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
48namespace 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 namespace __detail
66 {
67 template<typename _Tp, typename _Up>
68 concept __different_from
69 = !same_as<remove_cvref_t<_Tp>, remove_cvref_t<_Up>>;
70 } // namespace __detail
71
72 /// [concept.derived], concept derived_from
73 template<typename _Derived, typename _Base>
74 concept derived_from = __is_base_of(_Base, _Derived)
75 && is_convertible_v<const volatile _Derived*, const volatile _Base*>;
76
77 /// [concept.convertible], concept convertible_to
78 template<typename _From, typename _To>
79 concept convertible_to = is_convertible_v<_From, _To>
80 && requires { static_cast<_To>(std::declval<_From>()); };
81
82 /// [concept.commonref], concept common_reference_with
83 template<typename _Tp, typename _Up>
84 concept common_reference_with
85 = same_as<common_reference_t<_Tp, _Up>, common_reference_t<_Up, _Tp>>
86 && convertible_to<_Tp, common_reference_t<_Tp, _Up>>
87 && convertible_to<_Up, common_reference_t<_Tp, _Up>>;
88
89 /// [concept.common], concept common_with
90 template<typename _Tp, typename _Up>
91 concept common_with
92 = same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>>
93 && requires {
94 static_cast<common_type_t<_Tp, _Up>>(std::declval<_Tp>());
95 static_cast<common_type_t<_Tp, _Up>>(std::declval<_Up>());
96 }
97 && common_reference_with<add_lvalue_reference_t<const _Tp>,
98 add_lvalue_reference_t<const _Up>>
99 && common_reference_with<add_lvalue_reference_t<common_type_t<_Tp, _Up>>,
100 common_reference_t<
101 add_lvalue_reference_t<const _Tp>,
102 add_lvalue_reference_t<const _Up>>>;
103
104 // [concepts.arithmetic], arithmetic concepts
105
106 template<typename _Tp>
107 concept integral = is_integral_v<_Tp>;
108
109 template<typename _Tp>
110 concept signed_integral = integral<_Tp> && is_signed_v<_Tp>;
111
112 template<typename _Tp>
113 concept unsigned_integral = integral<_Tp> && !signed_integral<_Tp>;
114
115 template<typename _Tp>
116 concept floating_point = is_floating_point_v<_Tp>;
117
118 namespace __detail
119 {
120 template<typename _Tp>
121 using __cref = const remove_reference_t<_Tp>&;
122
123 template<typename _Tp>
124 concept __class_or_enum
125 = is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
126
127 template<typename _Tp>
128 constexpr bool __destructible_impl = false;
129 template<typename _Tp>
130 requires requires(_Tp& __t) { { __t.~_Tp() } noexcept; }
131 constexpr bool __destructible_impl<_Tp> = true;
132
133 template<typename _Tp>
134 constexpr bool __destructible = __destructible_impl<_Tp>;
135 template<typename _Tp>
136 constexpr bool __destructible<_Tp&> = true;
137 template<typename _Tp>
138 constexpr bool __destructible<_Tp&&> = true;
139 template<typename _Tp, size_t _Nm>
140 constexpr bool __destructible<_Tp[_Nm]> = __destructible<_Tp>;
141
142 } // namespace __detail
143
144 /// [concept.assignable], concept assignable_from
145 template<typename _Lhs, typename _Rhs>
146 concept assignable_from
147 = is_lvalue_reference_v<_Lhs>
148 && common_reference_with<__detail::__cref<_Lhs>, __detail::__cref<_Rhs>>
149 && requires(_Lhs __lhs, _Rhs&& __rhs) {
150 { __lhs = static_cast<_Rhs&&>(__rhs) } -> same_as<_Lhs>;
151 };
152
153 /// [concept.destructible], concept destructible
154 template<typename _Tp>
155 concept destructible = __detail::__destructible<_Tp>;
156
157 /// [concept.constructible], concept constructible_from
158 template<typename _Tp, typename... _Args>
159 concept constructible_from
160 = destructible<_Tp> && is_constructible_v<_Tp, _Args...>;
161
162 /// [concept.defaultinitializable], concept default_initializable
163 template<typename _Tp>
164 concept default_initializable = constructible_from<_Tp>
165 && requires
166 {
167 _Tp{};
168 (void) ::new _Tp;
169 };
170
171 /// [concept.moveconstructible], concept move_constructible
172 template<typename _Tp>
173 concept move_constructible
174 = constructible_from<_Tp, _Tp> && convertible_to<_Tp, _Tp>;
175
176 /// [concept.copyconstructible], concept copy_constructible
177 template<typename _Tp>
178 concept copy_constructible
179 = move_constructible<_Tp>
180 && constructible_from<_Tp, _Tp&> && convertible_to<_Tp&, _Tp>
181 && constructible_from<_Tp, const _Tp&> && convertible_to<const _Tp&, _Tp>
182 && constructible_from<_Tp, const _Tp> && convertible_to<const _Tp, _Tp>;
183
184 // [concept.swappable], concept swappable
185
186 namespace ranges
187 {
188 /// @cond undocumented
189 namespace __swap
190 {
191 template<typename _Tp> void swap(_Tp&, _Tp&) = delete;
192
193 template<typename _Tp, typename _Up>
194 concept __adl_swap
195 = (std::__detail::__class_or_enum<remove_reference_t<_Tp>>
196 || std::__detail::__class_or_enum<remove_reference_t<_Up>>)
197 && requires(_Tp&& __t, _Up&& __u) {
198 swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
199 };
200
201 struct _Swap
202 {
203 private:
204 template<typename _Tp, typename _Up>
205 static constexpr bool
206 _S_noexcept()
207 {
208 if constexpr (__adl_swap<_Tp, _Up>)
209 return noexcept(swap(std::declval<_Tp>(), std::declval<_Up>()));
210 else
211 return is_nothrow_move_constructible_v<remove_reference_t<_Tp>>
212 && is_nothrow_move_assignable_v<remove_reference_t<_Tp>>;
213 }
214
215 public:
216 template<typename _Tp, typename _Up>
217 requires __adl_swap<_Tp, _Up>
218 || (same_as<_Tp, _Up> && is_lvalue_reference_v<_Tp>
219 && move_constructible<remove_reference_t<_Tp>>
220 && assignable_from<_Tp, remove_reference_t<_Tp>>)
221 constexpr void
222 operator()(_Tp&& __t, _Up&& __u) const
223 noexcept(_S_noexcept<_Tp, _Up>())
224 {
225 if constexpr (__adl_swap<_Tp, _Up>)
226 swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
227 else
228 {
229 auto __tmp = static_cast<remove_reference_t<_Tp>&&>(__t);
230 __t = static_cast<remove_reference_t<_Tp>&&>(__u);
231 __u = static_cast<remove_reference_t<_Tp>&&>(__tmp);
232 }
233 }
234
235 template<typename _Tp, typename _Up, size_t _Num>
236 requires requires(const _Swap& __swap, _Tp& __e1, _Up& __e2) {
237 __swap(__e1, __e2);
238 }
239 constexpr void
240 operator()(_Tp (&__e1)[_Num], _Up (&__e2)[_Num]) const
241 noexcept(noexcept(std::declval<const _Swap&>()(*__e1, *__e2)))
242 {
243 for (size_t __n = 0; __n < _Num; ++__n)
244 (*this)(__e1[__n], __e2[__n]);
245 }
246 };
247 } // namespace __swap
248 /// @endcond
249
250 inline namespace _Cpo {
251 inline constexpr __swap::_Swap swap{};
252 }
253 } // namespace ranges
254
255 template<typename _Tp>
256 concept swappable
257 = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
258
259 template<typename _Tp, typename _Up>
260 concept swappable_with = common_reference_with<_Tp, _Up>
261 && requires(_Tp&& __t, _Up&& __u) {
262 ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Tp&&>(__t));
263 ranges::swap(static_cast<_Up&&>(__u), static_cast<_Up&&>(__u));
264 ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
265 ranges::swap(static_cast<_Up&&>(__u), static_cast<_Tp&&>(__t));
266 };
267
268 // [concepts.object], Object concepts
269
270 template<typename _Tp>
271 concept movable = is_object_v<_Tp> && move_constructible<_Tp>
272 && assignable_from<_Tp&, _Tp> && swappable<_Tp>;
273
274 template<typename _Tp>
275 concept copyable = copy_constructible<_Tp> && movable<_Tp>
276 && assignable_from<_Tp&, _Tp&> && assignable_from<_Tp&, const _Tp&>
277 && assignable_from<_Tp&, const _Tp>;
278
279 template<typename _Tp>
280 concept semiregular = copyable<_Tp> && default_initializable<_Tp>;
281
282 // [concepts.compare], comparison concepts
283
284 // [concept.booleantestable], Boolean testability
285 namespace __detail
286 {
287 template<typename _Tp>
288 concept __boolean_testable_impl = convertible_to<_Tp, bool>;
289
290 template<typename _Tp>
291 concept __boolean_testable
292 = __boolean_testable_impl<_Tp>
293 && requires(_Tp&& __t)
294 { { !static_cast<_Tp&&>(__t) } -> __boolean_testable_impl; };
295 } // namespace __detail
296
297 // [concept.equalitycomparable], concept equality_comparable
298
299 namespace __detail
300 {
301 template<typename _Tp, typename _Up>
302 concept __weakly_eq_cmp_with
303 = requires(__detail::__cref<_Tp> __t, __detail::__cref<_Up> __u) {
304 { __t == __u } -> __boolean_testable;
305 { __t != __u } -> __boolean_testable;
306 { __u == __t } -> __boolean_testable;
307 { __u != __t } -> __boolean_testable;
308 };
309 } // namespace __detail
310
311 template<typename _Tp>
312 concept equality_comparable = __detail::__weakly_eq_cmp_with<_Tp, _Tp>;
313
314 template<typename _Tp, typename _Up>
315 concept equality_comparable_with
316 = equality_comparable<_Tp> && equality_comparable<_Up>
317 && common_reference_with<__detail::__cref<_Tp>, __detail::__cref<_Up>>
318 && equality_comparable<common_reference_t<__detail::__cref<_Tp>,
319 __detail::__cref<_Up>>>
320 && __detail::__weakly_eq_cmp_with<_Tp, _Up>;
321
322 namespace __detail
323 {
324 template<typename _Tp, typename _Up>
325 concept __partially_ordered_with
326 = requires(const remove_reference_t<_Tp>& __t,
327 const remove_reference_t<_Up>& __u) {
328 { __t < __u } -> __boolean_testable;
329 { __t > __u } -> __boolean_testable;
330 { __t <= __u } -> __boolean_testable;
331 { __t >= __u } -> __boolean_testable;
332 { __u < __t } -> __boolean_testable;
333 { __u > __t } -> __boolean_testable;
334 { __u <= __t } -> __boolean_testable;
335 { __u >= __t } -> __boolean_testable;
336 };
337 } // namespace __detail
338
339 // [concept.totallyordered], concept totally_ordered
340 template<typename _Tp>
341 concept totally_ordered
342 = equality_comparable<_Tp>
343 && __detail::__partially_ordered_with<_Tp, _Tp>;
344
345 template<typename _Tp, typename _Up>
346 concept totally_ordered_with
347 = totally_ordered<_Tp> && totally_ordered<_Up>
348 && equality_comparable_with<_Tp, _Up>
349 && totally_ordered<common_reference_t<__detail::__cref<_Tp>,
350 __detail::__cref<_Up>>>
351 && __detail::__partially_ordered_with<_Tp, _Up>;
352
353 template<typename _Tp>
354 concept regular = semiregular<_Tp> && equality_comparable<_Tp>;
355
356 // [concepts.callable], callable concepts
357
358 /// [concept.invocable], concept invocable
359 template<typename _Fn, typename... _Args>
360 concept invocable = is_invocable_v<_Fn, _Args...>;
361
362 /// [concept.regularinvocable], concept regular_invocable
363 template<typename _Fn, typename... _Args>
364 concept regular_invocable = invocable<_Fn, _Args...>;
365
366 /// [concept.predicate], concept predicate
367 template<typename _Fn, typename... _Args>
368 concept predicate = regular_invocable<_Fn, _Args...>
369 && __detail::__boolean_testable<invoke_result_t<_Fn, _Args...>>;
370
371 /// [concept.relation], concept relation
372 template<typename _Rel, typename _Tp, typename _Up>
373 concept relation
374 = predicate<_Rel, _Tp, _Tp> && predicate<_Rel, _Up, _Up>
375 && predicate<_Rel, _Tp, _Up> && predicate<_Rel, _Up, _Tp>;
376
377 /// [concept.equiv], concept equivalence_relation
378 template<typename _Rel, typename _Tp, typename _Up>
379 concept equivalence_relation = relation<_Rel, _Tp, _Up>;
380
381 /// [concept.strictweakorder], concept strict_weak_order
382 template<typename _Rel, typename _Tp, typename _Up>
383 concept strict_weak_order = relation<_Rel, _Tp, _Up>;
384
385_GLIBCXX_END_NAMESPACE_VERSION
386} // namespace
387#endif // __cpp_lib_concepts
388
389#endif /* _GLIBCXX_CONCEPTS */
390