libstdc++
concepts
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1// <concepts> -*- C++ -*-
2
3// Copyright (C) 2019-2022 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
46namespace 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 { 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 } // namespace __detail
120
121 /// [concept.assignable], concept assignable_from
122 template<typename _Lhs, typename _Rhs>
123 concept assignable_from
124 = is_lvalue_reference_v<_Lhs>
125 && common_reference_with<__detail::__cref<_Lhs>, __detail::__cref<_Rhs>>
126 && requires(_Lhs __lhs, _Rhs&& __rhs) {
127 { __lhs = static_cast<_Rhs&&>(__rhs) } -> same_as<_Lhs>;
128 };
129
130 /// [concept.destructible], concept destructible
131 template<typename _Tp>
132 concept destructible = is_nothrow_destructible_v<_Tp>;
133
134 /// [concept.constructible], concept constructible_from
135 template<typename _Tp, typename... _Args>
136 concept constructible_from
137 = destructible<_Tp> && is_constructible_v<_Tp, _Args...>;
138
139 /// [concept.defaultinitializable], concept default_initializable
140 template<typename _Tp>
141 concept default_initializable = constructible_from<_Tp>
142 && requires
143 {
144 _Tp{};
145 (void) ::new _Tp;
146 };
147
148 /// [concept.moveconstructible], concept move_constructible
149 template<typename _Tp>
150 concept move_constructible
151 = constructible_from<_Tp, _Tp> && convertible_to<_Tp, _Tp>;
152
153 /// [concept.copyconstructible], concept copy_constructible
154 template<typename _Tp>
155 concept copy_constructible
156 = move_constructible<_Tp>
157 && constructible_from<_Tp, _Tp&> && convertible_to<_Tp&, _Tp>
158 && constructible_from<_Tp, const _Tp&> && convertible_to<const _Tp&, _Tp>
159 && constructible_from<_Tp, const _Tp> && convertible_to<const _Tp, _Tp>;
160
161 // [concept.swappable], concept swappable
162
163 namespace ranges
164 {
165 namespace __cust_swap
166 {
167 template<typename _Tp> void swap(_Tp&, _Tp&) = delete;
168
169 template<typename _Tp, typename _Up>
170 concept __adl_swap
171 = (__detail::__class_or_enum<remove_reference_t<_Tp>>
172 || __detail::__class_or_enum<remove_reference_t<_Up>>)
173 && requires(_Tp&& __t, _Up&& __u) {
174 swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
175 };
176
177 struct _Swap
178 {
179 private:
180 template<typename _Tp, typename _Up>
181 static constexpr bool
182 _S_noexcept()
183 {
184 if constexpr (__adl_swap<_Tp, _Up>)
185 return noexcept(swap(std::declval<_Tp>(), std::declval<_Up>()));
186 else
187 return is_nothrow_move_constructible_v<remove_reference_t<_Tp>>
188 && is_nothrow_move_assignable_v<remove_reference_t<_Tp>>;
189 }
190
191 public:
192 template<typename _Tp, typename _Up>
193 requires __adl_swap<_Tp, _Up>
194 || (same_as<_Tp, _Up> && is_lvalue_reference_v<_Tp>
195 && move_constructible<remove_reference_t<_Tp>>
196 && assignable_from<_Tp, remove_reference_t<_Tp>>)
197 constexpr void
198 operator()(_Tp&& __t, _Up&& __u) const
199 noexcept(_S_noexcept<_Tp, _Up>())
200 {
201 if constexpr (__adl_swap<_Tp, _Up>)
202 swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
203 else
204 {
205 auto __tmp = static_cast<remove_reference_t<_Tp>&&>(__t);
206 __t = static_cast<remove_reference_t<_Tp>&&>(__u);
207 __u = static_cast<remove_reference_t<_Tp>&&>(__tmp);
208 }
209 }
210
211 template<typename _Tp, typename _Up, size_t _Num>
212 requires requires(const _Swap& __swap, _Tp& __e1, _Up& __e2) {
213 __swap(__e1, __e2);
214 }
215 constexpr void
216 operator()(_Tp (&__e1)[_Num], _Up (&__e2)[_Num]) const
217 noexcept(noexcept(std::declval<const _Swap&>()(*__e1, *__e2)))
218 {
219 for (size_t __n = 0; __n < _Num; ++__n)
220 (*this)(__e1[__n], __e2[__n]);
221 }
222 };
223 } // namespace __cust_swap
224
225 inline namespace __cust
226 {
227 inline constexpr __cust_swap::_Swap swap{};
228 } // inline namespace __cust
229 } // namespace ranges
230
231 template<typename _Tp>
232 concept swappable
233 = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
234
235 template<typename _Tp, typename _Up>
236 concept swappable_with = common_reference_with<_Tp, _Up>
237 && requires(_Tp&& __t, _Up&& __u) {
238 ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Tp&&>(__t));
239 ranges::swap(static_cast<_Up&&>(__u), static_cast<_Up&&>(__u));
240 ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
241 ranges::swap(static_cast<_Up&&>(__u), static_cast<_Tp&&>(__t));
242 };
243
244 // [concepts.object], Object concepts
245
246 template<typename _Tp>
247 concept movable = is_object_v<_Tp> && move_constructible<_Tp>
248 && assignable_from<_Tp&, _Tp> && swappable<_Tp>;
249
250 template<typename _Tp>
251 concept copyable = copy_constructible<_Tp> && movable<_Tp>
252 && assignable_from<_Tp&, _Tp&> && assignable_from<_Tp&, const _Tp&>
253 && assignable_from<_Tp&, const _Tp>;
254
255 template<typename _Tp>
256 concept semiregular = copyable<_Tp> && default_initializable<_Tp>;
257
258 // [concepts.compare], comparison concepts
259
260 // [concept.booleantestable], Boolean testability
261 namespace __detail
262 {
263 template<typename _Tp>
264 concept __boolean_testable_impl = convertible_to<_Tp, bool>;
265
266 template<typename _Tp>
267 concept __boolean_testable
268 = __boolean_testable_impl<_Tp>
269 && requires(_Tp&& __t)
270 { { !static_cast<_Tp&&>(__t) } -> __boolean_testable_impl; };
271 } // namespace __detail
272
273 // [concept.equalitycomparable], concept equality_comparable
274
275 namespace __detail
276 {
277 template<typename _Tp, typename _Up>
278 concept __weakly_eq_cmp_with
279 = requires(__detail::__cref<_Tp> __t, __detail::__cref<_Up> __u) {
280 { __t == __u } -> __boolean_testable;
281 { __t != __u } -> __boolean_testable;
282 { __u == __t } -> __boolean_testable;
283 { __u != __t } -> __boolean_testable;
284 };
285 } // namespace __detail
286
287 template<typename _Tp>
288 concept equality_comparable = __detail::__weakly_eq_cmp_with<_Tp, _Tp>;
289
290 template<typename _Tp, typename _Up>
291 concept equality_comparable_with
292 = equality_comparable<_Tp> && equality_comparable<_Up>
293 && common_reference_with<__detail::__cref<_Tp>, __detail::__cref<_Up>>
294 && equality_comparable<common_reference_t<__detail::__cref<_Tp>,
295 __detail::__cref<_Up>>>
296 && __detail::__weakly_eq_cmp_with<_Tp, _Up>;
297
298 namespace __detail
299 {
300 template<typename _Tp, typename _Up>
301 concept __partially_ordered_with
302 = requires(const remove_reference_t<_Tp>& __t,
303 const remove_reference_t<_Up>& __u) {
304 { __t < __u } -> __boolean_testable;
305 { __t > __u } -> __boolean_testable;
306 { __t <= __u } -> __boolean_testable;
307 { __t >= __u } -> __boolean_testable;
308 { __u < __t } -> __boolean_testable;
309 { __u > __t } -> __boolean_testable;
310 { __u <= __t } -> __boolean_testable;
311 { __u >= __t } -> __boolean_testable;
312 };
313 } // namespace __detail
314
315 // [concept.totallyordered], concept totally_ordered
316 template<typename _Tp>
317 concept totally_ordered
318 = equality_comparable<_Tp>
319 && __detail::__partially_ordered_with<_Tp, _Tp>;
320
321 template<typename _Tp, typename _Up>
322 concept totally_ordered_with
323 = totally_ordered<_Tp> && totally_ordered<_Up>
324 && equality_comparable_with<_Tp, _Up>
325 && totally_ordered<common_reference_t<__detail::__cref<_Tp>,
326 __detail::__cref<_Up>>>
327 && __detail::__partially_ordered_with<_Tp, _Up>;
328
329 template<typename _Tp>
330 concept regular = semiregular<_Tp> && equality_comparable<_Tp>;
331
332 // [concepts.callable], callable concepts
333
334 /// [concept.invocable], concept invocable
335 template<typename _Fn, typename... _Args>
336 concept invocable = is_invocable_v<_Fn, _Args...>;
337
338 /// [concept.regularinvocable], concept regular_invocable
339 template<typename _Fn, typename... _Args>
340 concept regular_invocable = invocable<_Fn, _Args...>;
341
342 /// [concept.predicate], concept predicate
343 template<typename _Fn, typename... _Args>
344 concept predicate = regular_invocable<_Fn, _Args...>
345 && __detail::__boolean_testable<invoke_result_t<_Fn, _Args...>>;
346
347 /// [concept.relation], concept relation
348 template<typename _Rel, typename _Tp, typename _Up>
349 concept relation
350 = predicate<_Rel, _Tp, _Tp> && predicate<_Rel, _Up, _Up>
351 && predicate<_Rel, _Tp, _Up> && predicate<_Rel, _Up, _Tp>;
352
353 /// [concept.equiv], concept equivalence_relation
354 template<typename _Rel, typename _Tp, typename _Up>
355 concept equivalence_relation = relation<_Rel, _Tp, _Up>;
356
357 /// [concept.strictweakorder], concept strict_weak_order
358 template<typename _Rel, typename _Tp, typename _Up>
359 concept strict_weak_order = relation<_Rel, _Tp, _Up>;
360
361_GLIBCXX_END_NAMESPACE_VERSION
362} // namespace
363#endif // C++2a
364
365#endif /* _GLIBCXX_CONCEPTS */