libstdc++
concepts
Go to the documentation of this file.
1 // <concepts> -*- C++ -*-
2 
3 // Copyright (C) 2019-2021 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 #if __cplusplus > 201703L && __cpp_concepts >= 201907L
34 
35 #pragma GCC system_header
36 
37 /**
38  * @defgroup concepts Concepts
39  * @ingroup utilities
40  *
41  * Concepts for checking type requirements.
42  */
43 
44 #include <type_traits>
45 
46 namespace std _GLIBCXX_VISIBILITY(default)
47 {
48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
49 
50 #define __cpp_lib_concepts 202002L
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(add_rvalue_reference_t<_From> (&__f)()) {
74  static_cast<_To>(__f());
75  };
76 
77  /// [concept.commonref], concept common_reference_with
78  template<typename _Tp, typename _Up>
79  concept common_reference_with
80  = same_as<common_reference_t<_Tp, _Up>, common_reference_t<_Up, _Tp>>
81  && convertible_to<_Tp, common_reference_t<_Tp, _Up>>
82  && convertible_to<_Up, common_reference_t<_Tp, _Up>>;
83 
84  /// [concept.common], concept common_with
85  template<typename _Tp, typename _Up>
86  concept common_with
87  = same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>>
88  && requires {
89  static_cast<common_type_t<_Tp, _Up>>(std::declval<_Tp>());
90  static_cast<common_type_t<_Tp, _Up>>(std::declval<_Up>());
91  }
92  && common_reference_with<add_lvalue_reference_t<const _Tp>,
93  add_lvalue_reference_t<const _Up>>
94  && common_reference_with<add_lvalue_reference_t<common_type_t<_Tp, _Up>>,
95  common_reference_t<
96  add_lvalue_reference_t<const _Tp>,
97  add_lvalue_reference_t<const _Up>>>;
98 
99  // [concepts.arithmetic], arithmetic concepts
100 
101  template<typename _Tp>
102  concept integral = is_integral_v<_Tp>;
103 
104  template<typename _Tp>
105  concept signed_integral = integral<_Tp> && is_signed_v<_Tp>;
106 
107  template<typename _Tp>
108  concept unsigned_integral = integral<_Tp> && !signed_integral<_Tp>;
109 
110  template<typename _Tp>
111  concept floating_point = is_floating_point_v<_Tp>;
112 
113  namespace __detail
114  {
115  template<typename _Tp>
116  using __cref = const remove_reference_t<_Tp>&;
117 
118  template<typename _Tp>
119  concept __class_or_enum
120  = is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
121  } // namespace __detail
122 
123  /// [concept.assignable], concept assignable_from
124  template<typename _Lhs, typename _Rhs>
125  concept assignable_from
126  = is_lvalue_reference_v<_Lhs>
127  && common_reference_with<__detail::__cref<_Lhs>, __detail::__cref<_Rhs>>
128  && requires(_Lhs __lhs, _Rhs&& __rhs) {
129  { __lhs = static_cast<_Rhs&&>(__rhs) } -> same_as<_Lhs>;
130  };
131 
132  /// [concept.destructible], concept destructible
133  template<typename _Tp>
134  concept destructible = is_nothrow_destructible_v<_Tp>;
135 
136  /// [concept.constructible], concept constructible_from
137  template<typename _Tp, typename... _Args>
138  concept constructible_from
139  = destructible<_Tp> && is_constructible_v<_Tp, _Args...>;
140 
141  /// [concept.defaultinitializable], concept default_initializable
142  template<typename _Tp>
143  concept default_initializable = constructible_from<_Tp>
144  && requires
145  {
146  _Tp{};
147  (void) ::new _Tp;
148  };
149 
150  /// [concept.moveconstructible], concept move_constructible
151  template<typename _Tp>
152  concept move_constructible
153  = constructible_from<_Tp, _Tp> && convertible_to<_Tp, _Tp>;
154 
155  /// [concept.copyconstructible], concept copy_constructible
156  template<typename _Tp>
157  concept copy_constructible
158  = move_constructible<_Tp>
159  && constructible_from<_Tp, _Tp&> && convertible_to<_Tp&, _Tp>
160  && constructible_from<_Tp, const _Tp&> && convertible_to<const _Tp&, _Tp>
161  && constructible_from<_Tp, const _Tp> && convertible_to<const _Tp, _Tp>;
162 
163  // [concept.swappable], concept swappable
164 
165  namespace ranges
166  {
167  namespace __cust_swap
168  {
169  template<typename _Tp> void swap(_Tp&, _Tp&) = delete;
170 
171  template<typename _Tp, typename _Up>
172  concept __adl_swap
173  = (__detail::__class_or_enum<remove_reference_t<_Tp>>
174  || __detail::__class_or_enum<remove_reference_t<_Up>>)
175  && requires(_Tp&& __t, _Up&& __u) {
176  swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
177  };
178 
179  struct _Swap
180  {
181  private:
182  template<typename _Tp, typename _Up>
183  static constexpr bool
184  _S_noexcept()
185  {
186  if constexpr (__adl_swap<_Tp, _Up>)
187  return noexcept(swap(std::declval<_Tp>(), std::declval<_Up>()));
188  else
189  return is_nothrow_move_constructible_v<remove_reference_t<_Tp>>
190  && is_nothrow_move_assignable_v<remove_reference_t<_Tp>>;
191  }
192 
193  public:
194  template<typename _Tp, typename _Up>
195  requires __adl_swap<_Tp, _Up>
196  || (same_as<_Tp, _Up> && is_lvalue_reference_v<_Tp>
197  && move_constructible<remove_reference_t<_Tp>>
198  && assignable_from<_Tp, remove_reference_t<_Tp>>)
199  constexpr void
200  operator()(_Tp&& __t, _Up&& __u) const
201  noexcept(_S_noexcept<_Tp, _Up>())
202  {
203  if constexpr (__adl_swap<_Tp, _Up>)
204  swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
205  else
206  {
207  auto __tmp = static_cast<remove_reference_t<_Tp>&&>(__t);
208  __t = static_cast<remove_reference_t<_Tp>&&>(__u);
209  __u = static_cast<remove_reference_t<_Tp>&&>(__tmp);
210  }
211  }
212 
213  template<typename _Tp, typename _Up, size_t _Num>
214  requires requires(const _Swap& __swap, _Tp& __e1, _Up& __e2) {
215  __swap(__e1, __e2);
216  }
217  constexpr void
218  operator()(_Tp (&__e1)[_Num], _Up (&__e2)[_Num]) const
219  noexcept(noexcept(std::declval<const _Swap&>()(*__e1, *__e2)))
220  {
221  for (size_t __n = 0; __n < _Num; ++__n)
222  (*this)(__e1[__n], __e2[__n]);
223  }
224  };
225  } // namespace __cust_swap
226 
227  inline namespace __cust
228  {
229  inline constexpr __cust_swap::_Swap swap{};
230  } // inline namespace __cust
231  } // namespace ranges
232 
233  template<typename _Tp>
234  concept swappable
235  = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
236 
237  template<typename _Tp, typename _Up>
238  concept swappable_with = common_reference_with<_Tp, _Up>
239  && requires(_Tp&& __t, _Up&& __u) {
240  ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Tp&&>(__t));
241  ranges::swap(static_cast<_Up&&>(__u), static_cast<_Up&&>(__u));
242  ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
243  ranges::swap(static_cast<_Up&&>(__u), static_cast<_Tp&&>(__t));
244  };
245 
246  // [concepts.object], Object concepts
247 
248  template<typename _Tp>
249  concept movable = is_object_v<_Tp> && move_constructible<_Tp>
250  && assignable_from<_Tp&, _Tp> && swappable<_Tp>;
251 
252  template<typename _Tp>
253  concept copyable = copy_constructible<_Tp> && movable<_Tp>
254  && assignable_from<_Tp&, _Tp&> && assignable_from<_Tp&, const _Tp&>
255  && assignable_from<_Tp&, const _Tp>;
256 
257  template<typename _Tp>
258  concept semiregular = copyable<_Tp> && default_initializable<_Tp>;
259 
260  // [concepts.compare], comparison concepts
261 
262  // [concept.booleantestable], Boolean testability
263  namespace __detail
264  {
265  template<typename _Tp>
266  concept __boolean_testable_impl = convertible_to<_Tp, bool>;
267 
268  template<typename _Tp>
269  concept __boolean_testable
270  = __boolean_testable_impl<_Tp>
271  && requires(_Tp&& __t)
272  { { !static_cast<_Tp&&>(__t) } -> __boolean_testable_impl; };
273  } // namespace __detail
274 
275  // [concept.equalitycomparable], concept equality_comparable
276 
277  namespace __detail
278  {
279  template<typename _Tp, typename _Up>
280  concept __weakly_eq_cmp_with
281  = requires(__detail::__cref<_Tp> __t, __detail::__cref<_Up> __u) {
282  { __t == __u } -> __boolean_testable;
283  { __t != __u } -> __boolean_testable;
284  { __u == __t } -> __boolean_testable;
285  { __u != __t } -> __boolean_testable;
286  };
287  } // namespace __detail
288 
289  template<typename _Tp>
290  concept equality_comparable = __detail::__weakly_eq_cmp_with<_Tp, _Tp>;
291 
292  template<typename _Tp, typename _Up>
293  concept equality_comparable_with
294  = equality_comparable<_Tp> && equality_comparable<_Up>
295  && common_reference_with<__detail::__cref<_Tp>, __detail::__cref<_Up>>
296  && equality_comparable<common_reference_t<__detail::__cref<_Tp>,
297  __detail::__cref<_Up>>>
298  && __detail::__weakly_eq_cmp_with<_Tp, _Up>;
299 
300  namespace __detail
301  {
302  template<typename _Tp, typename _Up>
303  concept __partially_ordered_with
304  = requires(const remove_reference_t<_Tp>& __t,
305  const remove_reference_t<_Up>& __u) {
306  { __t < __u } -> __boolean_testable;
307  { __t > __u } -> __boolean_testable;
308  { __t <= __u } -> __boolean_testable;
309  { __t >= __u } -> __boolean_testable;
310  { __u < __t } -> __boolean_testable;
311  { __u > __t } -> __boolean_testable;
312  { __u <= __t } -> __boolean_testable;
313  { __u >= __t } -> __boolean_testable;
314  };
315  } // namespace __detail
316 
317  // [concept.totallyordered], concept totally_ordered
318  template<typename _Tp>
319  concept totally_ordered
320  = equality_comparable<_Tp>
321  && __detail::__partially_ordered_with<_Tp, _Tp>;
322 
323  template<typename _Tp, typename _Up>
324  concept totally_ordered_with
325  = totally_ordered<_Tp> && totally_ordered<_Up>
326  && equality_comparable_with<_Tp, _Up>
327  && totally_ordered<common_reference_t<__detail::__cref<_Tp>,
328  __detail::__cref<_Up>>>
329  && __detail::__partially_ordered_with<_Tp, _Up>;
330 
331  template<typename _Tp>
332  concept regular = semiregular<_Tp> && equality_comparable<_Tp>;
333 
334  // [concepts.callable], callable concepts
335 
336  /// [concept.invocable], concept invocable
337  template<typename _Fn, typename... _Args>
338  concept invocable = is_invocable_v<_Fn, _Args...>;
339 
340  /// [concept.regularinvocable], concept regular_invocable
341  template<typename _Fn, typename... _Args>
342  concept regular_invocable = invocable<_Fn, _Args...>;
343 
344  /// [concept.predicate], concept predicate
345  template<typename _Fn, typename... _Args>
346  concept predicate = regular_invocable<_Fn, _Args...>
347  && __detail::__boolean_testable<invoke_result_t<_Fn, _Args...>>;
348 
349  /// [concept.relation], concept relation
350  template<typename _Rel, typename _Tp, typename _Up>
351  concept relation
352  = predicate<_Rel, _Tp, _Tp> && predicate<_Rel, _Up, _Up>
353  && predicate<_Rel, _Tp, _Up> && predicate<_Rel, _Up, _Tp>;
354 
355  /// [concept.equiv], concept equivalence_relation
356  template<typename _Rel, typename _Tp, typename _Up>
357  concept equivalence_relation = relation<_Rel, _Tp, _Up>;
358 
359  /// [concept.strictweakorder], concept strict_weak_order
360  template<typename _Rel, typename _Tp, typename _Up>
361  concept strict_weak_order = relation<_Rel, _Tp, _Up>;
362 
363 _GLIBCXX_END_NAMESPACE_VERSION
364 } // namespace
365 #endif // C++2a
366 
367 #endif /* _GLIBCXX_CONCEPTS */
typename invoke_result< _Fn, _Args...>::type invoke_result_t
std::invoke_result_t
Definition: type_traits:2933
constexpr bool is_invocable_v
std::is_invocable_v
Definition: type_traits:3001
typename remove_reference< _Tp >::type remove_reference_t
Alias template for remove_reference.
Definition: type_traits:1595