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
  40 namespace std _GLIBCXX_VISIBILITY(default)
  41 {
  42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  43
  44   // Adds a const reference to a non-reference type.
  45   template<typename _Tp>
  46     struct __add_c_ref
  47     { typedef const _Tp& type; };
  48
  49   template<typename _Tp>
  50     struct __add_c_ref<_Tp&>
  51     { typedef _Tp& type; };
  52
  53   // Adds a reference to a non-reference type.
  54   template<typename _Tp>
  55     struct __add_ref
  56     { typedef _Tp& type; };
  57
  58   template<typename _Tp>
  59     struct __add_ref<_Tp&>
  60     { typedef _Tp& type; };
  61
  62   // Adds an rvalue reference to a non-reference type.
  63   template<typename _Tp>
  64     struct __add_r_ref
  65     { typedef _Tp&& type; };
  66
  67   template<typename _Tp>
  68     struct __add_r_ref<_Tp&>
  69     { typedef _Tp& type; };
  70
  71   template<std::size_t _Idx, typename _Head, bool _IsEmpty>
  72     struct _Head_base;
  73
  74   template<std::size_t _Idx, typename _Head>
  75     struct _Head_base<_Idx, _Head, true>
  76     : public _Head
  77     {
  78       constexpr _Head_base()
  79       : _Head() { }
  80
  81       constexpr _Head_base(const _Head& __h)
  82       : _Head(__h) { }
  83
  84       template<typename _UHead>
  85         _Head_base(_UHead&& __h)
  86         : _Head(std::forward<_UHead>(__h)) { }
  87
  88       _Head&       _M_head()       { return *this; }
  89       const _Head& _M_head() const { return *this; }
  90     };
  91
  92   template<std::size_t _Idx, typename _Head>
  93     struct _Head_base<_Idx, _Head, false>
  94     {
  95       constexpr _Head_base()
  96       : _M_head_impl() { }
  97
  98       constexpr _Head_base(const _Head& __h)
  99       : _M_head_impl(__h) { }
 100
 101       template<typename _UHead>
 102         _Head_base(_UHead&& __h)
 103         : _M_head_impl(std::forward<_UHead>(__h)) { }
 104
 105       _Head&       _M_head()       { return _M_head_impl; }
 106       const _Head& _M_head() const { return _M_head_impl; }
 107
 108       _Head _M_head_impl;
 109     };
 110
 111   /**
 112    * Contains the actual implementation of the @c tuple template, stored
 113    * as a recursive inheritance hierarchy from the first element (most
 114    * derived class) to the last (least derived class). The @c Idx
 115    * parameter gives the 0-based index of the element stored at this
 116    * point in the hierarchy; we use it to implement a constant-time
 117    * get() operation.
 118    */
 119   template<std::size_t _Idx, typename... _Elements>
 120     struct _Tuple_impl;
 121
 122   /**
 123    * Zero-element tuple implementation. This is the basis case for the
 124    * inheritance recursion.
 125    */
 126   template<std::size_t _Idx>
 127     struct _Tuple_impl<_Idx>
 128     {
 129       template<std::size_t, typename...> friend class _Tuple_impl;
 130
 131     protected:
 132       void _M_swap(_Tuple_impl&) noexcept { /* no-op */ }
 133     };
 134
 135   /**
 136    * Recursive tuple implementation. Here we store the @c Head element
 137    * and derive from a @c Tuple_impl containing the remaining elements
 138    * (which contains the @c Tail).
 139    */
 140   template<std::size_t _Idx, typename _Head, typename... _Tail>
 141     struct _Tuple_impl<_Idx, _Head, _Tail...>
 142     : public _Tuple_impl<_Idx + 1, _Tail...>,
 143       private _Head_base<_Idx, _Head, std::is_empty<_Head>::value>
 144     {
 145       template<std::size_t, typename...> friend class _Tuple_impl;
 146
 147       typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
 148       typedef _Head_base<_Idx, _Head, std::is_empty<_Head>::value> _Base;
 149
 150       _Head&            _M_head()       { return _Base::_M_head(); }
 151       const _Head&      _M_head() const { return _Base::_M_head(); }
 152
 153       _Inherited&       _M_tail()       { return *this; }
 154       const _Inherited& _M_tail() const { return *this; }
 155
 156       constexpr _Tuple_impl()
 157       : _Inherited(), _Base() { }
 158
 159       explicit
 160       constexpr _Tuple_impl(const _Head& __head, const _Tail&... __tail)
 161       : _Inherited(__tail...), _Base(__head) { }
 162
 163       template<typename _UHead, typename... _UTail>
 164         explicit
 165         _Tuple_impl(_UHead&& __head, _UTail&&... __tail)
 166         : _Inherited(std::forward<_UTail>(__tail)...),
 167           _Base(std::forward<_UHead>(__head)) { }
 168
 169       constexpr _Tuple_impl(const _Tuple_impl&) = default;
 170
 171       _Tuple_impl(_Tuple_impl&& __in)
 172       : _Inherited(std::move(__in._M_tail())),
 173         _Base(std::forward<_Head>(__in._M_head())) { }
 174
 175       template<typename... _UElements>
 176         _Tuple_impl(const _Tuple_impl<_Idx, _UElements...>& __in)
 177         : _Inherited(__in._M_tail()), _Base(__in._M_head()) { }
 178
 179       template<typename _UHead, typename... _UTails>
 180         _Tuple_impl(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 181         : _Inherited(std::move(__in._M_tail())),
 182           _Base(std::forward<_UHead>(__in._M_head())) { }
 183
 184       _Tuple_impl&
 185       operator=(const _Tuple_impl& __in)
 186       {
 187         _M_head() = __in._M_head();
 188         _M_tail() = __in._M_tail();
 189         return *this;
 190       }
 191
 192       _Tuple_impl&
 193       operator=(_Tuple_impl&& __in)
 194       {
 195         _M_head() = std::forward<_Head>(__in._M_head());
 196         _M_tail() = std::move(__in._M_tail());
 197         return *this;
 198       }
 199
 200       template<typename... _UElements>
 201         _Tuple_impl&
 202         operator=(const _Tuple_impl<_Idx, _UElements...>& __in)
 203         {
 204           _M_head() = __in._M_head();
 205           _M_tail() = __in._M_tail();
 206           return *this;
 207         }
 208
 209       template<typename _UHead, typename... _UTails>
 210         _Tuple_impl&
 211         operator=(_Tuple_impl<_Idx, _UHead, _UTails...>&& __in)
 212         {
 213           _M_head() = std::forward<_UHead>(__in._M_head());
 214           _M_tail() = std::move(__in._M_tail());
 215           return *this;
 216         }
 217
 218     protected:
 219       void
 220       _M_swap(_Tuple_impl& __in)
 221       noexcept(noexcept(swap(std::declval<_Head&>(),
 222                              std::declval<_Head&>()))
 223                && noexcept(__in._M_tail()._M_swap(__in._M_tail())))
 224       {
 225         using std::swap;
 226         swap(this->_M_head(), __in._M_head());
 227         _Inherited::_M_swap(__in._M_tail());
 228       }
 229     };
 230
 231   /// tuple
 232   template<typename... _Elements>
 233     class tuple : public _Tuple_impl<0, _Elements...>
 234     {
 235       typedef _Tuple_impl<0, _Elements...> _Inherited;
 236
 237     public:
 238       constexpr tuple()
 239       : _Inherited() { }
 240
 241       explicit
 242       constexpr tuple(const _Elements&... __elements)
 243       : _Inherited(__elements...) { }
 244
 245       template<typename... _UElements, typename = typename
 246                std::enable_if<sizeof...(_UElements)
 247                               == sizeof...(_Elements)>::type>
 248         explicit
 249         tuple(_UElements&&... __elements)
 250         : _Inherited(std::forward<_UElements>(__elements)...) { }
 251
 252       constexpr tuple(const tuple&) = default;
 253
 254       tuple(tuple&& __in)
 255       : _Inherited(static_cast<_Inherited&&>(__in)) { }
 256
 257       template<typename... _UElements, typename = typename
 258                std::enable_if<sizeof...(_UElements)
 259                               == sizeof...(_Elements)>::type>
 260         tuple(const tuple<_UElements...>& __in)
 261         : _Inherited(static_cast<const _Tuple_impl<0, _UElements...>&>(__in))
 262         { }
 263
 264       template<typename... _UElements, typename = typename
 265                std::enable_if<sizeof...(_UElements)
 266                               == sizeof...(_Elements)>::type>
 267         tuple(tuple<_UElements...>&& __in)
 268         : _Inherited(static_cast<_Tuple_impl<0, _UElements...>&&>(__in)) { }
 269
 270       tuple&
 271       operator=(const tuple& __in)
 272       {
 273         static_cast<_Inherited&>(*this) = __in;
 274         return *this;
 275       }
 276
 277       tuple&
 278       operator=(tuple&& __in)
 279       {
 280         static_cast<_Inherited&>(*this) = std::move(__in);
 281         return *this;
 282       }
 283
 284       template<typename... _UElements, typename = typename
 285                std::enable_if<sizeof...(_UElements)
 286                               == sizeof...(_Elements)>::type>
 287         tuple&
 288         operator=(const tuple<_UElements...>& __in)
 289         {
 290           static_cast<_Inherited&>(*this) = __in;
 291           return *this;
 292         }
 293
 294       template<typename... _UElements, typename = typename
 295                std::enable_if<sizeof...(_UElements)
 296                               == sizeof...(_Elements)>::type>
 297         tuple&
 298         operator=(tuple<_UElements...>&& __in)
 299         {
 300           static_cast<_Inherited&>(*this) = std::move(__in);
 301           return *this;
 302         }
 303
 304       void
 305       swap(tuple& __in)
 306       noexcept(noexcept(__in._M_swap(__in)))
 307       { _Inherited::_M_swap(__in); }
 308     };
 309
 310   template<>
 311     class tuple<>
 312     {
 313     public:
 314       void swap(tuple&) noexcept { /* no-op */ }
 315     };
 316
 317   /// tuple (2-element), with construction and assignment from a pair.
 318   template<typename _T1, typename _T2>
 319     class tuple<_T1, _T2> : public _Tuple_impl<0, _T1, _T2>
 320     {
 321       typedef _Tuple_impl<0, _T1, _T2> _Inherited;
 322
 323     public:
 324       constexpr tuple()
 325       : _Inherited() { }
 326
 327       explicit
 328       constexpr tuple(const _T1& __a1, const _T2& __a2)
 329       : _Inherited(__a1, __a2) { }
 330
 331       template<typename _U1, typename _U2>
 332         explicit
 333         tuple(_U1&& __a1, _U2&& __a2)
 334         : _Inherited(std::forward<_U1>(__a1), std::forward<_U2>(__a2)) { }
 335
 336       constexpr tuple(const tuple&) = default;
 337
 338       tuple(tuple&& __in)
 339       : _Inherited(static_cast<_Inherited&&>(__in)) { }
 340
 341       template<typename _U1, typename _U2>
 342         tuple(const tuple<_U1, _U2>& __in)
 343         : _Inherited(static_cast<const _Tuple_impl<0, _U1, _U2>&>(__in)) { }
 344
 345       template<typename _U1, typename _U2>
 346         tuple(tuple<_U1, _U2>&& __in)
 347         : _Inherited(static_cast<_Tuple_impl<0, _U1, _U2>&&>(__in)) { }
 348
 349       template<typename _U1, typename _U2>
 350         tuple(const pair<_U1, _U2>& __in)
 351         : _Inherited(__in.first, __in.second) { }
 352
 353       template<typename _U1, typename _U2>
 354         tuple(pair<_U1, _U2>&& __in)
 355         : _Inherited(std::forward<_U1>(__in.first),
 356                      std::forward<_U2>(__in.second)) { }
 357
 358       tuple&
 359       operator=(const tuple& __in)
 360       {
 361         static_cast<_Inherited&>(*this) = __in;
 362         return *this;
 363       }
 364
 365       tuple&
 366       operator=(tuple&& __in)
 367       // noexcept has to wait is_nothrow_move_assignable
 368       {
 369         static_cast<_Inherited&>(*this) = std::move(__in);
 370         return *this;
 371       }
 372
 373       template<typename _U1, typename _U2>
 374         tuple&
 375         operator=(const tuple<_U1, _U2>& __in)
 376         {
 377           static_cast<_Inherited&>(*this) = __in;
 378           return *this;
 379         }
 380
 381       template<typename _U1, typename _U2>
 382         tuple&
 383         operator=(tuple<_U1, _U2>&& __in)
 384         {
 385           static_cast<_Inherited&>(*this) = std::move(__in);
 386           return *this;
 387         }
 388
 389       template<typename _U1, typename _U2>
 390         tuple&
 391         operator=(const pair<_U1, _U2>& __in)
 392         {
 393           this->_M_head() = __in.first;
 394           this->_M_tail()._M_head() = __in.second;
 395           return *this;
 396         }
 397
 398       template<typename _U1, typename _U2>
 399         tuple&
 400         operator=(pair<_U1, _U2>&& __in) noexcept
 401         {
 402           this->_M_head() = std::forward<_U1>(__in.first);
 403           this->_M_tail()._M_head() = std::forward<_U2>(__in.second);
 404           return *this;
 405         }
 406
 407       void
 408       swap(tuple& __in)
 409       noexcept(noexcept(__in._M_swap(__in)))
 410       { _Inherited::_M_swap(__in); }
 411     };
 412
 413   /// tuple (1-element).
 414   template<typename _T1>
 415     class tuple<_T1> : public _Tuple_impl<0, _T1>
 416     {
 417       typedef _Tuple_impl<0, _T1> _Inherited;
 418
 419     public:
 420       constexpr tuple()
 421       : _Inherited() { }
 422
 423       explicit
 424       constexpr tuple(const _T1& __a1)
 425       : _Inherited(__a1) { }
 426
 427       template<typename _U1, typename = typename
 428                std::enable_if<std::is_convertible<_U1, _T1>::value>::type>
 429         explicit
 430         tuple(_U1&& __a1)
 431         : _Inherited(std::forward<_U1>(__a1)) { }
 432
 433       constexpr tuple(const tuple&) = default;
 434
 435       tuple(tuple&& __in)
 436       : _Inherited(static_cast<_Inherited&&>(__in)) { }
 437
 438       template<typename _U1>
 439         tuple(const tuple<_U1>& __in)
 440         : _Inherited(static_cast<const _Tuple_impl<0, _U1>&>(__in)) { }
 441
 442       template<typename _U1>
 443         tuple(tuple<_U1>&& __in)
 444         : _Inherited(static_cast<_Tuple_impl<0, _U1>&&>(__in)) { }
 445
 446       tuple&
 447       operator=(const tuple& __in)
 448       {
 449         static_cast<_Inherited&>(*this) = __in;
 450         return *this;
 451       }
 452
 453       tuple&
 454       operator=(tuple&& __in)
 455       {
 456         static_cast<_Inherited&>(*this) = std::move(__in);
 457         return *this;
 458       }
 459
 460       template<typename _U1>
 461         tuple&
 462         operator=(const tuple<_U1>& __in)
 463         {
 464           static_cast<_Inherited&>(*this) = __in;
 465           return *this;
 466         }
 467
 468       template<typename _U1>
 469         tuple&
 470         operator=(tuple<_U1>&& __in)
 471         {
 472           static_cast<_Inherited&>(*this) = std::move(__in);
 473           return *this;
 474         }
 475
 476       void
 477       swap(tuple& __in)
 478       noexcept(noexcept(__in._M_swap(__in)))
 479       { _Inherited::_M_swap(__in); }
 480     };
 481
 482
 483   /// Gives the type of the ith element of a given tuple type.
 484   template<std::size_t __i, typename _Tp>
 485     struct tuple_element;
 486
 487   /**
 488    * Recursive case for tuple_element: strip off the first element in
 489    * the tuple and retrieve the (i-1)th element of the remaining tuple.
 490    */
 491   template<std::size_t __i, typename _Head, typename... _Tail>
 492     struct tuple_element<__i, tuple<_Head, _Tail...> >
 493     : tuple_element<__i - 1, tuple<_Tail...> > { };
 494
 495   /**
 496    * Basis case for tuple_element: The first element is the one we're seeking.
 497    */
 498   template<typename _Head, typename... _Tail>
 499     struct tuple_element<0, tuple<_Head, _Tail...> >
 500     {
 501       typedef _Head type;
 502     };
 503
 504   /// Finds the size of a given tuple type.
 505   template<typename _Tp>
 506     struct tuple_size;
 507
 508   /// class tuple_size
 509   template<typename... _Elements>
 510     struct tuple_size<tuple<_Elements...> >
 511     {
 512       static const std::size_t value = sizeof...(_Elements);
 513     };
 514
 515   template<typename... _Elements>
 516     const std::size_t tuple_size<tuple<_Elements...> >::value;
 517
 518   template<std::size_t __i, typename _Head, typename... _Tail>
 519     inline typename __add_ref<_Head>::type
 520     __get_helper(_Tuple_impl<__i, _Head, _Tail...>& __t)
 521     { return __t._M_head(); }
 522
 523   template<std::size_t __i, typename _Head, typename... _Tail>
 524     inline typename __add_c_ref<_Head>::type
 525     __get_helper(const _Tuple_impl<__i, _Head, _Tail...>& __t)
 526     { return __t._M_head(); }
 527
 528   // Return a reference (const reference, rvalue reference) to the ith element
 529   // of a tuple.  Any const or non-const ref elements are returned with their
 530   // original type.
 531   template<std::size_t __i, typename... _Elements>
 532     inline typename __add_ref<
 533                       typename tuple_element<__i, tuple<_Elements...>>::type
 534                     >::type
 535     get(tuple<_Elements...>& __t) noexcept
 536     { return __get_helper<__i>(__t); }
 537
 538   template<std::size_t __i, typename... _Elements>
 539     inline typename __add_c_ref<
 540                       typename tuple_element<__i, tuple<_Elements...>>::type
 541                     >::type
 542     get(const tuple<_Elements...>& __t) noexcept
 543     { return __get_helper<__i>(__t); }
 544
 545   template<std::size_t __i, typename... _Elements>
 546     inline typename __add_r_ref<
 547                       typename tuple_element<__i, tuple<_Elements...>>::type
 548                     >::type
 549     get(tuple<_Elements...>&& __t) noexcept
 550     { return std::forward<typename tuple_element<__i,
 551         tuple<_Elements...>>::type&&>(get<__i>(__t)); }
 552
 553   // This class helps construct the various comparison operations on tuples
 554   template<std::size_t __check_equal_size, std::size_t __i, std::size_t __j,
 555            typename _Tp, typename _Up>
 556     struct __tuple_compare;
 557
 558   template<std::size_t __i, std::size_t __j, typename _Tp, typename _Up>
 559     struct __tuple_compare<0, __i, __j, _Tp, _Up>
 560     {
 561       static bool __eq(const _Tp& __t, const _Up& __u)
 562       {
 563         return (get<__i>(__t) == get<__i>(__u) &&
 564                 __tuple_compare<0, __i + 1, __j, _Tp, _Up>::__eq(__t, __u));
 565       }
 566
 567       static bool __less(const _Tp& __t, const _Up& __u)
 568       {
 569         return ((get<__i>(__t) < get<__i>(__u))
 570                 || !(get<__i>(__u) < get<__i>(__t)) &&
 571                 __tuple_compare<0, __i + 1, __j, _Tp, _Up>::__less(__t, __u));
 572       }
 573     };
 574
 575   template<std::size_t __i, typename _Tp, typename _Up>
 576     struct __tuple_compare<0, __i, __i, _Tp, _Up>
 577     {
 578       static bool __eq(const _Tp&, const _Up&)
 579       { return true; }
 580
 581       static bool __less(const _Tp&, const _Up&)
 582       { return false; }
 583     };
 584
 585   template<typename... _TElements, typename... _UElements>
 586     bool
 587     operator==(const tuple<_TElements...>& __t,
 588                const tuple<_UElements...>& __u)
 589     {
 590       typedef tuple<_TElements...> _Tp;
 591       typedef tuple<_UElements...> _Up;
 592       return (__tuple_compare<tuple_size<_Tp>::value - tuple_size<_Up>::value,
 593               0, tuple_size<_Tp>::value, _Tp, _Up>::__eq(__t, __u));
 594     }
 595
 596   template<typename... _TElements, typename... _UElements>
 597     bool
 598     operator<(const tuple<_TElements...>& __t,
 599               const tuple<_UElements...>& __u)
 600     {
 601       typedef tuple<_TElements...> _Tp;
 602       typedef tuple<_UElements...> _Up;
 603       return (__tuple_compare<tuple_size<_Tp>::value - tuple_size<_Up>::value,
 604               0, tuple_size<_Tp>::value, _Tp, _Up>::__less(__t, __u));
 605     }
 606
 607   template<typename... _TElements, typename... _UElements>
 608     inline bool
 609     operator!=(const tuple<_TElements...>& __t,
 610                const tuple<_UElements...>& __u)
 611     { return !(__t == __u); }
 612
 613   template<typename... _TElements, typename... _UElements>
 614     inline bool
 615     operator>(const tuple<_TElements...>& __t,
 616               const tuple<_UElements...>& __u)
 617     { return __u < __t; }
 618
 619   template<typename... _TElements, typename... _UElements>
 620     inline bool
 621     operator<=(const tuple<_TElements...>& __t,
 622                const tuple<_UElements...>& __u)
 623     { return !(__u < __t); }
 624
 625   template<typename... _TElements, typename... _UElements>
 626     inline bool
 627     operator>=(const tuple<_TElements...>& __t,
 628                const tuple<_UElements...>& __u)
 629     { return !(__t < __u); }
 630
 631   // NB: DR 705.
 632   template<typename... _Elements>
 633     inline tuple<typename __decay_and_strip<_Elements>::__type...>
 634     make_tuple(_Elements&&... __args)
 635     {
 636       typedef tuple<typename __decay_and_strip<_Elements>::__type...>
 637         __result_type;
 638       return __result_type(std::forward<_Elements>(__args)...);
 639     }
 640
 641   template<typename... _Elements>
 642     inline tuple<_Elements&&...>
 643     forward_as_tuple(_Elements&&... __args) noexcept
 644     { return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
 645
 646   template<std::size_t...> struct __index_holder { };
 647
 648   template<std::size_t __i, typename _IdxHolder, typename... _Elements>
 649     struct __index_holder_impl;
 650
 651   template<std::size_t __i, std::size_t... _Indexes, typename _IdxHolder,
 652            typename... _Elements>
 653     struct __index_holder_impl<__i, __index_holder<_Indexes...>,
 654                                _IdxHolder, _Elements...>
 655     {
 656       typedef typename __index_holder_impl<__i + 1,
 657                                            __index_holder<_Indexes..., __i>,
 658                                            _Elements...>::type type;
 659     };
 660
 661   template<std::size_t __i, std::size_t... _Indexes>
 662     struct __index_holder_impl<__i, __index_holder<_Indexes...> >
 663     { typedef __index_holder<_Indexes...> type; };
 664
 665   template<typename... _Elements>
 666     struct __make_index_holder
 667     : __index_holder_impl<0, __index_holder<>, _Elements...> { };
 668
 669   template<typename... _TElements, std::size_t... _TIdx,
 670            typename... _UElements, std::size_t... _UIdx>
 671     inline tuple<_TElements..., _UElements...>
 672     __tuple_cat_helper(const tuple<_TElements...>& __t,
 673                        const __index_holder<_TIdx...>&,
 674                        const tuple<_UElements...>& __u,
 675                        const __index_holder<_UIdx...>&)
 676     { return tuple<_TElements..., _UElements...>(get<_TIdx>(__t)...,
 677                                                  get<_UIdx>(__u)...); }
 678
 679   template<typename... _TElements, std::size_t... _TIdx,
 680            typename... _UElements, std::size_t... _UIdx>
 681     inline tuple<_TElements..., _UElements...>
 682     __tuple_cat_helper(tuple<_TElements...>&& __t,
 683                        const __index_holder<_TIdx...>&,
 684                        const tuple<_UElements...>& __u,
 685                        const __index_holder<_UIdx...>&)
 686     { return tuple<_TElements..., _UElements...>
 687         (std::forward<_TElements>(get<_TIdx>(__t))..., get<_UIdx>(__u)...); }
 688
 689   template<typename... _TElements, std::size_t... _TIdx,
 690            typename... _UElements, std::size_t... _UIdx>
 691     inline tuple<_TElements..., _UElements...>
 692     __tuple_cat_helper(const tuple<_TElements...>& __t,
 693                        const __index_holder<_TIdx...>&,
 694                        tuple<_UElements...>&& __u,
 695                        const __index_holder<_UIdx...>&)
 696     { return tuple<_TElements..., _UElements...>
 697         (get<_TIdx>(__t)..., std::forward<_UElements>(get<_UIdx>(__u))...); }
 698
 699   template<typename... _TElements, std::size_t... _TIdx,
 700            typename... _UElements, std::size_t... _UIdx>
 701     inline tuple<_TElements..., _UElements...>
 702     __tuple_cat_helper(tuple<_TElements...>&& __t,
 703                        const __index_holder<_TIdx...>&,
 704                        tuple<_UElements...>&& __u,
 705                        const __index_holder<_UIdx...>&)
 706     { return tuple<_TElements..., _UElements...>
 707         (std::forward<_TElements>(get<_TIdx>(__t))...,
 708          std::forward<_UElements>(get<_UIdx>(__u))...); }
 709
 710   template<typename... _TElements, typename... _UElements>
 711     inline tuple<_TElements..., _UElements...>
 712     tuple_cat(const tuple<_TElements...>& __t, const tuple<_UElements...>& __u)
 713     {
 714       return __tuple_cat_helper(__t, typename
 715                                 __make_index_holder<_TElements...>::type(),
 716                                 __u, typename
 717                                 __make_index_holder<_UElements...>::type());
 718     }
 719
 720   template<typename... _TElements, typename... _UElements>
 721     inline tuple<_TElements..., _UElements...>
 722     tuple_cat(tuple<_TElements...>&& __t, const tuple<_UElements...>& __u)
 723     {
 724       return __tuple_cat_helper(std::move(__t), typename
 725                                  __make_index_holder<_TElements...>::type(),
 726                                  __u, typename
 727                                  __make_index_holder<_UElements...>::type());
 728     }
 729
 730   template<typename... _TElements, typename... _UElements>
 731     inline tuple<_TElements..., _UElements...>
 732     tuple_cat(const tuple<_TElements...>& __t, tuple<_UElements...>&& __u)
 733     {
 734       return __tuple_cat_helper(__t, typename
 735                                 __make_index_holder<_TElements...>::type(),
 736                                 std::move(__u), typename
 737                                 __make_index_holder<_UElements...>::type());
 738     }
 739
 740   template<typename... _TElements, typename... _UElements>
 741     inline tuple<_TElements..., _UElements...>
 742     tuple_cat(tuple<_TElements...>&& __t, tuple<_UElements...>&& __u)
 743     {
 744       return __tuple_cat_helper(std::move(__t), typename
 745                                 __make_index_holder<_TElements...>::type(),
 746                                 std::move(__u), typename
 747                                 __make_index_holder<_UElements...>::type());
 748     }
 749
 750   template<typename... _Elements>
 751     inline tuple<_Elements&...>
 752     tie(_Elements&... __args) noexcept
 753     { return tuple<_Elements&...>(__args...); }
 754
 755   template<typename... _Elements>
 756     inline void
 757     swap(tuple<_Elements...>& __x, tuple<_Elements...>& __y)
 758     noexcept(noexcept(__x.swap(__y)))
 759     { __x.swap(__y); }
 760
 761   // A class (and instance) which can be used in 'tie' when an element
 762   // of a tuple is not required
 763   struct _Swallow_assign
 764   {
 765     template<class _Tp>
 766       const _Swallow_assign&
 767       operator=(const _Tp&) const
 768       { return *this; }
 769   };
 770
 771   const _Swallow_assign ignore{};
 772
 773   /**
 774    * Stores a tuple of indices. Used by bind() to extract the elements
 775    * in a tuple.
 776    */
 777   template<int... _Indexes>
 778     struct _Index_tuple
 779     {
 780       typedef _Index_tuple<_Indexes..., sizeof...(_Indexes)> __next;
 781     };
 782
 783   /// Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
 784   template<std::size_t _Num>
 785     struct _Build_index_tuple
 786     {
 787       typedef typename _Build_index_tuple<_Num-1>::__type::__next __type;
 788     };
 789
 790   template<>
 791     struct _Build_index_tuple<0>
 792     {
 793       typedef _Index_tuple<> __type;
 794     };
 795
 796   // See stl_pair.h...
 797   template<class _T1, class _T2>
 798     template<typename _Tp, typename... _Args>
 799       inline _Tp
 800       pair<_T1, _T2>::
 801       __cons(tuple<_Args...>&& __tuple)
 802       {
 803         typedef typename _Build_index_tuple<sizeof...(_Args)>::__type
 804           _Indexes;
 805         return __do_cons<_Tp>(std::move(__tuple), _Indexes());
 806       }
 807
 808   template<class _T1, class _T2>
 809     template<typename _Tp, typename... _Args, int... _Indexes>
 810       inline _Tp
 811       pair<_T1, _T2>::
 812       __do_cons(tuple<_Args...>&& __tuple,
 813                 const _Index_tuple<_Indexes...>&)
 814       { return _Tp(std::forward<_Args>(get<_Indexes>(__tuple))...); }
 815
 816 _GLIBCXX_END_NAMESPACE_VERSION
 817 } // namespace
 818
 819 #endif // __GXX_EXPERIMENTAL_CXX0X__
 820
 821 #endif // _GLIBCXX_TUPLE