libstdc++
utility
Go to the documentation of this file.
1// <utility> -*- C++ -*-
2
3// Copyright (C) 2001-2020 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/*
26 *
27 * Copyright (c) 1994
28 * Hewlett-Packard Company
29 *
30 * Permission to use, copy, modify, distribute and sell this software
31 * and its documentation for any purpose is hereby granted without fee,
32 * provided that the above copyright notice appear in all copies and
33 * that both that copyright notice and this permission notice appear
34 * in supporting documentation. Hewlett-Packard Company makes no
35 * representations about the suitability of this software for any
36 * purpose. It is provided "as is" without express or implied warranty.
37 *
38 *
39 * Copyright (c) 1996,1997
40 * Silicon Graphics Computer Systems, Inc.
41 *
42 * Permission to use, copy, modify, distribute and sell this software
43 * and its documentation for any purpose is hereby granted without fee,
44 * provided that the above copyright notice appear in all copies and
45 * that both that copyright notice and this permission notice appear
46 * in supporting documentation. Silicon Graphics makes no
47 * representations about the suitability of this software for any
48 * purpose. It is provided "as is" without express or implied warranty.
49 */
50
51/** @file include/utility
52 * This is a Standard C++ Library header.
53 */
54
55#ifndef _GLIBCXX_UTILITY
56#define _GLIBCXX_UTILITY 1
57
58#pragma GCC system_header
59
60/**
61 * @defgroup utilities Utilities
62 *
63 * Components deemed generally useful. Includes pair, tuple,
64 * forward/move helpers, ratio, function object, metaprogramming and
65 * type traits, time, date, and memory functions.
66 */
67
68#include <bits/c++config.h>
69#include <bits/stl_relops.h>
70#include <bits/stl_pair.h>
71
72#if __cplusplus >= 201103L
73
74#include <type_traits>
75#include <bits/move.h>
76#include <initializer_list>
77
78#if __cplusplus > 201703L
79#include <ext/numeric_traits.h>
80#endif
81
82namespace std _GLIBCXX_VISIBILITY(default)
83{
84_GLIBCXX_BEGIN_NAMESPACE_VERSION
85
86 /// Finds the size of a given tuple type.
87 template<typename _Tp>
88 struct tuple_size;
89
90 // _GLIBCXX_RESOLVE_LIB_DEFECTS
91 // 2313. tuple_size should always derive from integral_constant<size_t, N>
92 // 2770. tuple_size<const T> specialization is not SFINAE compatible
93
94 template<typename _Tp,
95 typename _Up = typename remove_cv<_Tp>::type,
96 typename = typename enable_if<is_same<_Tp, _Up>::value>::type,
97 size_t = tuple_size<_Tp>::value>
98 using __enable_if_has_tuple_size = _Tp;
99
100 template<typename _Tp>
101 struct tuple_size<const __enable_if_has_tuple_size<_Tp>>
102 : public tuple_size<_Tp> { };
103
104 template<typename _Tp>
105 struct tuple_size<volatile __enable_if_has_tuple_size<_Tp>>
106 : public tuple_size<_Tp> { };
107
108 template<typename _Tp>
109 struct tuple_size<const volatile __enable_if_has_tuple_size<_Tp>>
110 : public tuple_size<_Tp> { };
111
112 /// Gives the type of the ith element of a given tuple type.
113 template<std::size_t __i, typename _Tp>
114 struct tuple_element;
115
116 // Duplicate of C++14's tuple_element_t for internal use in C++11 mode
117 template<std::size_t __i, typename _Tp>
118 using __tuple_element_t = typename tuple_element<__i, _Tp>::type;
119
120 template<std::size_t __i, typename _Tp>
121 struct tuple_element<__i, const _Tp>
122 {
123 typedef typename add_const<__tuple_element_t<__i, _Tp>>::type type;
124 };
125
126 template<std::size_t __i, typename _Tp>
127 struct tuple_element<__i, volatile _Tp>
128 {
129 typedef typename add_volatile<__tuple_element_t<__i, _Tp>>::type type;
130 };
131
132 template<std::size_t __i, typename _Tp>
133 struct tuple_element<__i, const volatile _Tp>
134 {
135 typedef typename add_cv<__tuple_element_t<__i, _Tp>>::type type;
136 };
137
138#if __cplusplus >= 201402L
139// The standard says this macro and alias template should be in <tuple>
140// but we define them here, to be available when the partial specializations
141// of tuple_element<pair<T,U>> and tuple_element<array<T,N>> are defined.
142#define __cpp_lib_tuple_element_t 201402L
143
144 template<std::size_t __i, typename _Tp>
145 using tuple_element_t = typename tuple_element<__i, _Tp>::type;
146#endif
147
148 // Various functions which give std::pair a tuple-like interface.
149
150 /// Partial specialization for std::pair
151 template<typename _T1, typename _T2>
152 struct __is_tuple_like_impl<std::pair<_T1, _T2>> : true_type
153 { };
154
155 /// Partial specialization for std::pair
156 template<class _Tp1, class _Tp2>
157 struct tuple_size<std::pair<_Tp1, _Tp2>>
158 : public integral_constant<std::size_t, 2> { };
159
160 /// Partial specialization for std::pair
161 template<class _Tp1, class _Tp2>
162 struct tuple_element<0, std::pair<_Tp1, _Tp2>>
163 { typedef _Tp1 type; };
164
165 /// Partial specialization for std::pair
166 template<class _Tp1, class _Tp2>
167 struct tuple_element<1, std::pair<_Tp1, _Tp2>>
168 { typedef _Tp2 type; };
169
170 template<std::size_t _Int>
171 struct __pair_get;
172
173 template<>
174 struct __pair_get<0>
175 {
176 template<typename _Tp1, typename _Tp2>
177 static constexpr _Tp1&
178 __get(std::pair<_Tp1, _Tp2>& __pair) noexcept
179 { return __pair.first; }
180
181 template<typename _Tp1, typename _Tp2>
182 static constexpr _Tp1&&
183 __move_get(std::pair<_Tp1, _Tp2>&& __pair) noexcept
184 { return std::forward<_Tp1>(__pair.first); }
185
186 template<typename _Tp1, typename _Tp2>
187 static constexpr const _Tp1&
188 __const_get(const std::pair<_Tp1, _Tp2>& __pair) noexcept
189 { return __pair.first; }
190
191 template<typename _Tp1, typename _Tp2>
192 static constexpr const _Tp1&&
193 __const_move_get(const std::pair<_Tp1, _Tp2>&& __pair) noexcept
194 { return std::forward<const _Tp1>(__pair.first); }
195 };
196
197 template<>
198 struct __pair_get<1>
199 {
200 template<typename _Tp1, typename _Tp2>
201 static constexpr _Tp2&
202 __get(std::pair<_Tp1, _Tp2>& __pair) noexcept
203 { return __pair.second; }
204
205 template<typename _Tp1, typename _Tp2>
206 static constexpr _Tp2&&
207 __move_get(std::pair<_Tp1, _Tp2>&& __pair) noexcept
208 { return std::forward<_Tp2>(__pair.second); }
209
210 template<typename _Tp1, typename _Tp2>
211 static constexpr const _Tp2&
212 __const_get(const std::pair<_Tp1, _Tp2>& __pair) noexcept
213 { return __pair.second; }
214
215 template<typename _Tp1, typename _Tp2>
216 static constexpr const _Tp2&&
217 __const_move_get(const std::pair<_Tp1, _Tp2>&& __pair) noexcept
218 { return std::forward<const _Tp2>(__pair.second); }
219 };
220
221 template<std::size_t _Int, class _Tp1, class _Tp2>
222 constexpr typename tuple_element<_Int, std::pair<_Tp1, _Tp2>>::type&
223 get(std::pair<_Tp1, _Tp2>& __in) noexcept
224 { return __pair_get<_Int>::__get(__in); }
225
226 template<std::size_t _Int, class _Tp1, class _Tp2>
227 constexpr typename tuple_element<_Int, std::pair<_Tp1, _Tp2>>::type&&
228 get(std::pair<_Tp1, _Tp2>&& __in) noexcept
229 { return __pair_get<_Int>::__move_get(std::move(__in)); }
230
231 template<std::size_t _Int, class _Tp1, class _Tp2>
232 constexpr const typename tuple_element<_Int, std::pair<_Tp1, _Tp2>>::type&
233 get(const std::pair<_Tp1, _Tp2>& __in) noexcept
234 { return __pair_get<_Int>::__const_get(__in); }
235
236 template<std::size_t _Int, class _Tp1, class _Tp2>
237 constexpr const typename tuple_element<_Int, std::pair<_Tp1, _Tp2>>::type&&
238 get(const std::pair<_Tp1, _Tp2>&& __in) noexcept
239 { return __pair_get<_Int>::__const_move_get(std::move(__in)); }
240
241#if __cplusplus >= 201402L
242
243#define __cpp_lib_tuples_by_type 201304
244
245 template <typename _Tp, typename _Up>
246 constexpr _Tp&
247 get(pair<_Tp, _Up>& __p) noexcept
248 { return __p.first; }
249
250 template <typename _Tp, typename _Up>
251 constexpr const _Tp&
252 get(const pair<_Tp, _Up>& __p) noexcept
253 { return __p.first; }
254
255 template <typename _Tp, typename _Up>
256 constexpr _Tp&&
257 get(pair<_Tp, _Up>&& __p) noexcept
258 { return std::move(__p.first); }
259
260 template <typename _Tp, typename _Up>
261 constexpr const _Tp&&
262 get(const pair<_Tp, _Up>&& __p) noexcept
263 { return std::move(__p.first); }
264
265 template <typename _Tp, typename _Up>
266 constexpr _Tp&
267 get(pair<_Up, _Tp>& __p) noexcept
268 { return __p.second; }
269
270 template <typename _Tp, typename _Up>
271 constexpr const _Tp&
272 get(const pair<_Up, _Tp>& __p) noexcept
273 { return __p.second; }
274
275 template <typename _Tp, typename _Up>
276 constexpr _Tp&&
277 get(pair<_Up, _Tp>&& __p) noexcept
278 { return std::move(__p.second); }
279
280 template <typename _Tp, typename _Up>
281 constexpr const _Tp&&
282 get(const pair<_Up, _Tp>&& __p) noexcept
283 { return std::move(__p.second); }
284
285#define __cpp_lib_exchange_function 201304
286
287 /// Assign @p __new_val to @p __obj and return its previous value.
288 template <typename _Tp, typename _Up = _Tp>
289 _GLIBCXX20_CONSTEXPR
290 inline _Tp
291 exchange(_Tp& __obj, _Up&& __new_val)
292 { return std::__exchange(__obj, std::forward<_Up>(__new_val)); }
293
294#endif // C++14
295
296 // Stores a tuple of indices. Used by tuple and pair, and by bind() to
297 // extract the elements in a tuple.
298 template<size_t... _Indexes> struct _Index_tuple { };
299
300#ifdef __has_builtin
301# if __has_builtin(__make_integer_seq)
302# define _GLIBCXX_USE_MAKE_INTEGER_SEQ 1
303# endif
304#endif
305
306 // Builds an _Index_tuple<0, 1, 2, ..., _Num-1>.
307 template<size_t _Num>
308 struct _Build_index_tuple
309 {
310#if _GLIBCXX_USE_MAKE_INTEGER_SEQ
311 template<typename, size_t... _Indices>
312 using _IdxTuple = _Index_tuple<_Indices...>;
313
314 using __type = __make_integer_seq<_IdxTuple, size_t, _Num>;
315#else
316 using __type = _Index_tuple<__integer_pack(_Num)...>;
317#endif
318 };
319
320#if __cplusplus > 201103L
321
322#define __cpp_lib_integer_sequence 201304
323
324 /// Class template integer_sequence
325 template<typename _Tp, _Tp... _Idx>
326 struct integer_sequence
327 {
328 typedef _Tp value_type;
329 static constexpr size_t size() noexcept { return sizeof...(_Idx); }
330 };
331
332 /// Alias template make_integer_sequence
333 template<typename _Tp, _Tp _Num>
334 using make_integer_sequence
335#if _GLIBCXX_USE_MAKE_INTEGER_SEQ
336 = __make_integer_seq<integer_sequence, _Tp, _Num>;
337#else
338 = integer_sequence<_Tp, __integer_pack(_Num)...>;
339#endif
340
341#undef _GLIBCXX_USE_MAKE_INTEGER_SEQ
342
343 /// Alias template index_sequence
344 template<size_t... _Idx>
345 using index_sequence = integer_sequence<size_t, _Idx...>;
346
347 /// Alias template make_index_sequence
348 template<size_t _Num>
349 using make_index_sequence = make_integer_sequence<size_t, _Num>;
350
351 /// Alias template index_sequence_for
352 template<typename... _Types>
353 using index_sequence_for = make_index_sequence<sizeof...(_Types)>;
354#endif
355
356#if __cplusplus > 201402L
357
358 struct in_place_t {
359 explicit in_place_t() = default;
360 };
361
362 inline constexpr in_place_t in_place{};
363
364 template<typename _Tp> struct in_place_type_t
365 {
366 explicit in_place_type_t() = default;
367 };
368
369 template<typename _Tp>
370 inline constexpr in_place_type_t<_Tp> in_place_type{};
371
372 template<size_t _Idx> struct in_place_index_t
373 {
374 explicit in_place_index_t() = default;
375 };
376
377 template<size_t _Idx>
378 inline constexpr in_place_index_t<_Idx> in_place_index{};
379
380 template<typename>
381 struct __is_in_place_type_impl : false_type
382 { };
383
384 template<typename _Tp>
385 struct __is_in_place_type_impl<in_place_type_t<_Tp>> : true_type
386 { };
387
388 template<typename _Tp>
389 struct __is_in_place_type
390 : public __is_in_place_type_impl<_Tp>
391 { };
392
393#define __cpp_lib_as_const 201510
394 template<typename _Tp>
395 constexpr add_const_t<_Tp>& as_const(_Tp& __t) noexcept { return __t; }
396
397 template<typename _Tp>
398 void as_const(const _Tp&&) = delete;
399
400#if __cplusplus > 201703L
401#define __cpp_lib_integer_comparison_functions 202002L
402
403 template<typename _Tp, typename _Up>
404 constexpr bool
405 cmp_equal(_Tp __t, _Up __u) noexcept
406 {
407 static_assert(__is_standard_integer<_Tp>::value);
408 static_assert(__is_standard_integer<_Up>::value);
409
410 if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
411 return __t == __u;
412 else if constexpr (is_signed_v<_Tp>)
413 return __t >= 0 && make_unsigned_t<_Tp>(__t) == __u;
414 else
415 return __u >= 0 && __t == make_unsigned_t<_Up>(__u);
416 }
417
418 template<typename _Tp, typename _Up>
419 constexpr bool
420 cmp_not_equal(_Tp __t, _Up __u) noexcept
421 { return !std::cmp_equal(__t, __u); }
422
423 template<typename _Tp, typename _Up>
424 constexpr bool
425 cmp_less(_Tp __t, _Up __u) noexcept
426 {
427 static_assert(__is_standard_integer<_Tp>::value);
428 static_assert(__is_standard_integer<_Up>::value);
429
430 if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
431 return __t < __u;
432 else if constexpr (is_signed_v<_Tp>)
433 return __t < 0 || make_unsigned_t<_Tp>(__t) < __u;
434 else
435 return __u >= 0 && __t < make_unsigned_t<_Up>(__u);
436 }
437
438 template<typename _Tp, typename _Up>
439 constexpr bool
440 cmp_greater(_Tp __t, _Up __u) noexcept
441 { return std::cmp_less(__u, __t); }
442
443 template<typename _Tp, typename _Up>
444 constexpr bool
445 cmp_less_equal(_Tp __t, _Up __u) noexcept
446 { return !std::cmp_less(__u, __t); }
447
448 template<typename _Tp, typename _Up>
449 constexpr bool
450 cmp_greater_equal(_Tp __t, _Up __u) noexcept
451 { return !std::cmp_less(__t, __u); }
452
453 template<typename _Up, typename _Tp>
454 constexpr bool
455 in_range(_Tp __t) noexcept
456 {
457 static_assert(__is_standard_integer<_Up>::value);
458 static_assert(__is_standard_integer<_Tp>::value);
459 using __gnu_cxx::__int_traits;
460
461 if constexpr (is_signed_v<_Tp> == is_signed_v<_Up>)
462 return __int_traits<_Up>::__min <= __t
463 && __t <= __int_traits<_Up>::__max;
464 else if constexpr (is_signed_v<_Tp>)
465 return __t >= 0
466 && make_unsigned_t<_Tp>(__t) <= __int_traits<_Up>::__max;
467 else
468 return __t <= make_unsigned_t<_Up>(__int_traits<_Up>::__max);
469 }
470#endif // C++20
471#endif // C++17
472
473_GLIBCXX_END_NAMESPACE_VERSION
474} // namespace
475
476#endif
477
478#endif /* _GLIBCXX_UTILITY */