libstdc++-v3/include/std/tuple

   1 // <tuple> -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009, 2010, 2011 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 #ifndef __GXX_EXPERIMENTAL_CXX0X__
  35 # include <bits/c++0x_warning.h>
  36 #else
  37
  38 #include <utility>
  39 #include <bits/uses_allocator.h>
  40
  41 namespace std _GLIBCXX_VISIBILITY(default)
  42 {
  43 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  44
  45   // Adds a const reference to a non-reference type.
  46   template<typename _Tp>
  47     struct __add_c_ref
  48     { typedef const _Tp& type; };
  49
  50   template<typename _Tp>
  51     struct __add_c_ref<_Tp&>
  52     { typedef _Tp& type; };
  53
  54   // Adds a reference to a non-reference type.
  55   template<typename _Tp>
  56     struct __add_ref
  57     { typedef _Tp& type; };
  58
  59   template<typename _Tp>
  60     struct __add_ref<_Tp&>
  61     { typedef _Tp& type; };
  62
  63   // Adds an rvalue reference to a non-reference type.
  64   template<typename _Tp>
  65     struct __add_r_ref
  66     { typedef _Tp&& type; };
  67
  68   template<typename _Tp>
  69     struct __add_r_ref<_Tp&>
  70     { typedef _Tp& type; };
  71
  72   // To work around c++/49225 aka c++/48322.
  73   template<typename...>
  74     struct __conv_types { };
  75
  76   template<typename _Tuple1, typename _Tuple2>
  77     struct __one_by_one_convertible
  78     : public false_type { };
  79
  80   template<typename _Tp, typename _Up>
  81     struct __one_by_one_convertible<__conv_types<_Tp>, __conv_types<_Up>>
  82     : public is_convertible<_Tp, _Up>::type { };
  83
  84   template<typename _T1, typename... _TR, typename _U1, typename... _UR>
  85     struct __one_by_one_convertible<__conv_types<_T1, _TR...>,
  86                                     __conv_types<_U1, _UR...>>
  87     : public __and_<is_convertible<_T1, _U1>,
  88                     __one_by_one_convertible<__conv_types<_TR...>,
  89                                              __conv_types<_UR...>>>::type
  90     { };
  91
  92   template<typename _Tuple1, typename _Tuple2>
  93     struct __all_convertible;
  94
  95   template<typename... _TTypes, typename... _UTypes>
  96     struct __all_convertible<__conv_types<_TTypes...>,
  97                              __conv_types<_UTypes...>>
  98     : public __one_by_one_convertible<__conv_types<_TTypes...>,
  99                                       __conv_types<_UTypes...>>::type { };
 100
 101   template<std::size_t _Idx, typename _Head, bool _IsEmpty>
 102     struct _Head_base;
 103
 104   template<std::size_t _Idx, typename _Head>
 105     struct _Head_base<_Idx, _Head, true>
 106     : public _Head
 107     {
 108       constexpr _Head_base()
 109       : _Head() { }
 110
 111       constexpr _Head_base(const _Head& __h)
 112       : _Head(__h) { }
 113
 114       template<typename _UHead, typename = typename
 115                enable_if<!is_convertible<_UHead,
 116                                          __uses_alloc_base>::value>::type>
 117         constexpr _Head_base(_UHead&& __h)
 118         : _Head(std::forward<_UHead>(__h)) { }
 119
 120       _Head_base(__uses_alloc0)
 121       : _Head() { }
 122
 123       template<typename _Alloc>
 124         _Head_base(__uses_alloc1<_Alloc> __a)
 125         : _Head(allocator_arg, *__a._M_a) { }
 126
 127       template<typename _Alloc>
 128         _Head_base(__uses_alloc2<_Alloc> __a)
 129         : _Head(*__a._M_a) { }
 130
 131       template<typename _UHead>
 132         _Head_base(__uses_alloc0, _UHead&& __uhead)
 133         : _Head(std::forward<_UHead>(__uhead)) { }
 134
 135       template<typename _Alloc, typename _UHead>
 136         _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
 137         : _Head(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead)) { }
 138
 139       template<typename _Alloc, typename _UHead>
 140         _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
 141         : _Head(std::forward<_UHead>(__uhead), *__a._M_a) { }
 142
 143       static constexpr _Head&
 144       _M_head(_Head_base& __b) noexcept { return __b; }
 145
 146       static constexpr const _Head&
 147       _M_head(const _Head_base& __b) noexcept { return __b; }
 148     };
 149
 150   template<std::size_t _Idx, typename _Head>
 151     struct _Head_base<_Idx, _Head, false>
 152     {
 153       constexpr _Head_base()
 154       : _M_head_impl() { }
 155
 156       constexpr _Head_base(const _Head& __h)
 157       : _M_head_impl(__h) { }
 158
 159       template<typename _UHead, typename = typename
 160                enable_if<!is_convertible<_UHead,
 161                                          __uses_alloc_base>::value>::type>
 162         constexpr _Head_base(_UHead&& __h)
 163         : _M_head_impl(std::forward<_UHead>(__h)) { }
 164
 165       _Head_base(__uses_alloc0)
 166       : _M_head_impl() { }
 167
 168       template<typename _Alloc>
 169         _Head_base(__uses_alloc1<_Alloc> __a)
 170         : _M_head_impl(allocator_arg, *__a._M_a) { }
 171
 172       template<typename _Alloc>
 173         _Head_base(__uses_alloc2<_Alloc> __a)
 174         : _M_head_impl(*__a._M_a) { }
 175
 176       template<typename _UHead>
 177         _Head_base(__uses_alloc0, _UHead&& __uhead)
 178         : _M_head_impl(std::forward<_UHead>(__uhead)) { }
 179
 180       template<typename _Alloc, typename _UHead>
 181         _Head_base(__uses_alloc1<_Alloc> __a, _UHead&& __uhead)
 182         : _M_head_impl(allocator_arg, *__a._M_a, std::forward<_UHead>(__uhead))
 183         { }
 184
 185       template<typename _Alloc, typename _UHead>
 186         _Head_base(__uses_alloc2<_Alloc> __a, _UHead&& __uhead)
 187         : _M_head_impl(std::forward<_UHead>(__uhead), *__a._M_a) { }
 188
 189       static constexpr _Head&
 190       _M_head(_Head_base& __b) noexcept { return __b._M_head_impl; }
 191
 192       static constexpr const _Head&
 193       _M_head(const _Head_base& __b) noexcept { return __b._M_head_impl; }
 194
 195       _Head _M_head_impl;
 196     };
 197
 198   /**
 199    * Contains the actual implementation of the @c tuple template, stored
 200    * as a recursive inheritance hierarchy from the first element (most
 201    * derived class) to the last (least derived class). The @c Idx
 202    * parameter gives the 0-based index of the element stored at this
 203    * point in the hierarchy; we use it to implement a constant-time
 204    * get() operation.
 205    */
 206   template<std::size_t _Idx, typename... _Elements>
 207     struct _Tuple_impl;
 208
 209   /**
 210    * Zero-element tuple implementation. This is the basis case for the
 211    * inheritance recursion.
 212    */
 213   template<std::size_t _Idx>
 214     struct _Tuple_impl<_Idx>
 215     {
 216       template<std::size_t, typename...> friend class _Tuple_impl;
 217
 218       _Tuple_impl() = default;
 219
 220       template<typename _Alloc>
 221         _Tuple_impl(allocator_arg_t, const _Alloc&) { }
 222
 223       template<typename _Alloc>
 224         _Tuple_impl(allocator_arg_t, const _Alloc&, const _Tuple_impl&) { }
 225
 226       template<typename _Alloc>
 227         _Tuple_impl(allocator_arg_t, const _Alloc&, _Tuple_impl&&) { }
 228
 229     protected:
 230       void _M_swap(_Tuple_impl&) noexcept { /* no-op */ }
 231     };
 232
 233   /**
 234    * Recursive tuple implementation. Here we store the @c Head element
 235    * and derive from a @c Tuple_impl containing the remaining elements
 236    * (which contains the @c Tail).
 237    */
 238   template<std::size_t _Idx, typename _Head, typename... _Tail>
 239     struct _Tuple_impl<_Idx, _Head, _Tail...>
 240     : public _Tuple_impl<_Idx + 1, _Tail...>,
 241       private _Head_base<_Idx, _Head, std::is_empty<_Head>::value>
 242     {
 243       template<std::size_t, typename...> friend class _Tuple_impl;
 244
 245       typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
 246       typedef _Head_base<_Idx, _Head, std::is_empty<_Head>::value> _Base;
 247
 248       static constexpr _Head&
 249       _M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 250
 251       static constexpr const _Head&
 252       _M_head(const _Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
 253
 254       static constexpr _Inherited&
 255       _M_tail(_Tuple_impl& __t) noexcept { return __t; }
 256
 257       static constexpr const _Inherited&
 258       _M_tail(const _Tuple_impl& __t) noexcept { return __t; }
 259
 260       constexpr _Tuple_impl()
 261       : _Inherited(), _Base() { }
 262
 263       explicit
 264       constexpr _Tuple_impl(const _Head& __head, const _Tail&... __tail)
 265       : _Inherited(__tail...), _Base(__head) { }
 266
 267       template<typename _UHead, typename... _UTail, typename = typename
 268                enable_if<sizeof...(_Tail) == sizeof...(_UTail)>::type>
 269         explicit
 270         constexpr _Tuple_impl(_UHead&& __head, _UTail&&... __tail)
 271         : _Inherited(std::forward<_UTail>(__tail)...),
 272           _Base(std::forward<_UHead>(__head)) { }
 273
 274       constexpr _Tuple_impl(const _Tuple_impl&) = default;
 275
 276       constexpr
 277       _Tuple_impl(_Tuple_impl&& __in)
 278       noexcept(__and_<is_nothrow_move_constructible<_Head>,
 279                       is_nothrow_move_constructible<_Inherited>>::value)
 280       : _Inherited(std::move(_M_tail(__in))),
 281         _Base(std::forward<_Head>(_M_head(__in))) { }
 282
 283       template<typename... _UElements>
 284         constexpr _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
 285         : _Inherited(_Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
 286           _Base(_Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
 287
 288       template<typename _UHead, typename... _UTails>
 289         constexpr _Tuple_impl(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 290         : _Inherited(std::move
 291                      (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
 292           _Base(std::forward<_UHead>
 293                 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
 294
 295       template<typename _Alloc>
 296         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a)
 297         : _Inherited(__tag, __a),
 298           _Base(__use_alloc<_Head>(__a)) { }
 299
 300       template<typename _Alloc>
 301         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 302                     const _Head& __head, const _Tail&... __tail)
 303         : _Inherited(__tag, __a, __tail...),
 304           _Base(__use_alloc<_Head, _Alloc, _Head>(__a), __head) { }
 305
 306       template<typename _Alloc, typename _UHead, typename... _UTail,
 307                typename = typename enable_if<sizeof...(_Tail)
 308                                              == sizeof...(_UTail)>::type>
 309         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 310                     _UHead&& __head, _UTail&&... __tail)
 311         : _Inherited(__tag, __a, std::forward<_UTail>(__tail)...),
 312           _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 313                 std::forward<_UHead>(__head)) { }
 314
 315       template<typename _Alloc>
 316         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 317                     const _Tuple_impl& __in)
 318         : _Inherited(__tag, __a, _M_tail(__in)),
 319           _Base(__use_alloc<_Head, _Alloc, _Head>(__a), _M_head(__in)) { }
 320
 321       template<typename _Alloc>
 322         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 323                     _Tuple_impl&& __in)
 324         : _Inherited(__tag, __a, std::move(_M_tail(__in))),
 325           _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 326                 std::forward<_Head>(_M_head(__in))) { }
 327
 328       template<typename _Alloc, typename... _UElements>
 329         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 330                     const _Tuple_impl<_Idx, _UElements...>& __in)
 331         : _Inherited(__tag, __a,
 332                      _Tuple_impl<_Idx, _UElements...>::_M_tail(__in)),
 333           _Base(__use_alloc<_Head, _Alloc, _Head>(__a),
 334                 _Tuple_impl<_Idx, _UElements...>::_M_head(__in)) { }
 335
 336       template<typename _Alloc, typename _UHead, typename... _UTails>
 337         _Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 338                     _Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 339         : _Inherited(__tag, __a, std::move
 340                      (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in))),
 341           _Base(__use_alloc<_Head, _Alloc, _UHead>(__a),
 342                 std::forward<_UHead>
 343                 (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in))) { }
 344
 345       _Tuple_impl&
 346       operator=(const _Tuple_impl& __in)
 347       {
 348         _M_head(*this) = _M_head(__in);
 349         _M_tail(*this) = _M_tail(__in);
 350         return *this;
 351       }
 352
 353       _Tuple_impl&
 354       operator=(_Tuple_impl&& __in)
 355       noexcept(__and_<is_nothrow_move_assignable<_Head>,
 356                       is_nothrow_move_assignable<_Inherited>>::value)
 357       {
 358         _M_head(*this) = std::forward<_Head>(_M_head(__in));
 359         _M_tail(*this) = std::move(_M_tail(__in));
 360         return *this;
 361       }
 362
 363       template<typename... _UElements>
 364         _Tuple_impl&
 365         operator=(const _Tuple_impl<_Idx, _UElements...>& __in)
 366         {
 367           _M_head(*this) = _Tuple_impl<_Idx, _UElements...>::_M_head(__in);
 368           _M_tail(*this) = _Tuple_impl<_Idx, _UElements...>::_M_tail(__in);
 369           return *this;
 370         }
 371
 372       template<typename _UHead, typename... _UTails>
 373         _Tuple_impl&
 374         operator=(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 375         {
 376           _M_head(*this) = std::forward<_UHead>
 377             (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_head(__in));
 378           _M_tail(*this) = std::move
 379             (_Tuple_impl<_Idx, _UHead, _UTails...>::_M_tail(__in));
 380           return *this;
 381         }
 382
 383     protected:
 384       void
 385       _M_swap(_Tuple_impl& __in)
 386       noexcept(noexcept(swap(std::declval<_Head&>(),
 387                              std::declval<_Head&>()))
 388                && noexcept(_M_tail(__in)._M_swap(_M_tail(__in))))
 389       {
 390         using std::swap;
 391         swap(_M_head(*this), _M_head(__in));
 392         _Inherited::_M_swap(_M_tail(__in));
 393       }
 394     };
 395
 396   /// Primary class template, tuple
 397   template<typename... _Elements>
 398     class tuple : public _Tuple_impl<0, _Elements...>
 399     {
 400       typedef _Tuple_impl<0, _Elements...> _Inherited;
 401
 402     public:
 403       constexpr tuple()
 404       : _Inherited() { }
 405
 406       explicit
 407       constexpr tuple(const _Elements&... __elements)
 408       : _Inherited(__elements...) { }
 409
 410       template<typename... _UElements, typename = typename
 411         enable_if<__and_<integral_constant<bool, sizeof...(_UElements)
 412                                            == sizeof...(_Elements)>,
 413                          __all_convertible<__conv_types<_UElements...>,
 414                                            __conv_types<_Elements...>>
 415                          >::value>::type>
 416         explicit
 417         constexpr tuple(_UElements&&... __elements)
 418         : _Inherited(std::forward<_UElements>(__elements)...) { }
 419
 420       constexpr tuple(const tuple&) = default;
 421
 422       constexpr tuple(tuple&&) = default;
 423
 424       template<typename... _UElements, typename = typename
 425         enable_if<__and_<integral_constant<bool, sizeof...(_UElements)
 426                                            == sizeof...(_Elements)>,
 427                          __all_convertible<__conv_types<const _UElements&...>,
 428                                            __conv_types<_Elements...>>
 429                          >::value>::type>
 430         constexpr tuple(const tuple<_UElements...>& __in)
 431         : _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 432         { }
 433
 434       template<typename... _UElements, typename = typename
 435         enable_if<__and_<integral_constant<bool, sizeof...(_UElements)
 436                                            == sizeof...(_Elements)>,
 437                          __all_convertible<__conv_types<_UElements...>,
 438                                            __conv_types<_Elements...>>
 439                          >::value>::type>
 440         constexpr tuple(tuple<_UElements...>&& __in)
 441         : _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
 442
 443       // Allocator-extended constructors.
 444
 445       template<typename _Alloc>
 446         tuple(allocator_arg_t __tag, const _Alloc& __a)
 447         : _Inherited(__tag, __a) { }
 448
 449       template<typename _Alloc>
 450         tuple(allocator_arg_t __tag, const _Alloc& __a,
 451               const _Elements&... __elements)
 452         : _Inherited(__tag, __a, __elements...) { }
 453
 454       template<typename _Alloc, typename... _UElements, typename = typename
 455                enable_if<sizeof...(_UElements)
 456                          == sizeof...(_Elements)>::type>
 457         tuple(allocator_arg_t __tag, const _Alloc& __a,
 458               _UElements&&... __elements)
 459         : _Inherited(__tag, __a, std::forward<_UElements>(__elements)...)
 460         { }
 461
 462       template<typename _Alloc>
 463         tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
 464         : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
 465
 466       template<typename _Alloc>
 467         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
 468         : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
 469
 470       template<typename _Alloc, typename... _UElements, typename = typename
 471                enable_if<sizeof...(_UElements)
 472                          == sizeof...(_Elements)>::type>
 473         tuple(allocator_arg_t __tag, const _Alloc& __a,
 474               const tuple<_UElements...>& __in)
 475         : _Inherited(__tag, __a,
 476                      static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 477         { }
 478
 479       template<typename _Alloc, typename... _UElements, typename = typename
 480                enable_if<sizeof...(_UElements)
 481                          == sizeof...(_Elements)>::type>
 482         tuple(allocator_arg_t __tag, const _Alloc& __a,
 483               tuple<_UElements...>&& __in)
 484         : _Inherited(__tag, __a,
 485                      static_cast<_Tuple_impl<0, _UElements...>&&>(__in))
 486         { }
 487
 488       tuple&
 489       operator=(const tuple& __in)
 490       {
 491         static_cast<_Inherited&>(*this) = __in;
 492         return *this;
 493       }
 494
 495       tuple&
 496       operator=(tuple&& __in)
 497       noexcept(is_nothrow_move_assignable<_Inherited>::value)
 498       {
 499         static_cast<_Inherited&>(*this) = std::move(__in);
 500         return *this;
 501       }
 502
 503       template<typename... _UElements, typename = typename
 504                enable_if<sizeof...(_UElements)
 505                          == sizeof...(_Elements)>::type>
 506         tuple&
 507         operator=(const tuple<_UElements...>& __in)
 508         {
 509           static_cast<_Inherited&>(*this) = __in;
 510           return *this;
 511         }
 512
 513       template<typename... _UElements, typename = typename
 514                enable_if<sizeof...(_UElements)
 515                          == sizeof...(_Elements)>::type>
 516         tuple&
 517         operator=(tuple<_UElements...>&& __in)
 518         {
 519           static_cast<_Inherited&>(*this) = std::move(__in);
 520           return *this;
 521         }
 522
 523       void
 524       swap(tuple& __in)
 525       noexcept(noexcept(__in._M_swap(__in)))
 526       { _Inherited::_M_swap(__in); }
 527     };
 528
 529   // Explicit specialization, zero-element tuple.
 530   template<>
 531     class tuple<>
 532     {
 533     public:
 534       void swap(tuple&) noexcept { /* no-op */ }
 535     };
 536
 537   /// Partial specialization, 2-element tuple.
 538   /// Includes construction and assignment from a pair.
 539   template<typename _T1, typename _T2>
 540     class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
 541     {
 542       typedef _Tuple_impl<0, _T1, _T2> _Inherited;
 543
 544     public:
 545       constexpr tuple()
 546       : _Inherited() { }
 547
 548       explicit
 549       constexpr tuple(const _T1& __a1, const _T2& __a2)
 550       : _Inherited(__a1, __a2) { }
 551
 552       template<typename _U1, typename _U2, typename = typename
 553                enable_if<__and_<is_convertible<_U1, _T1>,
 554                                 is_convertible<_U2, _T2>>::value>::type>
 555         explicit
 556         constexpr tuple(_U1&& __a1, _U2&& __a2)
 557         : _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
 558
 559       constexpr tuple(const tuple&) = default;
 560
 561       constexpr tuple(tuple&&) = default;
 562
 563       template<typename _U1, typename _U2, typename = typename
 564         enable_if<__and_<is_convertible<const _U1&, _T1>,
 565                          is_convertible<const _U2&, _T2>>::value>::type>
 566         constexpr tuple(const tuple<_U1, _U2>& __in)
 567         : _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
 568
 569       template<typename _U1, typename _U2, typename = typename
 570                enable_if<__and_<is_convertible<_U1, _T1>,
 571                                 is_convertible<_U2, _T2>>::value>::type>
 572         constexpr tuple(tuple<_U1, _U2>&& __in)
 573         : _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
 574
 575       template<typename _U1, typename _U2, typename = typename
 576         enable_if<__and_<is_convertible<const _U1&, _T1>,
 577                          is_convertible<const _U2&, _T2>>::value>::type>
 578         constexpr tuple(const pair<_U1, _U2>& __in)
 579         : _Inherited(__in.first, __in.second) { }
 580
 581       template<typename _U1, typename _U2, typename = typename
 582                enable_if<__and_<is_convertible<_U1, _T1>,
 583                                 is_convertible<_U2, _T2>>::value>::type>
 584         constexpr tuple(pair<_U1, _U2>&& __in)
 585         : _Inherited(std::forward<_U1>(__in.first),
 586                      std::forward<_U2>(__in.second)) { }
 587
 588       // Allocator-extended constructors.
 589
 590       template<typename _Alloc>
 591         tuple(allocator_arg_t __tag, const _Alloc& __a)
 592         : _Inherited(__tag, __a) { }
 593
 594       template<typename _Alloc>
 595         tuple(allocator_arg_t __tag, const _Alloc& __a,
 596               const _T1& __a1, const _T2& __a2)
 597         : _Inherited(__tag, __a, __a1, __a2) { }
 598
 599       template<typename _Alloc, typename _U1, typename _U2>
 600         tuple(allocator_arg_t __tag, const _Alloc& __a, _U1&& __a1, _U2&& __a2)
 601         : _Inherited(__tag, __a, std::forward<_U1>(__a1),
 602                      std::forward<_U2>(__a2)) { }
 603
 604       template<typename _Alloc>
 605         tuple(allocator_arg_t __tag, const _Alloc& __a, const tuple& __in)
 606         : _Inherited(__tag, __a, static_cast<const _Inherited&>(__in)) { }
 607
 608       template<typename _Alloc>
 609         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple&& __in)
 610         : _Inherited(__tag, __a, static_cast<_Inherited&&>(__in)) { }
 611
 612       template<typename _Alloc, typename _U1, typename _U2>
 613         tuple(allocator_arg_t __tag, const _Alloc& __a,
 614               const tuple<_U1, _U2>& __in)
 615         : _Inherited(__tag, __a,
 616                      static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in))
 617         { }
 618
 619       template<typename _Alloc, typename _U1, typename _U2>
 620         tuple(allocator_arg_t __tag, const _Alloc& __a, tuple<_U1, _U2>&& __in)
 621         : _Inherited(__tag, __a, static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in))
 622         { }
 623
 624       template<typename _Alloc, typename _U1, typename _U2>
 625         tuple(allocator_arg_t __tag, const _Alloc& __a,
 626               const pair<_U1, _U2>& __in)
 627         : _Inherited(__tag, __a, __in.first, __in.second) { }
 628
 629       template<typename _Alloc, typename _U1, typename _U2>
 630         tuple(allocator_arg_t __tag, const _Alloc& __a, pair<_U1, _U2>&& __in)
 631         : _Inherited(__tag, __a, std::forward<_U1>(__in.first),
 632                      std::forward<_U2>(__in.second)) { }
 633
 634       tuple&
 635       operator=(const tuple& __in)
 636       {
 637         static_cast<_Inherited&>(*this) = __in;
 638         return *this;
 639       }
 640
 641       tuple&
 642       operator=(tuple&& __in)
 643       noexcept(is_nothrow_move_assignable<_Inherited>::value)
 644       {
 645         static_cast<_Inherited&>(*this) = std::move(__in);
 646         return *this;
 647       }
 648
 649       template<typename _U1, typename _U2>
 650         tuple&
 651         operator=(const tuple<_U1, _U2>& __in)
 652         {
 653           static_cast<_Inherited&>(*this) = __in;
 654           return *this;
 655         }
 656
 657       template<typename _U1, typename _U2>
 658         tuple&
 659         operator=(tuple<_U1, _U2>&& __in)
 660         {
 661           static_cast<_Inherited&>(*this) = std::move(__in);
 662           return *this;
 663         }
 664
 665       template<typename _U1, typename _U2>
 666         tuple&
 667         operator=(const pair<_U1, _U2>& __in)
 668         {
 669           this->_M_head(*this) = __in.first;
 670           this->_M_tail(*this)._M_head(*this) = __in.second;
 671           return *this;
 672         }
 673
 674       template<typename _U1, typename _U2>
 675         tuple&
 676         operator=(pair<_U1, _U2>&& __in)
 677         {
 678           this->_M_head(*this) = std::forward<_U1>(__in.first);
 679           this->_M_tail(*this)._M_head(*this) = std::forward<_U2>(__in.second);
 680           return *this;
 681         }
 682
 683       void
 684       swap(tuple& __in)
 685       noexcept(noexcept(__in._M_swap(__in)))
 686       { _Inherited::_M_swap(__in); }
 687     };
 688
 689
 690   /// Gives the type of the ith element of a given tuple type.
 691   template<std::size_t __i, typename _Tp>
 692     struct tuple_element;
 693
 694   /**
 695    * Recursive case for tuple_element: strip off the first element in
 696    * the tuple and retrieve the (i-1)th element of the remaining tuple.
 697    */
 698   template<std::size_t __i, typename _Head, typename... _Tail>
 699     struct tuple_element<__i, tuple<_Head, _Tail...> >
 700     : tuple_element<__i - 1, tuple<_Tail...> > { };
 701
 702   /**
 703    * Basis case for tuple_element: The first element is the one we're seeking.
 704    */
 705   template<typename _Head, typename... _Tail>
 706     struct tuple_element<0, tuple<_Head, _Tail...> >
 707     {
 708       typedef _Head type;
 709     };
 710
 711   template<std::size_t __i, typename _Tp>
 712     struct tuple_element<__i, const _Tp>
 713     {
 714       typedef typename
 715       add_const<typename tuple_element<__i, _Tp>::type>::type type;
 716     };
 717
 718   template<std::size_t __i, typename _Tp>
 719     struct tuple_element<__i, volatile _Tp>
 720     {
 721       typedef typename
 722       add_volatile<typename tuple_element<__i, _Tp>::type>::type type;
 723     };
 724
 725   template<std::size_t __i, typename _Tp>
 726     struct tuple_element<__i, const volatile _Tp>
 727     {
 728       typedef typename
 729       add_cv<typename tuple_element<__i, _Tp>::type>::type type;
 730     };
 731
 732   /// Finds the size of a given tuple type.
 733   template<typename _Tp>
 734     struct tuple_size;
 735
 736   template<typename _Tp>
 737     struct tuple_size<const _Tp>
 738     : public integral_constant<
 739              typename remove_cv<decltype(tuple_size<_Tp>::value)>::type,
 740              tuple_size<_Tp>::value> { };
 741
 742   template<typename _Tp>
 743     struct tuple_size<volatile _Tp>
 744     : public integral_constant<
 745              typename remove_cv<decltype(tuple_size<_Tp>::value)>::type,
 746              tuple_size<_Tp>::value> { };
 747
 748   template<typename _Tp>
 749     struct tuple_size<const volatile _Tp>
 750     : public integral_constant<
 751              typename remove_cv<decltype(tuple_size<_Tp>::value)>::type,
 752              tuple_size<_Tp>::value> { };
 753
 754   /// class tuple_size
 755   template<typename... _Elements>
 756     struct tuple_size<tuple<_Elements...>>
 757     : public integral_constant<std::size_t, sizeof...(_Elements)> { };
 758
 759   template<std::size_t __i, typename _Head, typename... _Tail>
 760     constexpr typename __add_ref<_Head>::type
 761     __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 762     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 763
 764   template<std::size_t __i, typename _Head, typename... _Tail>
 765     constexpr typename __add_c_ref<_Head>::type
 766     __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t) noexcept
 767     { return _Tuple_impl<__i, _Head, _Tail...>::_M_head(__t); }
 768
 769   // Return a reference (const reference, rvalue reference) to the ith element
 770   // of a tuple.  Any const or non-const ref elements are returned with their
 771   // original type.
 772   template<std::size_t __i, typename... _Elements>
 773     constexpr typename __add_ref<
 774                       typename tuple_element<__i, tuple<_Elements...>>::type
 775                     >::type
 776     get(tuple<_Elements...>& __t) noexcept
 777     { return __get_helper<__i>(__t); }
 778
 779   template<std::size_t __i, typename... _Elements>
 780     constexpr typename __add_c_ref<
 781                       typename tuple_element<__i, tuple<_Elements...>>::type
 782                     >::type
 783     get(const tuple<_Elements...>& __t) noexcept
 784     { return __get_helper<__i>(__t); }
 785
 786   template<std::size_t __i, typename... _Elements>
 787     constexpr typename __add_r_ref<
 788                       typename tuple_element<__i, tuple<_Elements...>>::type
 789                     >::type
 790     get(tuple<_Elements...>&& __t) noexcept
 791     { return std::forward<typename tuple_element<__i,
 792         tuple<_Elements...>>::type&&>(get<__i>(__t)); }
 793
 794   // This class helps construct the various comparison operations on tuples
 795   template<std::size_t __check_equal_size, std::size_t __i, std::size_t __j,
 796            typename _Tp, typename _Up>
 797     struct __tuple_compare;
 798
 799   template<std::size_t __i, std::size_t __j, typename _Tp, typename _Up>
 800     struct __tuple_compare<0, __i, __j, _Tp, _Up>
 801     {
 802       static bool
 803       __eq(const _Tp& __t, const _Up& __u)
 804       {
 805         return (get<__i>(__t) == get<__i>(__u) &&
 806                 __tuple_compare<0, __i + 1, __j, _Tp, _Up>::__eq(__t, __u));
 807       }
 808
 809       static bool
 810       __less(const _Tp& __t, const _Up& __u)
 811       {
 812         return ((get<__i>(__t) < get<__i>(__u))
 813                 || !(get<__i>(__u) < get<__i>(__t)) &&
 814                 __tuple_compare<0, __i + 1, __j, _Tp, _Up>::__less(__t, __u));
 815       }
 816     };
 817
 818   template<std::size_t __i, typename _Tp, typename _Up>
 819     struct __tuple_compare<0, __i, __i, _Tp, _Up>
 820     {
 821       static bool
 822       __eq(const _Tp&, const _Up&) { return true; }
 823
 824       static bool
 825       __less(const _Tp&, const _Up&) { return false; }
 826     };
 827
 828   template<typename... _TElements, typename... _UElements>
 829     bool
 830     operator==(const tuple<_TElements...>& __t,
 831                const tuple<_UElements...>& __u)
 832     {
 833       typedef tuple<_TElements...> _Tp;
 834       typedef tuple<_UElements...> _Up;
 835       return (__tuple_compare<tuple_size<_Tp>::value - tuple_size<_Up>::value,
 836               0, tuple_size<_Tp>::value, _Tp, _Up>::__eq(__t, __u));
 837     }
 838
 839   template<typename... _TElements, typename... _UElements>
 840     bool
 841     operator<(const tuple<_TElements...>& __t,
 842               const tuple<_UElements...>& __u)
 843     {
 844       typedef tuple<_TElements...> _Tp;
 845       typedef tuple<_UElements...> _Up;
 846       return (__tuple_compare<tuple_size<_Tp>::value - tuple_size<_Up>::value,
 847               0, tuple_size<_Tp>::value, _Tp, _Up>::__less(__t, __u));
 848     }
 849
 850   template<typename... _TElements, typename... _UElements>
 851     inline bool
 852     operator!=(const tuple<_TElements...>& __t,
 853                const tuple<_UElements...>& __u)
 854     { return !(__t == __u); }
 855
 856   template<typename... _TElements, typename... _UElements>
 857     inline bool
 858     operator>(const tuple<_TElements...>& __t,
 859               const tuple<_UElements...>& __u)
 860     { return __u < __t; }
 861
 862   template<typename... _TElements, typename... _UElements>
 863     inline bool
 864     operator<=(const tuple<_TElements...>& __t,
 865                const tuple<_UElements...>& __u)
 866     { return !(__u < __t); }
 867
 868   template<typename... _TElements, typename... _UElements>
 869     inline bool
 870     operator>=(const tuple<_TElements...>& __t,
 871                const tuple<_UElements...>& __u)
 872     { return !(__t < __u); }
 873
 874   // NB: DR 705.
 875   template<typename... _Elements>
 876     constexpr tuple<typename __decay_and_strip<_Elements>::__type...>
 877     make_tuple(_Elements&&... __args)
 878     {
 879       typedef tuple<typename __decay_and_strip<_Elements>::__type...>
 880         __result_type;
 881       return __result_type(std::forward<_Elements>(__args)...);
 882     }
 883
 884   template<typename... _Elements>
 885     constexpr tuple<_Elements&&...>
 886     forward_as_tuple(_Elements&&... __args) noexcept
 887     { return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
 888
 889
 890   template<typename, std::size_t> struct array;
 891
 892   template<std::size_t _Int, typename _Tp, std::size_t _Nm>
 893     constexpr _Tp& get(array<_Tp, _Nm>&) noexcept;
 894
 895   template<std::size_t _Int, typename _Tp, std::size_t _Nm>
 896     constexpr _Tp&& get(array<_Tp, _Nm>&&) noexcept;
 897
 898   template<std::size_t _Int, typename _Tp, std::size_t _Nm>
 899     constexpr const _Tp& get(const array<_Tp, _Nm>&) noexcept;
 900
 901   template<typename>
 902     struct __is_tuple_like_impl : false_type
 903     { };
 904
 905   template<typename... _Tps>
 906     struct __is_tuple_like_impl<tuple<_Tps...>> : true_type
 907     { };
 908
 909   template<typename _T1, typename _T2>
 910     struct __is_tuple_like_impl<pair<_T1, _T2>> : true_type
 911     { };
 912
 913   template<typename _Tp, std::size_t _Nm>
 914     struct __is_tuple_like_impl<array<_Tp, _Nm>> : true_type
 915     { };
 916
 917   // Internal type trait that allows us to sfinae-protect tuple_cat.
 918   template<typename _Tp>
 919     struct __is_tuple_like
 920     : public __is_tuple_like_impl<typename std::remove_cv
 921             <typename std::remove_reference<_Tp>::type>::type>::type
 922     { };
 923
 924   // Stores a tuple of indices.  Also used by bind() to extract the elements
 925   // in a tuple.
 926   template<std::size_t... _Indexes>
 927     struct _Index_tuple
 928     {
 929       typedef _Index_tuple<_Indexes..., sizeof...(_Indexes)> __next;
 930     };
 931
 932   // Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
 933   template<std::size_t _Num>
 934     struct _Build_index_tuple
 935     {
 936       typedef typename _Build_index_tuple<_Num - 1>::__type::__next __type;
 937     };
 938
 939   template<>
 940     struct _Build_index_tuple<0>
 941     {
 942       typedef _Index_tuple<> __type;
 943     };
 944
 945   template<std::size_t, typename, typename, std::size_t>
 946     struct __make_tuple_impl;
 947
 948   template<std::size_t _Idx, typename _Tuple, typename... _Tp,
 949            std::size_t _Nm>
 950     struct __make_tuple_impl<_Idx, tuple<_Tp...>, _Tuple, _Nm>
 951     {
 952       typedef typename __make_tuple_impl<_Idx + 1, tuple<_Tp...,
 953         typename std::tuple_element<_Idx, _Tuple>::type>, _Tuple, _Nm>::__type
 954       __type;
 955     };
 956
 957   template<std::size_t _Nm, typename _Tuple, typename... _Tp>
 958     struct __make_tuple_impl<_Nm, tuple<_Tp...>, _Tuple, _Nm>
 959     {
 960       typedef tuple<_Tp...> __type;
 961     };
 962
 963   template<typename _Tuple>
 964     struct __do_make_tuple
 965     : public __make_tuple_impl<0, tuple<>, _Tuple,
 966                                std::tuple_size<_Tuple>::value>
 967     { };
 968
 969   // Returns the std::tuple equivalent of a tuple-like type.
 970   template<typename _Tuple>
 971     struct __make_tuple
 972     : public __do_make_tuple<typename std::remove_cv
 973             <typename std::remove_reference<_Tuple>::type>::type>
 974     { };
 975
 976   // Combines several std::tuple's into a single one.
 977   template<typename...>
 978     struct __combine_tuples;
 979
 980   template<>
 981     struct __combine_tuples<>
 982     {
 983       typedef tuple<> __type;
 984     };
 985
 986   template<typename... _Ts>
 987     struct __combine_tuples<tuple<_Ts...>>
 988     {
 989       typedef tuple<_Ts...> __type;
 990     };
 991
 992   template<typename... _T1s, typename... _T2s, typename... _Rem>
 993     struct __combine_tuples<tuple<_T1s...>, tuple<_T2s...>, _Rem...>
 994     {
 995       typedef typename __combine_tuples<tuple<_T1s..., _T2s...>,
 996                                         _Rem...>::__type __type;
 997     };
 998
 999   // Computes the result type of tuple_cat given a set of tuple-like types.
1000   template<typename... _Tpls>
1001     struct __tuple_cat_result
1002     {
1003       typedef typename __combine_tuples
1004         <typename __make_tuple<_Tpls>::__type...>::__type __type;
1005     };
1006
1007   // Helper to determine the index set for the first tuple-like
1008   // type of a given set.
1009   template<typename...>
1010     struct __make_1st_indices;
1011
1012   template<>
1013     struct __make_1st_indices<>
1014     {
1015       typedef std::_Index_tuple<> __type;
1016     };
1017
1018   template<typename _Tp, typename... _Tpls>
1019     struct __make_1st_indices<_Tp, _Tpls...>
1020     {
1021       typedef typename std::_Build_index_tuple<std::tuple_size<
1022         typename std::remove_reference<_Tp>::type>::value>::__type __type;
1023     };
1024
1025   // Performs the actual concatenation by step-wise expanding tuple-like
1026   // objects into the elements,  which are finally forwarded into the
1027   // result tuple.
1028   template<typename _Ret, typename _Indices, typename... _Tpls>
1029     struct __tuple_concater;
1030
1031   template<typename _Ret, std::size_t... _Is, typename _Tp, typename... _Tpls>
1032     struct __tuple_concater<_Ret, std::_Index_tuple<_Is...>, _Tp, _Tpls...>
1033     {
1034       template<typename... _Us>
1035         static constexpr _Ret
1036         _S_do(_Tp&& __tp, _Tpls&&... __tps, _Us&&... __us)
1037         {
1038           typedef typename __make_1st_indices<_Tpls...>::__type __idx;
1039           typedef __tuple_concater<_Ret, __idx, _Tpls...>      __next;
1040           return __next::_S_do(std::forward<_Tpls>(__tps)...,
1041                                std::forward<_Us>(__us)...,
1042                                std::get<_Is>(std::forward<_Tp>(__tp))...);
1043         }
1044     };
1045
1046   template<typename _Ret>
1047     struct __tuple_concater<_Ret, std::_Index_tuple<>>
1048     {
1049       template<typename... _Us>
1050         static constexpr _Ret
1051         _S_do(_Us&&... __us)
1052         {
1053           return _Ret(std::forward<_Us>(__us)...);
1054         }
1055     };
1056
1057   template<typename... _Tpls, typename = typename
1058            enable_if<__and_<__is_tuple_like<_Tpls>...>::value>::type>
1059     constexpr auto
1060     tuple_cat(_Tpls&&... __tpls)
1061     -> typename __tuple_cat_result<_Tpls...>::__type
1062     {
1063       typedef typename __tuple_cat_result<_Tpls...>::__type __ret;
1064       typedef typename __make_1st_indices<_Tpls...>::__type __idx;
1065       typedef __tuple_concater<__ret, __idx, _Tpls...> __concater;
1066       return __concater::_S_do(std::forward<_Tpls>(__tpls)...);
1067     }
1068
1069   template<typename... _Elements>
1070     inline tuple<_Elements&...>
1071     tie(_Elements&... __args) noexcept
1072     { return tuple<_Elements&...>(__args...); }
1073
1074   template<typename... _Elements>
1075     inline void
1076     swap(tuple<_Elements...>& __x, tuple<_Elements...>& __y)
1077     noexcept(noexcept(__x.swap(__y)))
1078     { __x.swap(__y); }
1079
1080   // A class (and instance) which can be used in 'tie' when an element
1081   // of a tuple is not required
1082   struct _Swallow_assign
1083   {
1084     template<class _Tp>
1085       const _Swallow_assign&
1086       operator=(const _Tp&) const
1087       { return *this; }
1088   };
1089
1090   const _Swallow_assign ignore{};
1091
1092   /// Partial specialization for tuples
1093   template<typename... _Types, typename _Alloc>
1094     struct uses_allocator<tuple<_Types...>, _Alloc> : true_type { };
1095
1096   // See stl_pair.h...
1097   template<class _T1, class _T2>
1098     template<typename _Tp, typename... _Args>
1099       inline _Tp
1100       pair<_T1, _T2>::__cons(tuple<_Args...>&& __tuple)
1101       {
1102         typedef typename _Build_index_tuple<sizeof...(_Args)>::__type
1103           _Indexes;
1104         return __do_cons<_Tp>(std::move(__tuple), _Indexes());
1105       }
1106
1107   template<class _T1, class _T2>
1108     template<typename _Tp, typename... _Args, std::size_t... _Indexes>
1109       inline _Tp
1110       pair<_T1, _T2>::__do_cons(tuple<_Args...>&& __tuple,
1111                                 const _Index_tuple<_Indexes...>&)
1112       { return _Tp(std::forward<_Args>(get<_Indexes>(__tuple))...); }
1113
1114 _GLIBCXX_END_NAMESPACE_VERSION
1115 } // namespace
1116
1117 #endif // __GXX_EXPERIMENTAL_CXX0X__
1118
1119 #endif // _GLIBCXX_TUPLE