libstdc++
iterator_concepts.h
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1 // Concepts and traits for use with iterators -*- C++ -*-
2 
3 // Copyright (C) 2019 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file bits/iterator_concepts.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{iterator}
28  */
29 
30 #ifndef _ITERATOR_CONCEPTS_H
31 #define _ITERATOR_CONCEPTS_H 1
32 
33 #pragma GCC system_header
34 
35 #include <concepts>
36 #include <bits/ptr_traits.h> // to_address
37 #include <bits/range_cmp.h> // identity, ranges::less
38 
39 #if __cpp_lib_concepts
40 namespace std _GLIBCXX_VISIBILITY(default)
41 {
42 _GLIBCXX_BEGIN_NAMESPACE_VERSION
43 
44  struct input_iterator_tag;
45  struct output_iterator_tag;
46  struct forward_iterator_tag;
47  struct bidirectional_iterator_tag;
48  struct random_access_iterator_tag;
49  struct contiguous_iterator_tag;
50 
51  template<typename _Iterator>
52  struct iterator_traits;
53 
54  template<typename _Tp> requires is_object_v<_Tp>
55  struct iterator_traits<_Tp*>;
56 
57  template<typename _Iterator, typename>
58  struct __iterator_traits;
59 
60  namespace __detail
61  {
62  template<typename _Tp>
63  using __with_ref = _Tp&;
64 
65  template<typename _Tp>
66  concept __can_reference = requires { typename __with_ref<_Tp>; };
67 
68  template<typename _Tp>
69  concept __dereferenceable = requires(_Tp& __t)
70  {
71  { *__t } -> __can_reference;
72  };
73 
74  // FIXME: needed due to PR c++/67704
75  template<__detail::__dereferenceable _Tp>
76  struct __iter_ref
77  {
78  using type = decltype(*std::declval<_Tp&>());
79  };
80  } // namespace __detail
81 
82  template<typename _Tp>
83  using iter_reference_t = typename __detail::__iter_ref<_Tp>::type;
84 
85  namespace ranges
86  {
87  namespace __cust_imove
88  {
89  template<typename _Tp>
90  concept __adl_imove
91  = (std::__detail::__class_or_enum<remove_reference_t<_Tp>>)
92  && requires(_Tp&& __t) { iter_move(static_cast<_Tp&&>(__t)); };
93 
94  struct _IMove
95  {
96  private:
97  template<typename _Tp>
98  static constexpr bool
99  _S_noexcept()
100  {
101  if constexpr (__adl_imove<_Tp>)
102  return noexcept(iter_move(std::declval<_Tp>()));
103  else
104  return noexcept(*std::declval<_Tp>());
105  }
106 
107  public:
108  template<typename _Tp>
109  requires __adl_imove<_Tp> || requires(_Tp& __e) { *__e; }
110  constexpr decltype(auto)
111  operator()(_Tp&& __e) const
112  noexcept(_S_noexcept<_Tp>())
113  {
114  if constexpr (__adl_imove<_Tp>)
115  return iter_move(static_cast<_Tp&&>(__e));
116  else if constexpr (is_reference_v<iter_reference_t<_Tp>>)
117  return std::move(*__e);
118  else
119  return *__e;
120  }
121  };
122  } // namespace __cust_imove
123 
124  inline namespace __cust
125  {
126  inline constexpr __cust_imove::_IMove iter_move{};
127  } // inline namespace __cust
128  } // namespace ranges
129 
130  namespace __detail
131  {
132  // FIXME: needed due to PR c++/67704
133  template<__detail::__dereferenceable _Tp>
134  struct __iter_rvalue_ref
135  { };
136 
137  template<__detail::__dereferenceable _Tp>
138  requires requires(_Tp& __t)
139  {
140  { ranges::iter_move(__t) } -> __detail::__can_reference;
141  }
142  struct __iter_rvalue_ref<_Tp>
143  { using type = decltype(ranges::iter_move(std::declval<_Tp&>())); };
144 
145  } // namespace __detail
146 
147  template<typename _Tp>
148  using iter_rvalue_reference_t
149  = typename __detail::__iter_rvalue_ref<_Tp>::type;
150 
151  template<typename> struct incrementable_traits { };
152 
153  template<typename _Tp> requires is_object_v<_Tp>
154  struct incrementable_traits<_Tp*>
155  { using difference_type = ptrdiff_t; };
156 
157  template<typename _Iter>
158  struct incrementable_traits<const _Iter>
159  : incrementable_traits<_Iter> { };
160 
161  template<typename _Tp> requires requires { typename _Tp::difference_type; }
162  struct incrementable_traits<_Tp>
163  { using difference_type = typename _Tp::difference_type; };
164 
165  template<typename _Tp>
166  requires (!requires { typename _Tp::difference_type; }
167  && requires(const _Tp& __a, const _Tp& __b)
168  {
169  requires (!is_void_v<remove_pointer_t<_Tp>>); // PR c++/78173
170  { __a - __b } -> integral;
171  })
172  struct incrementable_traits<_Tp>
173  {
174  using difference_type
175  = make_signed_t<decltype(std::declval<_Tp>() - std::declval<_Tp>())>;
176  };
177 
178  namespace __detail
179  {
180  // An iterator such that iterator_traits<_Iter> names a specialization
181  // generated from the primary template.
182  template<typename _Iter>
183  concept __primary_traits_iter
184  = __is_base_of(__iterator_traits<_Iter, void>, iterator_traits<_Iter>);
185 
186  template<typename _Iter, typename _Tp>
187  struct __iter_traits_impl
188  { using type = iterator_traits<_Iter>; };
189 
190  template<typename _Iter, typename _Tp>
191  requires __primary_traits_iter<_Iter>
192  struct __iter_traits_impl<_Iter, _Tp>
193  { using type = _Tp; };
194 
195  // ITER_TRAITS
196  template<typename _Iter, typename _Tp = _Iter>
197  using __iter_traits = typename __iter_traits_impl<_Iter, _Tp>::type;
198  } // namespace __detail
199 
200  template<typename _Tp>
201  using iter_difference_t = typename
202  __detail::__iter_traits<_Tp, incrementable_traits<_Tp>>::difference_type;
203 
204  namespace __detail
205  {
206  template<typename> struct __cond_value_type { };
207 
208  template<typename _Tp> requires is_object_v<_Tp>
209  struct __cond_value_type<_Tp>
210  { using value_type = remove_cv_t<_Tp>; };
211  } // namespace __detail
212 
213  template<typename> struct readable_traits { };
214 
215  template<typename _Tp>
216  struct readable_traits<_Tp*>
217  : __detail::__cond_value_type<_Tp>
218  { };
219 
220  template<typename _Iter> requires is_array_v<_Iter>
221  struct readable_traits<_Iter>
222  { using value_type = remove_cv_t<remove_extent_t<_Iter>>; };
223 
224  template<typename _Iter>
225  struct readable_traits<const _Iter>
226  : readable_traits<_Iter>
227  { };
228 
229  template<typename _Tp> requires requires { typename _Tp::value_type; }
230  struct readable_traits<_Tp>
231  : __detail::__cond_value_type<typename _Tp::value_type>
232  { };
233 
234  template<typename _Tp> requires requires { typename _Tp::element_type; }
235  struct readable_traits<_Tp>
236  : __detail::__cond_value_type<typename _Tp::element_type>
237  { };
238 
239  template<typename _Tp>
240  using iter_value_t = typename
241  __detail::__iter_traits<_Tp, readable_traits<_Tp>>::value_type;
242 
243  namespace __detail
244  {
245  template<typename _Iter>
246  concept __cpp17_iterator = copyable<_Iter>
247  && requires(_Iter __it)
248  {
249  { *__it } -> __can_reference;
250  { ++__it } -> same_as<_Iter&>;
251  { *__it++ } -> __can_reference;
252  };
253 
254  template<typename _Iter>
255  concept __cpp17_input_iterator = __cpp17_iterator<_Iter>
256  && equality_comparable<_Iter>
257  && requires(_Iter __it)
258  {
259  typename incrementable_traits<_Iter>::difference_type;
260  typename readable_traits<_Iter>::value_type;
261  typename common_reference_t<iter_reference_t<_Iter>&&,
262  typename readable_traits<_Iter>::value_type&>;
263  typename common_reference_t<decltype(*__it++)&&,
264  typename readable_traits<_Iter>::value_type&>;
265  requires signed_integral<typename incrementable_traits<_Iter>::difference_type>;
266  };
267 
268  template<typename _Iter>
269  concept __cpp17_fwd_iterator = __cpp17_input_iterator<_Iter>
270  && constructible_from<_Iter>
271  && is_lvalue_reference_v<iter_reference_t<_Iter>>
272  && same_as<remove_cvref_t<iter_reference_t<_Iter>>,
273  typename readable_traits<_Iter>::value_type>
274  && requires(_Iter __it)
275  {
276  { __it++ } -> convertible_to<const _Iter&>;
277  { *__it++ } -> same_as<iter_reference_t<_Iter>>;
278  };
279 
280  template<typename _Iter>
281  concept __cpp17_bidi_iterator = __cpp17_fwd_iterator<_Iter>
282  && requires(_Iter __it)
283  {
284  { --__it } -> same_as<_Iter&>;
285  { __it-- } -> convertible_to<const _Iter&>;
286  { *__it-- } -> same_as<iter_reference_t<_Iter>>;
287  };
288 
289  template<typename _Iter>
290  concept __cpp17_randacc_iterator = __cpp17_bidi_iterator<_Iter>
291  && totally_ordered<_Iter>
292  && requires(_Iter __it,
293  typename incrementable_traits<_Iter>::difference_type __n)
294  {
295  { __it += __n } -> same_as<_Iter&>;
296  { __it -= __n } -> same_as<_Iter&>;
297  { __it + __n } -> same_as<_Iter>;
298  { __n + __it } -> same_as<_Iter>;
299  { __it - __n } -> same_as<_Iter>;
300  { __it - __it } -> same_as<decltype(__n)>;
301  { __it[__n] } -> convertible_to<iter_reference_t<_Iter>>;
302  };
303 
304  template<typename _Iter>
305  concept __iter_with_nested_types = requires {
306  typename _Iter::iterator_category;
307  typename _Iter::value_type;
308  typename _Iter::difference_type;
309  typename _Iter::reference;
310  };
311 
312  template<typename _Iter>
313  concept __iter_without_nested_types = !__iter_with_nested_types<_Iter>;
314 
315  template<typename _Iter, bool __use_arrow = false>
316  struct __ptr
317  { using type = void; };
318 
319  template<typename _Iter> requires requires { typename _Iter::pointer; }
320  struct __ptr<_Iter, true>
321  { using type = typename _Iter::pointer; };
322 
323  template<typename _Iter> requires requires { typename _Iter::pointer; }
324  struct __ptr<_Iter, false>
325  { using type = typename _Iter::pointer; };
326 
327  template<typename _Iter>
328  requires (!requires { typename _Iter::pointer; }
329  && requires(_Iter& __it) { __it.operator->(); })
330  struct __ptr<_Iter, true>
331  { using type = decltype(std::declval<_Iter&>().operator->()); };
332 
333  template<typename _Iter>
334  struct __ref
335  { using type = iter_reference_t<_Iter>; };
336 
337  template<typename _Iter> requires requires { typename _Iter::reference; }
338  struct __ref<_Iter>
339  { using type = typename _Iter::reference; };
340 
341  template<typename _Iter>
342  struct __cat
343  { using type = input_iterator_tag; };
344 
345  template<typename _Iter>
346  requires requires { typename _Iter::iterator_category; }
347  struct __cat<_Iter>
348  { using type = typename _Iter::iterator_category; };
349 
350  template<typename _Iter>
351  requires (!requires { typename _Iter::iterator_category; }
352  && __detail::__cpp17_randacc_iterator<_Iter>)
353  struct __cat<_Iter>
354  { using type = random_access_iterator_tag; };
355 
356  template<typename _Iter>
357  requires (!requires { typename _Iter::iterator_category; }
358  && __detail::__cpp17_bidi_iterator<_Iter>)
359  struct __cat<_Iter>
360  { using type = bidirectional_iterator_tag; };
361 
362  template<typename _Iter>
363  requires (!requires { typename _Iter::iterator_category; }
364  && __detail::__cpp17_fwd_iterator<_Iter>)
365  struct __cat<_Iter>
366  { using type = forward_iterator_tag; };
367 
368  template<typename _Iter>
369  struct __diff
370  { using type = void; };
371 
372  template<typename _Iter>
373  requires requires {
374  typename incrementable_traits<_Iter>::difference_type;
375  }
376  struct __diff<_Iter>
377  {
378  using type = typename incrementable_traits<_Iter>::difference_type;
379  };
380 
381  } // namespace __detail
382 
383  template<typename _Iterator>
384  requires __detail::__iter_with_nested_types<_Iterator>
385  struct __iterator_traits<_Iterator, void>
386  {
387  using iterator_category = typename _Iterator::iterator_category;
388  using value_type = typename _Iterator::value_type;
389  using difference_type = typename _Iterator::difference_type;
390  using pointer = typename __detail::__ptr<_Iterator>::type;
391  using reference = typename _Iterator::reference;
392  };
393 
394  template<typename _Iterator>
395  requires __detail::__iter_without_nested_types<_Iterator>
396  && __detail::__cpp17_input_iterator<_Iterator>
397  struct __iterator_traits<_Iterator, void>
398  {
399  using iterator_category = typename __detail::__cat<_Iterator>::type;
400  using value_type
401  = typename readable_traits<_Iterator>::value_type;
402  using difference_type
403  = typename incrementable_traits<_Iterator>::difference_type;
404  using pointer = typename __detail::__ptr<_Iterator, true>::type;
405  using reference = typename __detail::__ref<_Iterator>::type;
406  };
407 
408  template<typename _Iterator>
409  requires __detail::__iter_without_nested_types<_Iterator>
410  && __detail::__cpp17_iterator<_Iterator>
411  struct __iterator_traits<_Iterator, void>
412  {
413  using iterator_category = output_iterator_tag;
414  using value_type = void;
415  using difference_type = typename __detail::__diff<_Iterator>::type;
416  using pointer = void;
417  using reference = void;
418  };
419 
420  namespace __detail
421  {
422  template<typename _Iter>
423  struct __iter_concept_impl;
424 
425  // ITER_CONCEPT(I) is ITER_TRAITS(I)::iterator_concept if that is valid.
426  template<typename _Iter>
427  requires requires { typename __iter_traits<_Iter>::iterator_concept; }
428  struct __iter_concept_impl<_Iter>
429  { using type = typename __iter_traits<_Iter>::iterator_concept; };
430 
431  // Otherwise, ITER_TRAITS(I)::iterator_category if that is valid.
432  template<typename _Iter>
433  requires (!requires { typename __iter_traits<_Iter>::iterator_concept; }
434  && requires { typename __iter_traits<_Iter>::iterator_category; })
435  struct __iter_concept_impl<_Iter>
436  { using type = typename __iter_traits<_Iter>::iterator_category; };
437 
438  // Otherwise, random_access_tag if iterator_traits<I> is not specialized.
439  template<typename _Iter>
440  requires (!requires { typename __iter_traits<_Iter>::iterator_concept; }
441  && !requires { typename __iter_traits<_Iter>::iterator_category; }
442  && __primary_traits_iter<_Iter>)
443  struct __iter_concept_impl<_Iter>
444  { using type = random_access_iterator_tag; };
445 
446  // Otherwise, there is no ITER_CONCEPT(I) type.
447  template<typename _Iter>
448  struct __iter_concept_impl
449  { };
450 
451  // ITER_CONCEPT
452  template<typename _Iter>
453  using __iter_concept = typename __iter_concept_impl<_Iter>::type;
454  } // namespace __detail
455 
456  /// Requirements for types that are readable by applying operator*.
457  template<typename _In>
458  concept readable = requires
459  {
460  typename iter_value_t<_In>;
461  typename iter_reference_t<_In>;
462  typename iter_rvalue_reference_t<_In>;
463  }
464  && common_reference_with<iter_reference_t<_In>&&, iter_value_t<_In>&>
465  && common_reference_with<iter_reference_t<_In>&&,
466  iter_rvalue_reference_t<_In>&&>
467  && common_reference_with<iter_rvalue_reference_t<_In>&&,
468  const iter_value_t<_In>&>;
469 
470  namespace __detail
471  {
472  // FIXME: needed due to PR c++/67704
473  template<readable _Tp>
474  struct __iter_common_ref
475  : common_reference<iter_reference_t<_Tp>, iter_value_t<_Tp>&>
476  { };
477  } // namespace __detail
478 
479  template<typename _Tp>
480  using iter_common_reference_t
481  = typename __detail::__iter_common_ref<_Tp>::type;
482 
483  /// Requirements for writing a value into an iterator's referenced object.
484  template<typename _Out, typename _Tp>
485  concept writable = requires(_Out&& __o, _Tp&& __t)
486  {
487  *__o = std::forward<_Tp>(__t);
488  *std::forward<_Out>(__o) = std::forward<_Tp>(__t);
489  const_cast<const iter_reference_t<_Out>&&>(*__o)
490  = std::forward<_Tp>(__t);
491  const_cast<const iter_reference_t<_Out>&&>(*std::forward<_Out>(__o))
492  = std::forward<_Tp>(__t);
493  };
494 
495  /// Requirements on types that can be incremented with ++.
496  template<typename _Iter>
497  concept weakly_incrementable = default_initializable<_Iter>
498  && movable<_Iter>
499  && requires(_Iter __i)
500  {
501  typename iter_difference_t<_Iter>;
502  requires signed_integral<iter_difference_t<_Iter>>;
503  { ++__i } -> same_as<_Iter&>;
504  __i++;
505  };
506 
507  template<typename _Iter>
508  concept incrementable = regular<_Iter> && weakly_incrementable<_Iter>
509  && requires(_Iter __i) { { __i++ } -> same_as<_Iter>; };
510 
511  template<typename _Iter>
512  concept input_or_output_iterator
513  = requires(_Iter __i) { { *__i } -> __detail::__can_reference; }
514  && weakly_incrementable<_Iter>;
515 
516  template<typename _Sent, typename _Iter>
517  concept sentinel_for = semiregular<_Sent>
518  && input_or_output_iterator<_Iter>
519  && __detail::__weakly_eq_cmp_with<_Sent, _Iter>;
520 
521  template<typename _Sent, typename _Iter>
522  inline constexpr bool disable_sized_sentinel_for = false;
523 
524  template<typename _Sent, typename _Iter>
525  concept sized_sentinel_for = sentinel_for<_Sent, _Iter>
526  && !disable_sized_sentinel_for<remove_cv_t<_Sent>, remove_cv_t<_Iter>>
527  && requires(const _Iter& __i, const _Sent& __s)
528  {
529  { __s - __i } -> same_as<iter_difference_t<_Iter>>;
530  { __i - __s } -> same_as<iter_difference_t<_Iter>>;
531  };
532 
533  template<typename _Iter>
534  concept input_iterator = input_or_output_iterator<_Iter>
535  && readable<_Iter>
536  && requires { typename __detail::__iter_concept<_Iter>; }
537  && derived_from<__detail::__iter_concept<_Iter>, input_iterator_tag>;
538 
539  template<typename _Iter, typename _Tp>
540  concept output_iterator = input_or_output_iterator<_Iter>
541  && writable<_Iter, _Tp>
542  && requires(_Iter __i, _Tp&& __t) { *__i++ = std::forward<_Tp>(__t); };
543 
544  template<typename _Iter>
545  concept forward_iterator = input_iterator<_Iter>
546  && derived_from<__detail::__iter_concept<_Iter>, forward_iterator_tag>
547  && incrementable<_Iter> && sentinel_for<_Iter, _Iter>;
548 
549  template<typename _Iter>
550  concept bidirectional_iterator = forward_iterator<_Iter>
551  && derived_from<__detail::__iter_concept<_Iter>,
552  bidirectional_iterator_tag>
553  && requires(_Iter __i)
554  {
555  { --__i } -> same_as<_Iter&>;
556  { __i-- } -> same_as<_Iter>;
557  };
558 
559  template<typename _Iter>
560  concept random_access_iterator = bidirectional_iterator<_Iter>
561  && derived_from<__detail::__iter_concept<_Iter>,
562  random_access_iterator_tag>
563  && totally_ordered<_Iter> && sized_sentinel_for<_Iter, _Iter>
564  && requires(_Iter __i, const _Iter __j,
565  const iter_difference_t<_Iter> __n)
566  {
567  { __i += __n } -> same_as<_Iter&>;
568  { __j + __n } -> same_as<_Iter>;
569  { __n + __j } -> same_as<_Iter>;
570  { __i -= __n } -> same_as<_Iter&>;
571  { __j - __n } -> same_as<_Iter>;
572  { __j[__n] } -> same_as<iter_reference_t<_Iter>>;
573  };
574 
575  template<typename _Iter>
576  concept contiguous_iterator = random_access_iterator<_Iter>
577  && derived_from<__detail::__iter_concept<_Iter>, contiguous_iterator_tag>
578  && is_lvalue_reference_v<iter_reference_t<_Iter>>
579  && same_as<iter_value_t<_Iter>, remove_cvref_t<iter_reference_t<_Iter>>>
580  && requires(const _Iter& __i)
581  {
582  { std::to_address(__i) }
583  -> same_as<add_pointer_t<iter_reference_t<_Iter>>>;
584  };
585 
586  // [indirectcallable], indirect callable requirements
587 
588  // [indirectcallable.indirectinvocable], indirect callables
589 
590  template<typename _Fn, typename _Iter>
591  concept indirectly_unary_invocable = readable<_Iter>
592  && copy_constructible<_Fn> && invocable<_Fn&, iter_value_t<_Iter>&>
593  && invocable<_Fn&, iter_reference_t<_Iter>>
594  && invocable<_Fn&, iter_common_reference_t<_Iter>>
595  && common_reference_with<invoke_result_t<_Fn&, iter_value_t<_Iter>&>,
596  invoke_result_t<_Fn&, iter_reference_t<_Iter>>>;
597 
598  template<typename _Fn, typename _Iter>
599  concept indirectly_regular_unary_invocable = readable<_Iter>
600  && copy_constructible<_Fn>
601  && regular_invocable<_Fn&, iter_value_t<_Iter>&>
602  && regular_invocable<_Fn&, iter_reference_t<_Iter>>
603  && regular_invocable<_Fn&, iter_common_reference_t<_Iter>>
604  && common_reference_with<invoke_result_t<_Fn&, iter_value_t<_Iter>&>,
605  invoke_result_t<_Fn&, iter_reference_t<_Iter>>>;
606 
607  template<typename _Fn, typename _Iter>
608  concept indirect_unary_predicate = readable<_Iter>
609  && copy_constructible<_Fn> && predicate<_Fn&, iter_value_t<_Iter>&>
610  && predicate<_Fn&, iter_reference_t<_Iter>>
611  && predicate<_Fn&, iter_common_reference_t<_Iter>>;
612 
613  template<typename _Fn, typename _I1, typename _I2>
614  concept indirect_binary_predicate = readable<_I1> && readable<_I2>
615  && copy_constructible<_Fn>
616  && predicate<_Fn&, iter_value_t<_I1>&, iter_value_t<_I2>&>
617  && predicate<_Fn&, iter_value_t<_I1>&, iter_reference_t<_I2>>
618  && predicate<_Fn&, iter_reference_t<_I1>, iter_value_t<_I2>&>
619  && predicate<_Fn&, iter_reference_t<_I1>, iter_reference_t<_I2>>
620  && predicate<_Fn&, iter_common_reference_t<_I1>,
621  iter_common_reference_t<_I2>>;
622 
623  template<typename _Fn, typename _I1, typename _I2 = _I1>
624  concept indirect_equivalence_relation = readable<_I1> && readable<_I2>
625  && copy_constructible<_Fn>
626  && equivalence_relation<_Fn&, iter_value_t<_I1>&, iter_value_t<_I2>&>
627  && equivalence_relation<_Fn&, iter_value_t<_I1>&, iter_reference_t<_I2>>
628  && equivalence_relation<_Fn&, iter_reference_t<_I1>, iter_value_t<_I2>&>
629  && equivalence_relation<_Fn&, iter_reference_t<_I1>,
630  iter_reference_t<_I2>>
631  && equivalence_relation<_Fn&, iter_common_reference_t<_I1>,
632  iter_common_reference_t<_I2>>;
633 
634  template<typename _Fn, typename _I1, typename _I2 = _I1>
635  concept indirect_strict_weak_order = readable<_I1> && readable<_I2>
636  && copy_constructible<_Fn>
637  && strict_weak_order<_Fn&, iter_value_t<_I1>&, iter_value_t<_I2>&>
638  && strict_weak_order<_Fn&, iter_value_t<_I1>&, iter_reference_t<_I2>>
639  && strict_weak_order<_Fn&, iter_reference_t<_I1>, iter_value_t<_I2>&>
640  && strict_weak_order<_Fn&, iter_reference_t<_I1>, iter_reference_t<_I2>>
641  && strict_weak_order<_Fn&, iter_common_reference_t<_I1>,
642  iter_common_reference_t<_I2>>;
643 
644  namespace __detail
645  {
646  // FIXME: needed due to PR c++/67704
647  template<typename _Fn, typename... _Is>
648  struct __indirect_result
649  { };
650 
651  template<typename _Fn, typename... _Is>
652  requires (readable<_Is> && ...)
653  && invocable<_Fn, iter_reference_t<_Is>...>
654  struct __indirect_result<_Fn, _Is...>
655  : invoke_result<_Fn, iter_reference_t<_Is>...>
656  { };
657  } // namespace __detail
658 
659  template<typename _Fn, typename... _Is>
660  using indirect_result_t = typename
661  __detail::__indirect_result<_Fn, _Is...>::type;
662 
663  /// [projected], projected
664  template<readable _Iter, indirectly_regular_unary_invocable<_Iter> _Proj>
665  struct projected
666  {
667  using value_type = remove_cvref_t<indirect_result_t<_Proj&, _Iter>>;
668 
669  indirect_result_t<_Proj&, _Iter> operator*() const; // not defined
670  };
671 
672  template<weakly_incrementable _Iter, typename _Proj>
673  struct incrementable_traits<projected<_Iter, _Proj>>
674  { using difference_type = iter_difference_t<_Iter>; };
675 
676  // [alg.req], common algorithm requirements
677 
678  /// [alg.req.ind.move], concept `indirectly_movable`
679 
680  template<typename _In, typename _Out>
681  concept indirectly_movable = readable<_In>
682  && writable<_Out, iter_rvalue_reference_t<_In>>;
683 
684  template<typename _In, typename _Out>
685  concept indirectly_movable_storable = indirectly_movable<_In, _Out>
686  && writable<_Out, iter_value_t<_In>> && movable<iter_value_t<_In>>
687  && constructible_from<iter_value_t<_In>, iter_rvalue_reference_t<_In>>
688  && assignable_from<iter_value_t<_In>&, iter_rvalue_reference_t<_In>>;
689 
690  /// [alg.req.ind.copy], concept `indirectly_copyable`
691  template<typename _In, typename _Out>
692  concept indirectly_copyable = readable<_In>
693  && writable<_Out, iter_reference_t<_In>>;
694 
695  template<typename _In, typename _Out>
696  concept indirectly_copyable_storable = indirectly_copyable<_In, _Out>
697  && writable<_Out, const iter_value_t<_In>&>
698  && copyable<iter_value_t<_In>>
699  && constructible_from<iter_value_t<_In>, iter_reference_t<_In>>
700  && assignable_from<iter_value_t<_In>&, iter_reference_t<_In>>;
701 
702 namespace ranges
703 {
704  namespace __cust_iswap
705  {
706  template<typename _It1, typename _It2>
707  void iter_swap(_It1, _It2) = delete;
708 
709  template<typename _Tp, typename _Up>
710  concept __adl_iswap
711  = (std::__detail::__class_or_enum<remove_reference_t<_Tp>>
712  || std::__detail::__class_or_enum<remove_reference_t<_Up>>)
713  && requires(_Tp&& __t, _Up&& __u) {
714  iter_swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
715  };
716 
717  template<typename _Xp, typename _Yp>
718  constexpr iter_value_t<remove_reference_t<_Xp>>
719  __iter_exchange_move(_Xp&& __x, _Yp&& __y)
720  noexcept(noexcept(iter_value_t<remove_reference_t<_Xp>>(iter_move(__x)))
721  && noexcept(*__x = iter_move(__y)))
722  {
723  iter_value_t<remove_reference_t<_Xp>> __old_value(iter_move(__x));
724  *__x = iter_move(__y);
725  return __old_value;
726  }
727 
728  struct _IterSwap
729  {
730  private:
731  template<typename _Tp, typename _Up>
732  static constexpr bool
733  _S_noexcept()
734  {
735  if constexpr (__adl_iswap<_Tp, _Up>)
736  return noexcept(iter_swap(std::declval<_Tp>(),
737  std::declval<_Up>()));
738  else if constexpr (readable<_Tp> && readable<_Up>
739  && swappable_with<iter_reference_t<_Tp>, iter_reference_t<_Up>>)
740  return noexcept(ranges::swap(*std::declval<_Tp>(),
741  *std::declval<_Up>()));
742  else
743  return noexcept(*std::declval<_Tp>()
744  = __iter_exchange_move(std::declval<_Up>(),
745  std::declval<_Tp>()));
746  }
747 
748  public:
749  template<typename _Tp, typename _Up>
750  requires __adl_iswap<_Tp, _Up>
751  || (readable<remove_reference_t<_Tp>>
752  && readable<remove_reference_t<_Up>>
753  && swappable_with<iter_reference_t<_Tp>, iter_reference_t<_Up>>)
754  || (indirectly_movable_storable<_Tp, _Up>
755  && indirectly_movable_storable<_Up, _Tp>)
756  constexpr void
757  operator()(_Tp&& __e1, _Up&& __e2) const
758  noexcept(_S_noexcept<_Tp, _Up>())
759  {
760  if constexpr (__adl_iswap<_Tp, _Up>)
761  iter_swap(static_cast<_Tp&&>(__e1), static_cast<_Up&&>(__e2));
762  else if constexpr (readable<_Tp> && readable<_Up>
763  && swappable_with<iter_reference_t<_Tp>, iter_reference_t<_Up>>)
764  ranges::swap(*__e1, *__e2);
765  else
766  *__e1 = __iter_exchange_move(__e2, __e1);
767  }
768  };
769  } // namespace __cust_iswap
770 
771  inline namespace __cust
772  {
773  inline constexpr __cust_iswap::_IterSwap iter_swap{};
774  } // inline namespace __cust
775 
776 } // namespace ranges
777 
778  /// [alg.req.ind.swap], concept `indirectly_swappable`
779  template<typename _I1, typename _I2 = _I1>
780  concept indirectly_swappable = readable<_I1> && readable<_I2>
781  && requires(_I1& __i1, _I2& __i2)
782  {
783  ranges::iter_swap(__i1, __i1);
784  ranges::iter_swap(__i2, __i2);
785  ranges::iter_swap(__i1, __i2);
786  ranges::iter_swap(__i2, __i1);
787  };
788 
789  /// [alg.req.ind.cmp], concept `indirectly_comparable`
790  template<typename _I1, typename _I2, typename _Rel, typename _P1 = identity,
791  typename _P2 = identity>
792  concept indirectly_comparable
793  = indirect_binary_predicate<_Rel, projected<_I1, _P1>,
794  projected<_I2, _P2>>;
795 
796  /// [alg.req.permutable], concept `permutable`
797  template<typename _Iter>
798  concept permutable = forward_iterator<_Iter>
799  && indirectly_movable_storable<_Iter, _Iter>
800  && indirectly_swappable<_Iter, _Iter>;
801 
802  /// [alg.req.mergeable], concept `mergeable`
803  template<typename _I1, typename _I2, typename _Out,
804  typename _Rel = ranges::less, typename _P1 = identity,
805  typename _P2 = identity>
806  concept mergeable = input_iterator<_I1> && input_iterator<_I2>
807  && weakly_incrementable<_Out> && indirectly_copyable<_I1, _Out>
808  && indirectly_copyable<_I2, _Out>
809  && indirect_strict_weak_order<_Rel, projected<_I1, _P1>,
810  projected<_I2, _P2>>;
811 
812  /// [alg.req.sortable], concept `sortable`
813  template<typename _Iter, typename _Rel = ranges::less,
814  typename _Proj = identity>
815  concept sortable = permutable<_Iter>
816  && indirect_strict_weak_order<_Rel, projected<_Iter, _Proj>>;
817 
818  struct unreachable_sentinel_t
819  {
820  template<weakly_incrementable _It>
821  friend constexpr bool
822  operator==(unreachable_sentinel_t, const _It&) noexcept
823  { return false; }
824  };
825 
826  inline constexpr unreachable_sentinel_t unreachable_sentinel{};
827 
828  struct default_sentinel_t { };
829  inline constexpr default_sentinel_t default_sentinel{};
830 
831 _GLIBCXX_END_NAMESPACE_VERSION
832 } // namespace std
833 #endif // C++20 library concepts
834 #endif // _ITERATOR_CONCEPTS_H
std
ISO C++ entities toplevel namespace is std.
std::operator*
constexpr complex< _Tp > operator*(const complex< _Tp > &__x, const complex< _Tp > &__y)
Return new complex value x times y.
Definition: complex:391
ptr_traits.h
range_cmp.h
std::remove_reference_t
typename remove_reference< _Tp >::type remove_reference_t
Alias template for remove_reference.
Definition: type_traits:1632
std::move
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:101
concepts