xref: /freebsd/contrib/llvm-project/libcxx/include/forward_list (revision a0ca4af9455b844c5e094fc1b09b1390ffa979fc)
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_FORWARD_LIST
11#define _LIBCPP_FORWARD_LIST
12
13/*
14    forward_list synopsis
15
16namespace std
17{
18
19template <class T, class Allocator = allocator<T>>
20class forward_list
21{
22public:
23    typedef T         value_type;
24    typedef Allocator allocator_type;
25
26    typedef value_type&                                                reference;
27    typedef const value_type&                                          const_reference;
28    typedef typename allocator_traits<allocator_type>::pointer         pointer;
29    typedef typename allocator_traits<allocator_type>::const_pointer   const_pointer;
30    typedef typename allocator_traits<allocator_type>::size_type       size_type;
31    typedef typename allocator_traits<allocator_type>::difference_type difference_type;
32
33    typedef <details> iterator;
34    typedef <details> const_iterator;
35
36    forward_list()
37        noexcept(is_nothrow_default_constructible<allocator_type>::value);
38    explicit forward_list(const allocator_type& a);
39    explicit forward_list(size_type n);
40    explicit forward_list(size_type n, const allocator_type& a); // C++14
41    forward_list(size_type n, const value_type& v);
42    forward_list(size_type n, const value_type& v, const allocator_type& a);
43    template <class InputIterator>
44        forward_list(InputIterator first, InputIterator last);
45    template <class InputIterator>
46        forward_list(InputIterator first, InputIterator last, const allocator_type& a);
47    template<container-compatible-range<T> R>
48        forward_list(from_range_t, R&& rg, const Allocator& = Allocator()); // C++23
49    forward_list(const forward_list& x);
50    forward_list(const forward_list& x, const allocator_type& a);
51    forward_list(forward_list&& x)
52        noexcept(is_nothrow_move_constructible<allocator_type>::value);
53    forward_list(forward_list&& x, const allocator_type& a);
54    forward_list(initializer_list<value_type> il);
55    forward_list(initializer_list<value_type> il, const allocator_type& a);
56
57    ~forward_list();
58
59    forward_list& operator=(const forward_list& x);
60    forward_list& operator=(forward_list&& x)
61        noexcept(
62             allocator_type::propagate_on_container_move_assignment::value &&
63             is_nothrow_move_assignable<allocator_type>::value);
64    forward_list& operator=(initializer_list<value_type> il);
65
66    template <class InputIterator>
67        void assign(InputIterator first, InputIterator last);
68    template<container-compatible-range<T> R>
69      void assign_range(R&& rg); // C++23
70    void assign(size_type n, const value_type& v);
71    void assign(initializer_list<value_type> il);
72
73    allocator_type get_allocator() const noexcept;
74
75    iterator       begin() noexcept;
76    const_iterator begin() const noexcept;
77    iterator       end() noexcept;
78    const_iterator end() const noexcept;
79
80    const_iterator cbegin() const noexcept;
81    const_iterator cend() const noexcept;
82
83    iterator       before_begin() noexcept;
84    const_iterator before_begin() const noexcept;
85    const_iterator cbefore_begin() const noexcept;
86
87    bool empty() const noexcept;
88    size_type max_size() const noexcept;
89
90    reference       front();
91    const_reference front() const;
92
93    template <class... Args> reference emplace_front(Args&&... args);  // reference in C++17
94    void push_front(const value_type& v);
95    void push_front(value_type&& v);
96    template<container-compatible-range<T> R>
97      void prepend_range(R&& rg); // C++23
98
99    void pop_front();
100
101    template <class... Args>
102        iterator emplace_after(const_iterator p, Args&&... args);
103    iterator insert_after(const_iterator p, const value_type& v);
104    iterator insert_after(const_iterator p, value_type&& v);
105    iterator insert_after(const_iterator p, size_type n, const value_type& v);
106    template <class InputIterator>
107        iterator insert_after(const_iterator p,
108                              InputIterator first, InputIterator last);
109    template<container-compatible-range<T> R>
110      iterator insert_range_after(const_iterator position, R&& rg); // C++23
111    iterator insert_after(const_iterator p, initializer_list<value_type> il);
112
113    iterator erase_after(const_iterator p);
114    iterator erase_after(const_iterator first, const_iterator last);
115
116    void swap(forward_list& x)
117        noexcept(allocator_traits<allocator_type>::is_always_equal::value);  // C++17
118
119    void resize(size_type n);
120    void resize(size_type n, const value_type& v);
121    void clear() noexcept;
122
123    void splice_after(const_iterator p, forward_list& x);
124    void splice_after(const_iterator p, forward_list&& x);
125    void splice_after(const_iterator p, forward_list& x, const_iterator i);
126    void splice_after(const_iterator p, forward_list&& x, const_iterator i);
127    void splice_after(const_iterator p, forward_list& x,
128                      const_iterator first, const_iterator last);
129    void splice_after(const_iterator p, forward_list&& x,
130                      const_iterator first, const_iterator last);
131    size_type remove(const value_type& v);           // void before C++20
132    template <class Predicate>
133      size_type remove_if(Predicate pred);           // void before C++20
134    size_type unique();                              // void before C++20
135    template <class BinaryPredicate>
136      size_type unique(BinaryPredicate binary_pred); // void before C++20
137    void merge(forward_list& x);
138    void merge(forward_list&& x);
139    template <class Compare> void merge(forward_list& x, Compare comp);
140    template <class Compare> void merge(forward_list&& x, Compare comp);
141    void sort();
142    template <class Compare> void sort(Compare comp);
143    void reverse() noexcept;
144};
145
146
147template <class InputIterator, class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
148    forward_list(InputIterator, InputIterator, Allocator = Allocator())
149    -> forward_list<typename iterator_traits<InputIterator>::value_type, Allocator>;  // C++17
150
151template<ranges::input_range R, class Allocator = allocator<ranges::range_value_t<R>>>
152  forward_list(from_range_t, R&&, Allocator = Allocator())
153      -> forward_list<ranges::range_value_t<R>, Allocator>; // C++23
154
155template <class T, class Allocator>
156    bool operator==(const forward_list<T, Allocator>& x,
157                    const forward_list<T, Allocator>& y);
158
159template <class T, class Allocator>
160    bool operator< (const forward_list<T, Allocator>& x,
161                    const forward_list<T, Allocator>& y); // removed in C++20
162
163template <class T, class Allocator>
164    bool operator!=(const forward_list<T, Allocator>& x,
165                    const forward_list<T, Allocator>& y); // removed in C++20
166
167template <class T, class Allocator>
168    bool operator> (const forward_list<T, Allocator>& x,
169                    const forward_list<T, Allocator>& y); // removed in C++20
170
171template <class T, class Allocator>
172    bool operator>=(const forward_list<T, Allocator>& x,
173                    const forward_list<T, Allocator>& y); // removed in C++20
174
175template <class T, class Allocator>
176    bool operator<=(const forward_list<T, Allocator>& x,
177                    const forward_list<T, Allocator>& y); // removed in C++20
178
179template<class T, class Allocator>
180    synth-three-way-result<T> operator<=>(const forward_list<T, Allocator>& x,
181                                          const forward_list<T, Allocator>& y); // since C++20
182
183template <class T, class Allocator>
184    void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y)
185         noexcept(noexcept(x.swap(y)));
186
187template <class T, class Allocator, class U>
188    typename forward_list<T, Allocator>::size_type
189    erase(forward_list<T, Allocator>& c, const U& value);       // C++20
190template <class T, class Allocator, class Predicate>
191    typename forward_list<T, Allocator>::size_type
192    erase_if(forward_list<T, Allocator>& c, Predicate pred);    // C++20
193
194}  // std
195
196*/
197
198#include <__algorithm/comp.h>
199#include <__algorithm/lexicographical_compare.h>
200#include <__algorithm/lexicographical_compare_three_way.h>
201#include <__algorithm/min.h>
202#include <__assert> // all public C++ headers provide the assertion handler
203#include <__availability>
204#include <__config>
205#include <__iterator/distance.h>
206#include <__iterator/iterator_traits.h>
207#include <__iterator/move_iterator.h>
208#include <__iterator/next.h>
209#include <__memory/addressof.h>
210#include <__memory/allocation_guard.h>
211#include <__memory/allocator.h>
212#include <__memory/allocator_traits.h>
213#include <__memory/compressed_pair.h>
214#include <__memory/construct_at.h>
215#include <__memory/pointer_traits.h>
216#include <__memory/swap_allocator.h>
217#include <__memory_resource/polymorphic_allocator.h>
218#include <__ranges/access.h>
219#include <__ranges/concepts.h>
220#include <__ranges/container_compatible_range.h>
221#include <__ranges/from_range.h>
222#include <__type_traits/conditional.h>
223#include <__type_traits/is_allocator.h>
224#include <__type_traits/is_const.h>
225#include <__type_traits/is_nothrow_default_constructible.h>
226#include <__type_traits/is_nothrow_move_assignable.h>
227#include <__type_traits/is_nothrow_move_constructible.h>
228#include <__type_traits/is_pointer.h>
229#include <__type_traits/is_same.h>
230#include <__type_traits/type_identity.h>
231#include <__utility/forward.h>
232#include <__utility/move.h>
233#include <limits>
234#include <new> // __launder
235#include <version>
236
237// standard-mandated includes
238
239// [iterator.range]
240#include <__iterator/access.h>
241#include <__iterator/data.h>
242#include <__iterator/empty.h>
243#include <__iterator/reverse_access.h>
244#include <__iterator/size.h>
245
246// [forward.list.syn]
247#include <compare>
248#include <initializer_list>
249
250#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
251#  pragma GCC system_header
252#endif
253
254_LIBCPP_PUSH_MACROS
255#include <__undef_macros>
256
257_LIBCPP_BEGIN_NAMESPACE_STD
258
259template <class _Tp, class _VoidPtr>
260struct __forward_list_node;
261template <class _NodePtr>
262struct __forward_begin_node;
263
264template <class>
265struct __forward_list_node_value_type;
266
267template <class _Tp, class _VoidPtr>
268struct __forward_list_node_value_type<__forward_list_node<_Tp, _VoidPtr> > {
269  typedef _Tp type;
270};
271
272template <class _NodePtr>
273struct __forward_node_traits {
274  typedef __remove_cv_t<typename pointer_traits<_NodePtr>::element_type> __node_type;
275  typedef typename __forward_list_node_value_type<__node_type>::type __node_value_type;
276  typedef _NodePtr __node_pointer;
277  typedef __forward_begin_node<_NodePtr> __begin_node;
278  typedef __rebind_pointer_t<_NodePtr, __begin_node> __begin_node_pointer;
279  typedef __rebind_pointer_t<_NodePtr, void> __void_pointer;
280
281#if defined(_LIBCPP_ABI_FORWARD_LIST_REMOVE_NODE_POINTER_UB)
282  typedef __begin_node_pointer __iter_node_pointer;
283#else
284  typedef __conditional_t<is_pointer<__void_pointer>::value, __begin_node_pointer, __node_pointer> __iter_node_pointer;
285#endif
286
287  typedef __conditional_t<is_same<__iter_node_pointer, __node_pointer>::value, __begin_node_pointer, __node_pointer>
288      __non_iter_node_pointer;
289
290  _LIBCPP_HIDE_FROM_ABI static __iter_node_pointer __as_iter_node(__iter_node_pointer __p) { return __p; }
291  _LIBCPP_HIDE_FROM_ABI static __iter_node_pointer __as_iter_node(__non_iter_node_pointer __p) {
292    return static_cast<__iter_node_pointer>(static_cast<__void_pointer>(__p));
293  }
294};
295
296template <class _NodePtr>
297struct __forward_begin_node {
298  typedef _NodePtr pointer;
299  typedef __rebind_pointer_t<_NodePtr, __forward_begin_node> __begin_node_pointer;
300
301  pointer __next_;
302
303  _LIBCPP_HIDE_FROM_ABI __forward_begin_node() : __next_(nullptr) {}
304  _LIBCPP_HIDE_FROM_ABI explicit __forward_begin_node(pointer __n) : __next_(__n) {}
305
306  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __next_as_begin() const {
307    return static_cast<__begin_node_pointer>(__next_);
308  }
309};
310
311template <class _Tp, class _VoidPtr>
312using __begin_node_of = __forward_begin_node<__rebind_pointer_t<_VoidPtr, __forward_list_node<_Tp, _VoidPtr> > >;
313
314template <class _Tp, class _VoidPtr>
315struct __forward_list_node : public __begin_node_of<_Tp, _VoidPtr> {
316  typedef _Tp value_type;
317  typedef __begin_node_of<_Tp, _VoidPtr> _Base;
318  typedef typename _Base::pointer _NodePtr;
319
320  // We allow starting the lifetime of nodes without initializing the value held by the node,
321  // since that is handled by the list itself in order to be allocator-aware.
322#ifndef _LIBCPP_CXX03_LANG
323
324private:
325  union {
326    _Tp __value_;
327  };
328
329public:
330  _LIBCPP_HIDE_FROM_ABI _Tp& __get_value() { return __value_; }
331#else
332
333private:
334  _ALIGNAS_TYPE(_Tp) char __buffer_[sizeof(_Tp)];
335
336public:
337  _LIBCPP_HIDE_FROM_ABI _Tp& __get_value() { return *std::__launder(reinterpret_cast<_Tp*>(&__buffer_)); }
338#endif
339
340  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_node(_NodePtr __next) : _Base(__next) {}
341  _LIBCPP_HIDE_FROM_ABI ~__forward_list_node() {}
342};
343
344template <class _Tp, class _Alloc = allocator<_Tp> >
345class _LIBCPP_TEMPLATE_VIS forward_list;
346template <class _NodeConstPtr>
347class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator;
348
349template <class _NodePtr>
350class _LIBCPP_TEMPLATE_VIS __forward_list_iterator {
351  typedef __forward_node_traits<_NodePtr> __traits;
352  typedef typename __traits::__node_pointer __node_pointer;
353  typedef typename __traits::__begin_node_pointer __begin_node_pointer;
354  typedef typename __traits::__iter_node_pointer __iter_node_pointer;
355  typedef typename __traits::__void_pointer __void_pointer;
356
357  __iter_node_pointer __ptr_;
358
359  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const {
360    return static_cast<__begin_node_pointer>(static_cast<__void_pointer>(__ptr_));
361  }
362  _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const {
363    return static_cast<__node_pointer>(static_cast<__void_pointer>(__ptr_));
364  }
365
366  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(nullptr_t) _NOEXCEPT : __ptr_(nullptr) {}
367
368  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(__begin_node_pointer __p) _NOEXCEPT
369      : __ptr_(__traits::__as_iter_node(__p)) {}
370
371  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_iterator(__node_pointer __p) _NOEXCEPT
372      : __ptr_(__traits::__as_iter_node(__p)) {}
373
374  template <class, class>
375  friend class _LIBCPP_TEMPLATE_VIS forward_list;
376  template <class>
377  friend class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator;
378
379public:
380  typedef forward_iterator_tag iterator_category;
381  typedef typename __traits::__node_value_type value_type;
382  typedef value_type& reference;
383  typedef typename pointer_traits<__node_pointer>::difference_type difference_type;
384  typedef __rebind_pointer_t<__node_pointer, value_type> pointer;
385
386  _LIBCPP_HIDE_FROM_ABI __forward_list_iterator() _NOEXCEPT : __ptr_(nullptr) {}
387
388  _LIBCPP_HIDE_FROM_ABI reference operator*() const { return __get_unsafe_node_pointer()->__get_value(); }
389  _LIBCPP_HIDE_FROM_ABI pointer operator->() const {
390    return pointer_traits<pointer>::pointer_to(__get_unsafe_node_pointer()->__get_value());
391  }
392
393  _LIBCPP_HIDE_FROM_ABI __forward_list_iterator& operator++() {
394    __ptr_ = __traits::__as_iter_node(__ptr_->__next_);
395    return *this;
396  }
397  _LIBCPP_HIDE_FROM_ABI __forward_list_iterator operator++(int) {
398    __forward_list_iterator __t(*this);
399    ++(*this);
400    return __t;
401  }
402
403  friend _LIBCPP_HIDE_FROM_ABI bool operator==(const __forward_list_iterator& __x, const __forward_list_iterator& __y) {
404    return __x.__ptr_ == __y.__ptr_;
405  }
406  friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const __forward_list_iterator& __x, const __forward_list_iterator& __y) {
407    return !(__x == __y);
408  }
409};
410
411template <class _NodeConstPtr>
412class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator {
413  static_assert((!is_const<typename pointer_traits<_NodeConstPtr>::element_type>::value), "");
414  typedef _NodeConstPtr _NodePtr;
415
416  typedef __forward_node_traits<_NodePtr> __traits;
417  typedef typename __traits::__node_type __node_type;
418  typedef typename __traits::__node_pointer __node_pointer;
419  typedef typename __traits::__begin_node_pointer __begin_node_pointer;
420  typedef typename __traits::__iter_node_pointer __iter_node_pointer;
421  typedef typename __traits::__void_pointer __void_pointer;
422
423  __iter_node_pointer __ptr_;
424
425  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __get_begin() const {
426    return static_cast<__begin_node_pointer>(static_cast<__void_pointer>(__ptr_));
427  }
428  _LIBCPP_HIDE_FROM_ABI __node_pointer __get_unsafe_node_pointer() const {
429    return static_cast<__node_pointer>(static_cast<__void_pointer>(__ptr_));
430  }
431
432  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(nullptr_t) _NOEXCEPT : __ptr_(nullptr) {}
433
434  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(__begin_node_pointer __p) _NOEXCEPT
435      : __ptr_(__traits::__as_iter_node(__p)) {}
436
437  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_const_iterator(__node_pointer __p) _NOEXCEPT
438      : __ptr_(__traits::__as_iter_node(__p)) {}
439
440  template <class, class>
441  friend class forward_list;
442
443public:
444  typedef forward_iterator_tag iterator_category;
445  typedef typename __traits::__node_value_type value_type;
446  typedef const value_type& reference;
447  typedef typename pointer_traits<__node_pointer>::difference_type difference_type;
448  typedef __rebind_pointer_t<__node_pointer, const value_type> pointer;
449
450  _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator() _NOEXCEPT : __ptr_(nullptr) {}
451  _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator(__forward_list_iterator<__node_pointer> __p) _NOEXCEPT
452      : __ptr_(__p.__ptr_) {}
453
454  _LIBCPP_HIDE_FROM_ABI reference operator*() const { return __get_unsafe_node_pointer()->__get_value(); }
455  _LIBCPP_HIDE_FROM_ABI pointer operator->() const {
456    return pointer_traits<pointer>::pointer_to(__get_unsafe_node_pointer()->__get_value());
457  }
458
459  _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator& operator++() {
460    __ptr_ = __traits::__as_iter_node(__ptr_->__next_);
461    return *this;
462  }
463  _LIBCPP_HIDE_FROM_ABI __forward_list_const_iterator operator++(int) {
464    __forward_list_const_iterator __t(*this);
465    ++(*this);
466    return __t;
467  }
468
469  friend _LIBCPP_HIDE_FROM_ABI bool
470  operator==(const __forward_list_const_iterator& __x, const __forward_list_const_iterator& __y) {
471    return __x.__ptr_ == __y.__ptr_;
472  }
473  friend _LIBCPP_HIDE_FROM_ABI bool
474  operator!=(const __forward_list_const_iterator& __x, const __forward_list_const_iterator& __y) {
475    return !(__x == __y);
476  }
477};
478
479template <class _Tp, class _Alloc>
480class __forward_list_base {
481protected:
482  typedef _Tp value_type;
483  typedef _Alloc allocator_type;
484
485  typedef typename allocator_traits<allocator_type>::void_pointer void_pointer;
486  typedef __forward_list_node<value_type, void_pointer> __node_type;
487  typedef __begin_node_of<value_type, void_pointer> __begin_node;
488  typedef __rebind_alloc<allocator_traits<allocator_type>, __node_type> __node_allocator;
489  typedef allocator_traits<__node_allocator> __node_traits;
490  typedef typename __node_traits::pointer __node_pointer;
491
492  typedef __rebind_alloc<allocator_traits<allocator_type>, __begin_node> __begin_node_allocator;
493  typedef typename allocator_traits<__begin_node_allocator>::pointer __begin_node_pointer;
494
495  __compressed_pair<__begin_node, __node_allocator> __before_begin_;
496
497  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() _NOEXCEPT {
498    return pointer_traits<__begin_node_pointer>::pointer_to(__before_begin_.first());
499  }
500  _LIBCPP_HIDE_FROM_ABI __begin_node_pointer __before_begin() const _NOEXCEPT {
501    return pointer_traits<__begin_node_pointer>::pointer_to(const_cast<__begin_node&>(__before_begin_.first()));
502  }
503
504  _LIBCPP_HIDE_FROM_ABI __node_allocator& __alloc() _NOEXCEPT { return __before_begin_.second(); }
505  _LIBCPP_HIDE_FROM_ABI const __node_allocator& __alloc() const _NOEXCEPT { return __before_begin_.second(); }
506
507  typedef __forward_list_iterator<__node_pointer> iterator;
508  typedef __forward_list_const_iterator<__node_pointer> const_iterator;
509
510  _LIBCPP_HIDE_FROM_ABI __forward_list_base() _NOEXCEPT_(is_nothrow_default_constructible<__node_allocator>::value)
511      : __before_begin_(__begin_node(), __default_init_tag()) {}
512  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_base(const allocator_type& __a)
513      : __before_begin_(__begin_node(), __node_allocator(__a)) {}
514  _LIBCPP_HIDE_FROM_ABI explicit __forward_list_base(const __node_allocator& __a)
515      : __before_begin_(__begin_node(), __a) {}
516#ifndef _LIBCPP_CXX03_LANG
517
518public:
519  _LIBCPP_HIDE_FROM_ABI __forward_list_base(__forward_list_base&& __x)
520      _NOEXCEPT_(is_nothrow_move_constructible<__node_allocator>::value);
521  _LIBCPP_HIDE_FROM_ABI __forward_list_base(__forward_list_base&& __x, const allocator_type& __a);
522#endif // _LIBCPP_CXX03_LANG
523
524private:
525  __forward_list_base(const __forward_list_base&);
526  __forward_list_base& operator=(const __forward_list_base&);
527
528public:
529  _LIBCPP_HIDE_FROM_ABI ~__forward_list_base();
530
531protected:
532  _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const __forward_list_base& __x) {
533    __copy_assign_alloc(__x, integral_constant<bool, __node_traits::propagate_on_container_copy_assignment::value>());
534  }
535
536  _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(__forward_list_base& __x)
537      _NOEXCEPT_(!__node_traits::propagate_on_container_move_assignment::value ||
538                 is_nothrow_move_assignable<__node_allocator>::value) {
539    __move_assign_alloc(__x, integral_constant<bool, __node_traits::propagate_on_container_move_assignment::value>());
540  }
541
542  template <class... _Args>
543  _LIBCPP_HIDE_FROM_ABI __node_pointer __create_node(__node_pointer __next, _Args&&... __args) {
544    __node_allocator& __a = __alloc();
545    __allocation_guard<__node_allocator> __guard(__a, 1);
546    // Begin the lifetime of the node itself. Note that this doesn't begin the lifetime of the value
547    // held inside the node, since we need to use the allocator's construct() method for that.
548    //
549    // We don't use the allocator's construct() method to construct the node itself since the
550    // Cpp17FooInsertable named requirements don't require the allocator's construct() method
551    // to work on anything other than the value_type.
552    std::__construct_at(std::addressof(*__guard.__get()), __next);
553
554    // Now construct the value_type using the allocator's construct() method.
555    __node_traits::construct(__a, std::addressof(__guard.__get()->__get_value()), std::forward<_Args>(__args)...);
556    return __guard.__release_ptr();
557  }
558
559  template <class... _Args>
560  _LIBCPP_HIDE_FROM_ABI void __delete_node(__node_pointer __node) {
561    // For the same reason as above, we use the allocator's destroy() method for the value_type,
562    // but not for the node itself.
563    __node_allocator& __a = __alloc();
564    __node_traits::destroy(__a, std::addressof(__node->__get_value()));
565    std::__destroy_at(std::addressof(*__node));
566    __node_traits::deallocate(__a, __node, 1);
567  }
568
569public:
570  _LIBCPP_HIDE_FROM_ABI void swap(__forward_list_base& __x)
571#if _LIBCPP_STD_VER >= 14
572      _NOEXCEPT;
573#else
574      _NOEXCEPT_(!__node_traits::propagate_on_container_swap::value || __is_nothrow_swappable<__node_allocator>::value);
575#endif
576
577protected:
578  _LIBCPP_HIDE_FROM_ABI void clear() _NOEXCEPT;
579
580private:
581  _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const __forward_list_base&, false_type) {}
582  _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const __forward_list_base& __x, true_type) {
583    if (__alloc() != __x.__alloc())
584      clear();
585    __alloc() = __x.__alloc();
586  }
587
588  _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(__forward_list_base&, false_type) _NOEXCEPT {}
589  _LIBCPP_HIDE_FROM_ABI void __move_assign_alloc(__forward_list_base& __x, true_type)
590      _NOEXCEPT_(is_nothrow_move_assignable<__node_allocator>::value) {
591    __alloc() = std::move(__x.__alloc());
592  }
593};
594
595#ifndef _LIBCPP_CXX03_LANG
596
597template <class _Tp, class _Alloc>
598inline __forward_list_base<_Tp, _Alloc>::__forward_list_base(__forward_list_base&& __x)
599    _NOEXCEPT_(is_nothrow_move_constructible<__node_allocator>::value)
600    : __before_begin_(std::move(__x.__before_begin_)) {
601  __x.__before_begin()->__next_ = nullptr;
602}
603
604template <class _Tp, class _Alloc>
605inline __forward_list_base<_Tp, _Alloc>::__forward_list_base(__forward_list_base&& __x, const allocator_type& __a)
606    : __before_begin_(__begin_node(), __node_allocator(__a)) {
607  if (__alloc() == __x.__alloc()) {
608    __before_begin()->__next_     = __x.__before_begin()->__next_;
609    __x.__before_begin()->__next_ = nullptr;
610  }
611}
612
613#endif // _LIBCPP_CXX03_LANG
614
615template <class _Tp, class _Alloc>
616__forward_list_base<_Tp, _Alloc>::~__forward_list_base() {
617  clear();
618}
619
620template <class _Tp, class _Alloc>
621inline void __forward_list_base<_Tp, _Alloc>::swap(__forward_list_base& __x)
622#if _LIBCPP_STD_VER >= 14
623    _NOEXCEPT
624#else
625    _NOEXCEPT_(!__node_traits::propagate_on_container_swap::value || __is_nothrow_swappable<__node_allocator>::value)
626#endif
627{
628  std::__swap_allocator(
629      __alloc(), __x.__alloc(), integral_constant<bool, __node_traits::propagate_on_container_swap::value>());
630  using std::swap;
631  swap(__before_begin()->__next_, __x.__before_begin()->__next_);
632}
633
634template <class _Tp, class _Alloc>
635void __forward_list_base<_Tp, _Alloc>::clear() _NOEXCEPT {
636  for (__node_pointer __p = __before_begin()->__next_; __p != nullptr;) {
637    __node_pointer __next = __p->__next_;
638    __delete_node(__p);
639    __p = __next;
640  }
641  __before_begin()->__next_ = nullptr;
642}
643
644template <class _Tp, class _Alloc /*= allocator<_Tp>*/>
645class _LIBCPP_TEMPLATE_VIS forward_list : private __forward_list_base<_Tp, _Alloc> {
646  typedef __forward_list_base<_Tp, _Alloc> base;
647  typedef typename base::__node_allocator __node_allocator;
648  typedef typename base::__node_type __node_type;
649  typedef typename base::__node_traits __node_traits;
650  typedef typename base::__node_pointer __node_pointer;
651  typedef typename base::__begin_node_pointer __begin_node_pointer;
652
653public:
654  typedef _Tp value_type;
655  typedef _Alloc allocator_type;
656
657  static_assert(is_same<value_type, typename allocator_type::value_type>::value,
658                "Allocator::value_type must be same type as value_type");
659
660  static_assert(is_same<allocator_type, __rebind_alloc<allocator_traits<allocator_type>, value_type> >::value,
661                "[allocator.requirements] states that rebinding an allocator to the same type should result in the "
662                "original allocator");
663
664  static_assert((!is_same<allocator_type, __node_allocator>::value),
665                "internal allocator type must differ from user-specified "
666                "type; otherwise overload resolution breaks");
667
668  typedef value_type& reference;
669  typedef const value_type& const_reference;
670  typedef typename allocator_traits<allocator_type>::pointer pointer;
671  typedef typename allocator_traits<allocator_type>::const_pointer const_pointer;
672  typedef typename allocator_traits<allocator_type>::size_type size_type;
673  typedef typename allocator_traits<allocator_type>::difference_type difference_type;
674
675  typedef typename base::iterator iterator;
676  typedef typename base::const_iterator const_iterator;
677#if _LIBCPP_STD_VER >= 20
678  typedef size_type __remove_return_type;
679#else
680  typedef void __remove_return_type;
681#endif
682
683  _LIBCPP_HIDE_FROM_ABI forward_list() _NOEXCEPT_(is_nothrow_default_constructible<__node_allocator>::value) {
684  } // = default;
685  _LIBCPP_HIDE_FROM_ABI explicit forward_list(const allocator_type& __a);
686  _LIBCPP_HIDE_FROM_ABI explicit forward_list(size_type __n);
687#if _LIBCPP_STD_VER >= 14
688  _LIBCPP_HIDE_FROM_ABI explicit forward_list(size_type __n, const allocator_type& __a);
689#endif
690  _LIBCPP_HIDE_FROM_ABI forward_list(size_type __n, const value_type& __v);
691
692  template <class = __enable_if_t<__is_allocator<_Alloc>::value> >
693  _LIBCPP_HIDE_FROM_ABI forward_list(size_type __n, const value_type& __v, const allocator_type& __a) : base(__a) {
694    insert_after(cbefore_begin(), __n, __v);
695  }
696
697  template <class _InputIterator>
698  _LIBCPP_HIDE_FROM_ABI
699  forward_list(_InputIterator __f,
700               _InputIterator __l,
701               __enable_if_t<__has_input_iterator_category<_InputIterator>::value>* = nullptr);
702  template <class _InputIterator>
703  _LIBCPP_HIDE_FROM_ABI
704  forward_list(_InputIterator __f,
705               _InputIterator __l,
706               const allocator_type& __a,
707               __enable_if_t<__has_input_iterator_category<_InputIterator>::value>* = nullptr);
708
709#if _LIBCPP_STD_VER >= 23
710  template <_ContainerCompatibleRange<_Tp> _Range>
711  _LIBCPP_HIDE_FROM_ABI forward_list(from_range_t, _Range&& __range, const allocator_type& __a = allocator_type())
712      : base(__a) {
713    prepend_range(std::forward<_Range>(__range));
714  }
715#endif
716
717  _LIBCPP_HIDE_FROM_ABI forward_list(const forward_list& __x);
718  _LIBCPP_HIDE_FROM_ABI forward_list(const forward_list& __x, const __type_identity_t<allocator_type>& __a);
719
720  _LIBCPP_HIDE_FROM_ABI forward_list& operator=(const forward_list& __x);
721
722#ifndef _LIBCPP_CXX03_LANG
723  _LIBCPP_HIDE_FROM_ABI forward_list(forward_list&& __x) _NOEXCEPT_(is_nothrow_move_constructible<base>::value)
724      : base(std::move(__x)) {}
725  _LIBCPP_HIDE_FROM_ABI forward_list(forward_list&& __x, const __type_identity_t<allocator_type>& __a);
726
727  _LIBCPP_HIDE_FROM_ABI forward_list(initializer_list<value_type> __il);
728  _LIBCPP_HIDE_FROM_ABI forward_list(initializer_list<value_type> __il, const allocator_type& __a);
729
730  _LIBCPP_HIDE_FROM_ABI forward_list& operator=(forward_list&& __x) _NOEXCEPT_(
731      __node_traits::propagate_on_container_move_assignment::value&& is_nothrow_move_assignable<allocator_type>::value);
732
733  _LIBCPP_HIDE_FROM_ABI forward_list& operator=(initializer_list<value_type> __il);
734
735  _LIBCPP_HIDE_FROM_ABI void assign(initializer_list<value_type> __il);
736#endif // _LIBCPP_CXX03_LANG
737
738  // ~forward_list() = default;
739
740  template <class _InputIterator, __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> = 0>
741  void _LIBCPP_HIDE_FROM_ABI assign(_InputIterator __f, _InputIterator __l);
742
743#if _LIBCPP_STD_VER >= 23
744  template <_ContainerCompatibleRange<_Tp> _Range>
745  _LIBCPP_HIDE_FROM_ABI void assign_range(_Range&& __range) {
746    __assign_with_sentinel(ranges::begin(__range), ranges::end(__range));
747  }
748#endif
749
750  _LIBCPP_HIDE_FROM_ABI void assign(size_type __n, const value_type& __v);
751
752  _LIBCPP_HIDE_FROM_ABI allocator_type get_allocator() const _NOEXCEPT { return allocator_type(base::__alloc()); }
753
754  _LIBCPP_HIDE_FROM_ABI iterator begin() _NOEXCEPT { return iterator(base::__before_begin()->__next_); }
755  _LIBCPP_HIDE_FROM_ABI const_iterator begin() const _NOEXCEPT {
756    return const_iterator(base::__before_begin()->__next_);
757  }
758  _LIBCPP_HIDE_FROM_ABI iterator end() _NOEXCEPT { return iterator(nullptr); }
759  _LIBCPP_HIDE_FROM_ABI const_iterator end() const _NOEXCEPT { return const_iterator(nullptr); }
760
761  _LIBCPP_HIDE_FROM_ABI const_iterator cbegin() const _NOEXCEPT {
762    return const_iterator(base::__before_begin()->__next_);
763  }
764  _LIBCPP_HIDE_FROM_ABI const_iterator cend() const _NOEXCEPT { return const_iterator(nullptr); }
765
766  _LIBCPP_HIDE_FROM_ABI iterator before_begin() _NOEXCEPT { return iterator(base::__before_begin()); }
767  _LIBCPP_HIDE_FROM_ABI const_iterator before_begin() const _NOEXCEPT { return const_iterator(base::__before_begin()); }
768  _LIBCPP_HIDE_FROM_ABI const_iterator cbefore_begin() const _NOEXCEPT {
769    return const_iterator(base::__before_begin());
770  }
771
772  _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_HIDE_FROM_ABI bool empty() const _NOEXCEPT {
773    return base::__before_begin()->__next_ == nullptr;
774  }
775  _LIBCPP_HIDE_FROM_ABI size_type max_size() const _NOEXCEPT {
776    return std::min<size_type>(__node_traits::max_size(base::__alloc()), numeric_limits<difference_type>::max());
777  }
778
779  _LIBCPP_HIDE_FROM_ABI reference front() { return base::__before_begin()->__next_->__get_value(); }
780  _LIBCPP_HIDE_FROM_ABI const_reference front() const { return base::__before_begin()->__next_->__get_value(); }
781
782#ifndef _LIBCPP_CXX03_LANG
783#  if _LIBCPP_STD_VER >= 17
784  template <class... _Args>
785  _LIBCPP_HIDE_FROM_ABI reference emplace_front(_Args&&... __args);
786#  else
787  template <class... _Args>
788  _LIBCPP_HIDE_FROM_ABI void emplace_front(_Args&&... __args);
789#  endif
790  _LIBCPP_HIDE_FROM_ABI void push_front(value_type&& __v);
791#endif // _LIBCPP_CXX03_LANG
792  _LIBCPP_HIDE_FROM_ABI void push_front(const value_type& __v);
793
794#if _LIBCPP_STD_VER >= 23
795  template <_ContainerCompatibleRange<_Tp> _Range>
796  _LIBCPP_HIDE_FROM_ABI void prepend_range(_Range&& __range) {
797    insert_range_after(cbefore_begin(), std::forward<_Range>(__range));
798  }
799#endif
800
801  _LIBCPP_HIDE_FROM_ABI void pop_front();
802
803#ifndef _LIBCPP_CXX03_LANG
804  template <class... _Args>
805  _LIBCPP_HIDE_FROM_ABI iterator emplace_after(const_iterator __p, _Args&&... __args);
806
807  _LIBCPP_HIDE_FROM_ABI iterator insert_after(const_iterator __p, value_type&& __v);
808  _LIBCPP_HIDE_FROM_ABI iterator insert_after(const_iterator __p, initializer_list<value_type> __il) {
809    return insert_after(__p, __il.begin(), __il.end());
810  }
811#endif // _LIBCPP_CXX03_LANG
812  _LIBCPP_HIDE_FROM_ABI iterator insert_after(const_iterator __p, const value_type& __v);
813  _LIBCPP_HIDE_FROM_ABI iterator insert_after(const_iterator __p, size_type __n, const value_type& __v);
814  template <class _InputIterator, __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> = 0>
815  _LIBCPP_HIDE_FROM_ABI iterator insert_after(const_iterator __p, _InputIterator __f, _InputIterator __l);
816
817#if _LIBCPP_STD_VER >= 23
818  template <_ContainerCompatibleRange<_Tp> _Range>
819  _LIBCPP_HIDE_FROM_ABI iterator insert_range_after(const_iterator __position, _Range&& __range) {
820    return __insert_after_with_sentinel(__position, ranges::begin(__range), ranges::end(__range));
821  }
822#endif
823
824  template <class _InputIterator, class _Sentinel>
825  _LIBCPP_HIDE_FROM_ABI iterator __insert_after_with_sentinel(const_iterator __p, _InputIterator __f, _Sentinel __l);
826
827  _LIBCPP_HIDE_FROM_ABI iterator erase_after(const_iterator __p);
828  _LIBCPP_HIDE_FROM_ABI iterator erase_after(const_iterator __f, const_iterator __l);
829
830  _LIBCPP_HIDE_FROM_ABI void swap(forward_list& __x)
831#if _LIBCPP_STD_VER >= 14
832      _NOEXCEPT
833#else
834      _NOEXCEPT_(!__node_traits::propagate_on_container_swap::value || __is_nothrow_swappable<__node_allocator>::value)
835#endif
836  {
837    base::swap(__x);
838  }
839
840  _LIBCPP_HIDE_FROM_ABI void resize(size_type __n);
841  _LIBCPP_HIDE_FROM_ABI void resize(size_type __n, const value_type& __v);
842  _LIBCPP_HIDE_FROM_ABI void clear() _NOEXCEPT { base::clear(); }
843
844  _LIBCPP_HIDE_FROM_ABI void splice_after(const_iterator __p, forward_list&& __x);
845  _LIBCPP_HIDE_FROM_ABI void splice_after(const_iterator __p, forward_list&& __x, const_iterator __i);
846  _LIBCPP_HIDE_FROM_ABI void
847  splice_after(const_iterator __p, forward_list&& __x, const_iterator __f, const_iterator __l);
848  _LIBCPP_HIDE_FROM_ABI void splice_after(const_iterator __p, forward_list& __x);
849  _LIBCPP_HIDE_FROM_ABI void splice_after(const_iterator __p, forward_list& __x, const_iterator __i);
850  _LIBCPP_HIDE_FROM_ABI void
851  splice_after(const_iterator __p, forward_list& __x, const_iterator __f, const_iterator __l);
852  _LIBCPP_HIDE_FROM_ABI __remove_return_type remove(const value_type& __v);
853  template <class _Predicate>
854  _LIBCPP_HIDE_FROM_ABI __remove_return_type remove_if(_Predicate __pred);
855  _LIBCPP_HIDE_FROM_ABI __remove_return_type unique() { return unique(__equal_to()); }
856  template <class _BinaryPredicate>
857  _LIBCPP_HIDE_FROM_ABI __remove_return_type unique(_BinaryPredicate __binary_pred);
858#ifndef _LIBCPP_CXX03_LANG
859  _LIBCPP_HIDE_FROM_ABI void merge(forward_list&& __x) { merge(__x, __less<>()); }
860  template <class _Compare>
861  _LIBCPP_HIDE_FROM_ABI void merge(forward_list&& __x, _Compare __comp) {
862    merge(__x, std::move(__comp));
863  }
864#endif // _LIBCPP_CXX03_LANG
865  _LIBCPP_HIDE_FROM_ABI void merge(forward_list& __x) { merge(__x, __less<>()); }
866  template <class _Compare>
867  _LIBCPP_HIDE_FROM_ABI void merge(forward_list& __x, _Compare __comp);
868  _LIBCPP_HIDE_FROM_ABI void sort() { sort(__less<>()); }
869  template <class _Compare>
870  _LIBCPP_HIDE_FROM_ABI void sort(_Compare __comp);
871  _LIBCPP_HIDE_FROM_ABI void reverse() _NOEXCEPT;
872
873private:
874#ifndef _LIBCPP_CXX03_LANG
875  _LIBCPP_HIDE_FROM_ABI void __move_assign(forward_list& __x, true_type)
876      _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
877  _LIBCPP_HIDE_FROM_ABI void __move_assign(forward_list& __x, false_type);
878#endif // _LIBCPP_CXX03_LANG
879
880  template <class _Iter, class _Sent>
881  _LIBCPP_HIDE_FROM_ABI void __assign_with_sentinel(_Iter __f, _Sent __l);
882
883  template <class _Compare>
884  static _LIBCPP_HIDE_FROM_ABI __node_pointer __merge(__node_pointer __f1, __node_pointer __f2, _Compare& __comp);
885
886  // TODO: Make this _LIBCPP_HIDE_FROM_ABI
887  template <class _Compare>
888  static _LIBCPP_HIDDEN __node_pointer __sort(__node_pointer __f, difference_type __sz, _Compare& __comp);
889};
890
891#if _LIBCPP_STD_VER >= 17
892template <class _InputIterator,
893          class _Alloc = allocator<__iter_value_type<_InputIterator>>,
894          class        = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
895          class        = enable_if_t<__is_allocator<_Alloc>::value> >
896forward_list(_InputIterator, _InputIterator) -> forward_list<__iter_value_type<_InputIterator>, _Alloc>;
897
898template <class _InputIterator,
899          class _Alloc,
900          class = enable_if_t<__has_input_iterator_category<_InputIterator>::value>,
901          class = enable_if_t<__is_allocator<_Alloc>::value> >
902forward_list(_InputIterator, _InputIterator, _Alloc) -> forward_list<__iter_value_type<_InputIterator>, _Alloc>;
903#endif
904
905#if _LIBCPP_STD_VER >= 23
906template <ranges::input_range _Range,
907          class _Alloc = allocator<ranges::range_value_t<_Range>>,
908          class        = enable_if_t<__is_allocator<_Alloc>::value> >
909forward_list(from_range_t, _Range&&, _Alloc = _Alloc()) -> forward_list<ranges::range_value_t<_Range>, _Alloc>;
910#endif
911
912template <class _Tp, class _Alloc>
913inline forward_list<_Tp, _Alloc>::forward_list(const allocator_type& __a) : base(__a) {}
914
915template <class _Tp, class _Alloc>
916forward_list<_Tp, _Alloc>::forward_list(size_type __n) {
917  if (__n > 0) {
918    for (__begin_node_pointer __p = base::__before_begin(); __n > 0; --__n, __p = __p->__next_as_begin()) {
919      __p->__next_ = this->__create_node(/* next = */ nullptr);
920    }
921  }
922}
923
924#if _LIBCPP_STD_VER >= 14
925template <class _Tp, class _Alloc>
926forward_list<_Tp, _Alloc>::forward_list(size_type __n, const allocator_type& __base_alloc) : base(__base_alloc) {
927  if (__n > 0) {
928    for (__begin_node_pointer __p = base::__before_begin(); __n > 0; --__n, __p = __p->__next_as_begin()) {
929      __p->__next_ = this->__create_node(/* next = */ nullptr);
930    }
931  }
932}
933#endif
934
935template <class _Tp, class _Alloc>
936forward_list<_Tp, _Alloc>::forward_list(size_type __n, const value_type& __v) {
937  insert_after(cbefore_begin(), __n, __v);
938}
939
940template <class _Tp, class _Alloc>
941template <class _InputIterator>
942forward_list<_Tp, _Alloc>::forward_list(
943    _InputIterator __f, _InputIterator __l, __enable_if_t<__has_input_iterator_category<_InputIterator>::value>*) {
944  insert_after(cbefore_begin(), __f, __l);
945}
946
947template <class _Tp, class _Alloc>
948template <class _InputIterator>
949forward_list<_Tp, _Alloc>::forward_list(
950    _InputIterator __f,
951    _InputIterator __l,
952    const allocator_type& __a,
953    __enable_if_t<__has_input_iterator_category<_InputIterator>::value>*)
954    : base(__a) {
955  insert_after(cbefore_begin(), __f, __l);
956}
957
958template <class _Tp, class _Alloc>
959forward_list<_Tp, _Alloc>::forward_list(const forward_list& __x)
960    : base(__node_traits::select_on_container_copy_construction(__x.__alloc())) {
961  insert_after(cbefore_begin(), __x.begin(), __x.end());
962}
963
964template <class _Tp, class _Alloc>
965forward_list<_Tp, _Alloc>::forward_list(const forward_list& __x, const __type_identity_t<allocator_type>& __a)
966    : base(__a) {
967  insert_after(cbefore_begin(), __x.begin(), __x.end());
968}
969
970template <class _Tp, class _Alloc>
971forward_list<_Tp, _Alloc>& forward_list<_Tp, _Alloc>::operator=(const forward_list& __x) {
972  if (this != std::addressof(__x)) {
973    base::__copy_assign_alloc(__x);
974    assign(__x.begin(), __x.end());
975  }
976  return *this;
977}
978
979#ifndef _LIBCPP_CXX03_LANG
980template <class _Tp, class _Alloc>
981forward_list<_Tp, _Alloc>::forward_list(forward_list&& __x, const __type_identity_t<allocator_type>& __a)
982    : base(std::move(__x), __a) {
983  if (base::__alloc() != __x.__alloc()) {
984    typedef move_iterator<iterator> _Ip;
985    insert_after(cbefore_begin(), _Ip(__x.begin()), _Ip(__x.end()));
986  }
987}
988
989template <class _Tp, class _Alloc>
990forward_list<_Tp, _Alloc>::forward_list(initializer_list<value_type> __il) {
991  insert_after(cbefore_begin(), __il.begin(), __il.end());
992}
993
994template <class _Tp, class _Alloc>
995forward_list<_Tp, _Alloc>::forward_list(initializer_list<value_type> __il, const allocator_type& __a) : base(__a) {
996  insert_after(cbefore_begin(), __il.begin(), __il.end());
997}
998
999template <class _Tp, class _Alloc>
1000void forward_list<_Tp, _Alloc>::__move_assign(forward_list& __x, true_type)
1001    _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value) {
1002  clear();
1003  base::__move_assign_alloc(__x);
1004  base::__before_begin()->__next_ = __x.__before_begin()->__next_;
1005  __x.__before_begin()->__next_   = nullptr;
1006}
1007
1008template <class _Tp, class _Alloc>
1009void forward_list<_Tp, _Alloc>::__move_assign(forward_list& __x, false_type) {
1010  if (base::__alloc() == __x.__alloc())
1011    __move_assign(__x, true_type());
1012  else {
1013    typedef move_iterator<iterator> _Ip;
1014    assign(_Ip(__x.begin()), _Ip(__x.end()));
1015  }
1016}
1017
1018template <class _Tp, class _Alloc>
1019inline forward_list<_Tp, _Alloc>& forward_list<_Tp, _Alloc>::operator=(forward_list&& __x) _NOEXCEPT_(
1020    __node_traits::propagate_on_container_move_assignment::value&& is_nothrow_move_assignable<allocator_type>::value) {
1021  __move_assign(__x, integral_constant<bool, __node_traits::propagate_on_container_move_assignment::value>());
1022  return *this;
1023}
1024
1025template <class _Tp, class _Alloc>
1026inline forward_list<_Tp, _Alloc>& forward_list<_Tp, _Alloc>::operator=(initializer_list<value_type> __il) {
1027  assign(__il.begin(), __il.end());
1028  return *this;
1029}
1030
1031#endif // _LIBCPP_CXX03_LANG
1032
1033template <class _Tp, class _Alloc>
1034template <class _InputIterator, __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> >
1035void forward_list<_Tp, _Alloc>::assign(_InputIterator __f, _InputIterator __l) {
1036  __assign_with_sentinel(__f, __l);
1037}
1038
1039template <class _Tp, class _Alloc>
1040template <class _Iter, class _Sent>
1041_LIBCPP_HIDE_FROM_ABI void forward_list<_Tp, _Alloc>::__assign_with_sentinel(_Iter __f, _Sent __l) {
1042  iterator __i = before_begin();
1043  iterator __j = std::next(__i);
1044  iterator __e = end();
1045  for (; __j != __e && __f != __l; ++__i, (void)++__j, ++__f)
1046    *__j = *__f;
1047  if (__j == __e)
1048    __insert_after_with_sentinel(__i, std::move(__f), std::move(__l));
1049  else
1050    erase_after(__i, __e);
1051}
1052
1053template <class _Tp, class _Alloc>
1054void forward_list<_Tp, _Alloc>::assign(size_type __n, const value_type& __v) {
1055  iterator __i = before_begin();
1056  iterator __j = std::next(__i);
1057  iterator __e = end();
1058  for (; __j != __e && __n > 0; --__n, ++__i, ++__j)
1059    *__j = __v;
1060  if (__j == __e)
1061    insert_after(__i, __n, __v);
1062  else
1063    erase_after(__i, __e);
1064}
1065
1066#ifndef _LIBCPP_CXX03_LANG
1067
1068template <class _Tp, class _Alloc>
1069inline void forward_list<_Tp, _Alloc>::assign(initializer_list<value_type> __il) {
1070  assign(__il.begin(), __il.end());
1071}
1072
1073template <class _Tp, class _Alloc>
1074template <class... _Args>
1075#  if _LIBCPP_STD_VER >= 17
1076typename forward_list<_Tp, _Alloc>::reference
1077#  else
1078void
1079#  endif
1080forward_list<_Tp, _Alloc>::emplace_front(_Args&&... __args) {
1081  base::__before_begin()->__next_ =
1082      this->__create_node(/* next = */ base::__before_begin()->__next_, std::forward<_Args>(__args)...);
1083#  if _LIBCPP_STD_VER >= 17
1084  return base::__before_begin()->__next_->__get_value();
1085#  endif
1086}
1087
1088template <class _Tp, class _Alloc>
1089void forward_list<_Tp, _Alloc>::push_front(value_type&& __v) {
1090  base::__before_begin()->__next_ = this->__create_node(/* next = */ base::__before_begin()->__next_, std::move(__v));
1091}
1092
1093#endif // _LIBCPP_CXX03_LANG
1094
1095template <class _Tp, class _Alloc>
1096void forward_list<_Tp, _Alloc>::push_front(const value_type& __v) {
1097  base::__before_begin()->__next_ = this->__create_node(/* next = */ base::__before_begin()->__next_, __v);
1098}
1099
1100template <class _Tp, class _Alloc>
1101void forward_list<_Tp, _Alloc>::pop_front() {
1102  __node_pointer __p              = base::__before_begin()->__next_;
1103  base::__before_begin()->__next_ = __p->__next_;
1104  this->__delete_node(__p);
1105}
1106
1107#ifndef _LIBCPP_CXX03_LANG
1108
1109template <class _Tp, class _Alloc>
1110template <class... _Args>
1111typename forward_list<_Tp, _Alloc>::iterator
1112forward_list<_Tp, _Alloc>::emplace_after(const_iterator __p, _Args&&... __args) {
1113  __begin_node_pointer const __r = __p.__get_begin();
1114  __r->__next_                   = this->__create_node(/* next = */ __r->__next_, std::forward<_Args>(__args)...);
1115  return iterator(__r->__next_);
1116}
1117
1118template <class _Tp, class _Alloc>
1119typename forward_list<_Tp, _Alloc>::iterator
1120forward_list<_Tp, _Alloc>::insert_after(const_iterator __p, value_type&& __v) {
1121  __begin_node_pointer const __r = __p.__get_begin();
1122  __r->__next_                   = this->__create_node(/* next = */ __r->__next_, std::move(__v));
1123  return iterator(__r->__next_);
1124}
1125
1126#endif // _LIBCPP_CXX03_LANG
1127
1128template <class _Tp, class _Alloc>
1129typename forward_list<_Tp, _Alloc>::iterator
1130forward_list<_Tp, _Alloc>::insert_after(const_iterator __p, const value_type& __v) {
1131  __begin_node_pointer const __r = __p.__get_begin();
1132  __r->__next_                   = this->__create_node(/* next = */ __r->__next_, __v);
1133  return iterator(__r->__next_);
1134}
1135
1136template <class _Tp, class _Alloc>
1137typename forward_list<_Tp, _Alloc>::iterator
1138forward_list<_Tp, _Alloc>::insert_after(const_iterator __p, size_type __n, const value_type& __v) {
1139  __begin_node_pointer __r = __p.__get_begin();
1140  if (__n > 0) {
1141    __node_pointer __first = this->__create_node(/* next = */ nullptr, __v);
1142    __node_pointer __last  = __first;
1143#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
1144    try {
1145#endif // _LIBCPP_HAS_NO_EXCEPTIONS
1146      for (--__n; __n != 0; --__n, __last = __last->__next_) {
1147        __last->__next_ = this->__create_node(/* next = */ nullptr, __v);
1148      }
1149#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
1150    } catch (...) {
1151      while (__first != nullptr) {
1152        __node_pointer __next = __first->__next_;
1153        this->__delete_node(__first);
1154        __first = __next;
1155      }
1156      throw;
1157    }
1158#endif // _LIBCPP_HAS_NO_EXCEPTIONS
1159    __last->__next_ = __r->__next_;
1160    __r->__next_    = __first;
1161    __r             = static_cast<__begin_node_pointer>(__last);
1162  }
1163  return iterator(__r);
1164}
1165
1166template <class _Tp, class _Alloc>
1167template <class _InputIterator, __enable_if_t<__has_input_iterator_category<_InputIterator>::value, int> >
1168typename forward_list<_Tp, _Alloc>::iterator
1169forward_list<_Tp, _Alloc>::insert_after(const_iterator __p, _InputIterator __f, _InputIterator __l) {
1170  return __insert_after_with_sentinel(__p, std::move(__f), std::move(__l));
1171}
1172
1173template <class _Tp, class _Alloc>
1174template <class _InputIterator, class _Sentinel>
1175_LIBCPP_HIDE_FROM_ABI typename forward_list<_Tp, _Alloc>::iterator
1176forward_list<_Tp, _Alloc>::__insert_after_with_sentinel(const_iterator __p, _InputIterator __f, _Sentinel __l) {
1177  __begin_node_pointer __r = __p.__get_begin();
1178
1179  if (__f != __l) {
1180    __node_pointer __first = this->__create_node(/* next = */ nullptr, *__f);
1181    __node_pointer __last  = __first;
1182
1183#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
1184    try {
1185#endif // _LIBCPP_HAS_NO_EXCEPTIONS
1186      for (++__f; __f != __l; ++__f, ((void)(__last = __last->__next_))) {
1187        __last->__next_ = this->__create_node(/* next = */ nullptr, *__f);
1188      }
1189#ifndef _LIBCPP_HAS_NO_EXCEPTIONS
1190    } catch (...) {
1191      while (__first != nullptr) {
1192        __node_pointer __next = __first->__next_;
1193        this->__delete_node(__first);
1194        __first = __next;
1195      }
1196      throw;
1197    }
1198#endif // _LIBCPP_HAS_NO_EXCEPTIONS
1199
1200    __last->__next_ = __r->__next_;
1201    __r->__next_    = __first;
1202    __r             = static_cast<__begin_node_pointer>(__last);
1203  }
1204
1205  return iterator(__r);
1206}
1207
1208template <class _Tp, class _Alloc>
1209typename forward_list<_Tp, _Alloc>::iterator forward_list<_Tp, _Alloc>::erase_after(const_iterator __f) {
1210  __begin_node_pointer __p = __f.__get_begin();
1211  __node_pointer __n       = __p->__next_;
1212  __p->__next_             = __n->__next_;
1213  this->__delete_node(__n);
1214  return iterator(__p->__next_);
1215}
1216
1217template <class _Tp, class _Alloc>
1218typename forward_list<_Tp, _Alloc>::iterator
1219forward_list<_Tp, _Alloc>::erase_after(const_iterator __f, const_iterator __l) {
1220  __node_pointer __e = __l.__get_unsafe_node_pointer();
1221  if (__f != __l) {
1222    __begin_node_pointer __bp = __f.__get_begin();
1223
1224    __node_pointer __n = __bp->__next_;
1225    if (__n != __e) {
1226      __bp->__next_ = __e;
1227      do {
1228        __node_pointer __tmp = __n->__next_;
1229        this->__delete_node(__n);
1230        __n = __tmp;
1231      } while (__n != __e);
1232    }
1233  }
1234  return iterator(__e);
1235}
1236
1237template <class _Tp, class _Alloc>
1238void forward_list<_Tp, _Alloc>::resize(size_type __n) {
1239  size_type __sz = 0;
1240  iterator __p   = before_begin();
1241  iterator __i   = begin();
1242  iterator __e   = end();
1243  for (; __i != __e && __sz < __n; ++__p, ++__i, ++__sz)
1244    ;
1245  if (__i != __e)
1246    erase_after(__p, __e);
1247  else {
1248    __n -= __sz;
1249    if (__n > 0) {
1250      for (__begin_node_pointer __ptr = __p.__get_begin(); __n > 0; --__n, __ptr = __ptr->__next_as_begin()) {
1251        __ptr->__next_ = this->__create_node(/* next = */ nullptr);
1252      }
1253    }
1254  }
1255}
1256
1257template <class _Tp, class _Alloc>
1258void forward_list<_Tp, _Alloc>::resize(size_type __n, const value_type& __v) {
1259  size_type __sz = 0;
1260  iterator __p   = before_begin();
1261  iterator __i   = begin();
1262  iterator __e   = end();
1263  for (; __i != __e && __sz < __n; ++__p, ++__i, ++__sz)
1264    ;
1265  if (__i != __e)
1266    erase_after(__p, __e);
1267  else {
1268    __n -= __sz;
1269    if (__n > 0) {
1270      for (__begin_node_pointer __ptr = __p.__get_begin(); __n > 0; --__n, __ptr = __ptr->__next_as_begin()) {
1271        __ptr->__next_ = this->__create_node(/* next = */ nullptr, __v);
1272      }
1273    }
1274  }
1275}
1276
1277template <class _Tp, class _Alloc>
1278void forward_list<_Tp, _Alloc>::splice_after(const_iterator __p, forward_list& __x) {
1279  if (!__x.empty()) {
1280    if (__p.__get_begin()->__next_ != nullptr) {
1281      const_iterator __lm1 = __x.before_begin();
1282      while (__lm1.__get_begin()->__next_ != nullptr)
1283        ++__lm1;
1284      __lm1.__get_begin()->__next_ = __p.__get_begin()->__next_;
1285    }
1286    __p.__get_begin()->__next_    = __x.__before_begin()->__next_;
1287    __x.__before_begin()->__next_ = nullptr;
1288  }
1289}
1290
1291template <class _Tp, class _Alloc>
1292void forward_list<_Tp, _Alloc>::splice_after(const_iterator __p, forward_list& /*__other*/, const_iterator __i) {
1293  const_iterator __lm1 = std::next(__i);
1294  if (__p != __i && __p != __lm1) {
1295    __i.__get_begin()->__next_   = __lm1.__get_begin()->__next_;
1296    __lm1.__get_begin()->__next_ = __p.__get_begin()->__next_;
1297    __p.__get_begin()->__next_   = __lm1.__get_unsafe_node_pointer();
1298  }
1299}
1300
1301template <class _Tp, class _Alloc>
1302void forward_list<_Tp, _Alloc>::splice_after(
1303    const_iterator __p, forward_list& /*__other*/, const_iterator __f, const_iterator __l) {
1304  if (__f != __l && __p != __f) {
1305    const_iterator __lm1 = __f;
1306    while (__lm1.__get_begin()->__next_ != __l.__get_begin())
1307      ++__lm1;
1308    if (__f != __lm1) {
1309      __lm1.__get_begin()->__next_ = __p.__get_begin()->__next_;
1310      __p.__get_begin()->__next_   = __f.__get_begin()->__next_;
1311      __f.__get_begin()->__next_   = __l.__get_unsafe_node_pointer();
1312    }
1313  }
1314}
1315
1316template <class _Tp, class _Alloc>
1317inline _LIBCPP_HIDE_FROM_ABI void forward_list<_Tp, _Alloc>::splice_after(const_iterator __p, forward_list&& __x) {
1318  splice_after(__p, __x);
1319}
1320
1321template <class _Tp, class _Alloc>
1322inline _LIBCPP_HIDE_FROM_ABI void
1323forward_list<_Tp, _Alloc>::splice_after(const_iterator __p, forward_list&& __x, const_iterator __i) {
1324  splice_after(__p, __x, __i);
1325}
1326
1327template <class _Tp, class _Alloc>
1328inline _LIBCPP_HIDE_FROM_ABI void forward_list<_Tp, _Alloc>::splice_after(
1329    const_iterator __p, forward_list&& __x, const_iterator __f, const_iterator __l) {
1330  splice_after(__p, __x, __f, __l);
1331}
1332
1333template <class _Tp, class _Alloc>
1334typename forward_list<_Tp, _Alloc>::__remove_return_type forward_list<_Tp, _Alloc>::remove(const value_type& __v) {
1335  forward_list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
1336  typename forward_list<_Tp, _Alloc>::size_type __count_removed = 0;
1337  const iterator __e                                            = end();
1338  for (iterator __i = before_begin(); __i.__get_begin()->__next_ != nullptr;) {
1339    if (__i.__get_begin()->__next_->__get_value() == __v) {
1340      ++__count_removed;
1341      iterator __j = std::next(__i, 2);
1342      for (; __j != __e && *__j == __v; ++__j)
1343        ++__count_removed;
1344      __deleted_nodes.splice_after(__deleted_nodes.before_begin(), *this, __i, __j);
1345      if (__j == __e)
1346        break;
1347      __i = __j;
1348    } else
1349      ++__i;
1350  }
1351
1352  return (__remove_return_type)__count_removed;
1353}
1354
1355template <class _Tp, class _Alloc>
1356template <class _Predicate>
1357typename forward_list<_Tp, _Alloc>::__remove_return_type forward_list<_Tp, _Alloc>::remove_if(_Predicate __pred) {
1358  forward_list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
1359  typename forward_list<_Tp, _Alloc>::size_type __count_removed = 0;
1360  const iterator __e                                            = end();
1361  for (iterator __i = before_begin(); __i.__get_begin()->__next_ != nullptr;) {
1362    if (__pred(__i.__get_begin()->__next_->__get_value())) {
1363      ++__count_removed;
1364      iterator __j = std::next(__i, 2);
1365      for (; __j != __e && __pred(*__j); ++__j)
1366        ++__count_removed;
1367      __deleted_nodes.splice_after(__deleted_nodes.before_begin(), *this, __i, __j);
1368      if (__j == __e)
1369        break;
1370      __i = __j;
1371    } else
1372      ++__i;
1373  }
1374
1375  return (__remove_return_type)__count_removed;
1376}
1377
1378template <class _Tp, class _Alloc>
1379template <class _BinaryPredicate>
1380typename forward_list<_Tp, _Alloc>::__remove_return_type
1381forward_list<_Tp, _Alloc>::unique(_BinaryPredicate __binary_pred) {
1382  forward_list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
1383  typename forward_list<_Tp, _Alloc>::size_type __count_removed = 0;
1384  for (iterator __i = begin(), __e = end(); __i != __e;) {
1385    iterator __j = std::next(__i);
1386    for (; __j != __e && __binary_pred(*__i, *__j); ++__j)
1387      ++__count_removed;
1388    if (__i.__get_begin()->__next_ != __j.__get_unsafe_node_pointer())
1389      __deleted_nodes.splice_after(__deleted_nodes.before_begin(), *this, __i, __j);
1390    __i = __j;
1391  }
1392
1393  return (__remove_return_type)__count_removed;
1394}
1395
1396template <class _Tp, class _Alloc>
1397template <class _Compare>
1398void forward_list<_Tp, _Alloc>::merge(forward_list& __x, _Compare __comp) {
1399  if (this != std::addressof(__x)) {
1400    base::__before_begin()->__next_ = __merge(base::__before_begin()->__next_, __x.__before_begin()->__next_, __comp);
1401    __x.__before_begin()->__next_   = nullptr;
1402  }
1403}
1404
1405template <class _Tp, class _Alloc>
1406template <class _Compare>
1407typename forward_list<_Tp, _Alloc>::__node_pointer
1408forward_list<_Tp, _Alloc>::__merge(__node_pointer __f1, __node_pointer __f2, _Compare& __comp) {
1409  if (__f1 == nullptr)
1410    return __f2;
1411  if (__f2 == nullptr)
1412    return __f1;
1413  __node_pointer __r;
1414  if (__comp(__f2->__get_value(), __f1->__get_value())) {
1415    __node_pointer __t = __f2;
1416    while (__t->__next_ != nullptr && __comp(__t->__next_->__get_value(), __f1->__get_value()))
1417      __t = __t->__next_;
1418    __r          = __f2;
1419    __f2         = __t->__next_;
1420    __t->__next_ = __f1;
1421  } else
1422    __r = __f1;
1423  __node_pointer __p = __f1;
1424  __f1               = __f1->__next_;
1425  while (__f1 != nullptr && __f2 != nullptr) {
1426    if (__comp(__f2->__get_value(), __f1->__get_value())) {
1427      __node_pointer __t = __f2;
1428      while (__t->__next_ != nullptr && __comp(__t->__next_->__get_value(), __f1->__get_value()))
1429        __t = __t->__next_;
1430      __p->__next_ = __f2;
1431      __f2         = __t->__next_;
1432      __t->__next_ = __f1;
1433    }
1434    __p  = __f1;
1435    __f1 = __f1->__next_;
1436  }
1437  if (__f2 != nullptr)
1438    __p->__next_ = __f2;
1439  return __r;
1440}
1441
1442template <class _Tp, class _Alloc>
1443template <class _Compare>
1444inline void forward_list<_Tp, _Alloc>::sort(_Compare __comp) {
1445  base::__before_begin()->__next_ = __sort(base::__before_begin()->__next_, std::distance(begin(), end()), __comp);
1446}
1447
1448template <class _Tp, class _Alloc>
1449template <class _Compare>
1450typename forward_list<_Tp, _Alloc>::__node_pointer
1451forward_list<_Tp, _Alloc>::__sort(__node_pointer __f1, difference_type __sz, _Compare& __comp) {
1452  switch (__sz) {
1453  case 0:
1454  case 1:
1455    return __f1;
1456  case 2:
1457    if (__comp(__f1->__next_->__get_value(), __f1->__get_value())) {
1458      __node_pointer __t = __f1->__next_;
1459      __t->__next_       = __f1;
1460      __f1->__next_      = nullptr;
1461      __f1               = __t;
1462    }
1463    return __f1;
1464  }
1465  difference_type __sz1 = __sz / 2;
1466  difference_type __sz2 = __sz - __sz1;
1467  __node_pointer __t    = std::next(iterator(__f1), __sz1 - 1).__get_unsafe_node_pointer();
1468  __node_pointer __f2   = __t->__next_;
1469  __t->__next_          = nullptr;
1470  return __merge(__sort(__f1, __sz1, __comp), __sort(__f2, __sz2, __comp), __comp);
1471}
1472
1473template <class _Tp, class _Alloc>
1474void forward_list<_Tp, _Alloc>::reverse() _NOEXCEPT {
1475  __node_pointer __p = base::__before_begin()->__next_;
1476  if (__p != nullptr) {
1477    __node_pointer __f = __p->__next_;
1478    __p->__next_       = nullptr;
1479    while (__f != nullptr) {
1480      __node_pointer __t = __f->__next_;
1481      __f->__next_       = __p;
1482      __p                = __f;
1483      __f                = __t;
1484    }
1485    base::__before_begin()->__next_ = __p;
1486  }
1487}
1488
1489template <class _Tp, class _Alloc>
1490_LIBCPP_HIDE_FROM_ABI bool operator==(const forward_list<_Tp, _Alloc>& __x, const forward_list<_Tp, _Alloc>& __y) {
1491  typedef forward_list<_Tp, _Alloc> _Cp;
1492  typedef typename _Cp::const_iterator _Ip;
1493  _Ip __ix = __x.begin();
1494  _Ip __ex = __x.end();
1495  _Ip __iy = __y.begin();
1496  _Ip __ey = __y.end();
1497  for (; __ix != __ex && __iy != __ey; ++__ix, ++__iy)
1498    if (!(*__ix == *__iy))
1499      return false;
1500  return (__ix == __ex) == (__iy == __ey);
1501}
1502
1503#if _LIBCPP_STD_VER <= 17
1504
1505template <class _Tp, class _Alloc>
1506inline _LIBCPP_HIDE_FROM_ABI bool
1507operator!=(const forward_list<_Tp, _Alloc>& __x, const forward_list<_Tp, _Alloc>& __y) {
1508  return !(__x == __y);
1509}
1510
1511template <class _Tp, class _Alloc>
1512inline _LIBCPP_HIDE_FROM_ABI bool
1513operator<(const forward_list<_Tp, _Alloc>& __x, const forward_list<_Tp, _Alloc>& __y) {
1514  return std::lexicographical_compare(__x.begin(), __x.end(), __y.begin(), __y.end());
1515}
1516
1517template <class _Tp, class _Alloc>
1518inline _LIBCPP_HIDE_FROM_ABI bool
1519operator>(const forward_list<_Tp, _Alloc>& __x, const forward_list<_Tp, _Alloc>& __y) {
1520  return __y < __x;
1521}
1522
1523template <class _Tp, class _Alloc>
1524inline _LIBCPP_HIDE_FROM_ABI bool
1525operator>=(const forward_list<_Tp, _Alloc>& __x, const forward_list<_Tp, _Alloc>& __y) {
1526  return !(__x < __y);
1527}
1528
1529template <class _Tp, class _Alloc>
1530inline _LIBCPP_HIDE_FROM_ABI bool
1531operator<=(const forward_list<_Tp, _Alloc>& __x, const forward_list<_Tp, _Alloc>& __y) {
1532  return !(__y < __x);
1533}
1534
1535#else // #if _LIBCPP_STD_VER <= 17
1536
1537template <class _Tp, class _Allocator>
1538_LIBCPP_HIDE_FROM_ABI __synth_three_way_result<_Tp>
1539operator<=>(const forward_list<_Tp, _Allocator>& __x, const forward_list<_Tp, _Allocator>& __y) {
1540  return std::lexicographical_compare_three_way(
1541      __x.begin(), __x.end(), __y.begin(), __y.end(), std::__synth_three_way<_Tp, _Tp>);
1542}
1543
1544#endif // #if _LIBCPP_STD_VER <= 17
1545
1546template <class _Tp, class _Alloc>
1547inline _LIBCPP_HIDE_FROM_ABI void swap(forward_list<_Tp, _Alloc>& __x, forward_list<_Tp, _Alloc>& __y)
1548    _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y))) {
1549  __x.swap(__y);
1550}
1551
1552#if _LIBCPP_STD_VER >= 20
1553template <class _Tp, class _Allocator, class _Predicate>
1554inline _LIBCPP_HIDE_FROM_ABI typename forward_list<_Tp, _Allocator>::size_type
1555erase_if(forward_list<_Tp, _Allocator>& __c, _Predicate __pred) {
1556  return __c.remove_if(__pred);
1557}
1558
1559template <class _Tp, class _Allocator, class _Up>
1560inline _LIBCPP_HIDE_FROM_ABI typename forward_list<_Tp, _Allocator>::size_type
1561erase(forward_list<_Tp, _Allocator>& __c, const _Up& __v) {
1562  return std::erase_if(__c, [&](auto& __elem) { return __elem == __v; });
1563}
1564#endif
1565
1566_LIBCPP_END_NAMESPACE_STD
1567
1568#if _LIBCPP_STD_VER >= 17
1569_LIBCPP_BEGIN_NAMESPACE_STD
1570namespace pmr {
1571template <class _ValueT>
1572using forward_list _LIBCPP_AVAILABILITY_PMR = std::forward_list<_ValueT, polymorphic_allocator<_ValueT>>;
1573} // namespace pmr
1574_LIBCPP_END_NAMESPACE_STD
1575#endif
1576
1577_LIBCPP_POP_MACROS
1578
1579#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
1580#  include <algorithm>
1581#  include <atomic>
1582#  include <concepts>
1583#  include <cstdint>
1584#  include <cstdlib>
1585#  include <cstring>
1586#  include <functional>
1587#  include <iosfwd>
1588#  include <iterator>
1589#  include <stdexcept>
1590#  include <type_traits>
1591#  include <typeinfo>
1592#endif
1593
1594#endif // _LIBCPP_FORWARD_LIST
1595