1 // Variable Templates For Type Traits -*- C++ -*-
3 // Copyright (C) 2014-2025 Free Software Foundation, Inc.
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25 /** @file experimental/type_traits
26 * This is a TS C++ Library header.
28 * This header defines variable templates for the C++14 type traits.
30 * Equivalent variable templates are defined in namespace `std` since C++17.
31 * @see variable_templates
38 // N3932 Variable Templates For Type Traits (Revision 1)
41 #ifndef _GLIBCXX_EXPERIMENTAL_TYPE_TRAITS
42 #define _GLIBCXX_EXPERIMENTAL_TYPE_TRAITS 1
44 #ifdef _GLIBCXX_SYSHDR
45 #pragma GCC system_header
48 #if __cplusplus >= 201402L
50 #include <type_traits>
51 #include <experimental/bits/lfts_config.h>
53 namespace std _GLIBCXX_VISIBILITY(default)
55 _GLIBCXX_BEGIN_NAMESPACE_VERSION
57 namespace experimental
59 inline namespace fundamentals_v1
61 /** @defgroup lfts_variable_templates Variable template for type traits
63 * @since Library Fundamentals TS v1. C++14.
64 * @see variable_templates
66 /** @ingroup lfts_variable_templates
69 #define __cpp_lib_experimental_type_trait_variable_templates 201402
71 // See C++14 20.10.4.1, primary type categories
72 template <typename _Tp>
73 constexpr bool is_void_v = is_void<_Tp>::value;
74 template <typename _Tp>
75 constexpr bool is_null_pointer_v = is_null_pointer<_Tp>::value;
76 template <typename _Tp>
77 constexpr bool is_integral_v = is_integral<_Tp>::value;
78 template <typename _Tp>
79 constexpr bool is_floating_point_v = is_floating_point<_Tp>::value;
80 template <typename _Tp>
81 constexpr bool is_array_v = is_array<_Tp>::value;
82 template <typename _Tp>
83 constexpr bool is_pointer_v = is_pointer<_Tp>::value;
84 template <typename _Tp>
85 constexpr bool is_lvalue_reference_v = is_lvalue_reference<_Tp>::value;
86 template <typename _Tp>
87 constexpr bool is_rvalue_reference_v = is_rvalue_reference<_Tp>::value;
88 template <typename _Tp>
89 constexpr bool is_member_object_pointer_v =
90 is_member_object_pointer<_Tp>::value;
91 template <typename _Tp>
92 constexpr bool is_member_function_pointer_v =
93 is_member_function_pointer<_Tp>::value;
94 template <typename _Tp>
95 constexpr bool is_enum_v = is_enum<_Tp>::value;
96 template <typename _Tp>
97 constexpr bool is_union_v = is_union<_Tp>::value;
98 template <typename _Tp>
99 constexpr bool is_class_v = is_class<_Tp>::value;
100 template <typename _Tp>
101 constexpr bool is_function_v = is_function<_Tp>::value;
103 // See C++14 20.10.4.2, composite type categories
104 template <typename _Tp>
105 constexpr bool is_reference_v = is_reference<_Tp>::value;
106 template <typename _Tp>
107 constexpr bool is_arithmetic_v = is_arithmetic<_Tp>::value;
108 template <typename _Tp>
109 constexpr bool is_fundamental_v = is_fundamental<_Tp>::value;
110 template <typename _Tp>
111 constexpr bool is_object_v = is_object<_Tp>::value;
112 template <typename _Tp>
113 constexpr bool is_scalar_v = is_scalar<_Tp>::value;
114 template <typename _Tp>
115 constexpr bool is_compound_v = is_compound<_Tp>::value;
116 template <typename _Tp>
117 constexpr bool is_member_pointer_v = is_member_pointer<_Tp>::value;
119 // See C++14 20.10.4.3, type properties
120 template <typename _Tp>
121 constexpr bool is_const_v = is_const<_Tp>::value;
122 template <typename _Tp>
123 constexpr bool is_volatile_v = is_volatile<_Tp>::value;
124 #pragma GCC diagnostic push
125 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
126 template <typename _Tp>
127 constexpr bool is_trivial_v = is_trivial<_Tp>::value;
128 #pragma GCC diagnostic pop
129 template <typename _Tp>
130 constexpr bool is_trivially_copyable_v = is_trivially_copyable<_Tp>::value;
131 template <typename _Tp>
132 constexpr bool is_standard_layout_v = is_standard_layout<_Tp>::value;
133 #pragma GCC diagnostic push
134 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
135 template <typename _Tp>
136 constexpr bool is_pod_v = is_pod<_Tp>::value;
137 template <typename _Tp>
138 constexpr bool is_literal_type_v = is_literal_type<_Tp>::value;
139 #pragma GCC diagnostic pop
140 template <typename _Tp>
141 constexpr bool is_empty_v = is_empty<_Tp>::value;
142 template <typename _Tp>
143 constexpr bool is_polymorphic_v = is_polymorphic<_Tp>::value;
144 template <typename _Tp>
145 constexpr bool is_abstract_v = is_abstract<_Tp>::value;
146 template <typename _Tp>
147 constexpr bool is_final_v = is_final<_Tp>::value;
148 template <typename _Tp>
149 constexpr bool is_signed_v = is_signed<_Tp>::value;
150 template <typename _Tp>
151 constexpr bool is_unsigned_v = is_unsigned<_Tp>::value;
152 template <typename _Tp, typename... _Args>
153 constexpr bool is_constructible_v = is_constructible<_Tp, _Args...>::value;
154 template <typename _Tp>
155 constexpr bool is_default_constructible_v =
156 is_default_constructible<_Tp>::value;
157 template <typename _Tp>
158 constexpr bool is_copy_constructible_v = is_copy_constructible<_Tp>::value;
159 template <typename _Tp>
160 constexpr bool is_move_constructible_v = is_move_constructible<_Tp>::value;
161 template <typename _Tp, typename _Up>
162 constexpr bool is_assignable_v = is_assignable<_Tp, _Up>::value;
163 template <typename _Tp>
164 constexpr bool is_copy_assignable_v = is_copy_assignable<_Tp>::value;
165 template <typename _Tp>
166 constexpr bool is_move_assignable_v = is_move_assignable<_Tp>::value;
167 template <typename _Tp>
168 constexpr bool is_destructible_v = is_destructible<_Tp>::value;
169 template <typename _Tp, typename... _Args>
170 constexpr bool is_trivially_constructible_v =
171 is_trivially_constructible<_Tp, _Args...>::value;
172 template <typename _Tp>
173 constexpr bool is_trivially_default_constructible_v =
174 is_trivially_default_constructible<_Tp>::value;
175 template <typename _Tp>
176 constexpr bool is_trivially_copy_constructible_v =
177 is_trivially_copy_constructible<_Tp>::value;
178 template <typename _Tp>
179 constexpr bool is_trivially_move_constructible_v =
180 is_trivially_move_constructible<_Tp>::value;
181 template <typename _Tp, typename _Up>
182 constexpr bool is_trivially_assignable_v =
183 is_trivially_assignable<_Tp, _Up>::value;
184 template <typename _Tp>
185 constexpr bool is_trivially_copy_assignable_v =
186 is_trivially_copy_assignable<_Tp>::value;
187 template <typename _Tp>
188 constexpr bool is_trivially_move_assignable_v =
189 is_trivially_move_assignable<_Tp>::value;
190 template <typename _Tp>
191 constexpr bool is_trivially_destructible_v =
192 is_trivially_destructible<_Tp>::value;
193 template <typename _Tp, typename... _Args>
194 constexpr bool is_nothrow_constructible_v =
195 is_nothrow_constructible<_Tp, _Args...>::value;
196 template <typename _Tp>
197 constexpr bool is_nothrow_default_constructible_v =
198 is_nothrow_default_constructible<_Tp>::value;
199 template <typename _Tp>
200 constexpr bool is_nothrow_copy_constructible_v =
201 is_nothrow_copy_constructible<_Tp>::value;
202 template <typename _Tp>
203 constexpr bool is_nothrow_move_constructible_v =
204 is_nothrow_move_constructible<_Tp>::value;
205 template <typename _Tp, typename _Up>
206 constexpr bool is_nothrow_assignable_v =
207 is_nothrow_assignable<_Tp, _Up>::value;
208 template <typename _Tp>
209 constexpr bool is_nothrow_copy_assignable_v =
210 is_nothrow_copy_assignable<_Tp>::value;
211 template <typename _Tp>
212 constexpr bool is_nothrow_move_assignable_v =
213 is_nothrow_move_assignable<_Tp>::value;
214 template <typename _Tp>
215 constexpr bool is_nothrow_destructible_v =
216 is_nothrow_destructible<_Tp>::value;
217 template <typename _Tp>
218 constexpr bool has_virtual_destructor_v =
219 has_virtual_destructor<_Tp>::value;
221 // See C++14 20.10.5, type property queries
222 template <typename _Tp>
223 constexpr size_t alignment_of_v = alignment_of<_Tp>::value;
224 template <typename _Tp>
225 constexpr size_t rank_v = rank<_Tp>::value;
226 template <typename _Tp, unsigned _Idx = 0>
227 constexpr size_t extent_v = extent<_Tp, _Idx>::value;
229 // See C++14 20.10.6, type relations
230 template <typename _Tp, typename _Up>
231 constexpr bool is_same_v = false;
232 template <typename _Tp>
233 constexpr bool is_same_v<_Tp, _Tp> = true;
234 template <typename _Base, typename _Derived>
235 constexpr bool is_base_of_v = is_base_of<_Base, _Derived>::value;
236 template <typename _From, typename _To>
237 constexpr bool is_convertible_v = is_convertible<_From, _To>::value;
240 // 3.3.2, Other type transformations
241 // invocation_type (still unimplemented)
242 // raw_invocation_type (still unimplemented)
243 // invocation_type_t (still unimplemented)
244 // raw_invocation_type_t (still unimplemented)
245 } // namespace fundamentals_v1
247 inline namespace fundamentals_v2
250 * @defgroup lfts_detect Detection idiom
251 * @ingroup libfund-ts
252 * @since Library Fundamentals TS v2. C++14.
254 /** @ingroup lfts_detect
257 #define __cpp_lib_experimental_detect 201505
261 /// A metafunction that always yields void, used for detecting valid types.
262 template<typename...> using void_t = void;
264 #pragma GCC diagnostic push
265 #pragma GCC diagnostic ignored "-Wctor-dtor-privacy"
267 struct __nonesuchbase {};
268 struct nonesuch : private __nonesuchbase
270 ~nonesuch() = delete;
271 nonesuch(nonesuch const&) = delete;
272 void operator=(nonesuch const&) = delete;
274 #pragma GCC diagnostic pop
276 template<typename _Default, template<typename...> class _Op, typename... _Args>
277 using detected_or = std::__detected_or<_Default, _Op, _Args...>;
279 template<typename _Default, template<typename...> class _Op, typename... _Args>
280 using detected_or_t = typename detected_or<_Default, _Op, _Args...>::type;
282 template<template<typename...> class _Op, typename... _Args>
283 using detected_t = detected_or_t<nonesuch, _Op, _Args...>;
285 template<template<typename...> class _Op, typename... _Args>
286 using is_detected = typename detected_or<void, _Op, _Args...>::__is_detected;
288 template<template<typename...> class _Op, typename... _Args>
289 constexpr bool is_detected_v = is_detected<_Op, _Args...>::value;
291 template<typename _Expected, template<typename...> class _Op, typename... _Args>
292 using is_detected_exact = is_same<_Expected, detected_t<_Op, _Args...>>;
294 template<typename _Expected, template<typename...> class _Op, typename... _Args>
295 constexpr bool is_detected_exact_v
296 = is_detected_exact<_Expected, _Op, _Args...>::value;
298 template<typename _To, template<typename...> class _Op, typename... _Args>
299 using is_detected_convertible
300 = is_convertible<detected_t<_Op, _Args...>, _To>;
302 template<typename _To, template<typename...> class _Op, typename... _Args>
303 constexpr bool is_detected_convertible_v
304 = is_detected_convertible<_To, _Op, _Args...>::value;
308 * @defgroup lfts_logical Logical operator traits
309 * @ingroup libfund-ts
310 * @since Library Fundamentals TS v2. C++14.
312 /** @ingroup lfts_logical
315 #define __cpp_lib_experimental_logical_traits 201511
317 template<typename... _Bn>
322 template<typename... _Bn>
327 template<typename _Pp>
332 template<typename... _Bn>
333 constexpr bool conjunction_v
334 = conjunction<_Bn...>::value;
336 template<typename... _Bn>
337 constexpr bool disjunction_v
338 = disjunction<_Bn...>::value;
340 template<typename _Pp>
341 constexpr bool negation_v
342 = negation<_Pp>::value;
344 } // namespace fundamentals_v2
345 } // namespace experimental
347 _GLIBCXX_END_NAMESPACE_VERSION
350 #endif // __cplusplus <= 201103L
352 #endif // _GLIBCXX_EXPERIMENTAL_TYPE_TRAITS