libstdc++-v3/include/std/concepts

   1 // <concepts> -*- C++ -*-
   2
   3 // Copyright (C) 2019-2024 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/concepts
  26  *  This is a Standard C++ Library header.
  27  *  @ingroup concepts
  28  */
  29
  30 #ifndef _GLIBCXX_CONCEPTS
  31 #define _GLIBCXX_CONCEPTS 1
  32
  33 #pragma GCC system_header
  34
  35 #define __glibcxx_want_concepts
  36 #include <bits/version.h>
  37
  38 #ifdef __cpp_lib_concepts // C++ >= 20 && concepts
  39 /**
  40  * @defgroup concepts Concepts
  41  * @ingroup utilities
  42  *
  43  * Concepts for checking type requirements.
  44  */
  45
  46 #include <type_traits>
  47
  48 namespace std _GLIBCXX_VISIBILITY(default)
  49 {
  50 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  51
  52   // [concepts.lang], language-related concepts
  53
  54   namespace __detail
  55   {
  56     template<typename _Tp, typename _Up>
  57       concept __same_as = std::is_same_v<_Tp, _Up>;
  58   } // namespace __detail
  59
  60   /// [concept.same], concept same_as
  61   template<typename _Tp, typename _Up>
  62     concept same_as
  63       = __detail::__same_as<_Tp, _Up> && __detail::__same_as<_Up, _Tp>;
  64
  65   /// [concept.derived], concept derived_from
  66   template<typename _Derived, typename _Base>
  67     concept derived_from = __is_base_of(_Base, _Derived)
  68       && is_convertible_v<const volatile _Derived*, const volatile _Base*>;
  69
  70   /// [concept.convertible], concept convertible_to
  71   template<typename _From, typename _To>
  72     concept convertible_to = is_convertible_v<_From, _To>
  73       && requires { static_cast<_To>(std::declval<_From>()); };
  74
  75   /// [concept.commonref], concept common_reference_with
  76   template<typename _Tp, typename _Up>
  77     concept common_reference_with
  78       = same_as<common_reference_t<_Tp, _Up>, common_reference_t<_Up, _Tp>>
  79       && convertible_to<_Tp, common_reference_t<_Tp, _Up>>
  80       && convertible_to<_Up, common_reference_t<_Tp, _Up>>;
  81
  82   /// [concept.common], concept common_with
  83   template<typename _Tp, typename _Up>
  84     concept common_with
  85       = same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>>
  86       && requires {
  87         static_cast<common_type_t<_Tp, _Up>>(std::declval<_Tp>());
  88         static_cast<common_type_t<_Tp, _Up>>(std::declval<_Up>());
  89       }
  90       && common_reference_with<add_lvalue_reference_t<const _Tp>,
  91                                add_lvalue_reference_t<const _Up>>
  92       && common_reference_with<add_lvalue_reference_t<common_type_t<_Tp, _Up>>,
  93                                common_reference_t<
  94                                  add_lvalue_reference_t<const _Tp>,
  95                                  add_lvalue_reference_t<const _Up>>>;
  96
  97   // [concepts.arithmetic], arithmetic concepts
  98
  99   template<typename _Tp>
 100     concept integral = is_integral_v<_Tp>;
 101
 102   template<typename _Tp>
 103     concept signed_integral = integral<_Tp> && is_signed_v<_Tp>;
 104
 105   template<typename _Tp>
 106     concept unsigned_integral = integral<_Tp> && !signed_integral<_Tp>;
 107
 108   template<typename _Tp>
 109     concept floating_point = is_floating_point_v<_Tp>;
 110
 111   namespace __detail
 112   {
 113     template<typename _Tp>
 114       using __cref = const remove_reference_t<_Tp>&;
 115
 116     template<typename _Tp>
 117       concept __class_or_enum
 118         = is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
 119
 120     template<typename _Tp>
 121       constexpr bool __destructible_impl = false;
 122     template<typename _Tp>
 123       requires requires(_Tp& __t) { { __t.~_Tp() } noexcept; }
 124       constexpr bool __destructible_impl<_Tp> = true;
 125
 126     template<typename _Tp>
 127       constexpr bool __destructible = __destructible_impl<_Tp>;
 128     template<typename _Tp>
 129       constexpr bool __destructible<_Tp&> = true;
 130     template<typename _Tp>
 131       constexpr bool __destructible<_Tp&&> = true;
 132     template<typename _Tp, size_t _Nm>
 133       constexpr bool __destructible<_Tp[_Nm]> = __destructible<_Tp>;
 134
 135   } // namespace __detail
 136
 137   /// [concept.assignable], concept assignable_from
 138   template<typename _Lhs, typename _Rhs>
 139     concept assignable_from
 140       = is_lvalue_reference_v<_Lhs>
 141       && common_reference_with<__detail::__cref<_Lhs>, __detail::__cref<_Rhs>>
 142       && requires(_Lhs __lhs, _Rhs&& __rhs) {
 143         { __lhs = static_cast<_Rhs&&>(__rhs) } -> same_as<_Lhs>;
 144       };
 145
 146   /// [concept.destructible], concept destructible
 147   template<typename _Tp>
 148     concept destructible = __detail::__destructible<_Tp>;
 149
 150   /// [concept.constructible], concept constructible_from
 151   template<typename _Tp, typename... _Args>
 152     concept constructible_from
 153       = destructible<_Tp> && is_constructible_v<_Tp, _Args...>;
 154
 155   /// [concept.defaultinitializable], concept default_initializable
 156   template<typename _Tp>
 157     concept default_initializable = constructible_from<_Tp>
 158       && requires
 159       {
 160         _Tp{};
 161         (void) ::new _Tp;
 162       };
 163
 164   /// [concept.moveconstructible], concept move_constructible
 165   template<typename _Tp>
 166     concept move_constructible
 167     = constructible_from<_Tp, _Tp> && convertible_to<_Tp, _Tp>;
 168
 169   /// [concept.copyconstructible], concept copy_constructible
 170   template<typename _Tp>
 171     concept copy_constructible
 172       = move_constructible<_Tp>
 173       && constructible_from<_Tp, _Tp&> && convertible_to<_Tp&, _Tp>
 174       && constructible_from<_Tp, const _Tp&> && convertible_to<const _Tp&, _Tp>
 175       && constructible_from<_Tp, const _Tp> && convertible_to<const _Tp, _Tp>;
 176
 177   // [concept.swappable], concept swappable
 178
 179   namespace ranges
 180   {
 181     /// @cond undocumented
 182     namespace __swap
 183     {
 184       template<typename _Tp> void swap(_Tp&, _Tp&) = delete;
 185
 186       template<typename _Tp, typename _Up>
 187         concept __adl_swap
 188           = (__detail::__class_or_enum<remove_reference_t<_Tp>>
 189             || __detail::__class_or_enum<remove_reference_t<_Up>>)
 190           && requires(_Tp&& __t, _Up&& __u) {
 191             swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
 192           };
 193
 194       struct _Swap
 195       {
 196       private:
 197         template<typename _Tp, typename _Up>
 198           static constexpr bool
 199           _S_noexcept()
 200           {
 201             if constexpr (__adl_swap<_Tp, _Up>)
 202               return noexcept(swap(std::declval<_Tp>(), std::declval<_Up>()));
 203             else
 204               return is_nothrow_move_constructible_v<remove_reference_t<_Tp>>
 205                    && is_nothrow_move_assignable_v<remove_reference_t<_Tp>>;
 206           }
 207
 208       public:
 209         template<typename _Tp, typename _Up>
 210           requires __adl_swap<_Tp, _Up>
 211           || (same_as<_Tp, _Up> && is_lvalue_reference_v<_Tp>
 212               && move_constructible<remove_reference_t<_Tp>>
 213               && assignable_from<_Tp, remove_reference_t<_Tp>>)
 214           constexpr void
 215           operator()(_Tp&& __t, _Up&& __u) const
 216           noexcept(_S_noexcept<_Tp, _Up>())
 217           {
 218             if constexpr (__adl_swap<_Tp, _Up>)
 219               swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
 220             else
 221               {
 222                 auto __tmp = static_cast<remove_reference_t<_Tp>&&>(__t);
 223                 __t = static_cast<remove_reference_t<_Tp>&&>(__u);
 224                 __u = static_cast<remove_reference_t<_Tp>&&>(__tmp);
 225               }
 226           }
 227
 228         template<typename _Tp, typename _Up, size_t _Num>
 229           requires requires(const _Swap& __swap, _Tp& __e1, _Up& __e2) {
 230             __swap(__e1, __e2);
 231           }
 232           constexpr void
 233           operator()(_Tp (&__e1)[_Num], _Up (&__e2)[_Num]) const
 234           noexcept(noexcept(std::declval<const _Swap&>()(*__e1, *__e2)))
 235           {
 236             for (size_t __n = 0; __n < _Num; ++__n)
 237               (*this)(__e1[__n], __e2[__n]);
 238           }
 239       };
 240     } // namespace __swap
 241     /// @endcond
 242
 243     inline namespace _Cpo {
 244       inline constexpr __swap::_Swap swap{};
 245     }
 246   } // namespace ranges
 247
 248   template<typename _Tp>
 249     concept swappable
 250       = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
 251
 252   template<typename _Tp, typename _Up>
 253     concept swappable_with = common_reference_with<_Tp, _Up>
 254       && requires(_Tp&& __t, _Up&& __u) {
 255         ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Tp&&>(__t));
 256         ranges::swap(static_cast<_Up&&>(__u), static_cast<_Up&&>(__u));
 257         ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
 258         ranges::swap(static_cast<_Up&&>(__u), static_cast<_Tp&&>(__t));
 259       };
 260
 261   // [concepts.object], Object concepts
 262
 263   template<typename _Tp>
 264     concept movable = is_object_v<_Tp> && move_constructible<_Tp>
 265       && assignable_from<_Tp&, _Tp> && swappable<_Tp>;
 266
 267   template<typename _Tp>
 268     concept copyable = copy_constructible<_Tp> && movable<_Tp>
 269       && assignable_from<_Tp&, _Tp&> && assignable_from<_Tp&, const _Tp&>
 270       && assignable_from<_Tp&, const _Tp>;
 271
 272   template<typename _Tp>
 273     concept semiregular = copyable<_Tp> && default_initializable<_Tp>;
 274
 275   // [concepts.compare], comparison concepts
 276
 277   // [concept.booleantestable], Boolean testability
 278   namespace __detail
 279   {
 280     template<typename _Tp>
 281       concept __boolean_testable_impl = convertible_to<_Tp, bool>;
 282
 283     template<typename _Tp>
 284       concept __boolean_testable
 285         = __boolean_testable_impl<_Tp>
 286           && requires(_Tp&& __t)
 287           { { !static_cast<_Tp&&>(__t) } -> __boolean_testable_impl; };
 288   } // namespace __detail
 289
 290   // [concept.equalitycomparable], concept equality_comparable
 291
 292   namespace __detail
 293   {
 294     template<typename _Tp, typename _Up>
 295       concept __weakly_eq_cmp_with
 296         = requires(__detail::__cref<_Tp> __t, __detail::__cref<_Up> __u) {
 297           { __t == __u } -> __boolean_testable;
 298           { __t != __u } -> __boolean_testable;
 299           { __u == __t } -> __boolean_testable;
 300           { __u != __t } -> __boolean_testable;
 301         };
 302   } // namespace __detail
 303
 304   template<typename _Tp>
 305     concept equality_comparable = __detail::__weakly_eq_cmp_with<_Tp, _Tp>;
 306
 307   template<typename _Tp, typename _Up>
 308     concept equality_comparable_with
 309       = equality_comparable<_Tp> && equality_comparable<_Up>
 310       && common_reference_with<__detail::__cref<_Tp>, __detail::__cref<_Up>>
 311       && equality_comparable<common_reference_t<__detail::__cref<_Tp>,
 312                                                 __detail::__cref<_Up>>>
 313       && __detail::__weakly_eq_cmp_with<_Tp, _Up>;
 314
 315   namespace __detail
 316   {
 317     template<typename _Tp, typename _Up>
 318       concept __partially_ordered_with
 319         = requires(const remove_reference_t<_Tp>& __t,
 320                    const remove_reference_t<_Up>& __u) {
 321           { __t <  __u } -> __boolean_testable;
 322           { __t >  __u } -> __boolean_testable;
 323           { __t <= __u } -> __boolean_testable;
 324           { __t >= __u } -> __boolean_testable;
 325           { __u <  __t } -> __boolean_testable;
 326           { __u >  __t } -> __boolean_testable;
 327           { __u <= __t } -> __boolean_testable;
 328           { __u >= __t } -> __boolean_testable;
 329         };
 330   } // namespace __detail
 331
 332   // [concept.totallyordered], concept totally_ordered
 333   template<typename _Tp>
 334     concept totally_ordered
 335       = equality_comparable<_Tp>
 336       && __detail::__partially_ordered_with<_Tp, _Tp>;
 337
 338   template<typename _Tp, typename _Up>
 339     concept totally_ordered_with
 340       = totally_ordered<_Tp> && totally_ordered<_Up>
 341       && equality_comparable_with<_Tp, _Up>
 342       && totally_ordered<common_reference_t<__detail::__cref<_Tp>,
 343                                             __detail::__cref<_Up>>>
 344       && __detail::__partially_ordered_with<_Tp, _Up>;
 345
 346   template<typename _Tp>
 347     concept regular = semiregular<_Tp> && equality_comparable<_Tp>;
 348
 349   // [concepts.callable], callable concepts
 350
 351   /// [concept.invocable], concept invocable
 352   template<typename _Fn, typename... _Args>
 353     concept invocable = is_invocable_v<_Fn, _Args...>;
 354
 355   /// [concept.regularinvocable], concept regular_invocable
 356   template<typename _Fn, typename... _Args>
 357     concept regular_invocable = invocable<_Fn, _Args...>;
 358
 359   /// [concept.predicate], concept predicate
 360   template<typename _Fn, typename... _Args>
 361     concept predicate = regular_invocable<_Fn, _Args...>
 362       && __detail::__boolean_testable<invoke_result_t<_Fn, _Args...>>;
 363
 364   /// [concept.relation], concept relation
 365   template<typename _Rel, typename _Tp, typename _Up>
 366     concept relation
 367       = predicate<_Rel, _Tp, _Tp> && predicate<_Rel, _Up, _Up>
 368       && predicate<_Rel, _Tp, _Up> && predicate<_Rel, _Up, _Tp>;
 369
 370   /// [concept.equiv], concept equivalence_relation
 371   template<typename _Rel, typename _Tp, typename _Up>
 372     concept equivalence_relation = relation<_Rel, _Tp, _Up>;
 373
 374   /// [concept.strictweakorder], concept strict_weak_order
 375   template<typename _Rel, typename _Tp, typename _Up>
 376     concept strict_weak_order = relation<_Rel, _Tp, _Up>;
 377
 378 _GLIBCXX_END_NAMESPACE_VERSION
 379 } // namespace
 380 #endif // __cpp_lib_concepts
 381
 382 #endif /* _GLIBCXX_CONCEPTS */