1// -*- C++ -*-
2//===-------------------------- iterator ----------------------------------===//
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_ITERATOR
11#define _LIBCPP_ITERATOR
12
13/*
14    iterator synopsis
15
16#include <concepts>
17
18namespace std
19{
20template<class> struct incrementable_traits;       // since C++20
21template<class T>
22  using iter_difference_t = see below;             // since C++20
23
24template<class> struct indirectly_readable_traits; // since C++20
25template<class T>
26  using iter_value_t = see below;                  // since C++20
27
28template<class Iterator>
29struct iterator_traits;
30
31template<class T>
32  requires is_object_v<T>                    // since C++20
33struct iterator_traits<T*>;
34
35template<dereferenceable T>
36  using iter_reference_t = decltype(*declval<T&>());
37
38namespace ranges::inline unspecified {
39    inline constexpr unspecified iter_move = unspecified; // since C++20, nodiscard as an extension
40}}
41
42template<dereferenceable T>
43  requires ...
44using iter_rvalue_reference_t = decltype(ranges::iter_move(declval<T&>())); // since C++20
45
46// [iterator.concepts], iterator concepts
47// [iterator.concept.readable], concept indirectly_readable
48template<class In>
49  concept indirectly_readable = see below;                      // since C++20
50
51template<indirectly_readable T>
52  using iter_common_reference_t =
53    common_reference_t<iter_reference_t<T>, iter_value_t<T>&>;  // since C++20
54
55// [iterator.concept.writable], concept indirectly_writable
56template<class Out, class T>
57  concept indirectly_writable = see below;                // since C++20
58
59// [iterator.concept.winc], concept weakly_incrementable
60template<class I>
61  concept weakly_incrementable = see below;                // since C++20
62
63// [iterator.concept.inc], concept incrementable
64template<class I>
65  concept incrementable = see below;                       // since C++20
66
67// [iterator.concept.iterator], concept input_or_output_iterator
68  template<class I>
69    concept input_or_output_iterator = see below;          // since C++20
70
71// [iterator.concept.sentinel], concept sentinel_for
72template<class S, class I>
73  concept sentinel_for = see below;                        // since C++20
74
75// [iterator.concept.sizedsentinel], concept sized_sentinel_for
76template<class S, class I>
77  inline constexpr bool disable_sized_sentinel_for = false;
78
79template<class S, class I>
80  concept sized_sentinel_for = see below;
81
82// [iterator.concept.input], concept input_iterator
83template<class I>
84  concept input_iterator = see below;                      // since C++20
85
86// [iterator.concept.forward], concept forward_iterator
87template<class I>
88  concept forward_iterator = see below;                    // since C++20
89
90// [iterator.concept.bidir], concept bidirectional_iterator
91template<class I>
92  concept bidirectional_iterator = see below;              // since C++20
93
94// [iterator.concept.random.access], concept random_access_iterator
95template<class I>
96  concept random_access_iterator = see below;              // since C++20
97
98// [indirectcallable]
99// [indirectcallable.indirectinvocable]
100template<class F, class I>
101  concept indirectly_unary_invocable = see below;          // since C++20
102
103template<class F, class I>
104  concept indirectly_regular_unary_invocable = see below;  // since C++20
105
106template<class F, class I>
107  concept indirect_unary_predicate = see below;            // since C++20
108
109template<class F, class I1, class I2>
110  concept indirect_binary_predicate = see below;           // since C++20
111
112template<class F, class I1, class I2 = I1>
113  concept indirect_equivalence_relation = see below;       // since C++20
114
115template<class F, class I1, class I2 = I1>
116  concept indirect_strict_weak_order = see below;          // since C++20
117
118template<class F, class... Is>
119  using indirect_result_t = see below;                     // since C++20
120
121// [projected], projected
122template<indirectly_readable I, indirectly_regular_unary_invocable<I> Proj>
123  struct projected;                                        // since C++20
124
125template<weakly_incrementable I, indirectly_regular_unary_invocable<I> Proj>
126  struct incrementable_traits<projected<I, Proj>>;         // since C++20
127
128// [alg.req.ind.move], concept indirectly_movable
129template<class In, class Out>
130  concept indirectly_movable = see below;                  // since C++20
131
132template<class In, class Out>
133  concept indirectly_movable_storable = see below;         // since C++20
134
135template<class Category, class T, class Distance = ptrdiff_t,
136         class Pointer = T*, class Reference = T&>
137struct iterator                                            // deprecated in C++17
138{
139    typedef T         value_type;
140    typedef Distance  difference_type;
141    typedef Pointer   pointer;
142    typedef Reference reference;
143    typedef Category  iterator_category;
144};
145
146struct input_iterator_tag  {};
147struct output_iterator_tag {};
148struct forward_iterator_tag       : public input_iterator_tag         {};
149struct bidirectional_iterator_tag : public forward_iterator_tag       {};
150struct random_access_iterator_tag : public bidirectional_iterator_tag {};
151
152// 27.4.3, iterator operations
153template <class InputIterator, class Distance>  // constexpr in C++17
154  constexpr void advance(InputIterator& i, Distance n);
155
156template <class InputIterator>  // constexpr in C++17
157  constexpr typename iterator_traits<InputIterator>::difference_type
158    distance(InputIterator first, InputIterator last);
159
160template <class InputIterator>  // constexpr in C++17
161  constexpr InputIterator next(InputIterator x,
162typename iterator_traits<InputIterator>::difference_type n = 1);
163
164template <class BidirectionalIterator>  // constexpr in C++17
165  constexpr BidirectionalIterator prev(BidirectionalIterator x,
166    typename iterator_traits<BidirectionalIterator>::difference_type n = 1);
167
168// [range.iter.ops], range iterator operations
169namespace ranges {
170  // [range.iter.op.advance], ranges::advance
171  template<input_or_output_iterator I>
172    constexpr void advance(I& i, iter_difference_t<I> n);                          // since C++20
173  template<input_or_output_iterator I, sentinel_for<I> S>
174    constexpr void advance(I& i, S bound);                                         // since C++20
175  template<input_or_output_iterator I, sentinel_for<I> S>
176    constexpr iter_difference_t<I> advance(I& i, iter_difference_t<I> n, S bound); // since C++20
177}
178
179template <class Iterator>
180class reverse_iterator
181    : public iterator<typename iterator_traits<Iterator>::iterator_category, // until C++17
182                      typename iterator_traits<Iterator>::value_type,
183                      typename iterator_traits<Iterator>::difference_type,
184                      typename iterator_traits<Iterator>::pointer,
185                      typename iterator_traits<Iterator>::reference>
186{
187protected:
188    Iterator current;
189public:
190    typedef Iterator                                            iterator_type;
191    typedef typename iterator_traits<Iterator>::difference_type difference_type;
192    typedef typename iterator_traits<Iterator>::reference       reference;
193    typedef typename iterator_traits<Iterator>::pointer         pointer;
194
195    constexpr reverse_iterator();
196    constexpr explicit reverse_iterator(Iterator x);
197    template <class U> constexpr reverse_iterator(const reverse_iterator<U>& u);
198    template <class U> constexpr reverse_iterator& operator=(const reverse_iterator<U>& u);
199    constexpr Iterator base() const;
200    constexpr reference operator*() const;
201    constexpr pointer   operator->() const;
202    constexpr reverse_iterator& operator++();
203    constexpr reverse_iterator  operator++(int);
204    constexpr reverse_iterator& operator--();
205    constexpr reverse_iterator  operator--(int);
206    constexpr reverse_iterator  operator+ (difference_type n) const;
207    constexpr reverse_iterator& operator+=(difference_type n);
208    constexpr reverse_iterator  operator- (difference_type n) const;
209    constexpr reverse_iterator& operator-=(difference_type n);
210    constexpr reference         operator[](difference_type n) const;
211};
212
213template <class Iterator1, class Iterator2>
214constexpr bool                          // constexpr in C++17
215operator==(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
216
217template <class Iterator1, class Iterator2>
218constexpr bool                          // constexpr in C++17
219operator<(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
220
221template <class Iterator1, class Iterator2>
222constexpr bool                          // constexpr in C++17
223operator!=(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
224
225template <class Iterator1, class Iterator2>
226constexpr bool                          // constexpr in C++17
227operator>(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
228
229template <class Iterator1, class Iterator2>
230constexpr bool                          // constexpr in C++17
231operator>=(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
232
233template <class Iterator1, class Iterator2>
234constexpr bool                          // constexpr in C++17
235operator<=(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
236
237template <class Iterator1, class Iterator2>
238constexpr auto
239operator-(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y)
240-> decltype(__y.base() - __x.base());   // constexpr in C++17
241
242template <class Iterator>
243constexpr reverse_iterator<Iterator>
244operator+(typename reverse_iterator<Iterator>::difference_type n,
245          const reverse_iterator<Iterator>& x);   // constexpr in C++17
246
247template <class Iterator>
248constexpr reverse_iterator<Iterator> make_reverse_iterator(Iterator i); // C++14, constexpr in C++17
249
250template <class Container>
251class back_insert_iterator
252    : public iterator<output_iterator_tag, void, void, void, void> // until C++17
253{
254protected:
255    Container* container;
256public:
257    typedef Container                   container_type;
258    typedef void                        value_type;
259    typedef void                        difference_type; // until C++20
260    typedef ptrdiff_t                   difference_type; // since C++20
261    typedef void                        reference;
262    typedef void                        pointer;
263
264    explicit back_insert_iterator(Container& x);  // constexpr in C++20
265    back_insert_iterator& operator=(const typename Container::value_type& value);  // constexpr in C++20
266    back_insert_iterator& operator*();  // constexpr in C++20
267    back_insert_iterator& operator++();  // constexpr in C++20
268    back_insert_iterator  operator++(int);  // constexpr in C++20
269};
270
271template <class Container> back_insert_iterator<Container> back_inserter(Container& x);  // constexpr in C++20
272
273template <class Container>
274class front_insert_iterator
275    : public iterator<output_iterator_tag, void, void, void, void> // until C++17
276{
277protected:
278    Container* container;
279public:
280    typedef Container                    container_type;
281    typedef void                         value_type;
282    typedef void                         difference_type; // until C++20
283    typedef ptrdiff_t                    difference_type; // since C++20
284    typedef void                         reference;
285    typedef void                         pointer;
286
287    explicit front_insert_iterator(Container& x);  // constexpr in C++20
288    front_insert_iterator& operator=(const typename Container::value_type& value);  // constexpr in C++20
289    front_insert_iterator& operator*();  // constexpr in C++20
290    front_insert_iterator& operator++();  // constexpr in C++20
291    front_insert_iterator  operator++(int);  // constexpr in C++20
292};
293
294template <class Container> front_insert_iterator<Container> front_inserter(Container& x);  // constexpr in C++20
295
296template <class Container>
297class insert_iterator
298    : public iterator<output_iterator_tag, void, void, void, void> // until C++17
299{
300protected:
301    Container* container;
302    typename Container::iterator iter;
303public:
304    typedef Container              container_type;
305    typedef void                   value_type;
306    typedef void                   difference_type; // until C++20
307    typedef ptrdiff_t              difference_type; // since C++20
308    typedef void                   reference;
309    typedef void                   pointer;
310
311    insert_iterator(Container& x, typename Container::iterator i);  // constexpr in C++20
312    insert_iterator& operator=(const typename Container::value_type& value);  // constexpr in C++20
313    insert_iterator& operator*();  // constexpr in C++20
314    insert_iterator& operator++();  // constexpr in C++20
315    insert_iterator& operator++(int);  // constexpr in C++20
316};
317
318template <class Container, class Iterator>
319insert_iterator<Container> inserter(Container& x, Iterator i);  // constexpr in C++20
320
321template <class Iterator>
322class move_iterator {
323public:
324    typedef Iterator                                              iterator_type;
325    typedef typename iterator_traits<Iterator>::difference_type   difference_type;
326    typedef Iterator                                              pointer;
327    typedef typename iterator_traits<Iterator>::value_type        value_type;
328    typedef typename iterator_traits<Iterator>::iterator_category iterator_category;
329    typedef value_type&&                                          reference;
330
331    constexpr move_iterator();  // all the constexprs are in C++17
332    constexpr explicit move_iterator(Iterator i);
333    template <class U>
334      constexpr move_iterator(const move_iterator<U>& u);
335    template <class U>
336      constexpr move_iterator& operator=(const move_iterator<U>& u);
337    constexpr iterator_type base() const;
338    constexpr reference operator*() const;
339    constexpr pointer operator->() const;
340    constexpr move_iterator& operator++();
341    constexpr move_iterator operator++(int);
342    constexpr move_iterator& operator--();
343    constexpr move_iterator operator--(int);
344    constexpr move_iterator operator+(difference_type n) const;
345    constexpr move_iterator& operator+=(difference_type n);
346    constexpr move_iterator operator-(difference_type n) const;
347    constexpr move_iterator& operator-=(difference_type n);
348    constexpr unspecified operator[](difference_type n) const;
349private:
350    Iterator current; // exposition only
351};
352
353template <class Iterator1, class Iterator2>
354constexpr bool   // constexpr in C++17
355operator==(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
356
357template <class Iterator1, class Iterator2>
358constexpr bool   // constexpr in C++17
359operator!=(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
360
361template <class Iterator1, class Iterator2>
362constexpr bool   // constexpr in C++17
363operator<(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
364
365template <class Iterator1, class Iterator2>
366constexpr bool   // constexpr in C++17
367operator<=(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
368
369template <class Iterator1, class Iterator2>
370constexpr bool   // constexpr in C++17
371operator>(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
372
373template <class Iterator1, class Iterator2>
374constexpr bool   // constexpr in C++17
375operator>=(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
376
377template <class Iterator1, class Iterator2>
378constexpr auto   // constexpr in C++17
379operator-(const move_iterator<Iterator1>& x,
380          const move_iterator<Iterator2>& y) -> decltype(x.base() - y.base());
381
382template <class Iterator>
383constexpr move_iterator<Iterator> operator+(   // constexpr in C++17
384            typename move_iterator<Iterator>::difference_type n,
385            const move_iterator<Iterator>& x);
386
387template <class Iterator>   // constexpr in C++17
388constexpr  move_iterator<Iterator> make_move_iterator(const Iterator& i);
389
390// [default.sentinel], default sentinel
391struct default_sentinel_t;
392inline constexpr default_sentinel_t default_sentinel{};
393
394template <class T, class charT = char, class traits = char_traits<charT>, class Distance = ptrdiff_t>
395class istream_iterator
396    : public iterator<input_iterator_tag, T, Distance, const T*, const T&> // until C++17
397{
398public:
399    typedef input_iterator_tag           iterator_category;
400    typedef T                            value_type;
401    typedef Distance                     difference_type;
402    typedef const T*                     pointer;
403    typedef const T&                     reference;
404
405    typedef charT                        char_type;
406    typedef traits                       traits_type;
407    typedef basic_istream<charT, traits> istream_type;
408
409    constexpr istream_iterator();
410    istream_iterator(istream_type& s);
411    istream_iterator(const istream_iterator& x);
412    ~istream_iterator();
413
414    const T& operator*() const;
415    const T* operator->() const;
416    istream_iterator& operator++();
417    istream_iterator  operator++(int);
418};
419
420template <class T, class charT, class traits, class Distance>
421bool operator==(const istream_iterator<T,charT,traits,Distance>& x,
422                const istream_iterator<T,charT,traits,Distance>& y);
423template <class T, class charT, class traits, class Distance>
424bool operator!=(const istream_iterator<T,charT,traits,Distance>& x,
425                const istream_iterator<T,charT,traits,Distance>& y);
426
427template <class T, class charT = char, class traits = char_traits<charT> >
428class ostream_iterator
429    : public iterator<output_iterator_tag, void, void, void, void> // until C++17
430{
431public:
432    typedef output_iterator_tag         iterator_category;
433    typedef void                        value_type;
434    typedef void                        difference_type; // until C++20
435    typedef ptrdiff_t                   difference_type; // since C++20
436    typedef void                        pointer;
437    typedef void                        reference;
438
439    typedef charT char_type;
440    typedef traits traits_type;
441    typedef basic_ostream<charT,traits> ostream_type;
442
443    ostream_iterator(ostream_type& s);
444    ostream_iterator(ostream_type& s, const charT* delimiter);
445    ostream_iterator(const ostream_iterator& x);
446    ~ostream_iterator();
447    ostream_iterator& operator=(const T& value);
448
449    ostream_iterator& operator*();
450    ostream_iterator& operator++();
451    ostream_iterator& operator++(int);
452};
453
454template<class charT, class traits = char_traits<charT> >
455class istreambuf_iterator
456    : public iterator<input_iterator_tag, charT, traits::off_type, unspecified, charT> // until C++17
457{
458public:
459    typedef input_iterator_tag              iterator_category;
460    typedef charT                           value_type;
461    typedef traits::off_type                difference_type;
462    typedef unspecified                     pointer;
463    typedef charT                           reference;
464
465    typedef charT                           char_type;
466    typedef traits                          traits_type;
467    typedef traits::int_type                int_type;
468    typedef basic_streambuf<charT, traits>  streambuf_type;
469    typedef basic_istream<charT, traits>    istream_type;
470
471    istreambuf_iterator() noexcept;
472    istreambuf_iterator(istream_type& s) noexcept;
473    istreambuf_iterator(streambuf_type* s) noexcept;
474    istreambuf_iterator(a-private-type) noexcept;
475
476    charT                operator*() const;
477    pointer operator->() const;
478    istreambuf_iterator& operator++();
479    a-private-type       operator++(int);
480
481    bool equal(const istreambuf_iterator& b) const;
482};
483
484template <class charT, class traits>
485bool operator==(const istreambuf_iterator<charT,traits>& a,
486                const istreambuf_iterator<charT,traits>& b);
487template <class charT, class traits>
488bool operator!=(const istreambuf_iterator<charT,traits>& a,
489                const istreambuf_iterator<charT,traits>& b);
490
491template <class charT, class traits = char_traits<charT> >
492class ostreambuf_iterator
493    : public iterator<output_iterator_tag, void, void, void, void> // until C++17
494{
495public:
496    typedef output_iterator_tag            iterator_category;
497    typedef void                           value_type;
498    typedef void                           difference_type; // until C++20
499    typedef ptrdiff_t                      difference_type; // since C++20
500    typedef void                           pointer;
501    typedef void                           reference;
502
503    typedef charT                          char_type;
504    typedef traits                         traits_type;
505    typedef basic_streambuf<charT, traits> streambuf_type;
506    typedef basic_ostream<charT, traits>   ostream_type;
507
508    ostreambuf_iterator(ostream_type& s) noexcept;
509    ostreambuf_iterator(streambuf_type* s) noexcept;
510    ostreambuf_iterator& operator=(charT c);
511    ostreambuf_iterator& operator*();
512    ostreambuf_iterator& operator++();
513    ostreambuf_iterator& operator++(int);
514    bool failed() const noexcept;
515};
516
517template <class C> constexpr auto begin(C& c) -> decltype(c.begin());
518template <class C> constexpr auto begin(const C& c) -> decltype(c.begin());
519template <class C> constexpr auto end(C& c) -> decltype(c.end());
520template <class C> constexpr auto end(const C& c) -> decltype(c.end());
521template <class T, size_t N> constexpr T* begin(T (&array)[N]);
522template <class T, size_t N> constexpr T* end(T (&array)[N]);
523
524template <class C> auto constexpr cbegin(const C& c) -> decltype(std::begin(c));        // C++14
525template <class C> auto constexpr cend(const C& c) -> decltype(std::end(c));            // C++14
526template <class C> auto constexpr rbegin(C& c) -> decltype(c.rbegin());                 // C++14
527template <class C> auto constexpr rbegin(const C& c) -> decltype(c.rbegin());           // C++14
528template <class C> auto constexpr rend(C& c) -> decltype(c.rend());                     // C++14
529template <class C> constexpr auto rend(const C& c) -> decltype(c.rend());               // C++14
530template <class E> reverse_iterator<const E*> constexpr rbegin(initializer_list<E> il); // C++14
531template <class E> reverse_iterator<const E*> constexpr rend(initializer_list<E> il);   // C++14
532template <class T, size_t N> reverse_iterator<T*> constexpr rbegin(T (&array)[N]);      // C++14
533template <class T, size_t N> reverse_iterator<T*> constexpr rend(T (&array)[N]);        // C++14
534template <class C> constexpr auto crbegin(const C& c) -> decltype(std::rbegin(c));      // C++14
535template <class C> constexpr auto crend(const C& c) -> decltype(std::rend(c));          // C++14
536
537// 24.8, container access:
538template <class C> constexpr auto size(const C& c) -> decltype(c.size());         // C++17
539template <class T, size_t N> constexpr size_t size(const T (&array)[N]) noexcept; // C++17
540
541template <class C> constexpr auto ssize(const C& c)
542    -> common_type_t<ptrdiff_t, make_signed_t<decltype(c.size())>>;                    // C++20
543template <class T, ptrdiff_t> constexpr ptrdiff_t ssize(const T (&array)[N]) noexcept; // C++20
544
545template <class C> constexpr auto empty(const C& c) -> decltype(c.empty());       // C++17
546template <class T, size_t N> constexpr bool empty(const T (&array)[N]) noexcept;  // C++17
547template <class E> constexpr bool empty(initializer_list<E> il) noexcept;         // C++17
548template <class C> constexpr auto data(C& c) -> decltype(c.data());               // C++17
549template <class C> constexpr auto data(const C& c) -> decltype(c.data());         // C++17
550template <class T, size_t N> constexpr T* data(T (&array)[N]) noexcept;           // C++17
551template <class E> constexpr const E* data(initializer_list<E> il) noexcept;      // C++17
552
553}  // std
554
555*/
556
557#include <__config>
558#include <__debug>
559#include <__functional_base>
560#include <__iterator/advance.h>
561#include <__iterator/back_insert_iterator.h>
562#include <__iterator/concepts.h>
563#include <__iterator/default_sentinel.h>
564#include <__iterator/front_insert_iterator.h>
565#include <__iterator/incrementable_traits.h>
566#include <__iterator/insert_iterator.h>
567#include <__iterator/istream_iterator.h>
568#include <__iterator/istreambuf_iterator.h>
569#include <__iterator/iter_move.h>
570#include <__iterator/iter_swap.h>
571#include <__iterator/iterator_traits.h>
572#include <__iterator/iterator.h>
573#include <__iterator/move_iterator.h>
574#include <__iterator/next.h>
575#include <__iterator/ostream_iterator.h>
576#include <__iterator/ostreambuf_iterator.h>
577#include <__iterator/prev.h>
578#include <__iterator/projected.h>
579#include <__iterator/readable_traits.h>
580#include <__iterator/reverse_iterator.h>
581#include <__iterator/wrap_iter.h>
582#include <__memory/addressof.h>
583#include <__memory/pointer_traits.h>
584#include <__utility/forward.h>
585#include <compare>
586#include <concepts> // Mandated by the Standard.
587#include <cstddef>
588#include <initializer_list>
589#include <type_traits>
590#include <version>
591
592#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
593#pragma GCC system_header
594#endif
595
596_LIBCPP_BEGIN_NAMESPACE_STD
597
598template <class _InputIter>
599inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
600typename iterator_traits<_InputIter>::difference_type
601__distance(_InputIter __first, _InputIter __last, input_iterator_tag)
602{
603    typename iterator_traits<_InputIter>::difference_type __r(0);
604    for (; __first != __last; ++__first)
605        ++__r;
606    return __r;
607}
608
609template <class _RandIter>
610inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
611typename iterator_traits<_RandIter>::difference_type
612__distance(_RandIter __first, _RandIter __last, random_access_iterator_tag)
613{
614    return __last - __first;
615}
616
617template <class _InputIter>
618inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
619typename iterator_traits<_InputIter>::difference_type
620distance(_InputIter __first, _InputIter __last)
621{
622    return _VSTD::__distance(__first, __last, typename iterator_traits<_InputIter>::iterator_category());
623}
624
625template <class _Tp, size_t _Np>
626_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
627_Tp*
628begin(_Tp (&__array)[_Np])
629{
630    return __array;
631}
632
633template <class _Tp, size_t _Np>
634_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
635_Tp*
636end(_Tp (&__array)[_Np])
637{
638    return __array + _Np;
639}
640
641#if !defined(_LIBCPP_CXX03_LANG)
642
643template <class _Cp>
644_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
645auto
646begin(_Cp& __c) -> decltype(__c.begin())
647{
648    return __c.begin();
649}
650
651template <class _Cp>
652_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
653auto
654begin(const _Cp& __c) -> decltype(__c.begin())
655{
656    return __c.begin();
657}
658
659template <class _Cp>
660_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
661auto
662end(_Cp& __c) -> decltype(__c.end())
663{
664    return __c.end();
665}
666
667template <class _Cp>
668_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
669auto
670end(const _Cp& __c) -> decltype(__c.end())
671{
672    return __c.end();
673}
674
675#if _LIBCPP_STD_VER > 11
676
677template <class _Tp, size_t _Np>
678_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
679reverse_iterator<_Tp*> rbegin(_Tp (&__array)[_Np])
680{
681    return reverse_iterator<_Tp*>(__array + _Np);
682}
683
684template <class _Tp, size_t _Np>
685_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
686reverse_iterator<_Tp*> rend(_Tp (&__array)[_Np])
687{
688    return reverse_iterator<_Tp*>(__array);
689}
690
691template <class _Ep>
692_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
693reverse_iterator<const _Ep*> rbegin(initializer_list<_Ep> __il)
694{
695    return reverse_iterator<const _Ep*>(__il.end());
696}
697
698template <class _Ep>
699_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
700reverse_iterator<const _Ep*> rend(initializer_list<_Ep> __il)
701{
702    return reverse_iterator<const _Ep*>(__il.begin());
703}
704
705template <class _Cp>
706_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
707auto cbegin(const _Cp& __c) -> decltype(_VSTD::begin(__c))
708{
709    return _VSTD::begin(__c);
710}
711
712template <class _Cp>
713_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
714auto cend(const _Cp& __c) -> decltype(_VSTD::end(__c))
715{
716    return _VSTD::end(__c);
717}
718
719template <class _Cp>
720_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
721auto rbegin(_Cp& __c) -> decltype(__c.rbegin())
722{
723    return __c.rbegin();
724}
725
726template <class _Cp>
727_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
728auto rbegin(const _Cp& __c) -> decltype(__c.rbegin())
729{
730    return __c.rbegin();
731}
732
733template <class _Cp>
734_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
735auto rend(_Cp& __c) -> decltype(__c.rend())
736{
737    return __c.rend();
738}
739
740template <class _Cp>
741_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
742auto rend(const _Cp& __c) -> decltype(__c.rend())
743{
744    return __c.rend();
745}
746
747template <class _Cp>
748_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
749auto crbegin(const _Cp& __c) -> decltype(_VSTD::rbegin(__c))
750{
751    return _VSTD::rbegin(__c);
752}
753
754template <class _Cp>
755_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
756auto crend(const _Cp& __c) -> decltype(_VSTD::rend(__c))
757{
758    return _VSTD::rend(__c);
759}
760
761#endif
762
763
764#else  // defined(_LIBCPP_CXX03_LANG)
765
766template <class _Cp>
767_LIBCPP_INLINE_VISIBILITY
768typename _Cp::iterator
769begin(_Cp& __c)
770{
771    return __c.begin();
772}
773
774template <class _Cp>
775_LIBCPP_INLINE_VISIBILITY
776typename _Cp::const_iterator
777begin(const _Cp& __c)
778{
779    return __c.begin();
780}
781
782template <class _Cp>
783_LIBCPP_INLINE_VISIBILITY
784typename _Cp::iterator
785end(_Cp& __c)
786{
787    return __c.end();
788}
789
790template <class _Cp>
791_LIBCPP_INLINE_VISIBILITY
792typename _Cp::const_iterator
793end(const _Cp& __c)
794{
795    return __c.end();
796}
797
798#endif // !defined(_LIBCPP_CXX03_LANG)
799
800#if _LIBCPP_STD_VER > 14
801
802// #if _LIBCPP_STD_VER > 11
803// template <>
804// struct _LIBCPP_TEMPLATE_VIS plus<void>
805// {
806//     template <class _T1, class _T2>
807//     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
808//     auto operator()(_T1&& __t, _T2&& __u) const
809//     _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u)))
810//     -> decltype        (_VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u))
811//         { return        _VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u); }
812//     typedef void is_transparent;
813// };
814// #endif
815
816template <class _Cont>
817_LIBCPP_INLINE_VISIBILITY
818constexpr auto size(const _Cont& __c)
819_NOEXCEPT_(noexcept(__c.size()))
820-> decltype        (__c.size())
821{ return            __c.size(); }
822
823template <class _Tp, size_t _Sz>
824_LIBCPP_INLINE_VISIBILITY
825constexpr size_t size(const _Tp (&)[_Sz]) noexcept { return _Sz; }
826
827#if _LIBCPP_STD_VER > 17
828template <class _Cont>
829_LIBCPP_INLINE_VISIBILITY
830constexpr auto ssize(const _Cont& __c)
831_NOEXCEPT_(noexcept(static_cast<common_type_t<ptrdiff_t, make_signed_t<decltype(__c.size())>>>(__c.size())))
832->                              common_type_t<ptrdiff_t, make_signed_t<decltype(__c.size())>>
833{ return            static_cast<common_type_t<ptrdiff_t, make_signed_t<decltype(__c.size())>>>(__c.size()); }
834
835template <class _Tp, ptrdiff_t _Sz>
836_LIBCPP_INLINE_VISIBILITY
837constexpr ptrdiff_t ssize(const _Tp (&)[_Sz]) noexcept { return _Sz; }
838#endif
839
840template <class _Cont>
841_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
842constexpr auto empty(const _Cont& __c)
843_NOEXCEPT_(noexcept(__c.empty()))
844-> decltype        (__c.empty())
845{ return            __c.empty(); }
846
847template <class _Tp, size_t _Sz>
848_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
849constexpr bool empty(const _Tp (&)[_Sz]) noexcept { return false; }
850
851template <class _Ep>
852_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
853constexpr bool empty(initializer_list<_Ep> __il) noexcept { return __il.size() == 0; }
854
855template <class _Cont> constexpr
856_LIBCPP_INLINE_VISIBILITY
857auto data(_Cont& __c)
858_NOEXCEPT_(noexcept(__c.data()))
859-> decltype        (__c.data())
860{ return            __c.data(); }
861
862template <class _Cont> constexpr
863_LIBCPP_INLINE_VISIBILITY
864auto data(const _Cont& __c)
865_NOEXCEPT_(noexcept(__c.data()))
866-> decltype        (__c.data())
867{ return            __c.data(); }
868
869template <class _Tp, size_t _Sz>
870_LIBCPP_INLINE_VISIBILITY
871constexpr _Tp* data(_Tp (&__array)[_Sz]) noexcept { return __array; }
872
873template <class _Ep>
874_LIBCPP_INLINE_VISIBILITY
875constexpr const _Ep* data(initializer_list<_Ep> __il) noexcept { return __il.begin(); }
876#endif
877
878template <class _Container, class _Predicate>
879typename _Container::size_type
880__libcpp_erase_if_container(_Container& __c, _Predicate& __pred) {
881  typename _Container::size_type __old_size = __c.size();
882
883  const typename _Container::iterator __last = __c.end();
884  for (typename _Container::iterator __iter = __c.begin(); __iter != __last;) {
885    if (__pred(*__iter))
886      __iter = __c.erase(__iter);
887    else
888      ++__iter;
889  }
890
891  return __old_size - __c.size();
892}
893
894_LIBCPP_END_NAMESPACE_STD
895
896#endif // _LIBCPP_ITERATOR
897