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    forward_list(const forward_list& x);
48    forward_list(const forward_list& x, const allocator_type& a);
49    forward_list(forward_list&& x)
50        noexcept(is_nothrow_move_constructible<allocator_type>::value);
51    forward_list(forward_list&& x, const allocator_type& a);
52    forward_list(initializer_list<value_type> il);
53    forward_list(initializer_list<value_type> il, const allocator_type& a);
54
55    ~forward_list();
56
57    forward_list& operator=(const forward_list& x);
58    forward_list& operator=(forward_list&& x)
59        noexcept(
60             allocator_type::propagate_on_container_move_assignment::value &&
61             is_nothrow_move_assignable<allocator_type>::value);
62    forward_list& operator=(initializer_list<value_type> il);
63
64    template <class InputIterator>
65        void assign(InputIterator first, InputIterator last);
66    void assign(size_type n, const value_type& v);
67    void assign(initializer_list<value_type> il);
68
69    allocator_type get_allocator() const noexcept;
70
71    iterator       begin() noexcept;
72    const_iterator begin() const noexcept;
73    iterator       end() noexcept;
74    const_iterator end() const noexcept;
75
76    const_iterator cbegin() const noexcept;
77    const_iterator cend() const noexcept;
78
79    iterator       before_begin() noexcept;
80    const_iterator before_begin() const noexcept;
81    const_iterator cbefore_begin() const noexcept;
82
83    bool empty() const noexcept;
84    size_type max_size() const noexcept;
85
86    reference       front();
87    const_reference front() const;
88
89    template <class... Args> reference emplace_front(Args&&... args);  // reference in C++17
90    void push_front(const value_type& v);
91    void push_front(value_type&& v);
92
93    void pop_front();
94
95    template <class... Args>
96        iterator emplace_after(const_iterator p, Args&&... args);
97    iterator insert_after(const_iterator p, const value_type& v);
98    iterator insert_after(const_iterator p, value_type&& v);
99    iterator insert_after(const_iterator p, size_type n, const value_type& v);
100    template <class InputIterator>
101        iterator insert_after(const_iterator p,
102                              InputIterator first, InputIterator last);
103    iterator insert_after(const_iterator p, initializer_list<value_type> il);
104
105    iterator erase_after(const_iterator p);
106    iterator erase_after(const_iterator first, const_iterator last);
107
108    void swap(forward_list& x)
109        noexcept(allocator_traits<allocator_type>::is_always_equal::value);  // C++17
110
111    void resize(size_type n);
112    void resize(size_type n, const value_type& v);
113    void clear() noexcept;
114
115    void splice_after(const_iterator p, forward_list& x);
116    void splice_after(const_iterator p, forward_list&& x);
117    void splice_after(const_iterator p, forward_list& x, const_iterator i);
118    void splice_after(const_iterator p, forward_list&& x, const_iterator i);
119    void splice_after(const_iterator p, forward_list& x,
120                      const_iterator first, const_iterator last);
121    void splice_after(const_iterator p, forward_list&& x,
122                      const_iterator first, const_iterator last);
123    size_type remove(const value_type& v);           // void before C++20
124    template <class Predicate>
125      size_type remove_if(Predicate pred);           // void before C++20
126    size_type unique();                              // void before C++20
127    template <class BinaryPredicate>
128      size_type unique(BinaryPredicate binary_pred); // void before C++20
129    void merge(forward_list& x);
130    void merge(forward_list&& x);
131    template <class Compare> void merge(forward_list& x, Compare comp);
132    template <class Compare> void merge(forward_list&& x, Compare comp);
133    void sort();
134    template <class Compare> void sort(Compare comp);
135    void reverse() noexcept;
136};
137
138
139template <class InputIterator, class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
140    forward_list(InputIterator, InputIterator, Allocator = Allocator())
141    -> forward_list<typename iterator_traits<InputIterator>::value_type, Allocator>;  // C++17
142
143template <class T, class Allocator>
144    bool operator==(const forward_list<T, Allocator>& x,
145                    const forward_list<T, Allocator>& y);
146
147template <class T, class Allocator>
148    bool operator< (const forward_list<T, Allocator>& x,
149                    const forward_list<T, Allocator>& y);
150
151template <class T, class Allocator>
152    bool operator!=(const forward_list<T, Allocator>& x,
153                    const forward_list<T, Allocator>& y);
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);
162
163template <class T, class Allocator>
164    bool operator<=(const forward_list<T, Allocator>& x,
165                    const forward_list<T, Allocator>& y);
166
167template <class T, class Allocator>
168    void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y)
169         noexcept(noexcept(x.swap(y)));
170
171template <class T, class Allocator, class U>
172    typename forward_list<T, Allocator>::size_type
173    erase(forward_list<T, Allocator>& c, const U& value);       // C++20
174template <class T, class Allocator, class Predicate>
175    typename forward_list<T, Allocator>::size_type
176    erase_if(forward_list<T, Allocator>& c, Predicate pred);    // C++20
177
178}  // std
179
180*/
181
182#include <__algorithm/comp.h>
183#include <__algorithm/lexicographical_compare.h>
184#include <__algorithm/min.h>
185#include <__assert> // all public C++ headers provide the assertion handler
186#include <__config>
187#include <__iterator/distance.h>
188#include <__iterator/iterator_traits.h>
189#include <__iterator/move_iterator.h>
190#include <__iterator/next.h>
191#include <__memory/swap_allocator.h>
192#include <__utility/forward.h>
193#include <limits>
194#include <memory>
195#include <type_traits>
196#include <version>
197
198#ifndef _LIBCPP_REMOVE_TRANSITIVE_INCLUDES
199#  include <algorithm>
200#  include <functional>
201#  include <iterator>
202#endif
203
204// standard-mandated includes
205
206// [iterator.range]
207#include <__iterator/access.h>
208#include <__iterator/data.h>
209#include <__iterator/empty.h>
210#include <__iterator/reverse_access.h>
211#include <__iterator/size.h>
212
213// [forward.list.syn]
214#include <compare>
215#include <initializer_list>
216
217#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
218#  pragma GCC system_header
219#endif
220
221_LIBCPP_PUSH_MACROS
222#include <__undef_macros>
223
224
225_LIBCPP_BEGIN_NAMESPACE_STD
226
227template <class _Tp, class _VoidPtr> struct __forward_list_node;
228template <class _NodePtr> struct __forward_begin_node;
229
230
231template <class>
232struct __forward_list_node_value_type;
233
234template <class _Tp, class _VoidPtr>
235struct __forward_list_node_value_type<__forward_list_node<_Tp, _VoidPtr> > {
236  typedef _Tp type;
237};
238
239template <class _NodePtr>
240struct __forward_node_traits {
241
242  typedef typename remove_cv<
243        typename pointer_traits<_NodePtr>::element_type>::type  __node;
244  typedef typename __forward_list_node_value_type<__node>::type __node_value_type;
245  typedef _NodePtr                                              __node_pointer;
246  typedef __forward_begin_node<_NodePtr>                        __begin_node;
247  typedef typename __rebind_pointer<_NodePtr, __begin_node>::type
248                                                                __begin_node_pointer;
249  typedef typename __rebind_pointer<_NodePtr, void>::type       __void_pointer;
250
251#if defined(_LIBCPP_ABI_FORWARD_LIST_REMOVE_NODE_POINTER_UB)
252  typedef __begin_node_pointer __iter_node_pointer;
253#else
254  typedef typename conditional<
255          is_pointer<__void_pointer>::value,
256          __begin_node_pointer,
257          __node_pointer
258    >::type __iter_node_pointer;
259#endif
260
261  typedef typename conditional<
262          is_same<__iter_node_pointer, __node_pointer>::value,
263          __begin_node_pointer,
264          __node_pointer
265    >::type __non_iter_node_pointer;
266
267  _LIBCPP_INLINE_VISIBILITY
268  static __iter_node_pointer __as_iter_node(__iter_node_pointer __p) {
269      return __p;
270  }
271  _LIBCPP_INLINE_VISIBILITY
272  static __iter_node_pointer __as_iter_node(__non_iter_node_pointer __p) {
273      return static_cast<__iter_node_pointer>(static_cast<__void_pointer>(__p));
274  }
275};
276
277template <class _NodePtr>
278struct __forward_begin_node
279{
280    typedef _NodePtr pointer;
281    typedef typename __rebind_pointer<_NodePtr, __forward_begin_node>::type __begin_node_pointer;
282
283    pointer __next_;
284
285    _LIBCPP_INLINE_VISIBILITY __forward_begin_node() : __next_(nullptr) {}
286
287    _LIBCPP_INLINE_VISIBILITY
288    __begin_node_pointer __next_as_begin() const {
289        return static_cast<__begin_node_pointer>(__next_);
290    }
291};
292
293template <class _Tp, class _VoidPtr>
294struct _LIBCPP_HIDDEN __begin_node_of
295{
296    typedef __forward_begin_node<
297        typename __rebind_pointer<_VoidPtr, __forward_list_node<_Tp, _VoidPtr> >::type
298    > type;
299};
300
301template <class _Tp, class _VoidPtr>
302struct _LIBCPP_STANDALONE_DEBUG __forward_list_node
303    : public __begin_node_of<_Tp, _VoidPtr>::type
304{
305    typedef _Tp value_type;
306
307    value_type __value_;
308};
309
310
311template <class _Tp, class _Alloc = allocator<_Tp> > class _LIBCPP_TEMPLATE_VIS forward_list;
312template<class _NodeConstPtr> class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator;
313
314template <class _NodePtr>
315class _LIBCPP_TEMPLATE_VIS __forward_list_iterator
316{
317    typedef __forward_node_traits<_NodePtr>         __traits;
318    typedef typename __traits::__node_pointer       __node_pointer;
319    typedef typename __traits::__begin_node_pointer __begin_node_pointer;
320    typedef typename __traits::__iter_node_pointer  __iter_node_pointer;
321    typedef typename __traits::__void_pointer       __void_pointer;
322
323    __iter_node_pointer __ptr_;
324
325    _LIBCPP_INLINE_VISIBILITY
326    __begin_node_pointer __get_begin() const {
327        return static_cast<__begin_node_pointer>(
328                static_cast<__void_pointer>(__ptr_));
329    }
330    _LIBCPP_INLINE_VISIBILITY
331    __node_pointer __get_unsafe_node_pointer() const {
332        return static_cast<__node_pointer>(
333                static_cast<__void_pointer>(__ptr_));
334    }
335
336    _LIBCPP_INLINE_VISIBILITY
337    explicit __forward_list_iterator(nullptr_t) _NOEXCEPT : __ptr_(nullptr) {}
338
339    _LIBCPP_INLINE_VISIBILITY
340    explicit __forward_list_iterator(__begin_node_pointer __p) _NOEXCEPT
341        : __ptr_(__traits::__as_iter_node(__p)) {}
342
343    _LIBCPP_INLINE_VISIBILITY
344    explicit __forward_list_iterator(__node_pointer __p) _NOEXCEPT
345        : __ptr_(__traits::__as_iter_node(__p)) {}
346
347    template<class, class> friend class _LIBCPP_TEMPLATE_VIS forward_list;
348    template<class> friend class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator;
349
350public:
351    typedef forward_iterator_tag                              iterator_category;
352    typedef typename __traits::__node_value_type              value_type;
353    typedef value_type&                                       reference;
354    typedef typename pointer_traits<__node_pointer>::difference_type
355                                                              difference_type;
356    typedef typename __rebind_pointer<__node_pointer, value_type>::type pointer;
357
358    _LIBCPP_INLINE_VISIBILITY
359    __forward_list_iterator() _NOEXCEPT : __ptr_(nullptr) {}
360
361    _LIBCPP_INLINE_VISIBILITY
362    reference operator*() const {return __get_unsafe_node_pointer()->__value_;}
363    _LIBCPP_INLINE_VISIBILITY
364    pointer operator->() const {
365        return pointer_traits<pointer>::pointer_to(__get_unsafe_node_pointer()->__value_);
366    }
367
368    _LIBCPP_INLINE_VISIBILITY
369    __forward_list_iterator& operator++()
370    {
371        __ptr_ = __traits::__as_iter_node(__ptr_->__next_);
372        return *this;
373    }
374    _LIBCPP_INLINE_VISIBILITY
375    __forward_list_iterator operator++(int)
376    {
377        __forward_list_iterator __t(*this);
378        ++(*this);
379        return __t;
380    }
381
382    friend _LIBCPP_INLINE_VISIBILITY
383    bool operator==(const __forward_list_iterator& __x,
384                    const __forward_list_iterator& __y)
385        {return __x.__ptr_ == __y.__ptr_;}
386    friend _LIBCPP_INLINE_VISIBILITY
387    bool operator!=(const __forward_list_iterator& __x,
388                    const __forward_list_iterator& __y)
389        {return !(__x == __y);}
390};
391
392template <class _NodeConstPtr>
393class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator
394{
395    static_assert((!is_const<typename pointer_traits<_NodeConstPtr>::element_type>::value), "");
396    typedef _NodeConstPtr _NodePtr;
397
398    typedef __forward_node_traits<_NodePtr>         __traits;
399    typedef typename __traits::__node               __node;
400    typedef typename __traits::__node_pointer       __node_pointer;
401    typedef typename __traits::__begin_node_pointer __begin_node_pointer;
402    typedef typename __traits::__iter_node_pointer  __iter_node_pointer;
403    typedef typename __traits::__void_pointer       __void_pointer;
404
405    __iter_node_pointer __ptr_;
406
407    __begin_node_pointer __get_begin() const {
408        return static_cast<__begin_node_pointer>(
409                static_cast<__void_pointer>(__ptr_));
410    }
411    __node_pointer __get_unsafe_node_pointer() const {
412        return static_cast<__node_pointer>(
413                static_cast<__void_pointer>(__ptr_));
414    }
415
416    _LIBCPP_INLINE_VISIBILITY
417    explicit __forward_list_const_iterator(nullptr_t) _NOEXCEPT
418        : __ptr_(nullptr) {}
419
420    _LIBCPP_INLINE_VISIBILITY
421    explicit __forward_list_const_iterator(__begin_node_pointer __p) _NOEXCEPT
422        : __ptr_(__traits::__as_iter_node(__p)) {}
423
424    _LIBCPP_INLINE_VISIBILITY
425    explicit __forward_list_const_iterator(__node_pointer __p) _NOEXCEPT
426        : __ptr_(__traits::__as_iter_node(__p)) {}
427
428
429    template<class, class> friend class forward_list;
430
431public:
432    typedef forward_iterator_tag                              iterator_category;
433    typedef typename __traits::__node_value_type              value_type;
434    typedef const value_type&                                 reference;
435    typedef typename pointer_traits<__node_pointer>::difference_type
436                                                              difference_type;
437    typedef typename __rebind_pointer<__node_pointer, const value_type>::type
438                                                              pointer;
439
440    _LIBCPP_INLINE_VISIBILITY
441    __forward_list_const_iterator() _NOEXCEPT : __ptr_(nullptr) {}
442    _LIBCPP_INLINE_VISIBILITY
443    __forward_list_const_iterator(__forward_list_iterator<__node_pointer> __p) _NOEXCEPT
444        : __ptr_(__p.__ptr_) {}
445
446    _LIBCPP_INLINE_VISIBILITY
447    reference operator*() const {return __get_unsafe_node_pointer()->__value_;}
448    _LIBCPP_INLINE_VISIBILITY
449    pointer operator->() const {return pointer_traits<pointer>::pointer_to(
450                __get_unsafe_node_pointer()->__value_);}
451
452    _LIBCPP_INLINE_VISIBILITY
453    __forward_list_const_iterator& operator++()
454    {
455        __ptr_ = __traits::__as_iter_node(__ptr_->__next_);
456        return *this;
457    }
458    _LIBCPP_INLINE_VISIBILITY
459    __forward_list_const_iterator operator++(int)
460    {
461        __forward_list_const_iterator __t(*this);
462        ++(*this);
463        return __t;
464    }
465
466    friend _LIBCPP_INLINE_VISIBILITY
467    bool operator==(const __forward_list_const_iterator& __x,
468                    const __forward_list_const_iterator& __y)
469        {return __x.__ptr_ == __y.__ptr_;}
470    friend _LIBCPP_INLINE_VISIBILITY
471    bool operator!=(const __forward_list_const_iterator& __x,
472                           const __forward_list_const_iterator& __y)
473        {return !(__x == __y);}
474};
475
476template <class _Tp, class _Alloc>
477class __forward_list_base
478{
479protected:
480    typedef _Tp    value_type;
481    typedef _Alloc allocator_type;
482
483    typedef typename allocator_traits<allocator_type>::void_pointer  void_pointer;
484    typedef __forward_list_node<value_type, void_pointer>            __node;
485    typedef typename __begin_node_of<value_type, void_pointer>::type __begin_node;
486    typedef typename __rebind_alloc_helper<allocator_traits<allocator_type>, __node>::type __node_allocator;
487    typedef allocator_traits<__node_allocator>        __node_traits;
488    typedef typename __node_traits::pointer           __node_pointer;
489
490    typedef typename __rebind_alloc_helper<
491        allocator_traits<allocator_type>, __begin_node
492    >::type                                           __begin_node_allocator;
493    typedef typename allocator_traits<__begin_node_allocator>::pointer
494                                                      __begin_node_pointer;
495
496    static_assert((!is_same<allocator_type, __node_allocator>::value),
497                  "internal allocator type must differ from user-specified "
498                  "type; otherwise overload resolution breaks");
499
500    __compressed_pair<__begin_node, __node_allocator> __before_begin_;
501
502    _LIBCPP_INLINE_VISIBILITY
503    __begin_node_pointer        __before_begin() _NOEXCEPT
504        {return pointer_traits<__begin_node_pointer>::pointer_to(__before_begin_.first());}
505    _LIBCPP_INLINE_VISIBILITY
506    __begin_node_pointer __before_begin() const _NOEXCEPT
507        {return pointer_traits<__begin_node_pointer>::pointer_to(const_cast<__begin_node&>(__before_begin_.first()));}
508
509    _LIBCPP_INLINE_VISIBILITY
510          __node_allocator& __alloc() _NOEXCEPT
511            {return __before_begin_.second();}
512    _LIBCPP_INLINE_VISIBILITY
513    const __node_allocator& __alloc() const _NOEXCEPT
514        {return __before_begin_.second();}
515
516    typedef __forward_list_iterator<__node_pointer>             iterator;
517    typedef __forward_list_const_iterator<__node_pointer>       const_iterator;
518
519    _LIBCPP_INLINE_VISIBILITY
520    __forward_list_base()
521        _NOEXCEPT_(is_nothrow_default_constructible<__node_allocator>::value)
522        : __before_begin_(__begin_node(), __default_init_tag()) {}
523    _LIBCPP_INLINE_VISIBILITY
524    explicit __forward_list_base(const allocator_type& __a)
525        : __before_begin_(__begin_node(), __node_allocator(__a)) {}
526    _LIBCPP_INLINE_VISIBILITY
527    explicit __forward_list_base(const __node_allocator& __a)
528        : __before_begin_(__begin_node(), __a) {}
529#ifndef _LIBCPP_CXX03_LANG
530public:
531    _LIBCPP_INLINE_VISIBILITY
532    __forward_list_base(__forward_list_base&& __x)
533        _NOEXCEPT_(is_nothrow_move_constructible<__node_allocator>::value);
534    _LIBCPP_INLINE_VISIBILITY
535    __forward_list_base(__forward_list_base&& __x, const allocator_type& __a);
536#endif // _LIBCPP_CXX03_LANG
537
538private:
539    __forward_list_base(const __forward_list_base&);
540    __forward_list_base& operator=(const __forward_list_base&);
541
542public:
543    ~__forward_list_base();
544
545protected:
546    _LIBCPP_INLINE_VISIBILITY
547    void __copy_assign_alloc(const __forward_list_base& __x)
548        {__copy_assign_alloc(__x, integral_constant<bool,
549              __node_traits::propagate_on_container_copy_assignment::value>());}
550
551    _LIBCPP_INLINE_VISIBILITY
552    void __move_assign_alloc(__forward_list_base& __x)
553        _NOEXCEPT_(!__node_traits::propagate_on_container_move_assignment::value ||
554                   is_nothrow_move_assignable<__node_allocator>::value)
555        {__move_assign_alloc(__x, integral_constant<bool,
556              __node_traits::propagate_on_container_move_assignment::value>());}
557
558public:
559    _LIBCPP_INLINE_VISIBILITY
560    void swap(__forward_list_base& __x)
561#if _LIBCPP_STD_VER >= 14
562        _NOEXCEPT;
563#else
564        _NOEXCEPT_(!__node_traits::propagate_on_container_swap::value ||
565                    __is_nothrow_swappable<__node_allocator>::value);
566#endif
567protected:
568    void clear() _NOEXCEPT;
569
570private:
571    _LIBCPP_INLINE_VISIBILITY
572    void __copy_assign_alloc(const __forward_list_base&, false_type) {}
573    _LIBCPP_INLINE_VISIBILITY
574    void __copy_assign_alloc(const __forward_list_base& __x, true_type)
575    {
576        if (__alloc() != __x.__alloc())
577            clear();
578        __alloc() = __x.__alloc();
579    }
580
581    _LIBCPP_INLINE_VISIBILITY
582    void __move_assign_alloc(__forward_list_base&, false_type) _NOEXCEPT
583        {}
584    _LIBCPP_INLINE_VISIBILITY
585    void __move_assign_alloc(__forward_list_base& __x, true_type)
586        _NOEXCEPT_(is_nothrow_move_assignable<__node_allocator>::value)
587        {__alloc() = _VSTD::move(__x.__alloc());}
588};
589
590#ifndef _LIBCPP_CXX03_LANG
591
592template <class _Tp, class _Alloc>
593inline
594__forward_list_base<_Tp, _Alloc>::__forward_list_base(__forward_list_base&& __x)
595        _NOEXCEPT_(is_nothrow_move_constructible<__node_allocator>::value)
596    : __before_begin_(_VSTD::move(__x.__before_begin_))
597{
598    __x.__before_begin()->__next_ = nullptr;
599}
600
601template <class _Tp, class _Alloc>
602inline
603__forward_list_base<_Tp, _Alloc>::__forward_list_base(__forward_list_base&& __x,
604                                                      const allocator_type& __a)
605    : __before_begin_(__begin_node(), __node_allocator(__a))
606{
607    if (__alloc() == __x.__alloc())
608    {
609        __before_begin()->__next_ = __x.__before_begin()->__next_;
610        __x.__before_begin()->__next_ = nullptr;
611    }
612}
613
614#endif // _LIBCPP_CXX03_LANG
615
616template <class _Tp, class _Alloc>
617__forward_list_base<_Tp, _Alloc>::~__forward_list_base()
618{
619    clear();
620}
621
622template <class _Tp, class _Alloc>
623inline
624void
625__forward_list_base<_Tp, _Alloc>::swap(__forward_list_base& __x)
626#if _LIBCPP_STD_VER >= 14
627        _NOEXCEPT
628#else
629        _NOEXCEPT_(!__node_traits::propagate_on_container_swap::value ||
630                    __is_nothrow_swappable<__node_allocator>::value)
631#endif
632{
633    _VSTD::__swap_allocator(__alloc(), __x.__alloc(),
634            integral_constant<bool, __node_traits::propagate_on_container_swap::value>());
635    using _VSTD::swap;
636    swap(__before_begin()->__next_, __x.__before_begin()->__next_);
637}
638
639template <class _Tp, class _Alloc>
640void
641__forward_list_base<_Tp, _Alloc>::clear() _NOEXCEPT
642{
643    __node_allocator& __a = __alloc();
644    for (__node_pointer __p = __before_begin()->__next_; __p != nullptr;)
645    {
646        __node_pointer __next = __p->__next_;
647        __node_traits::destroy(__a, _VSTD::addressof(__p->__value_));
648        __node_traits::deallocate(__a, __p, 1);
649        __p = __next;
650    }
651    __before_begin()->__next_ = nullptr;
652}
653
654template <class _Tp, class _Alloc /*= allocator<_Tp>*/>
655class _LIBCPP_TEMPLATE_VIS forward_list
656    : private __forward_list_base<_Tp, _Alloc>
657{
658    typedef __forward_list_base<_Tp, _Alloc> base;
659    typedef typename base::__node_allocator  __node_allocator;
660    typedef typename base::__node               __node;
661    typedef typename base::__node_traits        __node_traits;
662    typedef typename base::__node_pointer       __node_pointer;
663    typedef typename base::__begin_node_pointer __begin_node_pointer;
664
665public:
666    typedef _Tp    value_type;
667    typedef _Alloc allocator_type;
668
669    static_assert((is_same<typename allocator_type::value_type, value_type>::value),
670                  "Allocator::value_type must be same type as value_type");
671
672    typedef value_type&                                                 reference;
673    typedef const value_type&                                           const_reference;
674    typedef typename allocator_traits<allocator_type>::pointer          pointer;
675    typedef typename allocator_traits<allocator_type>::const_pointer    const_pointer;
676    typedef typename allocator_traits<allocator_type>::size_type        size_type;
677    typedef typename allocator_traits<allocator_type>::difference_type  difference_type;
678
679    typedef typename base::iterator       iterator;
680    typedef typename base::const_iterator const_iterator;
681#if _LIBCPP_STD_VER > 17
682    typedef size_type                                __remove_return_type;
683#else
684    typedef void                                     __remove_return_type;
685#endif
686
687    _LIBCPP_INLINE_VISIBILITY
688    forward_list()
689        _NOEXCEPT_(is_nothrow_default_constructible<__node_allocator>::value)
690        {} // = default;
691    _LIBCPP_INLINE_VISIBILITY
692    explicit forward_list(const allocator_type& __a);
693    explicit forward_list(size_type __n);
694#if _LIBCPP_STD_VER > 11
695    explicit forward_list(size_type __n, const allocator_type& __a);
696#endif
697    forward_list(size_type __n, const value_type& __v);
698
699    template <class = __enable_if_t<__is_allocator<_Alloc>::value> >
700    forward_list(size_type __n, const value_type& __v, const allocator_type& __a) : base(__a)
701    {
702        insert_after(cbefore_begin(), __n, __v);
703    }
704
705    template <class _InputIterator>
706        forward_list(_InputIterator __f, _InputIterator __l,
707                     __enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>* = nullptr);
708    template <class _InputIterator>
709        forward_list(_InputIterator __f, _InputIterator __l,
710                     const allocator_type& __a,
711                     __enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>* = nullptr);
712    forward_list(const forward_list& __x);
713    forward_list(const forward_list& __x, const __type_identity_t<allocator_type>& __a);
714
715    forward_list& operator=(const forward_list& __x);
716
717#ifndef _LIBCPP_CXX03_LANG
718    _LIBCPP_INLINE_VISIBILITY
719    forward_list(forward_list&& __x)
720        _NOEXCEPT_(is_nothrow_move_constructible<base>::value)
721        : base(_VSTD::move(__x)) {}
722    forward_list(forward_list&& __x, const __type_identity_t<allocator_type>& __a);
723
724    forward_list(initializer_list<value_type> __il);
725    forward_list(initializer_list<value_type> __il, const allocator_type& __a);
726
727    _LIBCPP_INLINE_VISIBILITY
728    forward_list& operator=(forward_list&& __x)
729        _NOEXCEPT_(
730             __node_traits::propagate_on_container_move_assignment::value &&
731             is_nothrow_move_assignable<allocator_type>::value);
732
733    _LIBCPP_INLINE_VISIBILITY
734    forward_list& operator=(initializer_list<value_type> __il);
735
736    _LIBCPP_INLINE_VISIBILITY
737    void assign(initializer_list<value_type> __il);
738#endif // _LIBCPP_CXX03_LANG
739
740    // ~forward_list() = default;
741
742    template <class _InputIterator>
743    __enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>
744        assign(_InputIterator __f, _InputIterator __l);
745    void assign(size_type __n, const value_type& __v);
746
747    _LIBCPP_INLINE_VISIBILITY
748    allocator_type get_allocator() const _NOEXCEPT
749        {return allocator_type(base::__alloc());}
750
751    _LIBCPP_INLINE_VISIBILITY
752    iterator       begin() _NOEXCEPT
753        {return       iterator(base::__before_begin()->__next_);}
754    _LIBCPP_INLINE_VISIBILITY
755    const_iterator begin() const _NOEXCEPT
756        {return const_iterator(base::__before_begin()->__next_);}
757    _LIBCPP_INLINE_VISIBILITY
758    iterator       end() _NOEXCEPT
759        {return       iterator(nullptr);}
760    _LIBCPP_INLINE_VISIBILITY
761    const_iterator end() const _NOEXCEPT
762        {return const_iterator(nullptr);}
763
764    _LIBCPP_INLINE_VISIBILITY
765    const_iterator cbegin() const _NOEXCEPT
766        {return const_iterator(base::__before_begin()->__next_);}
767    _LIBCPP_INLINE_VISIBILITY
768    const_iterator cend() const _NOEXCEPT
769        {return const_iterator(nullptr);}
770
771    _LIBCPP_INLINE_VISIBILITY
772    iterator       before_begin() _NOEXCEPT
773        {return       iterator(base::__before_begin());}
774    _LIBCPP_INLINE_VISIBILITY
775    const_iterator before_begin() const _NOEXCEPT
776        {return const_iterator(base::__before_begin());}
777    _LIBCPP_INLINE_VISIBILITY
778    const_iterator cbefore_begin() const _NOEXCEPT
779        {return const_iterator(base::__before_begin());}
780
781    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
782    bool empty() const _NOEXCEPT
783        {return base::__before_begin()->__next_ == nullptr;}
784    _LIBCPP_INLINE_VISIBILITY
785    size_type max_size() const _NOEXCEPT {
786        return _VSTD::min<size_type>(
787            __node_traits::max_size(base::__alloc()),
788            numeric_limits<difference_type>::max());
789    }
790
791    _LIBCPP_INLINE_VISIBILITY
792    reference       front()       {return base::__before_begin()->__next_->__value_;}
793    _LIBCPP_INLINE_VISIBILITY
794    const_reference front() const {return base::__before_begin()->__next_->__value_;}
795
796#ifndef _LIBCPP_CXX03_LANG
797#if _LIBCPP_STD_VER > 14
798    template <class... _Args> reference emplace_front(_Args&&... __args);
799#else
800    template <class... _Args> void      emplace_front(_Args&&... __args);
801#endif
802    void push_front(value_type&& __v);
803#endif // _LIBCPP_CXX03_LANG
804    void push_front(const value_type& __v);
805
806    void pop_front();
807
808#ifndef _LIBCPP_CXX03_LANG
809    template <class... _Args>
810        iterator emplace_after(const_iterator __p, _Args&&... __args);
811
812    iterator insert_after(const_iterator __p, value_type&& __v);
813    iterator insert_after(const_iterator __p, initializer_list<value_type> __il)
814        {return insert_after(__p, __il.begin(), __il.end());}
815#endif // _LIBCPP_CXX03_LANG
816    iterator insert_after(const_iterator __p, const value_type& __v);
817    iterator insert_after(const_iterator __p, size_type __n, const value_type& __v);
818    template <class _InputIterator>
819    _LIBCPP_INLINE_VISIBILITY
820    __enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, iterator>
821        insert_after(const_iterator __p, _InputIterator __f, _InputIterator __l);
822
823    iterator erase_after(const_iterator __p);
824    iterator erase_after(const_iterator __f, const_iterator __l);
825
826    _LIBCPP_INLINE_VISIBILITY
827    void swap(forward_list& __x)
828#if _LIBCPP_STD_VER >= 14
829        _NOEXCEPT
830#else
831        _NOEXCEPT_(!__node_traits::propagate_on_container_swap::value ||
832                   __is_nothrow_swappable<__node_allocator>::value)
833#endif
834        {base::swap(__x);}
835
836    void resize(size_type __n);
837    void resize(size_type __n, const value_type& __v);
838    _LIBCPP_INLINE_VISIBILITY
839    void clear() _NOEXCEPT {base::clear();}
840
841    _LIBCPP_INLINE_VISIBILITY
842    void splice_after(const_iterator __p, forward_list&& __x);
843    _LIBCPP_INLINE_VISIBILITY
844    void splice_after(const_iterator __p, forward_list&& __x, const_iterator __i);
845    _LIBCPP_INLINE_VISIBILITY
846    void splice_after(const_iterator __p, forward_list&& __x,
847                      const_iterator __f, const_iterator __l);
848    void splice_after(const_iterator __p, forward_list& __x);
849    void splice_after(const_iterator __p, forward_list& __x, const_iterator __i);
850    void splice_after(const_iterator __p, forward_list& __x,
851                      const_iterator __f, const_iterator __l);
852    __remove_return_type remove(const value_type& __v);
853    template <class _Predicate> __remove_return_type remove_if(_Predicate __pred);
854    _LIBCPP_INLINE_VISIBILITY
855    __remove_return_type unique() {return unique(__equal_to<value_type>());}
856    template <class _BinaryPredicate> __remove_return_type unique(_BinaryPredicate __binary_pred);
857#ifndef _LIBCPP_CXX03_LANG
858    _LIBCPP_INLINE_VISIBILITY
859    void merge(forward_list&& __x) {merge(__x, __less<value_type>());}
860    template <class _Compare>
861        _LIBCPP_INLINE_VISIBILITY
862        void merge(forward_list&& __x, _Compare __comp)
863        {merge(__x, _VSTD::move(__comp));}
864#endif // _LIBCPP_CXX03_LANG
865    _LIBCPP_INLINE_VISIBILITY
866    void merge(forward_list& __x) {merge(__x, __less<value_type>());}
867    template <class _Compare> void merge(forward_list& __x, _Compare __comp);
868    _LIBCPP_INLINE_VISIBILITY
869    void sort() {sort(__less<value_type>());}
870    template <class _Compare> _LIBCPP_INLINE_VISIBILITY void sort(_Compare __comp);
871    void reverse() _NOEXCEPT;
872
873private:
874
875#ifndef _LIBCPP_CXX03_LANG
876    void __move_assign(forward_list& __x, true_type)
877        _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
878    void __move_assign(forward_list& __x, false_type);
879#endif // _LIBCPP_CXX03_LANG
880
881    template <class _Compare>
882        static
883        __node_pointer
884        __merge(__node_pointer __f1, __node_pointer __f2, _Compare& __comp);
885
886    template <class _Compare>
887        static
888        __node_pointer
889        __sort(__node_pointer __f, difference_type __sz, _Compare& __comp);
890};
891
892
893#if _LIBCPP_STD_VER >= 17
894template<class _InputIterator,
895         class _Alloc = allocator<__iter_value_type<_InputIterator>>,
896         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
897         class = enable_if_t<__is_allocator<_Alloc>::value>
898         >
899forward_list(_InputIterator, _InputIterator)
900  -> forward_list<__iter_value_type<_InputIterator>, _Alloc>;
901
902template<class _InputIterator,
903         class _Alloc,
904         class = enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>,
905         class = enable_if_t<__is_allocator<_Alloc>::value>
906         >
907forward_list(_InputIterator, _InputIterator, _Alloc)
908  -> forward_list<__iter_value_type<_InputIterator>, _Alloc>;
909#endif
910
911template <class _Tp, class _Alloc>
912inline
913forward_list<_Tp, _Alloc>::forward_list(const allocator_type& __a)
914    : base(__a)
915{
916}
917
918template <class _Tp, class _Alloc>
919forward_list<_Tp, _Alloc>::forward_list(size_type __n)
920{
921    if (__n > 0)
922    {
923        __node_allocator& __a = base::__alloc();
924        typedef __allocator_destructor<__node_allocator> _Dp;
925        unique_ptr<__node, _Dp> __h(nullptr, _Dp(__a, 1));
926        for (__begin_node_pointer __p = base::__before_begin(); __n > 0; --__n,
927                                                             __p = __p->__next_as_begin())
928        {
929            __h.reset(__node_traits::allocate(__a, 1));
930            __node_traits::construct(__a, _VSTD::addressof(__h->__value_));
931            __h->__next_ = nullptr;
932            __p->__next_ = __h.release();
933        }
934    }
935}
936
937#if _LIBCPP_STD_VER > 11
938template <class _Tp, class _Alloc>
939forward_list<_Tp, _Alloc>::forward_list(size_type __n,
940                                        const allocator_type& __base_alloc)
941    : base ( __base_alloc )
942{
943    if (__n > 0)
944    {
945        __node_allocator& __a = base::__alloc();
946        typedef __allocator_destructor<__node_allocator> _Dp;
947        unique_ptr<__node, _Dp> __h(nullptr, _Dp(__a, 1));
948        for (__begin_node_pointer __p = base::__before_begin(); __n > 0; --__n,
949                                                             __p = __p->__next_as_begin())
950        {
951            __h.reset(__node_traits::allocate(__a, 1));
952            __node_traits::construct(__a, _VSTD::addressof(__h->__value_));
953            __h->__next_ = nullptr;
954            __p->__next_ = __h.release();
955        }
956    }
957}
958#endif
959
960template <class _Tp, class _Alloc>
961forward_list<_Tp, _Alloc>::forward_list(size_type __n, const value_type& __v)
962{
963    insert_after(cbefore_begin(), __n, __v);
964}
965
966template <class _Tp, class _Alloc>
967template <class _InputIterator>
968forward_list<_Tp, _Alloc>::forward_list(_InputIterator __f, _InputIterator __l,
969                                        __enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>*)
970{
971    insert_after(cbefore_begin(), __f, __l);
972}
973
974template <class _Tp, class _Alloc>
975template <class _InputIterator>
976forward_list<_Tp, _Alloc>::forward_list(_InputIterator __f, _InputIterator __l,
977                                        const allocator_type& __a,
978                                        __enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value>*)
979    : base(__a)
980{
981    insert_after(cbefore_begin(), __f, __l);
982}
983
984template <class _Tp, class _Alloc>
985forward_list<_Tp, _Alloc>::forward_list(const forward_list& __x)
986    : base(
987          __node_traits::select_on_container_copy_construction(__x.__alloc())) {
988  insert_after(cbefore_begin(), __x.begin(), __x.end());
989}
990
991template <class _Tp, class _Alloc>
992forward_list<_Tp, _Alloc>::forward_list(const forward_list& __x,
993                                        const __type_identity_t<allocator_type>& __a)
994    : base(__a)
995{
996    insert_after(cbefore_begin(), __x.begin(), __x.end());
997}
998
999template <class _Tp, class _Alloc>
1000forward_list<_Tp, _Alloc>&
1001forward_list<_Tp, _Alloc>::operator=(const forward_list& __x)
1002{
1003    if (this != _VSTD::addressof(__x))
1004    {
1005        base::__copy_assign_alloc(__x);
1006        assign(__x.begin(), __x.end());
1007    }
1008    return *this;
1009}
1010
1011#ifndef _LIBCPP_CXX03_LANG
1012template <class _Tp, class _Alloc>
1013forward_list<_Tp, _Alloc>::forward_list(forward_list&& __x,
1014                                        const __type_identity_t<allocator_type>& __a)
1015    : base(_VSTD::move(__x), __a)
1016{
1017    if (base::__alloc() != __x.__alloc())
1018    {
1019        typedef move_iterator<iterator> _Ip;
1020        insert_after(cbefore_begin(), _Ip(__x.begin()), _Ip(__x.end()));
1021    }
1022}
1023
1024template <class _Tp, class _Alloc>
1025forward_list<_Tp, _Alloc>::forward_list(initializer_list<value_type> __il)
1026{
1027    insert_after(cbefore_begin(), __il.begin(), __il.end());
1028}
1029
1030template <class _Tp, class _Alloc>
1031forward_list<_Tp, _Alloc>::forward_list(initializer_list<value_type> __il,
1032                                        const allocator_type& __a)
1033    : base(__a)
1034{
1035    insert_after(cbefore_begin(), __il.begin(), __il.end());
1036}
1037
1038template <class _Tp, class _Alloc>
1039void
1040forward_list<_Tp, _Alloc>::__move_assign(forward_list& __x, true_type)
1041    _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
1042{
1043    clear();
1044    base::__move_assign_alloc(__x);
1045    base::__before_begin()->__next_ = __x.__before_begin()->__next_;
1046    __x.__before_begin()->__next_ = nullptr;
1047}
1048
1049template <class _Tp, class _Alloc>
1050void
1051forward_list<_Tp, _Alloc>::__move_assign(forward_list& __x, false_type)
1052{
1053    if (base::__alloc() == __x.__alloc())
1054        __move_assign(__x, true_type());
1055    else
1056    {
1057        typedef move_iterator<iterator> _Ip;
1058        assign(_Ip(__x.begin()), _Ip(__x.end()));
1059    }
1060}
1061
1062template <class _Tp, class _Alloc>
1063inline
1064forward_list<_Tp, _Alloc>&
1065forward_list<_Tp, _Alloc>::operator=(forward_list&& __x)
1066    _NOEXCEPT_(
1067             __node_traits::propagate_on_container_move_assignment::value &&
1068             is_nothrow_move_assignable<allocator_type>::value)
1069{
1070    __move_assign(__x, integral_constant<bool,
1071          __node_traits::propagate_on_container_move_assignment::value>());
1072    return *this;
1073}
1074
1075template <class _Tp, class _Alloc>
1076inline
1077forward_list<_Tp, _Alloc>&
1078forward_list<_Tp, _Alloc>::operator=(initializer_list<value_type> __il)
1079{
1080    assign(__il.begin(), __il.end());
1081    return *this;
1082}
1083
1084#endif // _LIBCPP_CXX03_LANG
1085
1086template <class _Tp, class _Alloc>
1087template <class _InputIterator>
1088__enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, void>
1089forward_list<_Tp, _Alloc>::assign(_InputIterator __f, _InputIterator __l)
1090{
1091    iterator __i = before_begin();
1092    iterator __j = _VSTD::next(__i);
1093    iterator __e = end();
1094    for (; __j != __e && __f != __l; ++__i, (void) ++__j, ++__f)
1095        *__j = *__f;
1096    if (__j == __e)
1097        insert_after(__i, __f, __l);
1098    else
1099        erase_after(__i, __e);
1100}
1101
1102template <class _Tp, class _Alloc>
1103void
1104forward_list<_Tp, _Alloc>::assign(size_type __n, const value_type& __v)
1105{
1106    iterator __i = before_begin();
1107    iterator __j = _VSTD::next(__i);
1108    iterator __e = end();
1109    for (; __j != __e && __n > 0; --__n, ++__i, ++__j)
1110        *__j = __v;
1111    if (__j == __e)
1112        insert_after(__i, __n, __v);
1113    else
1114        erase_after(__i, __e);
1115}
1116
1117#ifndef _LIBCPP_CXX03_LANG
1118
1119template <class _Tp, class _Alloc>
1120inline
1121void
1122forward_list<_Tp, _Alloc>::assign(initializer_list<value_type> __il)
1123{
1124    assign(__il.begin(), __il.end());
1125}
1126
1127template <class _Tp, class _Alloc>
1128template <class... _Args>
1129#if _LIBCPP_STD_VER > 14
1130typename forward_list<_Tp, _Alloc>::reference
1131#else
1132void
1133#endif
1134forward_list<_Tp, _Alloc>::emplace_front(_Args&&... __args)
1135{
1136    __node_allocator& __a = base::__alloc();
1137    typedef __allocator_destructor<__node_allocator> _Dp;
1138    unique_ptr<__node, _Dp> __h(__node_traits::allocate(__a, 1), _Dp(__a, 1));
1139    __node_traits::construct(__a, _VSTD::addressof(__h->__value_),
1140                                  _VSTD::forward<_Args>(__args)...);
1141    __h->__next_ = base::__before_begin()->__next_;
1142    base::__before_begin()->__next_ = __h.release();
1143#if _LIBCPP_STD_VER > 14
1144    return base::__before_begin()->__next_->__value_;
1145#endif
1146}
1147
1148template <class _Tp, class _Alloc>
1149void
1150forward_list<_Tp, _Alloc>::push_front(value_type&& __v)
1151{
1152    __node_allocator& __a = base::__alloc();
1153    typedef __allocator_destructor<__node_allocator> _Dp;
1154    unique_ptr<__node, _Dp> __h(__node_traits::allocate(__a, 1), _Dp(__a, 1));
1155    __node_traits::construct(__a, _VSTD::addressof(__h->__value_), _VSTD::move(__v));
1156    __h->__next_ = base::__before_begin()->__next_;
1157    base::__before_begin()->__next_ = __h.release();
1158}
1159
1160#endif // _LIBCPP_CXX03_LANG
1161
1162template <class _Tp, class _Alloc>
1163void
1164forward_list<_Tp, _Alloc>::push_front(const value_type& __v)
1165{
1166    __node_allocator& __a = base::__alloc();
1167    typedef __allocator_destructor<__node_allocator> _Dp;
1168    unique_ptr<__node, _Dp> __h(__node_traits::allocate(__a, 1), _Dp(__a, 1));
1169    __node_traits::construct(__a, _VSTD::addressof(__h->__value_), __v);
1170    __h->__next_ = base::__before_begin()->__next_;
1171    base::__before_begin()->__next_ = __h.release();
1172}
1173
1174template <class _Tp, class _Alloc>
1175void
1176forward_list<_Tp, _Alloc>::pop_front()
1177{
1178    __node_allocator& __a = base::__alloc();
1179    __node_pointer __p = base::__before_begin()->__next_;
1180    base::__before_begin()->__next_ = __p->__next_;
1181    __node_traits::destroy(__a, _VSTD::addressof(__p->__value_));
1182    __node_traits::deallocate(__a, __p, 1);
1183}
1184
1185#ifndef _LIBCPP_CXX03_LANG
1186
1187template <class _Tp, class _Alloc>
1188template <class... _Args>
1189typename forward_list<_Tp, _Alloc>::iterator
1190forward_list<_Tp, _Alloc>::emplace_after(const_iterator __p, _Args&&... __args)
1191{
1192    __begin_node_pointer const __r = __p.__get_begin();
1193    __node_allocator& __a = base::__alloc();
1194    typedef __allocator_destructor<__node_allocator> _Dp;
1195    unique_ptr<__node, _Dp> __h(__node_traits::allocate(__a, 1), _Dp(__a, 1));
1196    __node_traits::construct(__a, _VSTD::addressof(__h->__value_),
1197                                  _VSTD::forward<_Args>(__args)...);
1198    __h->__next_ = __r->__next_;
1199    __r->__next_ = __h.release();
1200    return iterator(__r->__next_);
1201}
1202
1203template <class _Tp, class _Alloc>
1204typename forward_list<_Tp, _Alloc>::iterator
1205forward_list<_Tp, _Alloc>::insert_after(const_iterator __p, value_type&& __v)
1206{
1207    __begin_node_pointer const __r = __p.__get_begin();
1208    __node_allocator& __a = base::__alloc();
1209    typedef __allocator_destructor<__node_allocator> _Dp;
1210    unique_ptr<__node, _Dp> __h(__node_traits::allocate(__a, 1), _Dp(__a, 1));
1211    __node_traits::construct(__a, _VSTD::addressof(__h->__value_), _VSTD::move(__v));
1212    __h->__next_ = __r->__next_;
1213    __r->__next_ = __h.release();
1214    return iterator(__r->__next_);
1215}
1216
1217#endif // _LIBCPP_CXX03_LANG
1218
1219template <class _Tp, class _Alloc>
1220typename forward_list<_Tp, _Alloc>::iterator
1221forward_list<_Tp, _Alloc>::insert_after(const_iterator __p, const value_type& __v)
1222{
1223    __begin_node_pointer const __r = __p.__get_begin();
1224    __node_allocator& __a = base::__alloc();
1225    typedef __allocator_destructor<__node_allocator> _Dp;
1226    unique_ptr<__node, _Dp> __h(__node_traits::allocate(__a, 1), _Dp(__a, 1));
1227    __node_traits::construct(__a, _VSTD::addressof(__h->__value_), __v);
1228    __h->__next_ = __r->__next_;
1229    __r->__next_ = __h.release();
1230    return iterator(__r->__next_);
1231}
1232
1233template <class _Tp, class _Alloc>
1234typename forward_list<_Tp, _Alloc>::iterator
1235forward_list<_Tp, _Alloc>::insert_after(const_iterator __p, size_type __n,
1236                                        const value_type& __v)
1237{
1238    __begin_node_pointer __r = __p.__get_begin();
1239    if (__n > 0)
1240    {
1241        __node_allocator& __a = base::__alloc();
1242        typedef __allocator_destructor<__node_allocator> _Dp;
1243        unique_ptr<__node, _Dp> __h(__node_traits::allocate(__a, 1), _Dp(__a, 1));
1244        __node_traits::construct(__a, _VSTD::addressof(__h->__value_), __v);
1245        __node_pointer __first = __h.release();
1246        __node_pointer __last = __first;
1247#ifndef _LIBCPP_NO_EXCEPTIONS
1248        try
1249        {
1250#endif // _LIBCPP_NO_EXCEPTIONS
1251            for (--__n; __n != 0; --__n, __last = __last->__next_)
1252            {
1253                __h.reset(__node_traits::allocate(__a, 1));
1254                __node_traits::construct(__a, _VSTD::addressof(__h->__value_), __v);
1255                __last->__next_ = __h.release();
1256            }
1257#ifndef _LIBCPP_NO_EXCEPTIONS
1258        }
1259        catch (...)
1260        {
1261            while (__first != nullptr)
1262            {
1263                __node_pointer __next = __first->__next_;
1264                __node_traits::destroy(__a, _VSTD::addressof(__first->__value_));
1265                __node_traits::deallocate(__a, __first, 1);
1266                __first = __next;
1267            }
1268            throw;
1269        }
1270#endif // _LIBCPP_NO_EXCEPTIONS
1271        __last->__next_ = __r->__next_;
1272        __r->__next_ = __first;
1273        __r = static_cast<__begin_node_pointer>(__last);
1274    }
1275    return iterator(__r);
1276}
1277
1278template <class _Tp, class _Alloc>
1279template <class _InputIterator>
1280__enable_if_t<__is_cpp17_input_iterator<_InputIterator>::value, typename forward_list<_Tp, _Alloc>::iterator>
1281forward_list<_Tp, _Alloc>::insert_after(const_iterator __p,
1282                                        _InputIterator __f, _InputIterator __l)
1283{
1284    __begin_node_pointer __r = __p.__get_begin();
1285    if (__f != __l)
1286    {
1287        __node_allocator& __a = base::__alloc();
1288        typedef __allocator_destructor<__node_allocator> _Dp;
1289        unique_ptr<__node, _Dp> __h(__node_traits::allocate(__a, 1), _Dp(__a, 1));
1290        __node_traits::construct(__a, _VSTD::addressof(__h->__value_), *__f);
1291        __node_pointer __first = __h.release();
1292        __node_pointer __last = __first;
1293#ifndef _LIBCPP_NO_EXCEPTIONS
1294        try
1295        {
1296#endif // _LIBCPP_NO_EXCEPTIONS
1297            for (++__f; __f != __l; ++__f, ((void)(__last = __last->__next_)))
1298            {
1299                __h.reset(__node_traits::allocate(__a, 1));
1300                __node_traits::construct(__a, _VSTD::addressof(__h->__value_), *__f);
1301                __last->__next_ = __h.release();
1302            }
1303#ifndef _LIBCPP_NO_EXCEPTIONS
1304        }
1305        catch (...)
1306        {
1307            while (__first != nullptr)
1308            {
1309                __node_pointer __next = __first->__next_;
1310                __node_traits::destroy(__a, _VSTD::addressof(__first->__value_));
1311                __node_traits::deallocate(__a, __first, 1);
1312                __first = __next;
1313            }
1314            throw;
1315        }
1316#endif // _LIBCPP_NO_EXCEPTIONS
1317        __last->__next_ = __r->__next_;
1318        __r->__next_ = __first;
1319        __r = static_cast<__begin_node_pointer>(__last);
1320    }
1321    return iterator(__r);
1322}
1323
1324template <class _Tp, class _Alloc>
1325typename forward_list<_Tp, _Alloc>::iterator
1326forward_list<_Tp, _Alloc>::erase_after(const_iterator __f)
1327{
1328    __begin_node_pointer __p = __f.__get_begin();
1329    __node_pointer __n = __p->__next_;
1330    __p->__next_ = __n->__next_;
1331    __node_allocator& __a = base::__alloc();
1332    __node_traits::destroy(__a, _VSTD::addressof(__n->__value_));
1333    __node_traits::deallocate(__a, __n, 1);
1334    return iterator(__p->__next_);
1335}
1336
1337template <class _Tp, class _Alloc>
1338typename forward_list<_Tp, _Alloc>::iterator
1339forward_list<_Tp, _Alloc>::erase_after(const_iterator __f, const_iterator __l)
1340{
1341    __node_pointer __e = __l.__get_unsafe_node_pointer();
1342    if (__f != __l)
1343    {
1344        __begin_node_pointer __bp = __f.__get_begin();
1345
1346        __node_pointer __n = __bp->__next_;
1347        if (__n != __e)
1348        {
1349            __bp->__next_ = __e;
1350            __node_allocator& __a = base::__alloc();
1351            do
1352            {
1353                __node_pointer __tmp = __n->__next_;
1354                __node_traits::destroy(__a, _VSTD::addressof(__n->__value_));
1355                __node_traits::deallocate(__a, __n, 1);
1356                __n = __tmp;
1357            } while (__n != __e);
1358        }
1359    }
1360    return iterator(__e);
1361}
1362
1363template <class _Tp, class _Alloc>
1364void
1365forward_list<_Tp, _Alloc>::resize(size_type __n)
1366{
1367    size_type __sz = 0;
1368    iterator __p = before_begin();
1369    iterator __i = begin();
1370    iterator __e = end();
1371    for (; __i != __e && __sz < __n; ++__p, ++__i, ++__sz)
1372        ;
1373    if (__i != __e)
1374        erase_after(__p, __e);
1375    else
1376    {
1377        __n -= __sz;
1378        if (__n > 0)
1379        {
1380            __node_allocator& __a = base::__alloc();
1381            typedef __allocator_destructor<__node_allocator> _Dp;
1382            unique_ptr<__node, _Dp> __h(nullptr, _Dp(__a, 1));
1383            for (__begin_node_pointer __ptr = __p.__get_begin(); __n > 0; --__n,
1384                                                         __ptr = __ptr->__next_as_begin())
1385            {
1386                __h.reset(__node_traits::allocate(__a, 1));
1387                __node_traits::construct(__a, _VSTD::addressof(__h->__value_));
1388                __h->__next_ = nullptr;
1389                __ptr->__next_ = __h.release();
1390            }
1391        }
1392    }
1393}
1394
1395template <class _Tp, class _Alloc>
1396void
1397forward_list<_Tp, _Alloc>::resize(size_type __n, const value_type& __v)
1398{
1399    size_type __sz = 0;
1400    iterator __p = before_begin();
1401    iterator __i = begin();
1402    iterator __e = end();
1403    for (; __i != __e && __sz < __n; ++__p, ++__i, ++__sz)
1404        ;
1405    if (__i != __e)
1406        erase_after(__p, __e);
1407    else
1408    {
1409        __n -= __sz;
1410        if (__n > 0)
1411        {
1412            __node_allocator& __a = base::__alloc();
1413            typedef __allocator_destructor<__node_allocator> _Dp;
1414            unique_ptr<__node, _Dp> __h(nullptr, _Dp(__a, 1));
1415            for (__begin_node_pointer __ptr = __p.__get_begin(); __n > 0; --__n,
1416                                                         __ptr = __ptr->__next_as_begin())
1417            {
1418                __h.reset(__node_traits::allocate(__a, 1));
1419                __node_traits::construct(__a, _VSTD::addressof(__h->__value_), __v);
1420                __h->__next_ = nullptr;
1421                __ptr->__next_ = __h.release();
1422            }
1423        }
1424    }
1425}
1426
1427template <class _Tp, class _Alloc>
1428void
1429forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
1430                                        forward_list& __x)
1431{
1432    if (!__x.empty())
1433    {
1434        if (__p.__get_begin()->__next_ != nullptr)
1435        {
1436            const_iterator __lm1 = __x.before_begin();
1437            while (__lm1.__get_begin()->__next_ != nullptr)
1438                ++__lm1;
1439            __lm1.__get_begin()->__next_ = __p.__get_begin()->__next_;
1440        }
1441        __p.__get_begin()->__next_ = __x.__before_begin()->__next_;
1442        __x.__before_begin()->__next_ = nullptr;
1443    }
1444}
1445
1446template <class _Tp, class _Alloc>
1447void
1448forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
1449                                        forward_list& /*__other*/,
1450                                        const_iterator __i)
1451{
1452    const_iterator __lm1 = _VSTD::next(__i);
1453    if (__p != __i && __p != __lm1)
1454    {
1455        __i.__get_begin()->__next_ = __lm1.__get_begin()->__next_;
1456        __lm1.__get_begin()->__next_ = __p.__get_begin()->__next_;
1457        __p.__get_begin()->__next_ = __lm1.__get_unsafe_node_pointer();
1458    }
1459}
1460
1461template <class _Tp, class _Alloc>
1462void
1463forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
1464                                        forward_list& /*__other*/,
1465                                        const_iterator __f, const_iterator __l)
1466{
1467    if (__f != __l && __p != __f)
1468    {
1469        const_iterator __lm1 = __f;
1470        while (__lm1.__get_begin()->__next_ != __l.__get_begin())
1471            ++__lm1;
1472        if (__f != __lm1)
1473        {
1474            __lm1.__get_begin()->__next_ = __p.__get_begin()->__next_;
1475            __p.__get_begin()->__next_ = __f.__get_begin()->__next_;
1476            __f.__get_begin()->__next_ = __l.__get_unsafe_node_pointer();
1477        }
1478    }
1479}
1480
1481template <class _Tp, class _Alloc>
1482inline _LIBCPP_INLINE_VISIBILITY
1483void
1484forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
1485                                        forward_list&& __x)
1486{
1487    splice_after(__p, __x);
1488}
1489
1490template <class _Tp, class _Alloc>
1491inline _LIBCPP_INLINE_VISIBILITY
1492void
1493forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
1494                                        forward_list&& __x,
1495                                        const_iterator __i)
1496{
1497    splice_after(__p, __x, __i);
1498}
1499
1500template <class _Tp, class _Alloc>
1501inline _LIBCPP_INLINE_VISIBILITY
1502void
1503forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
1504                                        forward_list&& __x,
1505                                        const_iterator __f, const_iterator __l)
1506{
1507    splice_after(__p, __x, __f, __l);
1508}
1509
1510template <class _Tp, class _Alloc>
1511typename forward_list<_Tp, _Alloc>::__remove_return_type
1512forward_list<_Tp, _Alloc>::remove(const value_type& __v)
1513{
1514    forward_list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
1515    typename forward_list<_Tp, _Alloc>::size_type __count_removed = 0;
1516    const iterator __e = end();
1517    for (iterator __i = before_begin(); __i.__get_begin()->__next_ != nullptr;)
1518    {
1519        if (__i.__get_begin()->__next_->__value_ == __v)
1520        {
1521            ++__count_removed;
1522            iterator __j = _VSTD::next(__i, 2);
1523            for (; __j != __e && *__j == __v; ++__j)
1524                ++__count_removed;
1525            __deleted_nodes.splice_after(__deleted_nodes.before_begin(), *this, __i, __j);
1526            if (__j == __e)
1527                break;
1528            __i = __j;
1529        }
1530        else
1531            ++__i;
1532    }
1533
1534    return (__remove_return_type) __count_removed;
1535}
1536
1537template <class _Tp, class _Alloc>
1538template <class _Predicate>
1539typename forward_list<_Tp, _Alloc>::__remove_return_type
1540forward_list<_Tp, _Alloc>::remove_if(_Predicate __pred)
1541{
1542    forward_list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
1543    typename forward_list<_Tp, _Alloc>::size_type __count_removed = 0;
1544    const iterator __e = end();
1545    for (iterator __i = before_begin(); __i.__get_begin()->__next_ != nullptr;)
1546    {
1547        if (__pred(__i.__get_begin()->__next_->__value_))
1548        {
1549            ++__count_removed;
1550            iterator __j = _VSTD::next(__i, 2);
1551            for (; __j != __e && __pred(*__j); ++__j)
1552                ++__count_removed;
1553            __deleted_nodes.splice_after(__deleted_nodes.before_begin(), *this, __i, __j);
1554            if (__j == __e)
1555                break;
1556            __i = __j;
1557        }
1558        else
1559            ++__i;
1560    }
1561
1562    return (__remove_return_type) __count_removed;
1563}
1564
1565template <class _Tp, class _Alloc>
1566template <class _BinaryPredicate>
1567typename forward_list<_Tp, _Alloc>::__remove_return_type
1568forward_list<_Tp, _Alloc>::unique(_BinaryPredicate __binary_pred)
1569{
1570    forward_list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
1571    typename forward_list<_Tp, _Alloc>::size_type __count_removed = 0;
1572    for (iterator __i = begin(), __e = end(); __i != __e;)
1573    {
1574        iterator __j = _VSTD::next(__i);
1575        for (; __j != __e && __binary_pred(*__i, *__j); ++__j)
1576            ++__count_removed;
1577        if (__i.__get_begin()->__next_ != __j.__get_unsafe_node_pointer())
1578            __deleted_nodes.splice_after(__deleted_nodes.before_begin(), *this, __i, __j);
1579        __i = __j;
1580    }
1581
1582    return (__remove_return_type) __count_removed;
1583}
1584
1585template <class _Tp, class _Alloc>
1586template <class _Compare>
1587void
1588forward_list<_Tp, _Alloc>::merge(forward_list& __x, _Compare __comp)
1589{
1590    if (this != _VSTD::addressof(__x))
1591    {
1592        base::__before_begin()->__next_ = __merge(base::__before_begin()->__next_,
1593                                                    __x.__before_begin()->__next_,
1594                                                    __comp);
1595        __x.__before_begin()->__next_ = nullptr;
1596    }
1597}
1598
1599template <class _Tp, class _Alloc>
1600template <class _Compare>
1601typename forward_list<_Tp, _Alloc>::__node_pointer
1602forward_list<_Tp, _Alloc>::__merge(__node_pointer __f1, __node_pointer __f2,
1603                                   _Compare& __comp)
1604{
1605    if (__f1 == nullptr)
1606        return __f2;
1607    if (__f2 == nullptr)
1608        return __f1;
1609    __node_pointer __r;
1610    if (__comp(__f2->__value_, __f1->__value_))
1611    {
1612        __node_pointer __t = __f2;
1613        while (__t->__next_ != nullptr &&
1614                             __comp(__t->__next_->__value_, __f1->__value_))
1615            __t = __t->__next_;
1616        __r = __f2;
1617        __f2 = __t->__next_;
1618        __t->__next_ = __f1;
1619    }
1620    else
1621        __r = __f1;
1622    __node_pointer __p = __f1;
1623    __f1 = __f1->__next_;
1624    while (__f1 != nullptr && __f2 != nullptr)
1625    {
1626        if (__comp(__f2->__value_, __f1->__value_))
1627        {
1628            __node_pointer __t = __f2;
1629            while (__t->__next_ != nullptr &&
1630                                 __comp(__t->__next_->__value_, __f1->__value_))
1631                __t = __t->__next_;
1632            __p->__next_ = __f2;
1633            __f2 = __t->__next_;
1634            __t->__next_ = __f1;
1635        }
1636        __p = __f1;
1637        __f1 = __f1->__next_;
1638    }
1639    if (__f2 != nullptr)
1640        __p->__next_ = __f2;
1641    return __r;
1642}
1643
1644template <class _Tp, class _Alloc>
1645template <class _Compare>
1646inline
1647void
1648forward_list<_Tp, _Alloc>::sort(_Compare __comp)
1649{
1650    base::__before_begin()->__next_ = __sort(base::__before_begin()->__next_,
1651                                       _VSTD::distance(begin(), end()), __comp);
1652}
1653
1654template <class _Tp, class _Alloc>
1655template <class _Compare>
1656typename forward_list<_Tp, _Alloc>::__node_pointer
1657forward_list<_Tp, _Alloc>::__sort(__node_pointer __f1, difference_type __sz,
1658                                  _Compare& __comp)
1659{
1660    switch (__sz)
1661    {
1662    case 0:
1663    case 1:
1664        return __f1;
1665    case 2:
1666        if (__comp(__f1->__next_->__value_, __f1->__value_))
1667        {
1668            __node_pointer __t = __f1->__next_;
1669            __t->__next_ = __f1;
1670            __f1->__next_ = nullptr;
1671            __f1 = __t;
1672        }
1673        return __f1;
1674    }
1675    difference_type __sz1 = __sz / 2;
1676    difference_type __sz2 = __sz - __sz1;
1677    __node_pointer __t = _VSTD::next(iterator(__f1), __sz1 - 1).__get_unsafe_node_pointer();
1678    __node_pointer __f2 = __t->__next_;
1679    __t->__next_ = nullptr;
1680    return __merge(__sort(__f1, __sz1, __comp),
1681                   __sort(__f2, __sz2, __comp), __comp);
1682}
1683
1684template <class _Tp, class _Alloc>
1685void
1686forward_list<_Tp, _Alloc>::reverse() _NOEXCEPT
1687{
1688    __node_pointer __p = base::__before_begin()->__next_;
1689    if (__p != nullptr)
1690    {
1691        __node_pointer __f = __p->__next_;
1692        __p->__next_ = nullptr;
1693        while (__f != nullptr)
1694        {
1695            __node_pointer __t = __f->__next_;
1696            __f->__next_ = __p;
1697            __p = __f;
1698            __f = __t;
1699        }
1700        base::__before_begin()->__next_ = __p;
1701    }
1702}
1703
1704template <class _Tp, class _Alloc>
1705bool operator==(const forward_list<_Tp, _Alloc>& __x,
1706                const forward_list<_Tp, _Alloc>& __y)
1707{
1708    typedef forward_list<_Tp, _Alloc> _Cp;
1709    typedef typename _Cp::const_iterator _Ip;
1710    _Ip __ix = __x.begin();
1711    _Ip __ex = __x.end();
1712    _Ip __iy = __y.begin();
1713    _Ip __ey = __y.end();
1714    for (; __ix != __ex && __iy != __ey; ++__ix, ++__iy)
1715        if (!(*__ix == *__iy))
1716            return false;
1717    return (__ix == __ex) == (__iy == __ey);
1718}
1719
1720template <class _Tp, class _Alloc>
1721inline _LIBCPP_INLINE_VISIBILITY
1722bool operator!=(const forward_list<_Tp, _Alloc>& __x,
1723                const forward_list<_Tp, _Alloc>& __y)
1724{
1725    return !(__x == __y);
1726}
1727
1728template <class _Tp, class _Alloc>
1729inline _LIBCPP_INLINE_VISIBILITY
1730bool operator< (const forward_list<_Tp, _Alloc>& __x,
1731                const forward_list<_Tp, _Alloc>& __y)
1732{
1733    return _VSTD::lexicographical_compare(__x.begin(), __x.end(),
1734                                         __y.begin(), __y.end());
1735}
1736
1737template <class _Tp, class _Alloc>
1738inline _LIBCPP_INLINE_VISIBILITY
1739bool operator> (const forward_list<_Tp, _Alloc>& __x,
1740                const forward_list<_Tp, _Alloc>& __y)
1741{
1742    return __y < __x;
1743}
1744
1745template <class _Tp, class _Alloc>
1746inline _LIBCPP_INLINE_VISIBILITY
1747bool operator>=(const forward_list<_Tp, _Alloc>& __x,
1748                const forward_list<_Tp, _Alloc>& __y)
1749{
1750    return !(__x < __y);
1751}
1752
1753template <class _Tp, class _Alloc>
1754inline _LIBCPP_INLINE_VISIBILITY
1755bool operator<=(const forward_list<_Tp, _Alloc>& __x,
1756                const forward_list<_Tp, _Alloc>& __y)
1757{
1758    return !(__y < __x);
1759}
1760
1761template <class _Tp, class _Alloc>
1762inline _LIBCPP_INLINE_VISIBILITY
1763void
1764swap(forward_list<_Tp, _Alloc>& __x, forward_list<_Tp, _Alloc>& __y)
1765    _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y)))
1766{
1767    __x.swap(__y);
1768}
1769
1770#if _LIBCPP_STD_VER > 17
1771template <class _Tp, class _Allocator, class _Predicate>
1772inline _LIBCPP_INLINE_VISIBILITY
1773    typename forward_list<_Tp, _Allocator>::size_type
1774    erase_if(forward_list<_Tp, _Allocator>& __c, _Predicate __pred) {
1775  return __c.remove_if(__pred);
1776}
1777
1778template <class _Tp, class _Allocator, class _Up>
1779inline _LIBCPP_INLINE_VISIBILITY
1780    typename forward_list<_Tp, _Allocator>::size_type
1781    erase(forward_list<_Tp, _Allocator>& __c, const _Up& __v) {
1782  return _VSTD::erase_if(__c, [&](auto& __elem) { return __elem == __v; });
1783}
1784#endif
1785
1786_LIBCPP_END_NAMESPACE_STD
1787
1788_LIBCPP_POP_MACROS
1789
1790#endif // _LIBCPP_FORWARD_LIST
1791