libstdc++-v3/include/std/utility

   1 // <utility> -*- C++ -*-
   2
   3 // Copyright (C) 2001-2020 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 /*
  26  *
  27  * Copyright (c) 1994
  28  * Hewlett-Packard Company
  29  *
  30  * Permission to use, copy, modify, distribute and sell this software
  31  * and its documentation for any purpose is hereby granted without fee,
  32  * provided that the above copyright notice appear in all copies and
  33  * that both that copyright notice and this permission notice appear
  34  * in supporting documentation.  Hewlett-Packard Company makes no
  35  * representations about the suitability of this software for any
  36  * purpose.  It is provided "as is" without express or implied warranty.
  37  *
  38  *
  39  * Copyright (c) 1996,1997
  40  * Silicon Graphics Computer Systems, Inc.
  41  *
  42  * Permission to use, copy, modify, distribute and sell this software
  43  * and its documentation for any purpose is hereby granted without fee,
  44  * provided that the above copyright notice appear in all copies and
  45  * that both that copyright notice and this permission notice appear
  46  * in supporting documentation.  Silicon Graphics makes no
  47  * representations about the suitability of this software for any
  48  * purpose.  It is provided "as is" without express or implied warranty.
  49  */
  50
  51 /** @file include/utility
  52  *  This is a Standard C++ Library header.
  53  */
  54
  55 #ifndef _GLIBCXX_UTILITY
  56 #define _GLIBCXX_UTILITY 1
  57
  58 #pragma GCC system_header
  59
  60 /**
  61  * @defgroup utilities Utilities
  62  *
  63  * Components deemed generally useful. Includes pair, tuple,
  64  * forward/move helpers, ratio, function object, metaprogramming and
  65  * type traits, time, date, and memory functions.
  66  */
  67
  68 #include <bits/c++config.h>
  69 #include <bits/stl_relops.h>
  70 #include <bits/stl_pair.h>
  71
  72 #if __cplusplus >= 201103L
  73
  74 #include <type_traits>
  75 #include <bits/move.h>
  76 #include <initializer_list>
  77
  78 namespace std _GLIBCXX_VISIBILITY(default)
  79 {
  80 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  81
  82   /// Finds the size of a given tuple type.
  83   template<typename _Tp>
  84     struct tuple_size;
  85
  86   // _GLIBCXX_RESOLVE_LIB_DEFECTS
  87   // 2313. tuple_size should always derive from integral_constant<size_t, N>
  88   // 2770. tuple_size<const T> specialization is not SFINAE compatible
  89
  90   template<typename _Tp,
  91            typename _Up = typename remove_cv<_Tp>::type,
  92            typename = typename enable_if<is_same<_Tp, _Up>::value>::type,
  93            size_t = tuple_size<_Tp>::value>
  94     using __enable_if_has_tuple_size = _Tp;
  95
  96   template<typename _Tp>
  97     struct tuple_size<const __enable_if_has_tuple_size<_Tp>>
  98     : public tuple_size<_Tp> { };
  99
 100   template<typename _Tp>
 101     struct tuple_size<volatile __enable_if_has_tuple_size<_Tp>>
 102     : public tuple_size<_Tp> { };
 103
 104   template<typename _Tp>
 105     struct tuple_size<const volatile __enable_if_has_tuple_size<_Tp>>
 106     : public tuple_size<_Tp> { };
 107
 108   /// Gives the type of the ith element of a given tuple type.
 109   template<std::size_t __i, typename _Tp>
 110     struct tuple_element;
 111
 112   // Duplicate of C++14's tuple_element_t for internal use in C++11 mode
 113   template<std::size_t __i, typename _Tp>
 114     using __tuple_element_t = typename tuple_element<__i, _Tp>::type;
 115
 116   template<std::size_t __i, typename _Tp>
 117     struct tuple_element<__i, const _Tp>
 118     {
 119       typedef typename add_const<__tuple_element_t<__i, _Tp>>::type type;
 120     };
 121
 122   template<std::size_t __i, typename _Tp>
 123     struct tuple_element<__i, volatile _Tp>
 124     {
 125       typedef typename add_volatile<__tuple_element_t<__i, _Tp>>::type type;
 126     };
 127
 128   template<std::size_t __i, typename _Tp>
 129     struct tuple_element<__i, const volatile _Tp>
 130     {
 131       typedef typename add_cv<__tuple_element_t<__i, _Tp>>::type type;
 132     };
 133
 134 #if __cplusplus >= 201402L
 135 // The standard says this macro and alias template should be in <tuple>
 136 // but we define them here, to be available when the partial specializations
 137 // of tuple_element<pair<T,U>> and tuple_element<array<T,N>> are defined.
 138 #define __cpp_lib_tuple_element_t 201402L
 139
 140   template<std::size_t __i, typename _Tp>
 141     using tuple_element_t = typename tuple_element<__i, _Tp>::type;
 142 #endif
 143
 144   // Various functions which give std::pair a tuple-like interface.
 145
 146   /// Partial specialization for std::pair
 147   template<typename _T1, typename _T2>
 148     struct __is_tuple_like_impl<std::pair<_T1, _T2>> : true_type
 149     { };
 150
 151   /// Partial specialization for std::pair
 152   template<class _Tp1, class _Tp2>
 153     struct tuple_size<std::pair<_Tp1, _Tp2>>
 154     : public integral_constant<std::size_t, 2> { };
 155
 156   /// Partial specialization for std::pair
 157   template<class _Tp1, class _Tp2>
 158     struct tuple_element<0, std::pair<_Tp1, _Tp2>>
 159     { typedef _Tp1 type; };
 160
 161   /// Partial specialization for std::pair
 162   template<class _Tp1, class _Tp2>
 163     struct tuple_element<1, std::pair<_Tp1, _Tp2>>
 164     { typedef _Tp2 type; };
 165
 166   template<std::size_t _Int>
 167     struct __pair_get;
 168
 169   template<>
 170     struct __pair_get<0>
 171     {
 172       template<typename _Tp1, typename _Tp2>
 173         static constexpr _Tp1&
 174         __get(std::pair<_Tp1, _Tp2>& __pair) noexcept
 175         { return __pair.first; }
 176
 177       template<typename _Tp1, typename _Tp2>
 178         static constexpr _Tp1&&
 179         __move_get(std::pair<_Tp1, _Tp2>&& __pair) noexcept
 180         { return std::forward<_Tp1>(__pair.first); }
 181
 182       template<typename _Tp1, typename _Tp2>
 183         static constexpr const _Tp1&
 184         __const_get(const std::pair<_Tp1, _Tp2>& __pair) noexcept
 185         { return __pair.first; }
 186
 187       template<typename _Tp1, typename _Tp2>
 188         static constexpr const _Tp1&&
 189         __const_move_get(const std::pair<_Tp1, _Tp2>&& __pair) noexcept
 190         { return std::forward<const _Tp1>(__pair.first); }
 191     };
 192
 193   template<>
 194     struct __pair_get<1>
 195     {
 196       template<typename _Tp1, typename _Tp2>
 197         static constexpr _Tp2&
 198         __get(std::pair<_Tp1, _Tp2>& __pair) noexcept
 199         { return __pair.second; }
 200
 201       template<typename _Tp1, typename _Tp2>
 202         static constexpr _Tp2&&
 203         __move_get(std::pair<_Tp1, _Tp2>&& __pair) noexcept
 204         { return std::forward<_Tp2>(__pair.second); }
 205
 206       template<typename _Tp1, typename _Tp2>
 207         static constexpr const _Tp2&
 208         __const_get(const std::pair<_Tp1, _Tp2>& __pair) noexcept
 209         { return __pair.second; }
 210
 211       template<typename _Tp1, typename _Tp2>
 212         static constexpr const _Tp2&&
 213         __const_move_get(const std::pair<_Tp1, _Tp2>&& __pair) noexcept
 214         { return std::forward<const _Tp2>(__pair.second); }
 215     };
 216
 217   template<std::size_t _Int, class _Tp1, class _Tp2>
 218     constexpr typename tuple_element<_Int, std::pair<_Tp1, _Tp2>>::type&
 219     get(std::pair<_Tp1, _Tp2>& __in) noexcept
 220     { return __pair_get<_Int>::__get(__in); }
 221
 222   template<std::size_t _Int, class _Tp1, class _Tp2>
 223     constexpr typename tuple_element<_Int, std::pair<_Tp1, _Tp2>>::type&&
 224     get(std::pair<_Tp1, _Tp2>&& __in) noexcept
 225     { return __pair_get<_Int>::__move_get(std::move(__in)); }
 226
 227   template<std::size_t _Int, class _Tp1, class _Tp2>
 228     constexpr const typename tuple_element<_Int, std::pair<_Tp1, _Tp2>>::type&
 229     get(const std::pair<_Tp1, _Tp2>& __in) noexcept
 230     { return __pair_get<_Int>::__const_get(__in); }
 231
 232   template<std::size_t _Int, class _Tp1, class _Tp2>
 233     constexpr const typename tuple_element<_Int, std::pair<_Tp1, _Tp2>>::type&&
 234     get(const std::pair<_Tp1, _Tp2>&& __in) noexcept
 235     { return __pair_get<_Int>::__const_move_get(std::move(__in)); }
 236
 237 #if __cplusplus > 201103L
 238
 239 #define __cpp_lib_tuples_by_type 201304
 240
 241   template <typename _Tp, typename _Up>
 242     constexpr _Tp&
 243     get(pair<_Tp, _Up>& __p) noexcept
 244     { return __p.first; }
 245
 246   template <typename _Tp, typename _Up>
 247     constexpr const _Tp&
 248     get(const pair<_Tp, _Up>& __p) noexcept
 249     { return __p.first; }
 250
 251   template <typename _Tp, typename _Up>
 252     constexpr _Tp&&
 253     get(pair<_Tp, _Up>&& __p) noexcept
 254     { return std::move(__p.first); }
 255
 256   template <typename _Tp, typename _Up>
 257     constexpr const _Tp&&
 258     get(const pair<_Tp, _Up>&& __p) noexcept
 259     { return std::move(__p.first); }
 260
 261   template <typename _Tp, typename _Up>
 262     constexpr _Tp&
 263     get(pair<_Up, _Tp>& __p) noexcept
 264     { return __p.second; }
 265
 266   template <typename _Tp, typename _Up>
 267     constexpr const _Tp&
 268     get(const pair<_Up, _Tp>& __p) noexcept
 269     { return __p.second; }
 270
 271   template <typename _Tp, typename _Up>
 272     constexpr _Tp&&
 273     get(pair<_Up, _Tp>&& __p) noexcept
 274     { return std::move(__p.second); }
 275
 276   template <typename _Tp, typename _Up>
 277     constexpr const _Tp&&
 278     get(const pair<_Up, _Tp>&& __p) noexcept
 279     { return std::move(__p.second); }
 280
 281 #define __cpp_lib_exchange_function 201304
 282
 283 #if __cplusplus > 201703L
 284 #  define __cpp_lib_constexpr_algorithms 201806L
 285 #endif
 286
 287   /// Assign @p __new_val to @p __obj and return its previous value.
 288   template <typename _Tp, typename _Up = _Tp>
 289     _GLIBCXX20_CONSTEXPR
 290     inline _Tp
 291     exchange(_Tp& __obj, _Up&& __new_val)
 292     { return std::__exchange(__obj, std::forward<_Up>(__new_val)); }
 293
 294 #endif
 295
 296   // Stores a tuple of indices.  Used by tuple and pair, and by bind() to
 297   // extract the elements in a tuple.
 298   template<size_t... _Indexes> struct _Index_tuple { };
 299
 300 #ifdef __has_builtin
 301 # if __has_builtin(__make_integer_seq)
 302 #  define _GLIBCXX_USE_MAKE_INTEGER_SEQ 1
 303 # endif
 304 #endif
 305
 306   // Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
 307   template<size_t _Num>
 308     struct _Build_index_tuple
 309     {
 310 #if _GLIBCXX_USE_MAKE_INTEGER_SEQ
 311       template<typename, size_t... _Indices>
 312         using _IdxTuple = _Index_tuple<_Indices...>;
 313
 314       using __type = __make_integer_seq<_IdxTuple, size_t, _Num>;
 315 #else
 316       using __type = _Index_tuple<__integer_pack(_Num)...>;
 317 #endif
 318     };
 319
 320 #if __cplusplus > 201103L
 321
 322 #define __cpp_lib_integer_sequence 201304
 323
 324   /// Class template integer_sequence
 325   template<typename _Tp, _Tp... _Idx>
 326     struct integer_sequence
 327     {
 328       typedef _Tp value_type;
 329       static constexpr size_t size() noexcept { return sizeof...(_Idx); }
 330     };
 331
 332   /// Alias template make_integer_sequence
 333   template<typename _Tp, _Tp _Num>
 334     using make_integer_sequence
 335 #if _GLIBCXX_USE_MAKE_INTEGER_SEQ
 336       = __make_integer_seq<integer_sequence, _Tp, _Num>;
 337 #else
 338       = integer_sequence<_Tp, __integer_pack(_Num)...>;
 339 #endif
 340
 341 #undef _GLIBCXX_USE_MAKE_INTEGER_SEQ
 342
 343   /// Alias template index_sequence
 344   template<size_t... _Idx>
 345     using index_sequence = integer_sequence<size_t, _Idx...>;
 346
 347   /// Alias template make_index_sequence
 348   template<size_t _Num>
 349     using make_index_sequence = make_integer_sequence<size_t, _Num>;
 350
 351   /// Alias template index_sequence_for
 352   template<typename... _Types>
 353     using index_sequence_for = make_index_sequence<sizeof...(_Types)>;
 354 #endif
 355
 356 #if __cplusplus > 201402L
 357
 358   struct in_place_t {
 359     explicit in_place_t() = default;
 360   };
 361
 362   inline constexpr in_place_t in_place{};
 363
 364   template<typename _Tp> struct in_place_type_t
 365   {
 366     explicit in_place_type_t() = default;
 367   };
 368
 369   template<typename _Tp>
 370     inline constexpr in_place_type_t<_Tp> in_place_type{};
 371
 372   template<size_t _Idx> struct in_place_index_t
 373   {
 374     explicit in_place_index_t() = default;
 375   };
 376
 377   template<size_t _Idx>
 378     inline constexpr in_place_index_t<_Idx> in_place_index{};
 379
 380   template<typename>
 381     struct __is_in_place_type_impl : false_type
 382     { };
 383
 384   template<typename _Tp>
 385     struct __is_in_place_type_impl<in_place_type_t<_Tp>> : true_type
 386     { };
 387
 388   template<typename _Tp>
 389     struct __is_in_place_type
 390       : public __is_in_place_type_impl<_Tp>
 391     { };
 392
 393 #define  __cpp_lib_as_const 201510
 394   template<typename _Tp>
 395     constexpr add_const_t<_Tp>& as_const(_Tp& __t) noexcept { return __t; }
 396
 397   template<typename _Tp>
 398     void as_const(const _Tp&&) = delete;
 399
 400 #endif // C++17
 401
 402 _GLIBCXX_END_NAMESPACE_VERSION
 403 } // namespace
 404
 405 #endif
 406
 407 #endif /* _GLIBCXX_UTILITY */