __tuple_element_t<__i, tuple<_Elements...>>&
 730     get(tuple<_Elements...>& __t) noexcept
 731     { return std::__get_helper<__i>(__t); }
 732
 733   /// Return a const reference to the ith element of a const tuple.
 734   template<std::size_t __i, typename... _Elements>
 735     constexpr const __tuple_element_t<__i, tuple<_Elements...>>&
 736     get(const tuple<_Elements...>& __t) noexcept
 737     { return std::__get_helper<__i>(__t); }
 738
 739   /// Return an rvalue reference to the ith element of a tuple rvalue.
 740   template<std::size_t __i, typename... _Elements>
 741     constexpr __tuple_element_t<__i, tuple<_Elements...>>&&
 742     get(tuple<_Elements...>&& __t) noexcept
 743     {
 744       typedef __tuple_element_t<__i, tuple<_Elements...>> __element_type;
 745       return std::forward<__element_type&&>(std::get<__i>(__t));
 746     }
 747
 748 #if __cplusplus > 201103L
 749
 750 #define __cpp_lib_tuples_by_type 201304
 751
 752   template<typename _Head, size_t __i, typename... _Tail>
 753     constexpr _Head&
 754     __get_helper2(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 755     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 756
 757   template<typename _Head, size_t __i, typename... _Tail>
 758     constexpr const _Head&
 759     __get_helper2(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 760     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 761
 762   /// Return a reference to the unique element of type _Tp of a tuple.
 763   template <typename _Tp, typename... _Types>
 764     constexpr _Tp&
 765     get(tuple<_Types...>& __t) noexcept
 766     { return std::__get_helper2<_Tp>(__t); }
 767
 768   /// Return a reference to the unique element of type _Tp of a tuple rvalue.
 769   template <typename _Tp, typename... _Types>
 770     constexpr _Tp&&
 771     get(tuple<_Types...>&& __t) noexcept
 772     { return std::forward<_Tp&&>(std::__get_helper2<_Tp>(__t)); }
 773
 774   /// Return a const reference to the unique element of type _Tp of a tuple.
 775   template <typename _Tp, typename... _Types>
 776     constexpr const _Tp&
 777     get(const tuple<_Types...>& __t) noexcept
 778     { return std::__get_helper2<_Tp>(__t); }
 779 #endif
 780
 781   // This class performs the comparison operations on tuples
 782   template<typename _Tp, typename _Up, size_t __i, size_t __size>
 783     struct __tuple_compare
 784     {
 785       static constexpr bool
 786       __eq(const _Tp& __t, const _Up& __u)
 787       {
 788         return bool(std::get<__i>(__t) == std::get<__i>(__u))
 789           && __tuple_compare<_Tp, _Up, __i + 1, __size>::__eq(__t, __u);
 790       }
 791
 792       static constexpr bool
 793       __less(const _Tp& __t, const _Up& __u)
 794       {
 795         return bool(std::get<__i>(__t) < std::get<__i>(__u))
 796           || (!bool(std::get<__i>(__u) < std::get<__i>(__t))
 797               && __tuple_compare<_Tp, _Up, __i + 1, __size>::__less(__t, __u));
 798       }
 799     };
 800
 801   template<typename _Tp, typename _Up, size_t __size>
 802     struct __tuple_compare<_Tp, _Up, __size, __size>
 803     {
 804       static constexpr bool
 805       __eq(const _Tp&, const _Up&) { return true; }
 806
 807       static constexpr bool
 808       __less(const _Tp&, const _Up&) { return false; }
 809     };
 810
 811   template<typename... _TElements, typename... _UElements>
 812     constexpr bool
 813     operator==(const tuple<_TElements...>& __t,
 814                const tuple<_UElements...>& __u)
 815     {
 816       static_assert(sizeof...(_TElements) == sizeof...(_UElements),
 817           "tuple objects can only be compared if they have equal sizes.");
 818       using __compare = __tuple_compare<tuple<_TElements...>,
 819                                         tuple<_UElements...>,
 820                                         0, sizeof...(_TElements)>;
 821       return __compare::__eq(__t, __u);
 822     }
 823
 824   template<typename... _TElements, typename... _UElements>
 825     constexpr bool
 826     operator<(const tuple<_TElements...>& __t,
 827               const tuple<_UElements...>& __u)
 828     {
 829       static_assert(sizeof...(_TElements) == sizeof...(_UElements),
 830           "tuple objects can only be compared if they have equal sizes.");
 831       using __compare = __tuple_compare<tuple<_TElements...>,
 832                                         tuple<_UElements...>,
 833                                         0, sizeof...(_TElements)>;
 834       return __compare::__less(__t, __u);
 835     }
 836
 837   template<typename... _TElements, typename... _UElements>
 838     constexpr bool
 839     operator!=(const tuple<_TElements...>& __t,
 840                const tuple<_UElements...>& __u)
 841     { return !(__t == __u); }
 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 !(__u < __t); }
 854
 855   template<typename... _TElements, typename... _UElements>
 856     constexpr bool
 857     operator>=(const tuple<_TElements...>& __t,
 858                const tuple<_UElements...>& __u)
 859     { return !(__t < __u); }
 860
 861   // NB: DR 705.
 862   template<typename... _Elements>
 863     constexpr tuple<typename __decay_and_strip<_Elements>::__type...>
 864     make_tuple(_Elements&&... __args)
 865     {
 866       typedef tuple<typename __decay_and_strip<_Elements>::__type...>
 867         __result_type;
 868       return __result_type(std::forward<_Elements>(__args)...);
 869     }
 870
 871   template<typename... _Elements>
 872     tuple<_Elements&&...>
 873     forward_as_tuple(_Elements&&... __args) noexcept
 874     { return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
 875
 876   template<typename>
 877     struct __is_tuple_like_impl : false_type
 878     { };
 879
 880   template<typename... _Tps>
 881     struct __is_tuple_like_impl<tuple<_Tps...>> : true_type
 882     { };
 883
 884   template<typename _T1, typename _T2>
 885     struct __is_tuple_like_impl<pair<_T1, _T2>> : true_type
 886     { };
 887
 888   template<typename _Tp, std::size_t _Nm>
 889     struct __is_tuple_like_impl<array<_Tp, _Nm>> : true_type
 890     { };
 891
 892   // Internal type trait that allows us to sfinae-protect tuple_cat.
 893   template<typename _Tp>
 894     struct __is_tuple_like
 895     : public __is_tuple_like_impl<typename std::remove_cv
 896             <typename std::remove_reference<_Tp>::type>::type>::type
 897     { };
 898
 899   template<size_t, typename, typename, size_t>
 900     struct __make_tuple_impl;
 901
 902   template<size_t _Idx, typename _Tuple, typename... _Tp, size_t _Nm>
 903     struct __make_tuple_impl<_Idx, tuple<_Tp...>, _Tuple, _Nm>
 904     : __make_tuple_impl<_Idx + 1,
 905                         tuple<_Tp..., __tuple_element_t<_Idx, _Tuple>>,
 906                         _Tuple, _Nm>
 907     { };
 908
 909   template<std::size_t _Nm, typename _Tuple, typename... _Tp>
 910     struct __make_tuple_impl<_Nm, tuple<_Tp...>, _Tuple, _Nm>
 911     {
 912       typedef tuple<_Tp...> __type;
 913     };
 914
 915   template<typename _Tuple>
 916     struct __do_make_tuple
 917     : __make_tuple_impl<0, tuple<>, _Tuple, std::tuple_size<_Tuple>::value>
 918     { };
 919
 920   // Returns the std::tuple equivalent of a tuple-like type.
 921   template<typename _Tuple>
 922     struct __make_tuple
 923     : public __do_make_tuple<typename std::remove_cv
 924             <typename std::remove_reference<_Tuple>::type>::type>
 925     { };
 926
 927   // Combines several std::tuple's into a single one.
 928   template<typename...>
 929     struct __combine_tuples;
 930
 931   template<>
 932     struct __combine_tuples<>
 933     {
 934       typedef tuple<> __type;
 935     };
 936
 937   template<typename... _Ts>
 938     struct __combine_tuples<tuple<_Ts...>>
 939     {
 940       typedef tuple<_Ts...> __type;
 941     };
 942
 943   template<typename... _T1s, typename... _T2s, typename... _Rem>
 944     struct __combine_tuples<tuple<_T1s...>, tuple<_T2s...>, _Rem...>
 945     {
 946       typedef typename __combine_tuples<tuple<_T1s..., _T2s...>,
 947                                         _Rem...>::__type __type;
 948     };
 949
 950   // Computes the result type of tuple_cat given a set of tuple-like types.
 951   template<typename... _Tpls>
 952     struct __tuple_cat_result
 953     {
 954       typedef typename __combine_tuples
 955         <typename __make_tuple<_Tpls>::__type...>::__type __type;
 956     };
 957
 958   // Helper to determine the index set for the first tuple-like
 959   // type of a given set.
 960   template<typename...>
 961     struct __make_1st_indices;
 962
 963   template<>
 964     struct __make_1st_indices<>
 965     {
 966       typedef std::_Index_tuple<> __type;
 967     };
 968
 969   template<typename _Tp, typename... _Tpls>
 970     struct __make_1st_indices<_Tp, _Tpls...>
 971     {
 972       typedef typename std::_Build_index_tuple<std::tuple_size<
 973         typename std::remove_reference<_Tp>::type>::value>::__type __type;
 974     };
 975
 976   // Performs the actual concatenation by step-wise expanding tuple-like
 977   // objects into the elements,  which are finally forwarded into the
 978   // result tuple.
 979   template<typename _Ret, typename _Indices, typename... _Tpls>
 980     struct __tuple_concater;
 981
 982   template<typename _Ret, std::size_t... _Is, typename _Tp, typename... _Tpls>
 983     struct __tuple_concater<_Ret, std::_Index_tuple<_Is...>, _Tp, _Tpls...>
 984     {
 985       template<typename... _Us>
 986         static constexpr _Ret
 987         _S_do(_Tp&& __tp, _Tpls&&... __tps, _Us&&... __us)
 988         {
 989           typedef typename __make_1st_indices<_Tpls...>::__type __idx;
 990           typedef __tuple_concater<_Ret, __idx, _Tpls...>      __next;
 991           return __next::_S_do(std::forward<_Tpls>(__tps)...,
 992                                std::forward<_Us>(__us)...,
 993                                std::get<_Is>(std::forward<_Tp>(__tp))...);
 994         }
 995     };
 996
 997   template<typename _Ret>
 998     struct __tuple_concater<_Ret, std::_Index_tuple<>>
 999     {
1000       template<typename... _Us>
1001         static constexpr _Ret
1002         _S_do(_Us&&... __us)
1003         {
1004           return _Ret(std::forward<_Us>(__us)...);
1005         }
1006     };
1007
1008   /// tuple_cat
1009   template<typename... _Tpls, typename = typename
1010            enable_if<__and_<__is_tuple_like<_Tpls>...>::value>::type>
1011     constexpr auto
1012     tuple_cat(_Tpls&&... __tpls)
1013     -> typename __tuple_cat_result<_Tpls...>::__type
1014     {
1015       typedef typename __tuple_cat_result<_Tpls...>::__type __ret;
1016       typedef typename __make_1st_indices<_Tpls...>::__type __idx;
1017       typedef __tuple_concater<__ret, __idx, _Tpls...> __concater;
1018       return __concater::_S_do(std::forward<_Tpls>(__tpls)...);
1019     }
1020
1021   /// tie
1022   template<typename... _Elements>
1023     inline tuple<_Elements&...>
1024     tie(_Elements&... __args) noexcept
1025     { return tuple<_Elements&...>(__args...); }
1026
1027   /// swap
1028   template<typename... _Elements>
1029     inline void
1030     swap(tuple<_Elements...>& __x, tuple<_Elements...>& __y)
1031     noexcept(noexcept(__x.swap(__y)))
1032     { __x.swap(__y); }
1033
1034   // A class (and instance) which can be used in 'tie' when an element
1035   // of a tuple is not required
1036   struct _Swallow_assign
1037   {
1038     template<class _Tp>
1039       const _Swallow_assign&
1040       operator=(const _Tp&) const
1041       { return *this; }
1042   };
1043
1044   const _Swallow_assign ignore{};
1045
1046   /// Partial specialization for tuples
1047   template<typename... _Types, typename _Alloc>
1048     struct uses_allocator<tuple<_Types...>, _Alloc> : true_type { };
1049
1050   // See stl_pair.h...
1051   template<class _T1, class _T2>
1052     template<typename... _Args1, typename... _Args2>
1053       inline
1054       pair<_T1, _T2>::
1055       pair(piecewise_construct_t,
1056            tuple<_Args1...> __first, tuple<_Args2...> __second)
1057       : pair(__first, __second,
1058              typename _Build_index_tuple<sizeof...(_Args1)>::__type(),
1059              typename _Build_index_tuple<sizeof...(_Args2)>::__type())
1060       { }
1061
1062   template<class _T1, class _T2>
1063     template<typename... _Args1, std::size_t... _Indexes1,
1064              typename... _Args2, std::size_t... _Indexes2>
1065       inline
1066       pair<_T1, _T2>::
1067       pair(tuple<_Args1...>& __tuple1, tuple<_Args2...>& __tuple2,
1068            _Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>)
1069       : first(std::forward<_Args1>(std::get<_Indexes1>(__tuple1))...),
1070         second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)
1071       { }
1072
1073   /// @}
1074
1075 _GLIBCXX_END_NAMESPACE_VERSION
1076 } // namespace std
1077
1078 #endif // C++11
1079
1080 #endif // _GLIBCXX_TUPLE