1 // <concepts> -*- C++ -*-
3 // Copyright (C) 2019 Free Software Foundation, Inc.
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)
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.
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.
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/>.
25 /** @file include/concepts
26 * This is __a Standard C++ Library header.
30 #ifndef _GLIBCXX_CONCEPTS
31 #define _GLIBCXX_CONCEPTS 1
33 #if __cplusplus > 201703L && __cpp_concepts
35 #pragma GCC system_header
38 * @defgroup concepts Concepts
41 * Concepts for checking type requirements.
44 #include <type_traits>
46 namespace std _GLIBCXX_VISIBILITY(default)
48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
50 #define __cpp_lib_concepts 201806L
52 // [concepts.lang], language-related concepts
56 template<typename _Tp, typename _Up>
57 concept __same_as = __is_same_as(_Tp, _Up);
58 } // namespace __detail
60 /// [concept.same], concept same_as
61 template<typename _Tp, typename _Up>
63 = __detail::__same_as<_Tp, _Up> && __detail::__same_as<_Up, _Tp>;
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*>;
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());
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>>;
84 /// [concept.common], concept common_with
85 template<typename _Tp, typename _Up>
87 = same_as<common_type_t<_Tp, _Up>, common_type_t<_Up, _Tp>>
89 static_cast<common_type_t<_Tp, _Up>>(std::declval<_Tp>());
90 static_cast<common_type_t<_Tp, _Up>>(std::declval<_Up>());
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>>,
96 add_lvalue_reference_t<const _Tp>,
97 add_lvalue_reference_t<const _Up>>>;
99 // [concepts.arithmetic], arithmetic concepts
101 template<typename _Tp>
102 concept integral = is_integral_v<_Tp>;
104 template<typename _Tp>
105 concept signed_integral = integral<_Tp> && is_signed_v<_Tp>;
107 template<typename _Tp>
108 concept unsigned_integral = integral<_Tp> && !signed_integral<_Tp>;
110 template<typename _Tp>
111 concept floating_point = is_floating_point_v<_Tp>;
115 template<typename _Tp>
116 using __cref = const remove_reference_t<_Tp>&;
117 } // namespace __detail
119 /// [concept.assignable], concept assignable_from
120 template<typename _Lhs, typename _Rhs>
121 concept assignable_from
122 = is_lvalue_reference_v<_Lhs>
123 && common_reference_with<__detail::__cref<_Lhs>, __detail::__cref<_Rhs>>
124 && requires(_Lhs __lhs, _Rhs&& __rhs) {
125 { __lhs = static_cast<_Rhs&&>(__rhs) } -> same_as<_Lhs>;
128 /// [concept.destructible], concept destructible
129 template<typename _Tp>
130 concept destructible = is_nothrow_destructible_v<_Tp>;
132 /// [concept.constructible], concept constructible_from
133 template<typename _Tp, typename... _Args>
134 concept constructible_from
135 = destructible<_Tp> && is_constructible_v<_Tp, _Args...>;
137 /// [concept.defaultconstructible], concept default_constructible
138 template<typename _Tp>
139 concept default_constructible = constructible_from<_Tp>;
141 /// [concept.moveconstructible], concept move_constructible
142 template<typename _Tp>
143 concept move_constructible
144 = constructible_from<_Tp, _Tp> && convertible_to<_Tp, _Tp>;
146 /// [concept.copyconstructible], concept copy_constructible
147 template<typename _Tp>
148 concept copy_constructible
149 = move_constructible<_Tp>
150 && constructible_from<_Tp, _Tp&> && convertible_to<_Tp&, _Tp>
151 && constructible_from<_Tp, const _Tp&> && convertible_to<const _Tp&, _Tp>
152 && constructible_from<_Tp, const _Tp> && convertible_to<const _Tp, _Tp>;
154 // [concept.swappable], concept swappable
158 namespace __cust_swap
160 template<typename _Tp> void swap(_Tp&, _Tp&) = delete;
162 template<typename _Tp>
163 concept __class_or_enum
164 = is_class_v<_Tp> || is_union_v<_Tp> || is_enum_v<_Tp>;
166 template<typename _Tp, typename _Up>
168 = (__class_or_enum<remove_cvref_t<_Tp>>
169 || __class_or_enum<remove_cvref_t<_Up>>)
170 && requires(_Tp&& __t, _Up&& __u) {
171 swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
176 template<typename _Tp, typename _Up>
177 requires __adl_swap<_Tp, _Up>
178 constexpr void operator()(_Tp&& __t, _Up&& __u) const
179 noexcept(noexcept(swap(std::declval<_Tp>(), std::declval<_Up>())))
180 { swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u)); }
182 template<typename _Tp, typename _Up, size_t _Num>
183 requires requires(const _Swap& __swap, _Tp& __e1, _Up& __e2) {
187 operator()(_Tp (&__e1)[_Num], _Up (&__e2)[_Num]) const
188 noexcept(noexcept(std::declval<const _Swap&>()(*__e1, *__e2)))
190 for (size_t __n = 0; __n < _Num; ++__n)
191 (*this)(__e1[__n], __e2[__n]);
194 template<typename _Tp>
195 requires (!__adl_swap<_Tp&, _Tp&>
196 && move_constructible<_Tp> && assignable_from<_Tp&, _Tp>)
198 operator()(_Tp& __e1, _Tp& __e2) const
199 noexcept(is_nothrow_move_constructible_v<_Tp>
200 && is_nothrow_move_assignable_v<_Tp>)
202 _Tp __tmp = static_cast<_Tp&&>(__e1);
203 __e1 = static_cast<_Tp&&>(__e2);
204 __e2 = static_cast<_Tp&&>(__tmp);
207 } // namespace __cust_swap
209 inline namespace __cust
211 inline constexpr __cust_swap::_Swap swap{};
212 } // inline namespace __cust
213 } // namespace ranges
215 template<typename _Tp>
217 = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
219 template<typename _Tp, typename _Up>
220 concept swappable_with = common_reference_with<_Tp, _Up>
221 && requires(_Tp&& __t, _Up&& __u) {
222 ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Tp&&>(__t));
223 ranges::swap(static_cast<_Up&&>(__u), static_cast<_Up&&>(__u));
224 ranges::swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
225 ranges::swap(static_cast<_Up&&>(__u), static_cast<_Tp&&>(__t));
228 // [concepts.object], Object concepts
230 template<typename _Tp>
231 concept movable = is_object_v<_Tp> && move_constructible<_Tp>
232 && assignable_from<_Tp&, _Tp> && swappable<_Tp>;
234 template<typename _Tp>
235 concept copyable = copy_constructible<_Tp> && movable<_Tp>
236 && assignable_from<_Tp&, const _Tp&>;
238 template<typename _Tp>
239 concept semiregular = copyable<_Tp> && default_constructible<_Tp>;
241 // [concepts.compare], comparison concepts
243 /// [concept.boolean], concept boolean
244 template<typename _Bp>
246 = movable<remove_cvref_t<_Bp>>
247 && requires(__detail::__cref<_Bp> __b1, __detail::__cref<_Bp> __b2,
249 { __b1 } -> convertible_to<bool>;
250 { !__b1 } -> convertible_to<bool>;
251 { __b1 && __b2 } -> same_as<bool>;
252 { __b1 && __a } -> same_as<bool>;
253 { __a && __b2 } -> same_as<bool>;
254 { __b1 || __b2 } -> same_as<bool>;
255 { __b1 || __a } -> same_as<bool>;
256 { __a || __b2 } -> same_as<bool>;
257 { __b1 == __b2 } -> convertible_to<bool>;
258 { __b1 == __a } -> convertible_to<bool>;
259 { __a == __b2 } -> convertible_to<bool>;
260 { __b1 != __b2 } -> convertible_to<bool>;
261 { __b1 != __a } -> convertible_to<bool>;
262 { __a != __b2 } -> convertible_to<bool>;
265 // [concept.equalitycomparable], concept equality_comparable
269 template<typename _Tp, typename _Up>
270 concept __weakly_eq_cmp_with
271 = requires(__detail::__cref<_Tp> __t, __detail::__cref<_Up> __u) {
272 { __t == __u } -> boolean;
273 { __t != __u } -> boolean;
274 { __u == __t } -> boolean;
275 { __u != __t } -> boolean;
277 } // namespace __detail
279 template<typename _Tp>
280 concept equality_comparable = __detail::__weakly_eq_cmp_with<_Tp, _Tp>;
282 template<typename _Tp, typename _Up>
283 concept equality_comparable_with
284 = equality_comparable<_Tp> && equality_comparable<_Up>
285 && common_reference_with<__detail::__cref<_Tp>, __detail::__cref<_Up>>
286 && equality_comparable<common_reference_t<__detail::__cref<_Tp>,
287 __detail::__cref<_Up>>>
288 && __detail::__weakly_eq_cmp_with<_Tp, _Up>;
290 // [concept.totallyordered], concept totally_ordered
291 template<typename _Tp>
292 concept totally_ordered
293 = equality_comparable<_Tp>
294 && requires(__detail::__cref<_Tp> __a, __detail::__cref<_Tp> __b) {
295 { __a < __b } -> boolean;
296 { __a > __b } -> boolean;
297 { __a <= __b } -> boolean;
298 { __a >= __b } -> boolean;
301 template<typename _Tp, typename _Up>
302 concept totally_ordered_with
303 = totally_ordered<_Tp> && totally_ordered<_Up>
304 && common_reference_with<__detail::__cref<_Tp>, __detail::__cref<_Up>>
305 && totally_ordered<common_reference_t<__detail::__cref<_Tp>,
306 __detail::__cref<_Up>>>
307 && equality_comparable_with<_Tp, _Up>
308 && requires(__detail::__cref<_Tp> __t, __detail::__cref<_Up> __u) {
309 { __t < __u } -> boolean;
310 { __t > __u } -> boolean;
311 { __t <= __u } -> boolean;
312 { __t >= __u } -> boolean;
313 { __u < __t } -> boolean;
314 { __u > __t } -> boolean;
315 { __u <= __t } -> boolean;
316 { __u >= __t } -> boolean;
319 template<typename _Tp>
320 concept regular = semiregular<_Tp> && equality_comparable<_Tp>;
322 // [concepts.callable], callable concepts
324 // [concept.invocable], concept invocable
325 template<typename _Fn, typename... _Args>
326 concept invocable = is_invocable_v<_Fn, _Args...>;
328 // [concept.regularinvocable], concept regular_invocable
329 template<typename _Fn, typename... _Args>
330 concept regular_invocable = invocable<_Fn, _Args...>;
332 // [concept.predicate], concept predicate
333 template<typename _Fn, typename... _Args>
334 concept predicate = regular_invocable<_Fn, _Args...>
335 && boolean<invoke_result_t<_Fn, _Args...>>;
337 // [concept.relation], concept relation
338 template<typename _Rel, typename _Tp, typename _Up>
340 = predicate<_Rel, _Tp, _Tp> && predicate<_Rel, _Up, _Up>
341 && predicate<_Rel, _Tp, _Up> && predicate<_Rel, _Up, _Tp>;
343 // [concept.strictweakorder], concept strict_weak_order
344 template<typename _Rel, typename _Tp, typename _Up>
345 concept strict_weak_order = relation<_Rel, _Tp, _Up>;
347 _GLIBCXX_END_NAMESPACE_VERSION
351 #endif /* _GLIBCXX_CONCEPTS */