1// -*- C++ -*- 2//===----------------------------------------------------------------------===// 3// 4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5// See https://llvm.org/LICENSE.txt for license information. 6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7// 8//===----------------------------------------------------------------------===// 9 10#ifndef _LIBCPP_TYPE_TRAITS 11#define _LIBCPP_TYPE_TRAITS 12 13/* 14 type_traits synopsis 15 16namespace std 17{ 18 19 // helper class: 20 template <class T, T v> struct integral_constant; 21 typedef integral_constant<bool, true> true_type; // C++11 22 typedef integral_constant<bool, false> false_type; // C++11 23 24 template <bool B> // C++14 25 using bool_constant = integral_constant<bool, B>; // C++14 26 typedef bool_constant<true> true_type; // C++14 27 typedef bool_constant<false> false_type; // C++14 28 29 // helper traits 30 template <bool, class T = void> struct enable_if; 31 template <bool, class T, class F> struct conditional; 32 33 // Primary classification traits: 34 template <class T> struct is_void; 35 template <class T> struct is_null_pointer; // C++14 36 template <class T> struct is_integral; 37 template <class T> struct is_floating_point; 38 template <class T> struct is_array; 39 template <class T> struct is_pointer; 40 template <class T> struct is_lvalue_reference; 41 template <class T> struct is_rvalue_reference; 42 template <class T> struct is_member_object_pointer; 43 template <class T> struct is_member_function_pointer; 44 template <class T> struct is_enum; 45 template <class T> struct is_union; 46 template <class T> struct is_class; 47 template <class T> struct is_function; 48 49 // Secondary classification traits: 50 template <class T> struct is_reference; 51 template <class T> struct is_arithmetic; 52 template <class T> struct is_fundamental; 53 template <class T> struct is_member_pointer; 54 template <class T> struct is_scoped_enum; // C++2b 55 template <class T> struct is_scalar; 56 template <class T> struct is_object; 57 template <class T> struct is_compound; 58 59 // Const-volatile properties and transformations: 60 template <class T> struct is_const; 61 template <class T> struct is_volatile; 62 template <class T> struct remove_const; 63 template <class T> struct remove_volatile; 64 template <class T> struct remove_cv; 65 template <class T> struct add_const; 66 template <class T> struct add_volatile; 67 template <class T> struct add_cv; 68 69 // Reference transformations: 70 template <class T> struct remove_reference; 71 template <class T> struct add_lvalue_reference; 72 template <class T> struct add_rvalue_reference; 73 74 // Pointer transformations: 75 template <class T> struct remove_pointer; 76 template <class T> struct add_pointer; 77 78 template<class T> struct type_identity; // C++20 79 template<class T> 80 using type_identity_t = typename type_identity<T>::type; // C++20 81 82 // Integral properties: 83 template <class T> struct is_signed; 84 template <class T> struct is_unsigned; 85 template <class T> struct make_signed; 86 template <class T> struct make_unsigned; 87 88 // Array properties and transformations: 89 template <class T> struct rank; 90 template <class T, unsigned I = 0> struct extent; 91 template <class T> struct remove_extent; 92 template <class T> struct remove_all_extents; 93 94 template <class T> struct is_bounded_array; // C++20 95 template <class T> struct is_unbounded_array; // C++20 96 97 // Member introspection: 98 template <class T> struct is_pod; 99 template <class T> struct is_trivial; 100 template <class T> struct is_trivially_copyable; 101 template <class T> struct is_standard_layout; 102 template <class T> struct is_literal_type; // Deprecated in C++17; removed in C++20 103 template <class T> struct is_empty; 104 template <class T> struct is_polymorphic; 105 template <class T> struct is_abstract; 106 template <class T> struct is_final; // C++14 107 template <class T> struct is_aggregate; // C++17 108 109 template <class T, class... Args> struct is_constructible; 110 template <class T> struct is_default_constructible; 111 template <class T> struct is_copy_constructible; 112 template <class T> struct is_move_constructible; 113 template <class T, class U> struct is_assignable; 114 template <class T> struct is_copy_assignable; 115 template <class T> struct is_move_assignable; 116 template <class T, class U> struct is_swappable_with; // C++17 117 template <class T> struct is_swappable; // C++17 118 template <class T> struct is_destructible; 119 120 template <class T, class... Args> struct is_trivially_constructible; 121 template <class T> struct is_trivially_default_constructible; 122 template <class T> struct is_trivially_copy_constructible; 123 template <class T> struct is_trivially_move_constructible; 124 template <class T, class U> struct is_trivially_assignable; 125 template <class T> struct is_trivially_copy_assignable; 126 template <class T> struct is_trivially_move_assignable; 127 template <class T> struct is_trivially_destructible; 128 129 template <class T, class... Args> struct is_nothrow_constructible; 130 template <class T> struct is_nothrow_default_constructible; 131 template <class T> struct is_nothrow_copy_constructible; 132 template <class T> struct is_nothrow_move_constructible; 133 template <class T, class U> struct is_nothrow_assignable; 134 template <class T> struct is_nothrow_copy_assignable; 135 template <class T> struct is_nothrow_move_assignable; 136 template <class T, class U> struct is_nothrow_swappable_with; // C++17 137 template <class T> struct is_nothrow_swappable; // C++17 138 template <class T> struct is_nothrow_destructible; 139 140 template <class T> struct has_virtual_destructor; 141 142 template<class T> struct has_unique_object_representations; // C++17 143 144 // Relationships between types: 145 template <class T, class U> struct is_same; 146 template <class Base, class Derived> struct is_base_of; 147 148 template <class From, class To> struct is_convertible; 149 template <typename From, typename To> struct is_nothrow_convertible; // C++20 150 template <typename From, typename To> inline constexpr bool is_nothrow_convertible_v; // C++20 151 152 template <class Fn, class... ArgTypes> struct is_invocable; 153 template <class R, class Fn, class... ArgTypes> struct is_invocable_r; 154 155 template <class Fn, class... ArgTypes> struct is_nothrow_invocable; 156 template <class R, class Fn, class... ArgTypes> struct is_nothrow_invocable_r; 157 158 // Alignment properties and transformations: 159 template <class T> struct alignment_of; 160 template <size_t Len, size_t Align = most_stringent_alignment_requirement> 161 struct aligned_storage; 162 template <size_t Len, class... Types> struct aligned_union; 163 template <class T> struct remove_cvref; // C++20 164 165 template <class T> struct decay; 166 template <class... T> struct common_type; 167 template <class T> struct underlying_type; 168 template <class> class result_of; // undefined; deprecated in C++17; removed in C++20 169 template <class Fn, class... ArgTypes> class result_of<Fn(ArgTypes...)>; // deprecated in C++17; removed in C++20 170 template <class Fn, class... ArgTypes> struct invoke_result; // C++17 171 172 // const-volatile modifications: 173 template <class T> 174 using remove_const_t = typename remove_const<T>::type; // C++14 175 template <class T> 176 using remove_volatile_t = typename remove_volatile<T>::type; // C++14 177 template <class T> 178 using remove_cv_t = typename remove_cv<T>::type; // C++14 179 template <class T> 180 using add_const_t = typename add_const<T>::type; // C++14 181 template <class T> 182 using add_volatile_t = typename add_volatile<T>::type; // C++14 183 template <class T> 184 using add_cv_t = typename add_cv<T>::type; // C++14 185 186 // reference modifications: 187 template <class T> 188 using remove_reference_t = typename remove_reference<T>::type; // C++14 189 template <class T> 190 using add_lvalue_reference_t = typename add_lvalue_reference<T>::type; // C++14 191 template <class T> 192 using add_rvalue_reference_t = typename add_rvalue_reference<T>::type; // C++14 193 194 // sign modifications: 195 template <class T> 196 using make_signed_t = typename make_signed<T>::type; // C++14 197 template <class T> 198 using make_unsigned_t = typename make_unsigned<T>::type; // C++14 199 200 // array modifications: 201 template <class T> 202 using remove_extent_t = typename remove_extent<T>::type; // C++14 203 template <class T> 204 using remove_all_extents_t = typename remove_all_extents<T>::type; // C++14 205 206 template <class T> 207 inline constexpr bool is_bounded_array_v 208 = is_bounded_array<T>::value; // C++20 209 inline constexpr bool is_unbounded_array_v 210 = is_unbounded_array<T>::value; // C++20 211 212 // pointer modifications: 213 template <class T> 214 using remove_pointer_t = typename remove_pointer<T>::type; // C++14 215 template <class T> 216 using add_pointer_t = typename add_pointer<T>::type; // C++14 217 218 // other transformations: 219 template <size_t Len, size_t Align=default-alignment> 220 using aligned_storage_t = typename aligned_storage<Len,Align>::type; // C++14 221 template <size_t Len, class... Types> 222 using aligned_union_t = typename aligned_union<Len,Types...>::type; // C++14 223 template <class T> 224 using remove_cvref_t = typename remove_cvref<T>::type; // C++20 225 template <class T> 226 using decay_t = typename decay<T>::type; // C++14 227 template <bool b, class T=void> 228 using enable_if_t = typename enable_if<b,T>::type; // C++14 229 template <bool b, class T, class F> 230 using conditional_t = typename conditional<b,T,F>::type; // C++14 231 template <class... T> 232 using common_type_t = typename common_type<T...>::type; // C++14 233 template <class T> 234 using underlying_type_t = typename underlying_type<T>::type; // C++14 235 template <class T> 236 using result_of_t = typename result_of<T>::type; // C++14; deprecated in C++17; removed in C++20 237 template <class Fn, class... ArgTypes> 238 using invoke_result_t = typename invoke_result<Fn, ArgTypes...>::type; // C++17 239 240 template <class...> 241 using void_t = void; // C++17 242 243 // See C++14 20.10.4.1, primary type categories 244 template <class T> inline constexpr bool is_void_v 245 = is_void<T>::value; // C++17 246 template <class T> inline constexpr bool is_null_pointer_v 247 = is_null_pointer<T>::value; // C++17 248 template <class T> inline constexpr bool is_integral_v 249 = is_integral<T>::value; // C++17 250 template <class T> inline constexpr bool is_floating_point_v 251 = is_floating_point<T>::value; // C++17 252 template <class T> inline constexpr bool is_array_v 253 = is_array<T>::value; // C++17 254 template <class T> inline constexpr bool is_pointer_v 255 = is_pointer<T>::value; // C++17 256 template <class T> inline constexpr bool is_lvalue_reference_v 257 = is_lvalue_reference<T>::value; // C++17 258 template <class T> inline constexpr bool is_rvalue_reference_v 259 = is_rvalue_reference<T>::value; // C++17 260 template <class T> inline constexpr bool is_member_object_pointer_v 261 = is_member_object_pointer<T>::value; // C++17 262 template <class T> inline constexpr bool is_member_function_pointer_v 263 = is_member_function_pointer<T>::value; // C++17 264 template <class T> inline constexpr bool is_enum_v 265 = is_enum<T>::value; // C++17 266 template <class T> inline constexpr bool is_union_v 267 = is_union<T>::value; // C++17 268 template <class T> inline constexpr bool is_class_v 269 = is_class<T>::value; // C++17 270 template <class T> inline constexpr bool is_function_v 271 = is_function<T>::value; // C++17 272 273 // See C++14 20.10.4.2, composite type categories 274 template <class T> inline constexpr bool is_reference_v 275 = is_reference<T>::value; // C++17 276 template <class T> inline constexpr bool is_arithmetic_v 277 = is_arithmetic<T>::value; // C++17 278 template <class T> inline constexpr bool is_fundamental_v 279 = is_fundamental<T>::value; // C++17 280 template <class T> inline constexpr bool is_object_v 281 = is_object<T>::value; // C++17 282 template <class T> inline constexpr bool is_scalar_v 283 = is_scalar<T>::value; // C++17 284 template <class T> inline constexpr bool is_compound_v 285 = is_compound<T>::value; // C++17 286 template <class T> inline constexpr bool is_member_pointer_v 287 = is_member_pointer<T>::value; // C++17 288 template <class T> inline constexpr bool is_scoped_enum_v 289 = is_scoped_enum<T>::value; // C++2b 290 291 // See C++14 20.10.4.3, type properties 292 template <class T> inline constexpr bool is_const_v 293 = is_const<T>::value; // C++17 294 template <class T> inline constexpr bool is_volatile_v 295 = is_volatile<T>::value; // C++17 296 template <class T> inline constexpr bool is_trivial_v 297 = is_trivial<T>::value; // C++17 298 template <class T> inline constexpr bool is_trivially_copyable_v 299 = is_trivially_copyable<T>::value; // C++17 300 template <class T> inline constexpr bool is_standard_layout_v 301 = is_standard_layout<T>::value; // C++17 302 template <class T> inline constexpr bool is_pod_v 303 = is_pod<T>::value; // C++17 304 template <class T> inline constexpr bool is_literal_type_v 305 = is_literal_type<T>::value; // C++17; deprecated in C++17; removed in C++20 306 template <class T> inline constexpr bool is_empty_v 307 = is_empty<T>::value; // C++17 308 template <class T> inline constexpr bool is_polymorphic_v 309 = is_polymorphic<T>::value; // C++17 310 template <class T> inline constexpr bool is_abstract_v 311 = is_abstract<T>::value; // C++17 312 template <class T> inline constexpr bool is_final_v 313 = is_final<T>::value; // C++17 314 template <class T> inline constexpr bool is_aggregate_v 315 = is_aggregate<T>::value; // C++17 316 template <class T> inline constexpr bool is_signed_v 317 = is_signed<T>::value; // C++17 318 template <class T> inline constexpr bool is_unsigned_v 319 = is_unsigned<T>::value; // C++17 320 template <class T, class... Args> inline constexpr bool is_constructible_v 321 = is_constructible<T, Args...>::value; // C++17 322 template <class T> inline constexpr bool is_default_constructible_v 323 = is_default_constructible<T>::value; // C++17 324 template <class T> inline constexpr bool is_copy_constructible_v 325 = is_copy_constructible<T>::value; // C++17 326 template <class T> inline constexpr bool is_move_constructible_v 327 = is_move_constructible<T>::value; // C++17 328 template <class T, class U> inline constexpr bool is_assignable_v 329 = is_assignable<T, U>::value; // C++17 330 template <class T> inline constexpr bool is_copy_assignable_v 331 = is_copy_assignable<T>::value; // C++17 332 template <class T> inline constexpr bool is_move_assignable_v 333 = is_move_assignable<T>::value; // C++17 334 template <class T, class U> inline constexpr bool is_swappable_with_v 335 = is_swappable_with<T, U>::value; // C++17 336 template <class T> inline constexpr bool is_swappable_v 337 = is_swappable<T>::value; // C++17 338 template <class T> inline constexpr bool is_destructible_v 339 = is_destructible<T>::value; // C++17 340 template <class T, class... Args> inline constexpr bool is_trivially_constructible_v 341 = is_trivially_constructible<T, Args...>::value; // C++17 342 template <class T> inline constexpr bool is_trivially_default_constructible_v 343 = is_trivially_default_constructible<T>::value; // C++17 344 template <class T> inline constexpr bool is_trivially_copy_constructible_v 345 = is_trivially_copy_constructible<T>::value; // C++17 346 template <class T> inline constexpr bool is_trivially_move_constructible_v 347 = is_trivially_move_constructible<T>::value; // C++17 348 template <class T, class U> inline constexpr bool is_trivially_assignable_v 349 = is_trivially_assignable<T, U>::value; // C++17 350 template <class T> inline constexpr bool is_trivially_copy_assignable_v 351 = is_trivially_copy_assignable<T>::value; // C++17 352 template <class T> inline constexpr bool is_trivially_move_assignable_v 353 = is_trivially_move_assignable<T>::value; // C++17 354 template <class T> inline constexpr bool is_trivially_destructible_v 355 = is_trivially_destructible<T>::value; // C++17 356 template <class T, class... Args> inline constexpr bool is_nothrow_constructible_v 357 = is_nothrow_constructible<T, Args...>::value; // C++17 358 template <class T> inline constexpr bool is_nothrow_default_constructible_v 359 = is_nothrow_default_constructible<T>::value; // C++17 360 template <class T> inline constexpr bool is_nothrow_copy_constructible_v 361 = is_nothrow_copy_constructible<T>::value; // C++17 362 template <class T> inline constexpr bool is_nothrow_move_constructible_v 363 = is_nothrow_move_constructible<T>::value; // C++17 364 template <class T, class U> inline constexpr bool is_nothrow_assignable_v 365 = is_nothrow_assignable<T, U>::value; // C++17 366 template <class T> inline constexpr bool is_nothrow_copy_assignable_v 367 = is_nothrow_copy_assignable<T>::value; // C++17 368 template <class T> inline constexpr bool is_nothrow_move_assignable_v 369 = is_nothrow_move_assignable<T>::value; // C++17 370 template <class T, class U> inline constexpr bool is_nothrow_swappable_with_v 371 = is_nothrow_swappable_with<T, U>::value; // C++17 372 template <class T> inline constexpr bool is_nothrow_swappable_v 373 = is_nothrow_swappable<T>::value; // C++17 374 template <class T> inline constexpr bool is_nothrow_destructible_v 375 = is_nothrow_destructible<T>::value; // C++17 376 template <class T> inline constexpr bool has_virtual_destructor_v 377 = has_virtual_destructor<T>::value; // C++17 378 template<class T> inline constexpr bool has_unique_object_representations_v // C++17 379 = has_unique_object_representations<T>::value; 380 381 // See C++14 20.10.5, type property queries 382 template <class T> inline constexpr size_t alignment_of_v 383 = alignment_of<T>::value; // C++17 384 template <class T> inline constexpr size_t rank_v 385 = rank<T>::value; // C++17 386 template <class T, unsigned I = 0> inline constexpr size_t extent_v 387 = extent<T, I>::value; // C++17 388 389 // See C++14 20.10.6, type relations 390 template <class T, class U> inline constexpr bool is_same_v 391 = is_same<T, U>::value; // C++17 392 template <class Base, class Derived> inline constexpr bool is_base_of_v 393 = is_base_of<Base, Derived>::value; // C++17 394 template <class From, class To> inline constexpr bool is_convertible_v 395 = is_convertible<From, To>::value; // C++17 396 template <class Fn, class... ArgTypes> inline constexpr bool is_invocable_v 397 = is_invocable<Fn, ArgTypes...>::value; // C++17 398 template <class R, class Fn, class... ArgTypes> inline constexpr bool is_invocable_r_v 399 = is_invocable_r<R, Fn, ArgTypes...>::value; // C++17 400 template <class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_v 401 = is_nothrow_invocable<Fn, ArgTypes...>::value; // C++17 402 template <class R, class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_r_v 403 = is_nothrow_invocable_r<R, Fn, ArgTypes...>::value; // C++17 404 405 // [meta.logical], logical operator traits: 406 template<class... B> struct conjunction; // C++17 407 template<class... B> 408 inline constexpr bool conjunction_v = conjunction<B...>::value; // C++17 409 template<class... B> struct disjunction; // C++17 410 template<class... B> 411 inline constexpr bool disjunction_v = disjunction<B...>::value; // C++17 412 template<class B> struct negation; // C++17 413 template<class B> 414 inline constexpr bool negation_v = negation<B>::value; // C++17 415 416} 417 418*/ 419#include <__assert> // all public C++ headers provide the assertion handler 420#include <__config> 421#include <__functional/invoke.h> 422#include <__type_traits/add_const.h> 423#include <__type_traits/add_cv.h> 424#include <__type_traits/add_lvalue_reference.h> 425#include <__type_traits/add_pointer.h> 426#include <__type_traits/add_rvalue_reference.h> 427#include <__type_traits/add_volatile.h> 428#include <__type_traits/alignment_of.h> 429#include <__type_traits/apply_cv.h> 430#include <__type_traits/conditional.h> 431#include <__type_traits/conjunction.h> 432#include <__type_traits/decay.h> 433#include <__type_traits/disjunction.h> 434#include <__type_traits/enable_if.h> 435#include <__type_traits/extent.h> 436#include <__type_traits/has_unique_object_representation.h> 437#include <__type_traits/has_virtual_destructor.h> 438#include <__type_traits/integral_constant.h> 439#include <__type_traits/is_abstract.h> 440#include <__type_traits/is_aggregate.h> 441#include <__type_traits/is_arithmetic.h> 442#include <__type_traits/is_array.h> 443#include <__type_traits/is_assignable.h> 444#include <__type_traits/is_base_of.h> 445#include <__type_traits/is_bounded_array.h> 446#include <__type_traits/is_callable.h> 447#include <__type_traits/is_class.h> 448#include <__type_traits/is_compound.h> 449#include <__type_traits/is_const.h> 450#include <__type_traits/is_constant_evaluated.h> 451#include <__type_traits/is_constructible.h> 452#include <__type_traits/is_convertible.h> 453#include <__type_traits/is_copy_assignable.h> 454#include <__type_traits/is_copy_constructible.h> 455#include <__type_traits/is_default_constructible.h> 456#include <__type_traits/is_destructible.h> 457#include <__type_traits/is_empty.h> 458#include <__type_traits/is_enum.h> 459#include <__type_traits/is_final.h> 460#include <__type_traits/is_floating_point.h> 461#include <__type_traits/is_function.h> 462#include <__type_traits/is_fundamental.h> 463#include <__type_traits/is_integral.h> 464#include <__type_traits/is_literal_type.h> 465#include <__type_traits/is_member_function_pointer.h> 466#include <__type_traits/is_member_object_pointer.h> 467#include <__type_traits/is_member_pointer.h> 468#include <__type_traits/is_move_assignable.h> 469#include <__type_traits/is_move_constructible.h> 470#include <__type_traits/is_nothrow_assignable.h> 471#include <__type_traits/is_nothrow_constructible.h> 472#include <__type_traits/is_nothrow_copy_assignable.h> 473#include <__type_traits/is_nothrow_copy_constructible.h> 474#include <__type_traits/is_nothrow_default_constructible.h> 475#include <__type_traits/is_nothrow_destructible.h> 476#include <__type_traits/is_nothrow_move_assignable.h> 477#include <__type_traits/is_nothrow_move_constructible.h> 478#include <__type_traits/is_null_pointer.h> 479#include <__type_traits/is_object.h> 480#include <__type_traits/is_pod.h> 481#include <__type_traits/is_pointer.h> 482#include <__type_traits/is_polymorphic.h> 483#include <__type_traits/is_reference.h> 484#include <__type_traits/is_reference_wrapper.h> 485#include <__type_traits/is_referenceable.h> 486#include <__type_traits/is_same.h> 487#include <__type_traits/is_scalar.h> 488#include <__type_traits/is_scoped_enum.h> 489#include <__type_traits/is_signed.h> 490#include <__type_traits/is_standard_layout.h> 491#include <__type_traits/is_trivial.h> 492#include <__type_traits/is_trivially_assignable.h> 493#include <__type_traits/is_trivially_constructible.h> 494#include <__type_traits/is_trivially_copy_assignable.h> 495#include <__type_traits/is_trivially_copy_constructible.h> 496#include <__type_traits/is_trivially_copyable.h> 497#include <__type_traits/is_trivially_default_constructible.h> 498#include <__type_traits/is_trivially_destructible.h> 499#include <__type_traits/is_trivially_move_assignable.h> 500#include <__type_traits/is_trivially_move_constructible.h> 501#include <__type_traits/is_unbounded_array.h> 502#include <__type_traits/is_union.h> 503#include <__type_traits/is_unsigned.h> 504#include <__type_traits/is_void.h> 505#include <__type_traits/is_volatile.h> 506#include <__type_traits/negation.h> 507#include <__type_traits/rank.h> 508#include <__type_traits/remove_all_extents.h> 509#include <__type_traits/remove_const.h> 510#include <__type_traits/remove_cv.h> 511#include <__type_traits/remove_extent.h> 512#include <__type_traits/remove_pointer.h> 513#include <__type_traits/remove_reference.h> 514#include <__type_traits/remove_volatile.h> 515#include <__type_traits/type_identity.h> 516#include <__type_traits/underlying_type.h> 517#include <__type_traits/void_t.h> 518#include <__utility/declval.h> 519#include <cstddef> 520#include <cstdint> 521#include <version> 522 523#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 524# pragma GCC system_header 525#endif 526 527_LIBCPP_BEGIN_NAMESPACE_STD 528 529template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS pair; 530template <class _Tp> struct _LIBCPP_TEMPLATE_VIS hash; 531 532template <bool> struct _MetaBase; 533template <> 534struct _MetaBase<true> { 535 template <class _Tp, class _Up> 536 using _SelectImpl _LIBCPP_NODEBUG = _Tp; 537 template <template <class...> class _FirstFn, template <class...> class, class ..._Args> 538 using _SelectApplyImpl _LIBCPP_NODEBUG = _FirstFn<_Args...>; 539 template <class _Result, class _First, class ..._Rest> 540 using _OrImpl _LIBCPP_NODEBUG = typename _MetaBase<_First::value != true && sizeof...(_Rest) != 0>::template _OrImpl<_First, _Rest...>; 541}; 542 543template <> 544struct _MetaBase<false> { 545 template <class _Tp, class _Up> 546 using _SelectImpl _LIBCPP_NODEBUG = _Up; 547 template <template <class...> class, template <class...> class _SecondFn, class ..._Args> 548 using _SelectApplyImpl _LIBCPP_NODEBUG = _SecondFn<_Args...>; 549 template <class _Result, class ...> 550 using _OrImpl _LIBCPP_NODEBUG = _Result; 551}; 552template <bool _Cond, class _IfRes, class _ElseRes> 553using _If _LIBCPP_NODEBUG = typename _MetaBase<_Cond>::template _SelectImpl<_IfRes, _ElseRes>; 554template <class ..._Rest> 555using _Or _LIBCPP_NODEBUG = typename _MetaBase< sizeof...(_Rest) != 0 >::template _OrImpl<false_type, _Rest...>; 556 557template <class ...> using __expand_to_true = true_type; 558template <class ..._Pred> 559__expand_to_true<__enable_if_t<_Pred::value>...> __and_helper(int); 560template <class ...> 561false_type __and_helper(...); 562template <class ..._Pred> 563using _And _LIBCPP_NODEBUG = decltype(__and_helper<_Pred...>(0)); 564 565template <template <class...> class _Func, class ..._Args> 566struct _Lazy : _Func<_Args...> {}; 567 568// Member detector base 569 570template <template <class...> class _Templ, class ..._Args, class = _Templ<_Args...> > 571true_type __sfinae_test_impl(int); 572template <template <class...> class, class ...> 573false_type __sfinae_test_impl(...); 574 575template <template <class ...> class _Templ, class ..._Args> 576using _IsValidExpansion _LIBCPP_NODEBUG = decltype(__sfinae_test_impl<_Templ, _Args...>(0)); 577 578template <class _Tp, bool> 579struct _LIBCPP_TEMPLATE_VIS __dependent_type : public _Tp {}; 580 581// is_same 582 583template <class _Tp> 584using __test_for_primary_template = __enable_if_t< 585 _IsSame<_Tp, typename _Tp::__primary_template>::value 586 >; 587template <class _Tp> 588using __is_primary_template = _IsValidExpansion< 589 __test_for_primary_template, _Tp 590 >; 591 592// is_integral 593 594// [basic.fundamental] defines five standard signed integer types; 595// __int128_t is an extended signed integer type. 596// The signed and unsigned integer types, plus bool and the 597// five types with "char" in their name, compose the "integral" types. 598 599template <class _Tp> struct __libcpp_is_signed_integer : public false_type {}; 600template <> struct __libcpp_is_signed_integer<signed char> : public true_type {}; 601template <> struct __libcpp_is_signed_integer<signed short> : public true_type {}; 602template <> struct __libcpp_is_signed_integer<signed int> : public true_type {}; 603template <> struct __libcpp_is_signed_integer<signed long> : public true_type {}; 604template <> struct __libcpp_is_signed_integer<signed long long> : public true_type {}; 605#ifndef _LIBCPP_HAS_NO_INT128 606template <> struct __libcpp_is_signed_integer<__int128_t> : public true_type {}; 607#endif 608 609template <class _Tp> struct __libcpp_is_unsigned_integer : public false_type {}; 610template <> struct __libcpp_is_unsigned_integer<unsigned char> : public true_type {}; 611template <> struct __libcpp_is_unsigned_integer<unsigned short> : public true_type {}; 612template <> struct __libcpp_is_unsigned_integer<unsigned int> : public true_type {}; 613template <> struct __libcpp_is_unsigned_integer<unsigned long> : public true_type {}; 614template <> struct __libcpp_is_unsigned_integer<unsigned long long> : public true_type {}; 615#ifndef _LIBCPP_HAS_NO_INT128 616template <> struct __libcpp_is_unsigned_integer<__uint128_t> : public true_type {}; 617#endif 618 619template <class _Tp> 620struct __unconstref { 621 typedef _LIBCPP_NODEBUG typename remove_const<typename remove_reference<_Tp>::type>::type type; 622}; 623 624template <class _Tp> 625using __uncvref_t _LIBCPP_NODEBUG = typename remove_cv<typename remove_reference<_Tp>::type>::type; 626 627// __is_same_uncvref 628 629template <class _Tp, class _Up> 630struct __is_same_uncvref : _IsSame<__uncvref_t<_Tp>, __uncvref_t<_Up> > {}; 631 632#if _LIBCPP_STD_VER > 17 633// remove_cvref - same as __uncvref 634template <class _Tp> 635struct remove_cvref { 636 using type _LIBCPP_NODEBUG = __uncvref_t<_Tp>; 637}; 638 639template <class _Tp> using remove_cvref_t = typename remove_cvref<_Tp>::type; 640#endif 641 642// is_nothrow_convertible 643 644#if _LIBCPP_STD_VER > 17 645 646template <typename _Tp> 647static void __test_noexcept(_Tp) noexcept; 648 649template<typename _Fm, typename _To> 650static bool_constant<noexcept(_VSTD::__test_noexcept<_To>(declval<_Fm>()))> 651__is_nothrow_convertible_test(); 652 653template <typename _Fm, typename _To> 654struct __is_nothrow_convertible_helper: decltype(__is_nothrow_convertible_test<_Fm, _To>()) 655{ }; 656 657template <typename _Fm, typename _To> 658struct is_nothrow_convertible : _Or< 659 _And<is_void<_To>, is_void<_Fm>>, 660 _Lazy<_And, is_convertible<_Fm, _To>, __is_nothrow_convertible_helper<_Fm, _To>> 661>::type { }; 662 663template <typename _Fm, typename _To> 664inline constexpr bool is_nothrow_convertible_v = is_nothrow_convertible<_Fm, _To>::value; 665 666#endif // _LIBCPP_STD_VER > 17 667 668// aligned_storage 669 670template <class _Hp, class _Tp> 671struct __type_list 672{ 673 typedef _Hp _Head; 674 typedef _Tp _Tail; 675}; 676 677template <class _Tp> 678struct __align_type 679{ 680 static const size_t value = _LIBCPP_PREFERRED_ALIGNOF(_Tp); 681 typedef _Tp type; 682}; 683 684struct __struct_double {long double __lx;}; 685struct __struct_double4 {double __lx[4];}; 686 687typedef 688 __type_list<__align_type<unsigned char>, 689 __type_list<__align_type<unsigned short>, 690 __type_list<__align_type<unsigned int>, 691 __type_list<__align_type<unsigned long>, 692 __type_list<__align_type<unsigned long long>, 693 __type_list<__align_type<double>, 694 __type_list<__align_type<long double>, 695 __type_list<__align_type<__struct_double>, 696 __type_list<__align_type<__struct_double4>, 697 __type_list<__align_type<int*>, 698 __nat 699 > > > > > > > > > > __all_types; 700 701template <size_t _Align> 702struct _ALIGNAS(_Align) __fallback_overaligned {}; 703 704template <class _TL, size_t _Align> struct __find_pod; 705 706template <class _Hp, size_t _Align> 707struct __find_pod<__type_list<_Hp, __nat>, _Align> 708{ 709 typedef typename conditional< 710 _Align == _Hp::value, 711 typename _Hp::type, 712 __fallback_overaligned<_Align> 713 >::type type; 714}; 715 716template <class _Hp, class _Tp, size_t _Align> 717struct __find_pod<__type_list<_Hp, _Tp>, _Align> 718{ 719 typedef typename conditional< 720 _Align == _Hp::value, 721 typename _Hp::type, 722 typename __find_pod<_Tp, _Align>::type 723 >::type type; 724}; 725 726template <class _TL, size_t _Len> struct __find_max_align; 727 728template <class _Hp, size_t _Len> 729struct __find_max_align<__type_list<_Hp, __nat>, _Len> : public integral_constant<size_t, _Hp::value> {}; 730 731template <size_t _Len, size_t _A1, size_t _A2> 732struct __select_align 733{ 734private: 735 static const size_t __min = _A2 < _A1 ? _A2 : _A1; 736 static const size_t __max = _A1 < _A2 ? _A2 : _A1; 737public: 738 static const size_t value = _Len < __max ? __min : __max; 739}; 740 741template <class _Hp, class _Tp, size_t _Len> 742struct __find_max_align<__type_list<_Hp, _Tp>, _Len> 743 : public integral_constant<size_t, __select_align<_Len, _Hp::value, __find_max_align<_Tp, _Len>::value>::value> {}; 744 745template <size_t _Len, size_t _Align = __find_max_align<__all_types, _Len>::value> 746struct _LIBCPP_TEMPLATE_VIS aligned_storage 747{ 748 typedef typename __find_pod<__all_types, _Align>::type _Aligner; 749 union type 750 { 751 _Aligner __align; 752 unsigned char __data[(_Len + _Align - 1)/_Align * _Align]; 753 }; 754}; 755 756#if _LIBCPP_STD_VER > 11 757template <size_t _Len, size_t _Align = __find_max_align<__all_types, _Len>::value> 758 using aligned_storage_t = typename aligned_storage<_Len, _Align>::type; 759#endif 760 761#define _CREATE_ALIGNED_STORAGE_SPECIALIZATION(n) \ 762template <size_t _Len>\ 763struct _LIBCPP_TEMPLATE_VIS aligned_storage<_Len, n>\ 764{\ 765 struct _ALIGNAS(n) type\ 766 {\ 767 unsigned char __lx[(_Len + n - 1)/n * n];\ 768 };\ 769} 770 771_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1); 772_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2); 773_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4); 774_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x8); 775_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x10); 776_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x20); 777_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x40); 778_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x80); 779_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x100); 780_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x200); 781_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x400); 782_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x800); 783_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1000); 784_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2000); 785// PE/COFF does not support alignment beyond 8192 (=0x2000) 786#if !defined(_LIBCPP_OBJECT_FORMAT_COFF) 787_CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4000); 788#endif // !defined(_LIBCPP_OBJECT_FORMAT_COFF) 789 790#undef _CREATE_ALIGNED_STORAGE_SPECIALIZATION 791 792 793// aligned_union 794 795template <size_t _I0, size_t ..._In> 796struct __static_max; 797 798template <size_t _I0> 799struct __static_max<_I0> 800{ 801 static const size_t value = _I0; 802}; 803 804template <size_t _I0, size_t _I1, size_t ..._In> 805struct __static_max<_I0, _I1, _In...> 806{ 807 static const size_t value = _I0 >= _I1 ? __static_max<_I0, _In...>::value : 808 __static_max<_I1, _In...>::value; 809}; 810 811template <size_t _Len, class _Type0, class ..._Types> 812struct aligned_union 813{ 814 static const size_t alignment_value = __static_max<_LIBCPP_PREFERRED_ALIGNOF(_Type0), 815 _LIBCPP_PREFERRED_ALIGNOF(_Types)...>::value; 816 static const size_t __len = __static_max<_Len, sizeof(_Type0), 817 sizeof(_Types)...>::value; 818 typedef typename aligned_storage<__len, alignment_value>::type type; 819}; 820 821#if _LIBCPP_STD_VER > 11 822template <size_t _Len, class ..._Types> using aligned_union_t = typename aligned_union<_Len, _Types...>::type; 823#endif 824 825template <class _Tp> 826struct __numeric_type 827{ 828 static void __test(...); 829 static float __test(float); 830 static double __test(char); 831 static double __test(int); 832 static double __test(unsigned); 833 static double __test(long); 834 static double __test(unsigned long); 835 static double __test(long long); 836 static double __test(unsigned long long); 837 static double __test(double); 838 static long double __test(long double); 839 840 typedef decltype(__test(declval<_Tp>())) type; 841 static const bool value = _IsNotSame<type, void>::value; 842}; 843 844template <> 845struct __numeric_type<void> 846{ 847 static const bool value = true; 848}; 849 850// __promote 851 852template <class _A1, class _A2 = void, class _A3 = void, 853 bool = __numeric_type<_A1>::value && 854 __numeric_type<_A2>::value && 855 __numeric_type<_A3>::value> 856class __promote_imp 857{ 858public: 859 static const bool value = false; 860}; 861 862template <class _A1, class _A2, class _A3> 863class __promote_imp<_A1, _A2, _A3, true> 864{ 865private: 866 typedef typename __promote_imp<_A1>::type __type1; 867 typedef typename __promote_imp<_A2>::type __type2; 868 typedef typename __promote_imp<_A3>::type __type3; 869public: 870 typedef decltype(__type1() + __type2() + __type3()) type; 871 static const bool value = true; 872}; 873 874template <class _A1, class _A2> 875class __promote_imp<_A1, _A2, void, true> 876{ 877private: 878 typedef typename __promote_imp<_A1>::type __type1; 879 typedef typename __promote_imp<_A2>::type __type2; 880public: 881 typedef decltype(__type1() + __type2()) type; 882 static const bool value = true; 883}; 884 885template <class _A1> 886class __promote_imp<_A1, void, void, true> 887{ 888public: 889 typedef typename __numeric_type<_A1>::type type; 890 static const bool value = true; 891}; 892 893template <class _A1, class _A2 = void, class _A3 = void> 894class __promote : public __promote_imp<_A1, _A2, _A3> {}; 895 896// make_signed / make_unsigned 897 898typedef 899 __type_list<signed char, 900 __type_list<signed short, 901 __type_list<signed int, 902 __type_list<signed long, 903 __type_list<signed long long, 904#ifndef _LIBCPP_HAS_NO_INT128 905 __type_list<__int128_t, 906#endif 907 __nat 908#ifndef _LIBCPP_HAS_NO_INT128 909 > 910#endif 911 > > > > > __signed_types; 912 913typedef 914 __type_list<unsigned char, 915 __type_list<unsigned short, 916 __type_list<unsigned int, 917 __type_list<unsigned long, 918 __type_list<unsigned long long, 919#ifndef _LIBCPP_HAS_NO_INT128 920 __type_list<__uint128_t, 921#endif 922 __nat 923#ifndef _LIBCPP_HAS_NO_INT128 924 > 925#endif 926 > > > > > __unsigned_types; 927 928template <class _TypeList, size_t _Size, bool = _Size <= sizeof(typename _TypeList::_Head)> struct __find_first; 929 930template <class _Hp, class _Tp, size_t _Size> 931struct __find_first<__type_list<_Hp, _Tp>, _Size, true> 932{ 933 typedef _LIBCPP_NODEBUG _Hp type; 934}; 935 936template <class _Hp, class _Tp, size_t _Size> 937struct __find_first<__type_list<_Hp, _Tp>, _Size, false> 938{ 939 typedef _LIBCPP_NODEBUG typename __find_first<_Tp, _Size>::type type; 940}; 941 942template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value> 943struct __make_signed {}; 944 945template <class _Tp> 946struct __make_signed<_Tp, true> 947{ 948 typedef typename __find_first<__signed_types, sizeof(_Tp)>::type type; 949}; 950 951template <> struct __make_signed<bool, true> {}; 952template <> struct __make_signed< signed short, true> {typedef short type;}; 953template <> struct __make_signed<unsigned short, true> {typedef short type;}; 954template <> struct __make_signed< signed int, true> {typedef int type;}; 955template <> struct __make_signed<unsigned int, true> {typedef int type;}; 956template <> struct __make_signed< signed long, true> {typedef long type;}; 957template <> struct __make_signed<unsigned long, true> {typedef long type;}; 958template <> struct __make_signed< signed long long, true> {typedef long long type;}; 959template <> struct __make_signed<unsigned long long, true> {typedef long long type;}; 960#ifndef _LIBCPP_HAS_NO_INT128 961template <> struct __make_signed<__int128_t, true> {typedef __int128_t type;}; 962template <> struct __make_signed<__uint128_t, true> {typedef __int128_t type;}; 963#endif 964 965template <class _Tp> 966struct _LIBCPP_TEMPLATE_VIS make_signed 967{ 968 typedef typename __apply_cv<_Tp, typename __make_signed<typename remove_cv<_Tp>::type>::type>::type type; 969}; 970 971#if _LIBCPP_STD_VER > 11 972template <class _Tp> using make_signed_t = typename make_signed<_Tp>::type; 973#endif 974 975template <class _Tp, bool = is_integral<_Tp>::value || is_enum<_Tp>::value> 976struct __make_unsigned {}; 977 978template <class _Tp> 979struct __make_unsigned<_Tp, true> 980{ 981 typedef typename __find_first<__unsigned_types, sizeof(_Tp)>::type type; 982}; 983 984template <> struct __make_unsigned<bool, true> {}; 985template <> struct __make_unsigned< signed short, true> {typedef unsigned short type;}; 986template <> struct __make_unsigned<unsigned short, true> {typedef unsigned short type;}; 987template <> struct __make_unsigned< signed int, true> {typedef unsigned int type;}; 988template <> struct __make_unsigned<unsigned int, true> {typedef unsigned int type;}; 989template <> struct __make_unsigned< signed long, true> {typedef unsigned long type;}; 990template <> struct __make_unsigned<unsigned long, true> {typedef unsigned long type;}; 991template <> struct __make_unsigned< signed long long, true> {typedef unsigned long long type;}; 992template <> struct __make_unsigned<unsigned long long, true> {typedef unsigned long long type;}; 993#ifndef _LIBCPP_HAS_NO_INT128 994template <> struct __make_unsigned<__int128_t, true> {typedef __uint128_t type;}; 995template <> struct __make_unsigned<__uint128_t, true> {typedef __uint128_t type;}; 996#endif 997 998template <class _Tp> 999struct _LIBCPP_TEMPLATE_VIS make_unsigned 1000{ 1001 typedef typename __apply_cv<_Tp, typename __make_unsigned<typename remove_cv<_Tp>::type>::type>::type type; 1002}; 1003 1004#if _LIBCPP_STD_VER > 11 1005template <class _Tp> using make_unsigned_t = typename make_unsigned<_Tp>::type; 1006#endif 1007 1008#ifndef _LIBCPP_CXX03_LANG 1009template <class _Tp> 1010_LIBCPP_HIDE_FROM_ABI constexpr 1011typename make_unsigned<_Tp>::type __to_unsigned_like(_Tp __x) noexcept { 1012 return static_cast<typename make_unsigned<_Tp>::type>(__x); 1013} 1014#endif 1015 1016template <class _Tp, class _Up> 1017using __copy_unsigned_t = __conditional_t<is_unsigned<_Tp>::value, typename make_unsigned<_Up>::type, _Up>; 1018 1019/// Helper to promote an integral to smallest 32, 64, or 128 bit representation. 1020/// 1021/// The restriction is the same as the integral version of to_char. 1022template <class _Tp> 1023#if _LIBCPP_STD_VER > 17 1024 requires (is_signed_v<_Tp> || is_unsigned_v<_Tp> || is_same_v<_Tp, char>) 1025#endif 1026using __make_32_64_or_128_bit_t = 1027 __copy_unsigned_t<_Tp, 1028 __conditional_t<sizeof(_Tp) <= sizeof(int32_t), int32_t, 1029 __conditional_t<sizeof(_Tp) <= sizeof(int64_t), int64_t, 1030#ifndef _LIBCPP_HAS_NO_INT128 1031 __conditional_t<sizeof(_Tp) <= sizeof(__int128_t), __int128_t, 1032 /* else */ void> 1033#else 1034 /* else */ void 1035#endif 1036 > > 1037 >; 1038 1039#if _LIBCPP_STD_VER > 17 1040// Let COND_RES(X, Y) be: 1041template <class _Tp, class _Up> 1042using __cond_type = decltype(false ? declval<_Tp>() : declval<_Up>()); 1043 1044template <class _Tp, class _Up, class = void> 1045struct __common_type3 {}; 1046 1047// sub-bullet 4 - "if COND_RES(CREF(D1), CREF(D2)) denotes a type..." 1048template <class _Tp, class _Up> 1049struct __common_type3<_Tp, _Up, void_t<__cond_type<const _Tp&, const _Up&>>> 1050{ 1051 using type = remove_cvref_t<__cond_type<const _Tp&, const _Up&>>; 1052}; 1053 1054template <class _Tp, class _Up, class = void> 1055struct __common_type2_imp : __common_type3<_Tp, _Up> {}; 1056#else 1057template <class _Tp, class _Up, class = void> 1058struct __common_type2_imp {}; 1059#endif 1060 1061// sub-bullet 3 - "if decay_t<decltype(false ? declval<D1>() : declval<D2>())> ..." 1062template <class _Tp, class _Up> 1063struct __common_type2_imp<_Tp, _Up, 1064 typename __void_t<decltype( 1065 true ? declval<_Tp>() : declval<_Up>() 1066 )>::type> 1067{ 1068 typedef _LIBCPP_NODEBUG typename decay<decltype( 1069 true ? declval<_Tp>() : declval<_Up>() 1070 )>::type type; 1071}; 1072 1073template <class, class = void> 1074struct __common_type_impl {}; 1075 1076// Clang provides variadic templates in C++03 as an extension. 1077#if !defined(_LIBCPP_CXX03_LANG) || defined(__clang__) 1078# define _LIBCPP_OPTIONAL_PACK(...) , __VA_ARGS__ 1079template <class... _Tp> 1080struct __common_types; 1081template <class... _Tp> 1082struct _LIBCPP_TEMPLATE_VIS common_type; 1083#else 1084# define _LIBCPP_OPTIONAL_PACK(...) 1085struct __no_arg; 1086template <class _Tp, class _Up, class = __no_arg> 1087struct __common_types; 1088template <class _Tp = __no_arg, class _Up = __no_arg, class _Vp = __no_arg, 1089 class _Unused = __no_arg> 1090struct common_type { 1091 static_assert(sizeof(_Unused) == 0, 1092 "common_type accepts at most 3 arguments in C++03"); 1093}; 1094#endif // _LIBCPP_CXX03_LANG 1095 1096template <class _Tp, class _Up> 1097struct __common_type_impl< 1098 __common_types<_Tp, _Up>, 1099 typename __void_t<typename common_type<_Tp, _Up>::type>::type> 1100{ 1101 typedef typename common_type<_Tp, _Up>::type type; 1102}; 1103 1104template <class _Tp, class _Up, class _Vp _LIBCPP_OPTIONAL_PACK(class... _Rest)> 1105struct __common_type_impl< 1106 __common_types<_Tp, _Up, _Vp _LIBCPP_OPTIONAL_PACK(_Rest...)>, 1107 typename __void_t<typename common_type<_Tp, _Up>::type>::type> 1108 : __common_type_impl<__common_types<typename common_type<_Tp, _Up>::type, 1109 _Vp _LIBCPP_OPTIONAL_PACK(_Rest...)> > { 1110}; 1111 1112// bullet 1 - sizeof...(Tp) == 0 1113 1114template <> 1115struct _LIBCPP_TEMPLATE_VIS common_type<> {}; 1116 1117// bullet 2 - sizeof...(Tp) == 1 1118 1119template <class _Tp> 1120struct _LIBCPP_TEMPLATE_VIS common_type<_Tp> 1121 : public common_type<_Tp, _Tp> {}; 1122 1123// bullet 3 - sizeof...(Tp) == 2 1124 1125// sub-bullet 1 - "If is_same_v<T1, D1> is false or ..." 1126template <class _Tp, class _Up> 1127struct _LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up> 1128 : conditional< 1129 _IsSame<_Tp, typename decay<_Tp>::type>::value && _IsSame<_Up, typename decay<_Up>::type>::value, 1130 __common_type2_imp<_Tp, _Up>, 1131 common_type<typename decay<_Tp>::type, typename decay<_Up>::type> 1132 >::type 1133{}; 1134 1135// bullet 4 - sizeof...(Tp) > 2 1136 1137template <class _Tp, class _Up, class _Vp _LIBCPP_OPTIONAL_PACK(class... _Rest)> 1138struct _LIBCPP_TEMPLATE_VIS 1139 common_type<_Tp, _Up, _Vp _LIBCPP_OPTIONAL_PACK(_Rest...)> 1140 : __common_type_impl< 1141 __common_types<_Tp, _Up, _Vp _LIBCPP_OPTIONAL_PACK(_Rest...)> > {}; 1142 1143#undef _LIBCPP_OPTIONAL_PACK 1144 1145#if _LIBCPP_STD_VER > 11 1146template <class ..._Tp> using common_type_t = typename common_type<_Tp...>::type; 1147#endif 1148 1149// Let COPYCV(FROM, TO) be an alias for type TO with the addition of FROM's 1150// top-level cv-qualifiers. 1151template <class _From, class _To> 1152struct __copy_cv 1153{ 1154 using type = _To; 1155}; 1156 1157template <class _From, class _To> 1158struct __copy_cv<const _From, _To> 1159{ 1160 using type = typename add_const<_To>::type; 1161}; 1162 1163template <class _From, class _To> 1164struct __copy_cv<volatile _From, _To> 1165{ 1166 using type = typename add_volatile<_To>::type; 1167}; 1168 1169template <class _From, class _To> 1170struct __copy_cv<const volatile _From, _To> 1171{ 1172 using type = typename add_cv<_To>::type; 1173}; 1174 1175template <class _From, class _To> 1176using __copy_cv_t = typename __copy_cv<_From, _To>::type; 1177 1178template <class _From, class _To> 1179struct __copy_cvref 1180{ 1181 using type = __copy_cv_t<_From, _To>; 1182}; 1183 1184template <class _From, class _To> 1185struct __copy_cvref<_From&, _To> 1186{ 1187 using type = typename add_lvalue_reference<__copy_cv_t<_From, _To> >::type; 1188}; 1189 1190template <class _From, class _To> 1191struct __copy_cvref<_From&&, _To> 1192{ 1193 using type = typename add_rvalue_reference<__copy_cv_t<_From, _To> >::type; 1194}; 1195 1196template <class _From, class _To> 1197using __copy_cvref_t = typename __copy_cvref<_From, _To>::type; 1198 1199 1200// common_reference 1201#if _LIBCPP_STD_VER > 17 1202// Let COND_RES(X, Y) be: 1203template <class _Xp, class _Yp> 1204using __cond_res = 1205 decltype(false ? declval<_Xp(&)()>()() : declval<_Yp(&)()>()()); 1206 1207// Let `XREF(A)` denote a unary alias template `T` such that `T<U>` denotes the same type as `U` 1208// with the addition of `A`'s cv and reference qualifiers, for a non-reference cv-unqualified type 1209// `U`. 1210// [Note: `XREF(A)` is `__xref<A>::template __apply`] 1211template <class _Tp> 1212struct __xref { 1213 template<class _Up> 1214 using __apply = __copy_cvref_t<_Tp, _Up>; 1215}; 1216 1217// Given types A and B, let X be remove_reference_t<A>, let Y be remove_reference_t<B>, 1218// and let COMMON-REF(A, B) be: 1219template<class _Ap, class _Bp, class _Xp = remove_reference_t<_Ap>, class _Yp = remove_reference_t<_Bp>> 1220struct __common_ref; 1221 1222template<class _Xp, class _Yp> 1223using __common_ref_t = typename __common_ref<_Xp, _Yp>::__type; 1224 1225template<class _Xp, class _Yp> 1226using __cv_cond_res = __cond_res<__copy_cv_t<_Xp, _Yp>&, __copy_cv_t<_Yp, _Xp>&>; 1227 1228 1229// If A and B are both lvalue reference types, COMMON-REF(A, B) is 1230// COND-RES(COPYCV(X, Y)&, COPYCV(Y, X)&) if that type exists and is a reference type. 1231template<class _Ap, class _Bp, class _Xp, class _Yp> 1232requires requires { typename __cv_cond_res<_Xp, _Yp>; } && is_reference_v<__cv_cond_res<_Xp, _Yp>> 1233struct __common_ref<_Ap&, _Bp&, _Xp, _Yp> 1234{ 1235 using __type = __cv_cond_res<_Xp, _Yp>; 1236}; 1237 1238// Otherwise, let C be remove_reference_t<COMMON-REF(X&, Y&)>&&. ... 1239template <class _Xp, class _Yp> 1240using __common_ref_C = remove_reference_t<__common_ref_t<_Xp&, _Yp&>>&&; 1241 1242 1243// .... If A and B are both rvalue reference types, C is well-formed, and 1244// is_convertible_v<A, C> && is_convertible_v<B, C> is true, then COMMON-REF(A, B) is C. 1245template<class _Ap, class _Bp, class _Xp, class _Yp> 1246requires 1247 requires { typename __common_ref_C<_Xp, _Yp>; } && 1248 is_convertible_v<_Ap&&, __common_ref_C<_Xp, _Yp>> && 1249 is_convertible_v<_Bp&&, __common_ref_C<_Xp, _Yp>> 1250struct __common_ref<_Ap&&, _Bp&&, _Xp, _Yp> 1251{ 1252 using __type = __common_ref_C<_Xp, _Yp>; 1253}; 1254 1255// Otherwise, let D be COMMON-REF(const X&, Y&). ... 1256template <class _Tp, class _Up> 1257using __common_ref_D = __common_ref_t<const _Tp&, _Up&>; 1258 1259// ... If A is an rvalue reference and B is an lvalue reference and D is well-formed and 1260// is_convertible_v<A, D> is true, then COMMON-REF(A, B) is D. 1261template<class _Ap, class _Bp, class _Xp, class _Yp> 1262requires requires { typename __common_ref_D<_Xp, _Yp>; } && 1263 is_convertible_v<_Ap&&, __common_ref_D<_Xp, _Yp>> 1264struct __common_ref<_Ap&&, _Bp&, _Xp, _Yp> 1265{ 1266 using __type = __common_ref_D<_Xp, _Yp>; 1267}; 1268 1269// Otherwise, if A is an lvalue reference and B is an rvalue reference, then 1270// COMMON-REF(A, B) is COMMON-REF(B, A). 1271template<class _Ap, class _Bp, class _Xp, class _Yp> 1272struct __common_ref<_Ap&, _Bp&&, _Xp, _Yp> : __common_ref<_Bp&&, _Ap&> {}; 1273 1274// Otherwise, COMMON-REF(A, B) is ill-formed. 1275template<class _Ap, class _Bp, class _Xp, class _Yp> 1276struct __common_ref {}; 1277 1278// Note C: For the common_reference trait applied to a parameter pack [...] 1279 1280template <class...> 1281struct common_reference; 1282 1283template <class... _Types> 1284using common_reference_t = typename common_reference<_Types...>::type; 1285 1286// bullet 1 - sizeof...(T) == 0 1287template<> 1288struct common_reference<> {}; 1289 1290// bullet 2 - sizeof...(T) == 1 1291template <class _Tp> 1292struct common_reference<_Tp> 1293{ 1294 using type = _Tp; 1295}; 1296 1297// bullet 3 - sizeof...(T) == 2 1298template <class _Tp, class _Up> struct __common_reference_sub_bullet3; 1299template <class _Tp, class _Up> struct __common_reference_sub_bullet2 : __common_reference_sub_bullet3<_Tp, _Up> {}; 1300template <class _Tp, class _Up> struct __common_reference_sub_bullet1 : __common_reference_sub_bullet2<_Tp, _Up> {}; 1301 1302// sub-bullet 1 - If T1 and T2 are reference types and COMMON-REF(T1, T2) is well-formed, then 1303// the member typedef `type` denotes that type. 1304template <class _Tp, class _Up> struct common_reference<_Tp, _Up> : __common_reference_sub_bullet1<_Tp, _Up> {}; 1305 1306template <class _Tp, class _Up> 1307requires is_reference_v<_Tp> && is_reference_v<_Up> && requires { typename __common_ref_t<_Tp, _Up>; } 1308struct __common_reference_sub_bullet1<_Tp, _Up> 1309{ 1310 using type = __common_ref_t<_Tp, _Up>; 1311}; 1312 1313// sub-bullet 2 - Otherwise, if basic_common_reference<remove_cvref_t<T1>, remove_cvref_t<T2>, XREF(T1), XREF(T2)>::type 1314// is well-formed, then the member typedef `type` denotes that type. 1315template <class, class, template <class> class, template <class> class> struct basic_common_reference {}; 1316 1317template <class _Tp, class _Up> 1318using __basic_common_reference_t = typename basic_common_reference< 1319 remove_cvref_t<_Tp>, remove_cvref_t<_Up>, 1320 __xref<_Tp>::template __apply, __xref<_Up>::template __apply>::type; 1321 1322template <class _Tp, class _Up> 1323requires requires { typename __basic_common_reference_t<_Tp, _Up>; } 1324struct __common_reference_sub_bullet2<_Tp, _Up> 1325{ 1326 using type = __basic_common_reference_t<_Tp, _Up>; 1327}; 1328 1329// sub-bullet 3 - Otherwise, if COND-RES(T1, T2) is well-formed, 1330// then the member typedef `type` denotes that type. 1331template <class _Tp, class _Up> 1332requires requires { typename __cond_res<_Tp, _Up>; } 1333struct __common_reference_sub_bullet3<_Tp, _Up> 1334{ 1335 using type = __cond_res<_Tp, _Up>; 1336}; 1337 1338 1339// sub-bullet 4 & 5 - Otherwise, if common_type_t<T1, T2> is well-formed, 1340// then the member typedef `type` denotes that type. 1341// - Otherwise, there shall be no member `type`. 1342template <class _Tp, class _Up> struct __common_reference_sub_bullet3 : common_type<_Tp, _Up> {}; 1343 1344// bullet 4 - If there is such a type `C`, the member typedef type shall denote the same type, if 1345// any, as `common_reference_t<C, Rest...>`. 1346template <class _Tp, class _Up, class _Vp, class... _Rest> 1347requires requires { typename common_reference_t<_Tp, _Up>; } 1348struct common_reference<_Tp, _Up, _Vp, _Rest...> 1349 : common_reference<common_reference_t<_Tp, _Up>, _Vp, _Rest...> 1350{}; 1351 1352// bullet 5 - Otherwise, there shall be no member `type`. 1353template <class...> struct common_reference {}; 1354 1355#endif // _LIBCPP_STD_VER > 17 1356 1357#ifndef _LIBCPP_CXX03_LANG 1358// First of all, we can't implement this check in C++03 mode because the {} 1359// default initialization syntax isn't valid. 1360// Second, we implement the trait in a funny manner with two defaulted template 1361// arguments to workaround Clang's PR43454. 1362template <class _Tp> 1363void __test_implicit_default_constructible(_Tp); 1364 1365template <class _Tp, class = void, class = typename is_default_constructible<_Tp>::type> 1366struct __is_implicitly_default_constructible 1367 : false_type 1368{ }; 1369 1370template <class _Tp> 1371struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), true_type> 1372 : true_type 1373{ }; 1374 1375template <class _Tp> 1376struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), false_type> 1377 : false_type 1378{ }; 1379#endif // !C++03 1380 1381// result_of 1382 1383#if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS) 1384template <class _Callable> class _LIBCPP_DEPRECATED_IN_CXX17 result_of; 1385 1386#ifndef _LIBCPP_CXX03_LANG 1387 1388template <class _Fp, class ..._Args> 1389class _LIBCPP_TEMPLATE_VIS result_of<_Fp(_Args...)> 1390 : public __invoke_of<_Fp, _Args...> 1391{ 1392}; 1393 1394#else // C++03 1395 1396template <class _Fn, bool, bool> 1397class __result_of 1398{ 1399}; 1400 1401template <class _Fn, class ..._Args> 1402class __result_of<_Fn(_Args...), true, false> 1403{ 1404public: 1405 typedef decltype(declval<_Fn>()(declval<_Args>()...)) type; 1406}; 1407 1408template <class _MP, class _Tp, bool _IsMemberFunctionPtr> 1409struct __result_of_mp; 1410 1411// member function pointer 1412 1413template <class _MP, class _Tp> 1414struct __result_of_mp<_MP, _Tp, true> 1415{ 1416 using type = typename __member_pointer_traits<_MP>::_ReturnType; 1417}; 1418 1419// member data pointer 1420 1421template <class _MP, class _Tp, bool> 1422struct __result_of_mdp; 1423 1424template <class _Rp, class _Class, class _Tp> 1425struct __result_of_mdp<_Rp _Class::*, _Tp, false> 1426{ 1427 using type = typename __apply_cv<decltype(*declval<_Tp>()), _Rp>::type&; 1428}; 1429 1430template <class _Rp, class _Class, class _Tp> 1431struct __result_of_mdp<_Rp _Class::*, _Tp, true> 1432{ 1433 using type = typename __apply_cv<_Tp, _Rp>::type&; 1434}; 1435 1436template <class _Rp, class _Class, class _Tp> 1437struct __result_of_mp<_Rp _Class::*, _Tp, false> 1438 : public __result_of_mdp<_Rp _Class::*, _Tp, 1439 is_base_of<_Class, typename remove_reference<_Tp>::type>::value> 1440{ 1441}; 1442 1443template <class _Fn, class _Tp> 1444class __result_of<_Fn(_Tp), false, true> // _Fn must be member pointer 1445 : public __result_of_mp<typename remove_reference<_Fn>::type, 1446 _Tp, 1447 is_member_function_pointer<typename remove_reference<_Fn>::type>::value> 1448{ 1449}; 1450 1451template <class _Fn, class _Tp, class ..._Args> 1452class __result_of<_Fn(_Tp, _Args...), false, true> // _Fn must be member pointer 1453 : public __result_of_mp<typename remove_reference<_Fn>::type, 1454 _Tp, 1455 is_member_function_pointer<typename remove_reference<_Fn>::type>::value> 1456{ 1457}; 1458 1459template <class _Fn, class ..._Args> 1460class _LIBCPP_TEMPLATE_VIS result_of<_Fn(_Args...)> 1461 : public __result_of<_Fn(_Args...), 1462 is_class<typename remove_reference<_Fn>::type>::value || 1463 is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value, 1464 is_member_pointer<typename remove_reference<_Fn>::type>::value 1465 > 1466{ 1467}; 1468 1469#endif // C++03 1470 1471#if _LIBCPP_STD_VER > 11 1472template <class _Tp> using result_of_t _LIBCPP_DEPRECATED_IN_CXX17 = typename result_of<_Tp>::type; 1473#endif // _LIBCPP_STD_VER > 11 1474#endif // _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_TYPE_TRAITS) 1475 1476// __swappable 1477 1478template <class _Tp> struct __is_swappable; 1479template <class _Tp> struct __is_nothrow_swappable; 1480 1481 1482#ifndef _LIBCPP_CXX03_LANG 1483template <class _Tp> 1484using __swap_result_t = typename enable_if<is_move_constructible<_Tp>::value && is_move_assignable<_Tp>::value>::type; 1485#else 1486template <class> 1487using __swap_result_t = void; 1488#endif 1489 1490template <class _Tp> 1491inline _LIBCPP_INLINE_VISIBILITY 1492_LIBCPP_CONSTEXPR_AFTER_CXX17 __swap_result_t<_Tp> 1493swap(_Tp& __x, _Tp& __y) _NOEXCEPT_(is_nothrow_move_constructible<_Tp>::value && 1494 is_nothrow_move_assignable<_Tp>::value); 1495 1496template<class _Tp, size_t _Np> 1497inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 1498typename enable_if< 1499 __is_swappable<_Tp>::value 1500>::type 1501swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value); 1502 1503namespace __detail 1504{ 1505// ALL generic swap overloads MUST already have a declaration available at this point. 1506 1507template <class _Tp, class _Up = _Tp, 1508 bool _NotVoid = !is_void<_Tp>::value && !is_void<_Up>::value> 1509struct __swappable_with 1510{ 1511 template <class _LHS, class _RHS> 1512 static decltype(swap(declval<_LHS>(), declval<_RHS>())) 1513 __test_swap(int); 1514 template <class, class> 1515 static __nat __test_swap(long); 1516 1517 // Extra parens are needed for the C++03 definition of decltype. 1518 typedef decltype((__test_swap<_Tp, _Up>(0))) __swap1; 1519 typedef decltype((__test_swap<_Up, _Tp>(0))) __swap2; 1520 1521 static const bool value = _IsNotSame<__swap1, __nat>::value 1522 && _IsNotSame<__swap2, __nat>::value; 1523}; 1524 1525template <class _Tp, class _Up> 1526struct __swappable_with<_Tp, _Up, false> : false_type {}; 1527 1528template <class _Tp, class _Up = _Tp, bool _Swappable = __swappable_with<_Tp, _Up>::value> 1529struct __nothrow_swappable_with { 1530 static const bool value = 1531#ifndef _LIBCPP_HAS_NO_NOEXCEPT 1532 noexcept(swap(declval<_Tp>(), declval<_Up>())) 1533 && noexcept(swap(declval<_Up>(), declval<_Tp>())); 1534#else 1535 false; 1536#endif 1537}; 1538 1539template <class _Tp, class _Up> 1540struct __nothrow_swappable_with<_Tp, _Up, false> : false_type {}; 1541 1542} // namespace __detail 1543 1544template <class _Tp> 1545struct __is_swappable 1546 : public integral_constant<bool, __detail::__swappable_with<_Tp&>::value> 1547{ 1548}; 1549 1550template <class _Tp> 1551struct __is_nothrow_swappable 1552 : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp&>::value> 1553{ 1554}; 1555 1556#if _LIBCPP_STD_VER > 14 1557 1558template <class _Tp, class _Up> 1559struct _LIBCPP_TEMPLATE_VIS is_swappable_with 1560 : public integral_constant<bool, __detail::__swappable_with<_Tp, _Up>::value> 1561{ 1562}; 1563 1564template <class _Tp> 1565struct _LIBCPP_TEMPLATE_VIS is_swappable 1566 : public conditional< 1567 __is_referenceable<_Tp>::value, 1568 is_swappable_with< 1569 typename add_lvalue_reference<_Tp>::type, 1570 typename add_lvalue_reference<_Tp>::type>, 1571 false_type 1572 >::type 1573{ 1574}; 1575 1576template <class _Tp, class _Up> 1577struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable_with 1578 : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp, _Up>::value> 1579{ 1580}; 1581 1582template <class _Tp> 1583struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable 1584 : public conditional< 1585 __is_referenceable<_Tp>::value, 1586 is_nothrow_swappable_with< 1587 typename add_lvalue_reference<_Tp>::type, 1588 typename add_lvalue_reference<_Tp>::type>, 1589 false_type 1590 >::type 1591{ 1592}; 1593 1594template <class _Tp, class _Up> 1595inline constexpr bool is_swappable_with_v = is_swappable_with<_Tp, _Up>::value; 1596 1597template <class _Tp> 1598inline constexpr bool is_swappable_v = is_swappable<_Tp>::value; 1599 1600template <class _Tp, class _Up> 1601inline constexpr bool is_nothrow_swappable_with_v = is_nothrow_swappable_with<_Tp, _Up>::value; 1602 1603template <class _Tp> 1604inline constexpr bool is_nothrow_swappable_v = is_nothrow_swappable<_Tp>::value; 1605 1606#endif // _LIBCPP_STD_VER > 14 1607 1608template <class _Tp, bool = is_enum<_Tp>::value> 1609struct __sfinae_underlying_type 1610{ 1611 typedef typename underlying_type<_Tp>::type type; 1612 typedef decltype(((type)1) + 0) __promoted_type; 1613}; 1614 1615template <class _Tp> 1616struct __sfinae_underlying_type<_Tp, false> {}; 1617 1618inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1619int __convert_to_integral(int __val) { return __val; } 1620 1621inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1622unsigned __convert_to_integral(unsigned __val) { return __val; } 1623 1624inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1625long __convert_to_integral(long __val) { return __val; } 1626 1627inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1628unsigned long __convert_to_integral(unsigned long __val) { return __val; } 1629 1630inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1631long long __convert_to_integral(long long __val) { return __val; } 1632 1633inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1634unsigned long long __convert_to_integral(unsigned long long __val) {return __val; } 1635 1636template<typename _Fp> 1637inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1638typename enable_if<is_floating_point<_Fp>::value, long long>::type 1639 __convert_to_integral(_Fp __val) { return __val; } 1640 1641#ifndef _LIBCPP_HAS_NO_INT128 1642inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1643__int128_t __convert_to_integral(__int128_t __val) { return __val; } 1644 1645inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1646__uint128_t __convert_to_integral(__uint128_t __val) { return __val; } 1647#endif 1648 1649template <class _Tp> 1650inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR 1651typename __sfinae_underlying_type<_Tp>::__promoted_type 1652__convert_to_integral(_Tp __val) { return __val; } 1653 1654// These traits are used in __tree and __hash_table 1655struct __extract_key_fail_tag {}; 1656struct __extract_key_self_tag {}; 1657struct __extract_key_first_tag {}; 1658 1659template <class _ValTy, class _Key, 1660 class _RawValTy = typename __unconstref<_ValTy>::type> 1661struct __can_extract_key 1662 : conditional<_IsSame<_RawValTy, _Key>::value, __extract_key_self_tag, 1663 __extract_key_fail_tag>::type {}; 1664 1665template <class _Pair, class _Key, class _First, class _Second> 1666struct __can_extract_key<_Pair, _Key, pair<_First, _Second> > 1667 : conditional<_IsSame<typename remove_const<_First>::type, _Key>::value, 1668 __extract_key_first_tag, __extract_key_fail_tag>::type {}; 1669 1670// __can_extract_map_key uses true_type/false_type instead of the tags. 1671// It returns true if _Key != _ContainerValueTy (the container is a map not a set) 1672// and _ValTy == _Key. 1673template <class _ValTy, class _Key, class _ContainerValueTy, 1674 class _RawValTy = typename __unconstref<_ValTy>::type> 1675struct __can_extract_map_key 1676 : integral_constant<bool, _IsSame<_RawValTy, _Key>::value> {}; 1677 1678// This specialization returns __extract_key_fail_tag for non-map containers 1679// because _Key == _ContainerValueTy 1680template <class _ValTy, class _Key, class _RawValTy> 1681struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy> 1682 : false_type {}; 1683 1684template <class _CharT> 1685using _IsCharLikeType = _And<is_standard_layout<_CharT>, is_trivial<_CharT> >; 1686 1687template<class _Tp> 1688using __make_const_lvalue_ref = const typename remove_reference<_Tp>::type&; 1689 1690template<bool _Const, class _Tp> 1691using __maybe_const = typename conditional<_Const, const _Tp, _Tp>::type; 1692 1693_LIBCPP_END_NAMESPACE_STD 1694 1695#endif // _LIBCPP_TYPE_TRAITS 1696