xref: /freebsd/contrib/llvm-project/libcxx/include/deque (revision 5b0945b57059d1cde0831d3afea7ec56c7d79508)
1// -*- C++ -*-
2//===---------------------------- deque -----------------------------------===//
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_DEQUE
11#define _LIBCPP_DEQUE
12
13/*
14    deque synopsis
15
16namespace std
17{
18
19template <class T, class Allocator = allocator<T> >
20class deque
21{
22public:
23    // types:
24    typedef T value_type;
25    typedef Allocator allocator_type;
26
27    typedef typename allocator_type::reference       reference;
28    typedef typename allocator_type::const_reference const_reference;
29    typedef implementation-defined                   iterator;
30    typedef implementation-defined                   const_iterator;
31    typedef typename allocator_type::size_type       size_type;
32    typedef typename allocator_type::difference_type difference_type;
33
34    typedef typename allocator_type::pointer         pointer;
35    typedef typename allocator_type::const_pointer   const_pointer;
36    typedef std::reverse_iterator<iterator>          reverse_iterator;
37    typedef std::reverse_iterator<const_iterator>    const_reverse_iterator;
38
39    // construct/copy/destroy:
40    deque() noexcept(is_nothrow_default_constructible<allocator_type>::value);
41    explicit deque(const allocator_type& a);
42    explicit deque(size_type n);
43    explicit deque(size_type n, const allocator_type& a); // C++14
44    deque(size_type n, const value_type& v);
45    deque(size_type n, const value_type& v, const allocator_type& a);
46    template <class InputIterator>
47        deque(InputIterator f, InputIterator l);
48    template <class InputIterator>
49        deque(InputIterator f, InputIterator l, const allocator_type& a);
50    deque(const deque& c);
51    deque(deque&& c)
52        noexcept(is_nothrow_move_constructible<allocator_type>::value);
53    deque(initializer_list<value_type> il, const Allocator& a = allocator_type());
54    deque(const deque& c, const allocator_type& a);
55    deque(deque&& c, const allocator_type& a);
56    ~deque();
57
58    deque& operator=(const deque& c);
59    deque& operator=(deque&& c)
60        noexcept(
61             allocator_type::propagate_on_container_move_assignment::value &&
62             is_nothrow_move_assignable<allocator_type>::value);
63    deque& operator=(initializer_list<value_type> il);
64
65    template <class InputIterator>
66        void assign(InputIterator f, InputIterator l);
67    void assign(size_type n, const value_type& v);
68    void assign(initializer_list<value_type> il);
69
70    allocator_type get_allocator() const noexcept;
71
72    // iterators:
73
74    iterator       begin() noexcept;
75    const_iterator begin() const noexcept;
76    iterator       end() noexcept;
77    const_iterator end() const noexcept;
78
79    reverse_iterator       rbegin() noexcept;
80    const_reverse_iterator rbegin() const noexcept;
81    reverse_iterator       rend() noexcept;
82    const_reverse_iterator rend() const noexcept;
83
84    const_iterator         cbegin() const noexcept;
85    const_iterator         cend() const noexcept;
86    const_reverse_iterator crbegin() const noexcept;
87    const_reverse_iterator crend() const noexcept;
88
89    // capacity:
90    size_type size() const noexcept;
91    size_type max_size() const noexcept;
92    void resize(size_type n);
93    void resize(size_type n, const value_type& v);
94    void shrink_to_fit();
95    bool empty() const noexcept;
96
97    // element access:
98    reference operator[](size_type i);
99    const_reference operator[](size_type i) const;
100    reference at(size_type i);
101    const_reference at(size_type i) const;
102    reference front();
103    const_reference front() const;
104    reference back();
105    const_reference back() const;
106
107    // modifiers:
108    void push_front(const value_type& v);
109    void push_front(value_type&& v);
110    void push_back(const value_type& v);
111    void push_back(value_type&& v);
112    template <class... Args> reference emplace_front(Args&&... args);  // reference in C++17
113    template <class... Args> reference emplace_back(Args&&... args);   // reference in C++17
114    template <class... Args> iterator emplace(const_iterator p, Args&&... args);
115    iterator insert(const_iterator p, const value_type& v);
116    iterator insert(const_iterator p, value_type&& v);
117    iterator insert(const_iterator p, size_type n, const value_type& v);
118    template <class InputIterator>
119        iterator insert(const_iterator p, InputIterator f, InputIterator l);
120    iterator insert(const_iterator p, initializer_list<value_type> il);
121    void pop_front();
122    void pop_back();
123    iterator erase(const_iterator p);
124    iterator erase(const_iterator f, const_iterator l);
125    void swap(deque& c)
126        noexcept(allocator_traits<allocator_type>::is_always_equal::value);  // C++17
127    void clear() noexcept;
128};
129
130template <class InputIterator, class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
131   deque(InputIterator, InputIterator, Allocator = Allocator())
132   -> deque<typename iterator_traits<InputIterator>::value_type, Allocator>;
133
134template <class T, class Allocator>
135    bool operator==(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
136template <class T, class Allocator>
137    bool operator< (const deque<T,Allocator>& x, const deque<T,Allocator>& y);
138template <class T, class Allocator>
139    bool operator!=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
140template <class T, class Allocator>
141    bool operator> (const deque<T,Allocator>& x, const deque<T,Allocator>& y);
142template <class T, class Allocator>
143    bool operator>=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
144template <class T, class Allocator>
145    bool operator<=(const deque<T,Allocator>& x, const deque<T,Allocator>& y);
146
147// specialized algorithms:
148template <class T, class Allocator>
149    void swap(deque<T,Allocator>& x, deque<T,Allocator>& y)
150         noexcept(noexcept(x.swap(y)));
151
152template <class T, class Allocator, class U>
153    void erase(deque<T, Allocator>& c, const U& value);       // C++20
154template <class T, class Allocator, class Predicate>
155    void erase_if(deque<T, Allocator>& c, Predicate pred);    // C++20
156
157}  // std
158
159*/
160
161#include <__config>
162#include <__split_buffer>
163#include <type_traits>
164#include <initializer_list>
165#include <iterator>
166#include <algorithm>
167#include <stdexcept>
168#include <version>
169
170#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
171#pragma GCC system_header
172#endif
173
174_LIBCPP_PUSH_MACROS
175#include <__undef_macros>
176
177
178_LIBCPP_BEGIN_NAMESPACE_STD
179
180template <class _Tp, class _Allocator> class __deque_base;
181template <class _Tp, class _Allocator = allocator<_Tp> > class _LIBCPP_TEMPLATE_VIS deque;
182
183template <class _ValueType, class _Pointer, class _Reference, class _MapPointer,
184          class _DiffType, _DiffType _BlockSize>
185class _LIBCPP_TEMPLATE_VIS __deque_iterator;
186
187template <class _RAIter,
188          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
189__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
190copy(_RAIter __f,
191     _RAIter __l,
192     __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
193     typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
194
195template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
196          class _OutputIterator>
197_OutputIterator
198copy(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
199     __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
200     _OutputIterator __r);
201
202template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
203          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
204__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
205copy(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
206     __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
207     __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r);
208
209template <class _RAIter,
210          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
211__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
212copy_backward(_RAIter __f,
213              _RAIter __l,
214              __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
215              typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
216
217template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
218          class _OutputIterator>
219_OutputIterator
220copy_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
221              __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
222              _OutputIterator __r);
223
224template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
225          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
226__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
227copy_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
228              __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
229              __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r);
230
231template <class _RAIter,
232          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
233__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
234move(_RAIter __f,
235     _RAIter __l,
236     __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
237     typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
238
239template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
240          class _OutputIterator>
241_OutputIterator
242move(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
243     __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
244     _OutputIterator __r);
245
246template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
247          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
248__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
249move(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
250     __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
251     __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r);
252
253template <class _RAIter,
254          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
255__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
256move_backward(_RAIter __f,
257              _RAIter __l,
258              __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
259              typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
260
261template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
262          class _OutputIterator>
263_OutputIterator
264move_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
265              __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
266              _OutputIterator __r);
267
268template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
269          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
270__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
271move_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
272              __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
273              __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r);
274
275template <class _ValueType, class _DiffType>
276struct __deque_block_size {
277  static const _DiffType value = sizeof(_ValueType) < 256 ? 4096 / sizeof(_ValueType) : 16;
278};
279
280template <class _ValueType, class _Pointer, class _Reference, class _MapPointer,
281          class _DiffType, _DiffType _BS =
282#ifdef _LIBCPP_ABI_INCOMPLETE_TYPES_IN_DEQUE
283// Keep template parameter to avoid changing all template declarations thoughout
284// this file.
285                               0
286#else
287                               __deque_block_size<_ValueType, _DiffType>::value
288#endif
289          >
290class _LIBCPP_TEMPLATE_VIS __deque_iterator
291{
292    typedef _MapPointer __map_iterator;
293public:
294    typedef _Pointer  pointer;
295    typedef _DiffType difference_type;
296private:
297    __map_iterator __m_iter_;
298    pointer        __ptr_;
299
300    static const difference_type __block_size;
301public:
302    typedef _ValueType                  value_type;
303    typedef random_access_iterator_tag  iterator_category;
304    typedef _Reference                  reference;
305
306    _LIBCPP_INLINE_VISIBILITY __deque_iterator() _NOEXCEPT
307#if _LIBCPP_STD_VER > 11
308     : __m_iter_(nullptr), __ptr_(nullptr)
309#endif
310     {}
311
312    template <class _Pp, class _Rp, class _MP>
313    _LIBCPP_INLINE_VISIBILITY
314    __deque_iterator(const __deque_iterator<value_type, _Pp, _Rp, _MP, difference_type, _BS>& __it,
315                typename enable_if<is_convertible<_Pp, pointer>::value>::type* = 0) _NOEXCEPT
316        : __m_iter_(__it.__m_iter_), __ptr_(__it.__ptr_) {}
317
318    _LIBCPP_INLINE_VISIBILITY reference operator*() const {return *__ptr_;}
319    _LIBCPP_INLINE_VISIBILITY pointer operator->() const {return __ptr_;}
320
321    _LIBCPP_INLINE_VISIBILITY __deque_iterator& operator++()
322    {
323        if (++__ptr_ - *__m_iter_ == __block_size)
324        {
325            ++__m_iter_;
326            __ptr_ = *__m_iter_;
327        }
328        return *this;
329    }
330
331    _LIBCPP_INLINE_VISIBILITY __deque_iterator operator++(int)
332    {
333        __deque_iterator __tmp = *this;
334        ++(*this);
335        return __tmp;
336    }
337
338    _LIBCPP_INLINE_VISIBILITY __deque_iterator& operator--()
339    {
340        if (__ptr_ == *__m_iter_)
341        {
342            --__m_iter_;
343            __ptr_ = *__m_iter_ + __block_size;
344        }
345        --__ptr_;
346        return *this;
347    }
348
349    _LIBCPP_INLINE_VISIBILITY __deque_iterator operator--(int)
350    {
351        __deque_iterator __tmp = *this;
352        --(*this);
353        return __tmp;
354    }
355
356    _LIBCPP_INLINE_VISIBILITY __deque_iterator& operator+=(difference_type __n)
357    {
358        if (__n != 0)
359        {
360            __n += __ptr_ - *__m_iter_;
361            if (__n > 0)
362            {
363                __m_iter_ += __n / __block_size;
364                __ptr_ = *__m_iter_ + __n % __block_size;
365            }
366            else // (__n < 0)
367            {
368                difference_type __z = __block_size - 1 - __n;
369                __m_iter_ -= __z / __block_size;
370                __ptr_ = *__m_iter_ + (__block_size - 1 - __z % __block_size);
371            }
372        }
373        return *this;
374    }
375
376    _LIBCPP_INLINE_VISIBILITY __deque_iterator& operator-=(difference_type __n)
377    {
378        return *this += -__n;
379    }
380
381    _LIBCPP_INLINE_VISIBILITY __deque_iterator operator+(difference_type __n) const
382    {
383        __deque_iterator __t(*this);
384        __t += __n;
385        return __t;
386    }
387
388    _LIBCPP_INLINE_VISIBILITY __deque_iterator operator-(difference_type __n) const
389    {
390        __deque_iterator __t(*this);
391        __t -= __n;
392        return __t;
393    }
394
395    _LIBCPP_INLINE_VISIBILITY
396    friend __deque_iterator operator+(difference_type __n, const __deque_iterator& __it)
397        {return __it + __n;}
398
399    _LIBCPP_INLINE_VISIBILITY
400    friend difference_type operator-(const __deque_iterator& __x, const __deque_iterator& __y)
401    {
402        if (__x != __y)
403            return (__x.__m_iter_ - __y.__m_iter_) * __block_size
404                 + (__x.__ptr_ - *__x.__m_iter_)
405                 - (__y.__ptr_ - *__y.__m_iter_);
406        return 0;
407    }
408
409    _LIBCPP_INLINE_VISIBILITY reference operator[](difference_type __n) const
410        {return *(*this + __n);}
411
412    _LIBCPP_INLINE_VISIBILITY friend
413        bool operator==(const __deque_iterator& __x, const __deque_iterator& __y)
414        {return __x.__ptr_ == __y.__ptr_;}
415
416    _LIBCPP_INLINE_VISIBILITY friend
417        bool operator!=(const __deque_iterator& __x, const __deque_iterator& __y)
418        {return !(__x == __y);}
419
420    _LIBCPP_INLINE_VISIBILITY friend
421        bool operator<(const __deque_iterator& __x, const __deque_iterator& __y)
422        {return __x.__m_iter_ < __y.__m_iter_ ||
423               (__x.__m_iter_ == __y.__m_iter_ && __x.__ptr_ < __y.__ptr_);}
424
425    _LIBCPP_INLINE_VISIBILITY friend
426        bool operator>(const __deque_iterator& __x, const __deque_iterator& __y)
427        {return __y < __x;}
428
429    _LIBCPP_INLINE_VISIBILITY friend
430        bool operator<=(const __deque_iterator& __x, const __deque_iterator& __y)
431        {return !(__y < __x);}
432
433    _LIBCPP_INLINE_VISIBILITY friend
434        bool operator>=(const __deque_iterator& __x, const __deque_iterator& __y)
435        {return !(__x < __y);}
436
437private:
438    _LIBCPP_INLINE_VISIBILITY __deque_iterator(__map_iterator __m, pointer __p) _NOEXCEPT
439        : __m_iter_(__m), __ptr_(__p) {}
440
441    template <class _Tp, class _Ap> friend class __deque_base;
442    template <class _Tp, class _Ap> friend class _LIBCPP_TEMPLATE_VIS deque;
443    template <class _Vp, class _Pp, class _Rp, class _MP, class _Dp, _Dp>
444        friend class _LIBCPP_TEMPLATE_VIS __deque_iterator;
445
446    template <class _RAIter,
447              class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
448    friend
449    __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
450    copy(_RAIter __f,
451         _RAIter __l,
452         __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
453         typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*);
454
455    template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
456              class _OutputIterator>
457    friend
458    _OutputIterator
459    copy(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
460         __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
461         _OutputIterator __r);
462
463    template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
464              class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
465    friend
466    __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
467    copy(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
468         __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
469         __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r);
470
471    template <class _RAIter,
472              class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
473    friend
474    __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
475    copy_backward(_RAIter __f,
476                  _RAIter __l,
477                  __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
478                  typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*);
479
480    template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
481              class _OutputIterator>
482    friend
483    _OutputIterator
484    copy_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
485                  __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
486                  _OutputIterator __r);
487
488    template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
489              class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
490    friend
491    __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
492    copy_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
493                  __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
494                  __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r);
495
496    template <class _RAIter,
497              class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
498    friend
499    __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
500    move(_RAIter __f,
501         _RAIter __l,
502         __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
503         typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*);
504
505    template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
506              class _OutputIterator>
507    friend
508    _OutputIterator
509    move(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
510         __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
511         _OutputIterator __r);
512
513    template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
514              class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
515    friend
516    __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
517    move(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
518         __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
519         __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r);
520
521    template <class _RAIter,
522              class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
523    friend
524    __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
525    move_backward(_RAIter __f,
526                  _RAIter __l,
527                  __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
528                  typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*);
529
530    template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
531              class _OutputIterator>
532    friend
533    _OutputIterator
534    move_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
535                  __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
536                  _OutputIterator __r);
537
538    template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
539              class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
540    friend
541    __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
542    move_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
543                  __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
544                  __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r);
545};
546
547template <class _ValueType, class _Pointer, class _Reference, class _MapPointer,
548          class _DiffType, _DiffType _BlockSize>
549const _DiffType __deque_iterator<_ValueType, _Pointer, _Reference, _MapPointer,
550                                 _DiffType, _BlockSize>::__block_size =
551    __deque_block_size<_ValueType, _DiffType>::value;
552
553// copy
554
555template <class _RAIter,
556          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
557__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
558copy(_RAIter __f,
559     _RAIter __l,
560     __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
561     typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
562{
563    typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::difference_type difference_type;
564    typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::pointer pointer;
565    const difference_type __block_size = __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::__block_size;
566    while (__f != __l)
567    {
568        pointer __rb = __r.__ptr_;
569        pointer __re = *__r.__m_iter_ + __block_size;
570        difference_type __bs = __re - __rb;
571        difference_type __n = __l - __f;
572        _RAIter __m = __l;
573        if (__n > __bs)
574        {
575            __n = __bs;
576            __m = __f + __n;
577        }
578        _VSTD::copy(__f, __m, __rb);
579        __f = __m;
580        __r += __n;
581    }
582    return __r;
583}
584
585template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
586          class _OutputIterator>
587_OutputIterator
588copy(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
589     __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
590     _OutputIterator __r)
591{
592    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::difference_type difference_type;
593    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::pointer pointer;
594    const difference_type __block_size = __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::__block_size;
595    difference_type __n = __l - __f;
596    while (__n > 0)
597    {
598        pointer __fb = __f.__ptr_;
599        pointer __fe = *__f.__m_iter_ + __block_size;
600        difference_type __bs = __fe - __fb;
601        if (__bs > __n)
602        {
603            __bs = __n;
604            __fe = __fb + __bs;
605        }
606        __r = _VSTD::copy(__fb, __fe, __r);
607        __n -= __bs;
608        __f += __bs;
609    }
610    return __r;
611}
612
613template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
614          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
615__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
616copy(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
617     __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
618     __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r)
619{
620    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::difference_type difference_type;
621    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::pointer pointer;
622    const difference_type __block_size = __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::__block_size;
623    difference_type __n = __l - __f;
624    while (__n > 0)
625    {
626        pointer __fb = __f.__ptr_;
627        pointer __fe = *__f.__m_iter_ + __block_size;
628        difference_type __bs = __fe - __fb;
629        if (__bs > __n)
630        {
631            __bs = __n;
632            __fe = __fb + __bs;
633        }
634        __r = _VSTD::copy(__fb, __fe, __r);
635        __n -= __bs;
636        __f += __bs;
637    }
638    return __r;
639}
640
641// copy_backward
642
643template <class _RAIter,
644          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
645__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
646copy_backward(_RAIter __f,
647              _RAIter __l,
648              __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
649              typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
650{
651    typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::difference_type difference_type;
652    typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::pointer pointer;
653    while (__f != __l)
654    {
655        __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __rp = _VSTD::prev(__r);
656        pointer __rb = *__rp.__m_iter_;
657        pointer __re = __rp.__ptr_ + 1;
658        difference_type __bs = __re - __rb;
659        difference_type __n = __l - __f;
660        _RAIter __m = __f;
661        if (__n > __bs)
662        {
663            __n = __bs;
664            __m = __l - __n;
665        }
666        _VSTD::copy_backward(__m, __l, __re);
667        __l = __m;
668        __r -= __n;
669    }
670    return __r;
671}
672
673template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
674          class _OutputIterator>
675_OutputIterator
676copy_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
677              __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
678              _OutputIterator __r)
679{
680    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::difference_type difference_type;
681    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::pointer pointer;
682    difference_type __n = __l - __f;
683    while (__n > 0)
684    {
685        --__l;
686        pointer __lb = *__l.__m_iter_;
687        pointer __le = __l.__ptr_ + 1;
688        difference_type __bs = __le - __lb;
689        if (__bs > __n)
690        {
691            __bs = __n;
692            __lb = __le - __bs;
693        }
694        __r = _VSTD::copy_backward(__lb, __le, __r);
695        __n -= __bs;
696        __l -= __bs - 1;
697    }
698    return __r;
699}
700
701template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
702          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
703__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
704copy_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
705              __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
706              __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r)
707{
708    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::difference_type difference_type;
709    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::pointer pointer;
710    difference_type __n = __l - __f;
711    while (__n > 0)
712    {
713        --__l;
714        pointer __lb = *__l.__m_iter_;
715        pointer __le = __l.__ptr_ + 1;
716        difference_type __bs = __le - __lb;
717        if (__bs > __n)
718        {
719            __bs = __n;
720            __lb = __le - __bs;
721        }
722        __r = _VSTD::copy_backward(__lb, __le, __r);
723        __n -= __bs;
724        __l -= __bs - 1;
725    }
726    return __r;
727}
728
729// move
730
731template <class _RAIter,
732          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
733__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
734move(_RAIter __f,
735     _RAIter __l,
736     __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
737     typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
738{
739    typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::difference_type difference_type;
740    typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::pointer pointer;
741    const difference_type __block_size = __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::__block_size;
742    while (__f != __l)
743    {
744        pointer __rb = __r.__ptr_;
745        pointer __re = *__r.__m_iter_ + __block_size;
746        difference_type __bs = __re - __rb;
747        difference_type __n = __l - __f;
748        _RAIter __m = __l;
749        if (__n > __bs)
750        {
751            __n = __bs;
752            __m = __f + __n;
753        }
754        _VSTD::move(__f, __m, __rb);
755        __f = __m;
756        __r += __n;
757    }
758    return __r;
759}
760
761template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
762          class _OutputIterator>
763_OutputIterator
764move(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
765     __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
766     _OutputIterator __r)
767{
768    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::difference_type difference_type;
769    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::pointer pointer;
770    const difference_type __block_size = __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::__block_size;
771    difference_type __n = __l - __f;
772    while (__n > 0)
773    {
774        pointer __fb = __f.__ptr_;
775        pointer __fe = *__f.__m_iter_ + __block_size;
776        difference_type __bs = __fe - __fb;
777        if (__bs > __n)
778        {
779            __bs = __n;
780            __fe = __fb + __bs;
781        }
782        __r = _VSTD::move(__fb, __fe, __r);
783        __n -= __bs;
784        __f += __bs;
785    }
786    return __r;
787}
788
789template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
790          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
791__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
792move(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
793     __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
794     __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r)
795{
796    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::difference_type difference_type;
797    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::pointer pointer;
798    const difference_type __block_size = __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::__block_size;
799    difference_type __n = __l - __f;
800    while (__n > 0)
801    {
802        pointer __fb = __f.__ptr_;
803        pointer __fe = *__f.__m_iter_ + __block_size;
804        difference_type __bs = __fe - __fb;
805        if (__bs > __n)
806        {
807            __bs = __n;
808            __fe = __fb + __bs;
809        }
810        __r = _VSTD::move(__fb, __fe, __r);
811        __n -= __bs;
812        __f += __bs;
813    }
814    return __r;
815}
816
817// move_backward
818
819template <class _RAIter,
820          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
821__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
822move_backward(_RAIter __f,
823              _RAIter __l,
824              __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
825              typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
826{
827    typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::difference_type difference_type;
828    typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::pointer pointer;
829    while (__f != __l)
830    {
831        __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __rp = _VSTD::prev(__r);
832        pointer __rb = *__rp.__m_iter_;
833        pointer __re = __rp.__ptr_ + 1;
834        difference_type __bs = __re - __rb;
835        difference_type __n = __l - __f;
836        _RAIter __m = __f;
837        if (__n > __bs)
838        {
839            __n = __bs;
840            __m = __l - __n;
841        }
842        _VSTD::move_backward(__m, __l, __re);
843        __l = __m;
844        __r -= __n;
845    }
846    return __r;
847}
848
849template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
850          class _OutputIterator>
851_OutputIterator
852move_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
853              __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
854              _OutputIterator __r)
855{
856    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::difference_type difference_type;
857    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::pointer pointer;
858    difference_type __n = __l - __f;
859    while (__n > 0)
860    {
861        --__l;
862        pointer __lb = *__l.__m_iter_;
863        pointer __le = __l.__ptr_ + 1;
864        difference_type __bs = __le - __lb;
865        if (__bs > __n)
866        {
867            __bs = __n;
868            __lb = __le - __bs;
869        }
870        __r = _VSTD::move_backward(__lb, __le, __r);
871        __n -= __bs;
872        __l -= __bs - 1;
873    }
874    return __r;
875}
876
877template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
878          class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
879__deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
880move_backward(__deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __f,
881              __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1> __l,
882              __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r)
883{
884    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::difference_type difference_type;
885    typedef typename __deque_iterator<_V1, _P1, _R1, _M1, _D1, _B1>::pointer pointer;
886    difference_type __n = __l - __f;
887    while (__n > 0)
888    {
889        --__l;
890        pointer __lb = *__l.__m_iter_;
891        pointer __le = __l.__ptr_ + 1;
892        difference_type __bs = __le - __lb;
893        if (__bs > __n)
894        {
895            __bs = __n;
896            __lb = __le - __bs;
897        }
898        __r = _VSTD::move_backward(__lb, __le, __r);
899        __n -= __bs;
900        __l -= __bs - 1;
901    }
902    return __r;
903}
904
905template <bool>
906class __deque_base_common
907{
908protected:
909    _LIBCPP_NORETURN void __throw_length_error() const;
910    _LIBCPP_NORETURN void __throw_out_of_range() const;
911};
912
913template <bool __b>
914void
915__deque_base_common<__b>::__throw_length_error() const
916{
917    _VSTD::__throw_length_error("deque");
918}
919
920template <bool __b>
921void
922__deque_base_common<__b>::__throw_out_of_range() const
923{
924    _VSTD::__throw_out_of_range("deque");
925}
926
927template <class _Tp, class _Allocator>
928class __deque_base
929    : protected __deque_base_common<true>
930{
931    __deque_base(const __deque_base& __c);
932    __deque_base& operator=(const __deque_base& __c);
933public:
934    typedef _Allocator                               allocator_type;
935    typedef allocator_traits<allocator_type>         __alloc_traits;
936    typedef typename __alloc_traits::size_type       size_type;
937
938    typedef _Tp                                      value_type;
939    typedef value_type&                              reference;
940    typedef const value_type&                        const_reference;
941    typedef typename __alloc_traits::difference_type difference_type;
942    typedef typename __alloc_traits::pointer         pointer;
943    typedef typename __alloc_traits::const_pointer   const_pointer;
944
945    static const difference_type __block_size;
946
947    typedef typename __rebind_alloc_helper<__alloc_traits, pointer>::type __pointer_allocator;
948    typedef allocator_traits<__pointer_allocator>        __map_traits;
949    typedef typename __map_traits::pointer               __map_pointer;
950    typedef typename __rebind_alloc_helper<__alloc_traits, const_pointer>::type __const_pointer_allocator;
951    typedef typename allocator_traits<__const_pointer_allocator>::const_pointer __map_const_pointer;
952    typedef __split_buffer<pointer, __pointer_allocator> __map;
953
954    typedef __deque_iterator<value_type, pointer, reference, __map_pointer,
955                             difference_type>    iterator;
956    typedef __deque_iterator<value_type, const_pointer, const_reference, __map_const_pointer,
957                             difference_type>    const_iterator;
958
959    struct __deque_block_range {
960      explicit __deque_block_range(pointer __b, pointer __e) _NOEXCEPT : __begin_(__b), __end_(__e) {}
961      const pointer __begin_;
962      const pointer __end_;
963    };
964
965    struct __deque_range {
966      iterator __pos_;
967      const iterator __end_;
968
969      __deque_range(iterator __pos, iterator __e) _NOEXCEPT
970        : __pos_(__pos), __end_(__e) {}
971
972      explicit operator bool() const _NOEXCEPT {
973        return __pos_ != __end_;
974      }
975
976      __deque_range begin() const {
977        return *this;
978      }
979
980      __deque_range end() const {
981        return __deque_range(__end_, __end_);
982      }
983      __deque_block_range operator*() const _NOEXCEPT {
984         if (__pos_.__m_iter_ == __end_.__m_iter_) {
985          return __deque_block_range(__pos_.__ptr_, __end_.__ptr_);
986        }
987        return __deque_block_range(__pos_.__ptr_, *__pos_.__m_iter_ + __block_size);
988      }
989
990      __deque_range& operator++() _NOEXCEPT {
991        if (__pos_.__m_iter_ == __end_.__m_iter_) {
992          __pos_ = __end_;
993        } else {
994          ++__pos_.__m_iter_;
995          __pos_.__ptr_ = *__pos_.__m_iter_;
996        }
997        return *this;
998      }
999
1000
1001      friend bool operator==(__deque_range const& __lhs, __deque_range const& __rhs) {
1002        return __lhs.__pos_ == __rhs.__pos_;
1003      }
1004      friend bool operator!=(__deque_range const& __lhs, __deque_range const& __rhs) {
1005        return !(__lhs == __rhs);
1006      }
1007    };
1008
1009
1010
1011    struct _ConstructTransaction {
1012      _ConstructTransaction(__deque_base* __db, __deque_block_range& __r)
1013        : __pos_(__r.__begin_), __end_(__r.__end_), __begin_(__r.__begin_), __base_(__db) {}
1014
1015
1016      ~_ConstructTransaction() {
1017        __base_->size() += (__pos_ - __begin_);
1018      }
1019
1020      pointer __pos_;
1021      const pointer __end_;
1022    private:
1023      const pointer __begin_;
1024      __deque_base * const __base_;
1025    };
1026
1027protected:
1028    __map __map_;
1029    size_type __start_;
1030    __compressed_pair<size_type, allocator_type> __size_;
1031
1032    iterator       begin() _NOEXCEPT;
1033    const_iterator begin() const _NOEXCEPT;
1034    iterator       end() _NOEXCEPT;
1035    const_iterator end() const _NOEXCEPT;
1036
1037    _LIBCPP_INLINE_VISIBILITY size_type&            size()          {return __size_.first();}
1038    _LIBCPP_INLINE_VISIBILITY
1039    const size_type& size() const _NOEXCEPT {return __size_.first();}
1040    _LIBCPP_INLINE_VISIBILITY allocator_type&       __alloc()       {return __size_.second();}
1041    _LIBCPP_INLINE_VISIBILITY
1042    const allocator_type& __alloc() const _NOEXCEPT {return __size_.second();}
1043
1044    _LIBCPP_INLINE_VISIBILITY
1045    __deque_base()
1046        _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value);
1047    _LIBCPP_INLINE_VISIBILITY
1048    explicit __deque_base(const allocator_type& __a);
1049public:
1050    ~__deque_base();
1051
1052#ifndef _LIBCPP_CXX03_LANG
1053    __deque_base(__deque_base&& __c)
1054        _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value);
1055    __deque_base(__deque_base&& __c, const allocator_type& __a);
1056#endif  // _LIBCPP_CXX03_LANG
1057
1058    void swap(__deque_base& __c)
1059#if _LIBCPP_STD_VER >= 14
1060        _NOEXCEPT;
1061#else
1062        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
1063                    __is_nothrow_swappable<allocator_type>::value);
1064#endif
1065protected:
1066    void clear() _NOEXCEPT;
1067
1068    bool __invariants() const;
1069
1070    _LIBCPP_INLINE_VISIBILITY
1071    void __move_assign(__deque_base& __c)
1072        _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value &&
1073                   is_nothrow_move_assignable<allocator_type>::value)
1074    {
1075        __map_ = _VSTD::move(__c.__map_);
1076        __start_ = __c.__start_;
1077        size() = __c.size();
1078        __move_assign_alloc(__c);
1079        __c.__start_ = __c.size() = 0;
1080    }
1081
1082    _LIBCPP_INLINE_VISIBILITY
1083    void __move_assign_alloc(__deque_base& __c)
1084        _NOEXCEPT_(!__alloc_traits::propagate_on_container_move_assignment::value ||
1085                   is_nothrow_move_assignable<allocator_type>::value)
1086        {__move_assign_alloc(__c, integral_constant<bool,
1087                      __alloc_traits::propagate_on_container_move_assignment::value>());}
1088
1089private:
1090    _LIBCPP_INLINE_VISIBILITY
1091    void __move_assign_alloc(__deque_base& __c, true_type)
1092        _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
1093        {
1094            __alloc() = _VSTD::move(__c.__alloc());
1095        }
1096
1097    _LIBCPP_INLINE_VISIBILITY
1098    void __move_assign_alloc(__deque_base&, false_type) _NOEXCEPT
1099        {}
1100};
1101
1102template <class _Tp, class _Allocator>
1103const typename __deque_base<_Tp, _Allocator>::difference_type
1104    __deque_base<_Tp, _Allocator>::__block_size =
1105        __deque_block_size<value_type, difference_type>::value;
1106
1107template <class _Tp, class _Allocator>
1108bool
1109__deque_base<_Tp, _Allocator>::__invariants() const
1110{
1111    if (!__map_.__invariants())
1112        return false;
1113    if (__map_.size() >= size_type(-1) / __block_size)
1114        return false;
1115    for (typename __map::const_iterator __i = __map_.begin(), __e = __map_.end();
1116         __i != __e; ++__i)
1117        if (*__i == nullptr)
1118            return false;
1119    if (__map_.size() != 0)
1120    {
1121        if (size() >= __map_.size() * __block_size)
1122            return false;
1123        if (__start_ >= __map_.size() * __block_size - size())
1124            return false;
1125    }
1126    else
1127    {
1128        if (size() != 0)
1129            return false;
1130        if (__start_ != 0)
1131            return false;
1132    }
1133    return true;
1134}
1135
1136template <class _Tp, class _Allocator>
1137typename __deque_base<_Tp, _Allocator>::iterator
1138__deque_base<_Tp, _Allocator>::begin() _NOEXCEPT
1139{
1140    __map_pointer __mp = __map_.begin() + __start_ / __block_size;
1141    return iterator(__mp, __map_.empty() ? 0 : *__mp + __start_ % __block_size);
1142}
1143
1144template <class _Tp, class _Allocator>
1145typename __deque_base<_Tp, _Allocator>::const_iterator
1146__deque_base<_Tp, _Allocator>::begin() const _NOEXCEPT
1147{
1148    __map_const_pointer __mp = static_cast<__map_const_pointer>(__map_.begin() + __start_ / __block_size);
1149    return const_iterator(__mp, __map_.empty() ? 0 : *__mp + __start_ % __block_size);
1150}
1151
1152template <class _Tp, class _Allocator>
1153typename __deque_base<_Tp, _Allocator>::iterator
1154__deque_base<_Tp, _Allocator>::end() _NOEXCEPT
1155{
1156    size_type __p = size() + __start_;
1157    __map_pointer __mp = __map_.begin() + __p / __block_size;
1158    return iterator(__mp, __map_.empty() ? 0 : *__mp + __p % __block_size);
1159}
1160
1161template <class _Tp, class _Allocator>
1162typename __deque_base<_Tp, _Allocator>::const_iterator
1163__deque_base<_Tp, _Allocator>::end() const _NOEXCEPT
1164{
1165    size_type __p = size() + __start_;
1166    __map_const_pointer __mp = static_cast<__map_const_pointer>(__map_.begin() + __p / __block_size);
1167    return const_iterator(__mp, __map_.empty() ? 0 : *__mp + __p % __block_size);
1168}
1169
1170template <class _Tp, class _Allocator>
1171inline
1172__deque_base<_Tp, _Allocator>::__deque_base()
1173    _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
1174    : __start_(0), __size_(0, __default_init_tag()) {}
1175
1176template <class _Tp, class _Allocator>
1177inline
1178__deque_base<_Tp, _Allocator>::__deque_base(const allocator_type& __a)
1179    : __map_(__pointer_allocator(__a)), __start_(0), __size_(0, __a) {}
1180
1181template <class _Tp, class _Allocator>
1182__deque_base<_Tp, _Allocator>::~__deque_base()
1183{
1184    clear();
1185    typename __map::iterator __i = __map_.begin();
1186    typename __map::iterator __e = __map_.end();
1187    for (; __i != __e; ++__i)
1188        __alloc_traits::deallocate(__alloc(), *__i, __block_size);
1189}
1190
1191#ifndef _LIBCPP_CXX03_LANG
1192
1193template <class _Tp, class _Allocator>
1194__deque_base<_Tp, _Allocator>::__deque_base(__deque_base&& __c)
1195    _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value)
1196    : __map_(_VSTD::move(__c.__map_)),
1197      __start_(_VSTD::move(__c.__start_)),
1198      __size_(_VSTD::move(__c.__size_))
1199{
1200    __c.__start_ = 0;
1201    __c.size() = 0;
1202}
1203
1204template <class _Tp, class _Allocator>
1205__deque_base<_Tp, _Allocator>::__deque_base(__deque_base&& __c, const allocator_type& __a)
1206    : __map_(_VSTD::move(__c.__map_), __pointer_allocator(__a)),
1207      __start_(_VSTD::move(__c.__start_)),
1208      __size_(_VSTD::move(__c.size()), __a)
1209{
1210    if (__a == __c.__alloc())
1211    {
1212        __c.__start_ = 0;
1213        __c.size() = 0;
1214    }
1215    else
1216    {
1217        __map_.clear();
1218        __start_ = 0;
1219        size() = 0;
1220    }
1221}
1222
1223#endif  // _LIBCPP_CXX03_LANG
1224
1225template <class _Tp, class _Allocator>
1226void
1227__deque_base<_Tp, _Allocator>::swap(__deque_base& __c)
1228#if _LIBCPP_STD_VER >= 14
1229        _NOEXCEPT
1230#else
1231        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
1232                    __is_nothrow_swappable<allocator_type>::value)
1233#endif
1234{
1235    __map_.swap(__c.__map_);
1236    _VSTD::swap(__start_, __c.__start_);
1237    _VSTD::swap(size(), __c.size());
1238    __swap_allocator(__alloc(), __c.__alloc());
1239}
1240
1241template <class _Tp, class _Allocator>
1242void
1243__deque_base<_Tp, _Allocator>::clear() _NOEXCEPT
1244{
1245    allocator_type& __a = __alloc();
1246    for (iterator __i = begin(), __e = end(); __i != __e; ++__i)
1247        __alloc_traits::destroy(__a, _VSTD::addressof(*__i));
1248    size() = 0;
1249    while (__map_.size() > 2)
1250    {
1251        __alloc_traits::deallocate(__a, __map_.front(), __block_size);
1252        __map_.pop_front();
1253    }
1254    switch (__map_.size())
1255    {
1256    case 1:
1257        __start_ = __block_size / 2;
1258        break;
1259    case 2:
1260        __start_ = __block_size;
1261        break;
1262    }
1263}
1264
1265template <class _Tp, class _Allocator /*= allocator<_Tp>*/>
1266class _LIBCPP_TEMPLATE_VIS deque
1267    : private __deque_base<_Tp, _Allocator>
1268{
1269public:
1270    // types:
1271
1272    typedef _Tp value_type;
1273    typedef _Allocator allocator_type;
1274
1275    static_assert((is_same<typename allocator_type::value_type, value_type>::value),
1276                  "Allocator::value_type must be same type as value_type");
1277
1278    typedef __deque_base<value_type, allocator_type> __base;
1279
1280    typedef typename __base::__alloc_traits        __alloc_traits;
1281    typedef typename __base::reference             reference;
1282    typedef typename __base::const_reference       const_reference;
1283    typedef typename __base::iterator              iterator;
1284    typedef typename __base::const_iterator        const_iterator;
1285    typedef typename __base::size_type             size_type;
1286    typedef typename __base::difference_type       difference_type;
1287
1288    typedef typename __base::pointer               pointer;
1289    typedef typename __base::const_pointer         const_pointer;
1290    typedef _VSTD::reverse_iterator<iterator>       reverse_iterator;
1291    typedef _VSTD::reverse_iterator<const_iterator> const_reverse_iterator;
1292
1293    using typename __base::__deque_range;
1294    using typename __base::__deque_block_range;
1295    using typename __base::_ConstructTransaction;
1296
1297    // construct/copy/destroy:
1298    _LIBCPP_INLINE_VISIBILITY
1299    deque()
1300        _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
1301        {}
1302    _LIBCPP_INLINE_VISIBILITY explicit deque(const allocator_type& __a) : __base(__a) {}
1303    explicit deque(size_type __n);
1304#if _LIBCPP_STD_VER > 11
1305    explicit deque(size_type __n, const _Allocator& __a);
1306#endif
1307    deque(size_type __n, const value_type& __v);
1308    deque(size_type __n, const value_type& __v, const allocator_type& __a);
1309    template <class _InputIter>
1310        deque(_InputIter __f, _InputIter __l,
1311              typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type* = 0);
1312    template <class _InputIter>
1313        deque(_InputIter __f, _InputIter __l, const allocator_type& __a,
1314              typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type* = 0);
1315    deque(const deque& __c);
1316    deque(const deque& __c, const allocator_type& __a);
1317
1318    deque& operator=(const deque& __c);
1319
1320#ifndef _LIBCPP_CXX03_LANG
1321    deque(initializer_list<value_type> __il);
1322    deque(initializer_list<value_type> __il, const allocator_type& __a);
1323
1324    _LIBCPP_INLINE_VISIBILITY
1325    deque& operator=(initializer_list<value_type> __il) {assign(__il); return *this;}
1326
1327    _LIBCPP_INLINE_VISIBILITY
1328    deque(deque&& __c) _NOEXCEPT_(is_nothrow_move_constructible<__base>::value);
1329    _LIBCPP_INLINE_VISIBILITY
1330    deque(deque&& __c, const allocator_type& __a);
1331    _LIBCPP_INLINE_VISIBILITY
1332    deque& operator=(deque&& __c)
1333        _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value &&
1334                   is_nothrow_move_assignable<allocator_type>::value);
1335
1336    _LIBCPP_INLINE_VISIBILITY
1337    void assign(initializer_list<value_type> __il) {assign(__il.begin(), __il.end());}
1338#endif  // _LIBCPP_CXX03_LANG
1339
1340    template <class _InputIter>
1341        void assign(_InputIter __f, _InputIter __l,
1342                    typename enable_if<__is_cpp17_input_iterator<_InputIter>::value &&
1343                                      !__is_cpp17_random_access_iterator<_InputIter>::value>::type* = 0);
1344    template <class _RAIter>
1345        void assign(_RAIter __f, _RAIter __l,
1346                    typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
1347    void assign(size_type __n, const value_type& __v);
1348
1349    _LIBCPP_INLINE_VISIBILITY
1350    allocator_type get_allocator() const _NOEXCEPT;
1351
1352    // iterators:
1353
1354    _LIBCPP_INLINE_VISIBILITY
1355    iterator       begin() _NOEXCEPT       {return __base::begin();}
1356    _LIBCPP_INLINE_VISIBILITY
1357    const_iterator begin() const _NOEXCEPT {return __base::begin();}
1358    _LIBCPP_INLINE_VISIBILITY
1359    iterator       end() _NOEXCEPT         {return __base::end();}
1360    _LIBCPP_INLINE_VISIBILITY
1361    const_iterator end()   const _NOEXCEPT {return __base::end();}
1362
1363    _LIBCPP_INLINE_VISIBILITY
1364    reverse_iterator       rbegin() _NOEXCEPT
1365        {return       reverse_iterator(__base::end());}
1366    _LIBCPP_INLINE_VISIBILITY
1367    const_reverse_iterator rbegin() const _NOEXCEPT
1368        {return const_reverse_iterator(__base::end());}
1369    _LIBCPP_INLINE_VISIBILITY
1370    reverse_iterator       rend() _NOEXCEPT
1371        {return       reverse_iterator(__base::begin());}
1372    _LIBCPP_INLINE_VISIBILITY
1373    const_reverse_iterator rend()   const _NOEXCEPT
1374        {return const_reverse_iterator(__base::begin());}
1375
1376    _LIBCPP_INLINE_VISIBILITY
1377    const_iterator         cbegin()  const _NOEXCEPT
1378        {return __base::begin();}
1379    _LIBCPP_INLINE_VISIBILITY
1380    const_iterator         cend()    const _NOEXCEPT
1381        {return __base::end();}
1382    _LIBCPP_INLINE_VISIBILITY
1383    const_reverse_iterator crbegin() const _NOEXCEPT
1384        {return const_reverse_iterator(__base::end());}
1385    _LIBCPP_INLINE_VISIBILITY
1386    const_reverse_iterator crend()   const _NOEXCEPT
1387        {return const_reverse_iterator(__base::begin());}
1388
1389    // capacity:
1390    _LIBCPP_INLINE_VISIBILITY
1391    size_type size() const _NOEXCEPT {return __base::size();}
1392    _LIBCPP_INLINE_VISIBILITY
1393    size_type max_size() const _NOEXCEPT
1394        {return std::min<size_type>(
1395            __alloc_traits::max_size(__base::__alloc()),
1396            numeric_limits<difference_type>::max());}
1397    void resize(size_type __n);
1398    void resize(size_type __n, const value_type& __v);
1399    void shrink_to_fit() _NOEXCEPT;
1400    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
1401    bool empty() const _NOEXCEPT {return __base::size() == 0;}
1402
1403    // element access:
1404    _LIBCPP_INLINE_VISIBILITY
1405    reference operator[](size_type __i) _NOEXCEPT;
1406    _LIBCPP_INLINE_VISIBILITY
1407    const_reference operator[](size_type __i) const _NOEXCEPT;
1408    _LIBCPP_INLINE_VISIBILITY
1409    reference at(size_type __i);
1410    _LIBCPP_INLINE_VISIBILITY
1411    const_reference at(size_type __i) const;
1412    _LIBCPP_INLINE_VISIBILITY
1413    reference front() _NOEXCEPT;
1414    _LIBCPP_INLINE_VISIBILITY
1415    const_reference front() const _NOEXCEPT;
1416    _LIBCPP_INLINE_VISIBILITY
1417    reference back() _NOEXCEPT;
1418    _LIBCPP_INLINE_VISIBILITY
1419    const_reference back() const _NOEXCEPT;
1420
1421    // 23.2.2.3 modifiers:
1422    void push_front(const value_type& __v);
1423    void push_back(const value_type& __v);
1424#ifndef _LIBCPP_CXX03_LANG
1425#if _LIBCPP_STD_VER > 14
1426    template <class... _Args> reference emplace_front(_Args&&... __args);
1427    template <class... _Args> reference emplace_back (_Args&&... __args);
1428#else
1429    template <class... _Args> void      emplace_front(_Args&&... __args);
1430    template <class... _Args> void      emplace_back (_Args&&... __args);
1431#endif
1432    template <class... _Args> iterator emplace(const_iterator __p, _Args&&... __args);
1433
1434    void push_front(value_type&& __v);
1435    void push_back(value_type&& __v);
1436    iterator insert(const_iterator __p, value_type&& __v);
1437
1438    _LIBCPP_INLINE_VISIBILITY
1439    iterator insert(const_iterator __p, initializer_list<value_type> __il)
1440        {return insert(__p, __il.begin(), __il.end());}
1441#endif  // _LIBCPP_CXX03_LANG
1442    iterator insert(const_iterator __p, const value_type& __v);
1443    iterator insert(const_iterator __p, size_type __n, const value_type& __v);
1444    template <class _InputIter>
1445        iterator insert(const_iterator __p, _InputIter __f, _InputIter __l,
1446                         typename enable_if<__is_cpp17_input_iterator<_InputIter>::value
1447                                         &&!__is_cpp17_forward_iterator<_InputIter>::value>::type* = 0);
1448    template <class _ForwardIterator>
1449        iterator insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l,
1450                               typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value
1451                                         &&!__is_cpp17_bidirectional_iterator<_ForwardIterator>::value>::type* = 0);
1452    template <class _BiIter>
1453        iterator insert(const_iterator __p, _BiIter __f, _BiIter __l,
1454                         typename enable_if<__is_cpp17_bidirectional_iterator<_BiIter>::value>::type* = 0);
1455
1456    void pop_front();
1457    void pop_back();
1458    iterator erase(const_iterator __p);
1459    iterator erase(const_iterator __f, const_iterator __l);
1460
1461    _LIBCPP_INLINE_VISIBILITY
1462    void swap(deque& __c)
1463#if _LIBCPP_STD_VER >= 14
1464        _NOEXCEPT;
1465#else
1466        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
1467                   __is_nothrow_swappable<allocator_type>::value);
1468#endif
1469    _LIBCPP_INLINE_VISIBILITY
1470    void clear() _NOEXCEPT;
1471
1472    _LIBCPP_INLINE_VISIBILITY
1473    bool __invariants() const {return __base::__invariants();}
1474
1475    typedef typename __base::__map_const_pointer __map_const_pointer;
1476
1477    _LIBCPP_INLINE_VISIBILITY
1478    static size_type __recommend_blocks(size_type __n)
1479    {
1480        return __n / __base::__block_size + (__n % __base::__block_size != 0);
1481    }
1482    _LIBCPP_INLINE_VISIBILITY
1483    size_type __capacity() const
1484    {
1485        return __base::__map_.size() == 0 ? 0 : __base::__map_.size() * __base::__block_size - 1;
1486    }
1487    _LIBCPP_INLINE_VISIBILITY
1488    size_type __block_count() const
1489    {
1490        return __base::__map_.size();
1491    }
1492
1493    _LIBCPP_INLINE_VISIBILITY
1494    size_type __front_spare() const
1495    {
1496        return __base::__start_;
1497    }
1498    _LIBCPP_INLINE_VISIBILITY
1499    size_type __front_spare_blocks() const {
1500      return __front_spare() / __base::__block_size;
1501    }
1502    _LIBCPP_INLINE_VISIBILITY
1503    size_type __back_spare() const
1504    {
1505        return __capacity() - (__base::__start_ + __base::size());
1506    }
1507    _LIBCPP_INLINE_VISIBILITY
1508    size_type __back_spare_blocks() const {
1509      return __back_spare() / __base::__block_size;
1510    }
1511
1512 private:
1513    _LIBCPP_INLINE_VISIBILITY
1514    bool __maybe_remove_front_spare(bool __keep_one = true) {
1515      if (__front_spare_blocks() >= 2 || (!__keep_one && __front_spare_blocks())) {
1516        __alloc_traits::deallocate(__base::__alloc(), __base::__map_.front(),
1517                                   __base::__block_size);
1518        __base::__map_.pop_front();
1519        __base::__start_ -= __base::__block_size;
1520        return true;
1521      }
1522      return false;
1523    }
1524
1525    _LIBCPP_INLINE_VISIBILITY
1526    bool __maybe_remove_back_spare(bool __keep_one = true) {
1527      if (__back_spare_blocks() >= 2 || (!__keep_one && __back_spare_blocks())) {
1528        __alloc_traits::deallocate(__base::__alloc(), __base::__map_.back(),
1529                                   __base::__block_size);
1530        __base::__map_.pop_back();
1531        return true;
1532      }
1533      return false;
1534    }
1535
1536    template <class _InpIter>
1537        void __append(_InpIter __f, _InpIter __l,
1538                 typename enable_if<__is_cpp17_input_iterator<_InpIter>::value &&
1539                                   !__is_cpp17_forward_iterator<_InpIter>::value>::type* = 0);
1540    template <class _ForIter>
1541        void __append(_ForIter __f, _ForIter __l,
1542                      typename enable_if<__is_cpp17_forward_iterator<_ForIter>::value>::type* = 0);
1543    void __append(size_type __n);
1544    void __append(size_type __n, const value_type& __v);
1545    void __erase_to_end(const_iterator __f);
1546    void __add_front_capacity();
1547    void __add_front_capacity(size_type __n);
1548    void __add_back_capacity();
1549    void __add_back_capacity(size_type __n);
1550    iterator __move_and_check(iterator __f, iterator __l, iterator __r,
1551                              const_pointer& __vt);
1552    iterator __move_backward_and_check(iterator __f, iterator __l, iterator __r,
1553                                       const_pointer& __vt);
1554    void __move_construct_and_check(iterator __f, iterator __l,
1555                                    iterator __r, const_pointer& __vt);
1556    void __move_construct_backward_and_check(iterator __f, iterator __l,
1557                                             iterator __r, const_pointer& __vt);
1558
1559    _LIBCPP_INLINE_VISIBILITY
1560    void __copy_assign_alloc(const deque& __c)
1561        {__copy_assign_alloc(__c, integral_constant<bool,
1562                      __alloc_traits::propagate_on_container_copy_assignment::value>());}
1563
1564    _LIBCPP_INLINE_VISIBILITY
1565    void __copy_assign_alloc(const deque& __c, true_type)
1566        {
1567            if (__base::__alloc() != __c.__alloc())
1568            {
1569                clear();
1570                shrink_to_fit();
1571            }
1572            __base::__alloc() = __c.__alloc();
1573            __base::__map_.__alloc() = __c.__map_.__alloc();
1574        }
1575
1576    _LIBCPP_INLINE_VISIBILITY
1577    void __copy_assign_alloc(const deque&, false_type)
1578        {}
1579
1580    void __move_assign(deque& __c, true_type)
1581        _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
1582    void __move_assign(deque& __c, false_type);
1583};
1584
1585#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
1586template<class _InputIterator,
1587         class _Alloc = typename std::allocator<typename iterator_traits<_InputIterator>::value_type>,
1588         class = typename enable_if<__is_allocator<_Alloc>::value, void>::type
1589         >
1590deque(_InputIterator, _InputIterator)
1591  -> deque<typename iterator_traits<_InputIterator>::value_type, _Alloc>;
1592
1593template<class _InputIterator,
1594         class _Alloc,
1595         class = typename enable_if<__is_allocator<_Alloc>::value, void>::type
1596         >
1597deque(_InputIterator, _InputIterator, _Alloc)
1598  -> deque<typename iterator_traits<_InputIterator>::value_type, _Alloc>;
1599#endif
1600
1601
1602template <class _Tp, class _Allocator>
1603deque<_Tp, _Allocator>::deque(size_type __n)
1604{
1605    if (__n > 0)
1606        __append(__n);
1607}
1608
1609#if _LIBCPP_STD_VER > 11
1610template <class _Tp, class _Allocator>
1611deque<_Tp, _Allocator>::deque(size_type __n, const _Allocator& __a)
1612    : __base(__a)
1613{
1614    if (__n > 0)
1615        __append(__n);
1616}
1617#endif
1618
1619template <class _Tp, class _Allocator>
1620deque<_Tp, _Allocator>::deque(size_type __n, const value_type& __v)
1621{
1622    if (__n > 0)
1623        __append(__n, __v);
1624}
1625
1626template <class _Tp, class _Allocator>
1627deque<_Tp, _Allocator>::deque(size_type __n, const value_type& __v, const allocator_type& __a)
1628    : __base(__a)
1629{
1630    if (__n > 0)
1631        __append(__n, __v);
1632}
1633
1634template <class _Tp, class _Allocator>
1635template <class _InputIter>
1636deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l,
1637              typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type*)
1638{
1639    __append(__f, __l);
1640}
1641
1642template <class _Tp, class _Allocator>
1643template <class _InputIter>
1644deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l, const allocator_type& __a,
1645              typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type*)
1646    : __base(__a)
1647{
1648    __append(__f, __l);
1649}
1650
1651template <class _Tp, class _Allocator>
1652deque<_Tp, _Allocator>::deque(const deque& __c)
1653    : __base(__alloc_traits::select_on_container_copy_construction(__c.__alloc()))
1654{
1655    __append(__c.begin(), __c.end());
1656}
1657
1658template <class _Tp, class _Allocator>
1659deque<_Tp, _Allocator>::deque(const deque& __c, const allocator_type& __a)
1660    : __base(__a)
1661{
1662    __append(__c.begin(), __c.end());
1663}
1664
1665template <class _Tp, class _Allocator>
1666deque<_Tp, _Allocator>&
1667deque<_Tp, _Allocator>::operator=(const deque& __c)
1668{
1669    if (this != &__c)
1670    {
1671        __copy_assign_alloc(__c);
1672        assign(__c.begin(), __c.end());
1673    }
1674    return *this;
1675}
1676
1677#ifndef _LIBCPP_CXX03_LANG
1678
1679template <class _Tp, class _Allocator>
1680deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il)
1681{
1682    __append(__il.begin(), __il.end());
1683}
1684
1685template <class _Tp, class _Allocator>
1686deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il, const allocator_type& __a)
1687    : __base(__a)
1688{
1689    __append(__il.begin(), __il.end());
1690}
1691
1692template <class _Tp, class _Allocator>
1693inline
1694deque<_Tp, _Allocator>::deque(deque&& __c)
1695    _NOEXCEPT_(is_nothrow_move_constructible<__base>::value)
1696    : __base(_VSTD::move(__c))
1697{
1698}
1699
1700template <class _Tp, class _Allocator>
1701inline
1702deque<_Tp, _Allocator>::deque(deque&& __c, const allocator_type& __a)
1703    : __base(_VSTD::move(__c), __a)
1704{
1705    if (__a != __c.__alloc())
1706    {
1707        typedef move_iterator<iterator> _Ip;
1708        assign(_Ip(__c.begin()), _Ip(__c.end()));
1709    }
1710}
1711
1712template <class _Tp, class _Allocator>
1713inline
1714deque<_Tp, _Allocator>&
1715deque<_Tp, _Allocator>::operator=(deque&& __c)
1716        _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value &&
1717                   is_nothrow_move_assignable<allocator_type>::value)
1718{
1719    __move_assign(__c, integral_constant<bool,
1720          __alloc_traits::propagate_on_container_move_assignment::value>());
1721    return *this;
1722}
1723
1724template <class _Tp, class _Allocator>
1725void
1726deque<_Tp, _Allocator>::__move_assign(deque& __c, false_type)
1727{
1728    if (__base::__alloc() != __c.__alloc())
1729    {
1730        typedef move_iterator<iterator> _Ip;
1731        assign(_Ip(__c.begin()), _Ip(__c.end()));
1732    }
1733    else
1734        __move_assign(__c, true_type());
1735}
1736
1737template <class _Tp, class _Allocator>
1738void
1739deque<_Tp, _Allocator>::__move_assign(deque& __c, true_type)
1740    _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
1741{
1742    clear();
1743    shrink_to_fit();
1744    __base::__move_assign(__c);
1745}
1746
1747#endif  // _LIBCPP_CXX03_LANG
1748
1749template <class _Tp, class _Allocator>
1750template <class _InputIter>
1751void
1752deque<_Tp, _Allocator>::assign(_InputIter __f, _InputIter __l,
1753                               typename enable_if<__is_cpp17_input_iterator<_InputIter>::value &&
1754                                                 !__is_cpp17_random_access_iterator<_InputIter>::value>::type*)
1755{
1756    iterator __i = __base::begin();
1757    iterator __e = __base::end();
1758    for (; __f != __l && __i != __e; ++__f, (void) ++__i)
1759        *__i = *__f;
1760    if (__f != __l)
1761        __append(__f, __l);
1762    else
1763        __erase_to_end(__i);
1764}
1765
1766template <class _Tp, class _Allocator>
1767template <class _RAIter>
1768void
1769deque<_Tp, _Allocator>::assign(_RAIter __f, _RAIter __l,
1770                               typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
1771{
1772    if (static_cast<size_type>(__l - __f) > __base::size())
1773    {
1774        _RAIter __m = __f + __base::size();
1775        _VSTD::copy(__f, __m, __base::begin());
1776        __append(__m, __l);
1777    }
1778    else
1779        __erase_to_end(_VSTD::copy(__f, __l, __base::begin()));
1780}
1781
1782template <class _Tp, class _Allocator>
1783void
1784deque<_Tp, _Allocator>::assign(size_type __n, const value_type& __v)
1785{
1786    if (__n > __base::size())
1787    {
1788        _VSTD::fill_n(__base::begin(), __base::size(), __v);
1789        __n -= __base::size();
1790        __append(__n, __v);
1791    }
1792    else
1793        __erase_to_end(_VSTD::fill_n(__base::begin(), __n, __v));
1794}
1795
1796template <class _Tp, class _Allocator>
1797inline
1798_Allocator
1799deque<_Tp, _Allocator>::get_allocator() const _NOEXCEPT
1800{
1801    return __base::__alloc();
1802}
1803
1804template <class _Tp, class _Allocator>
1805void
1806deque<_Tp, _Allocator>::resize(size_type __n)
1807{
1808    if (__n > __base::size())
1809        __append(__n - __base::size());
1810    else if (__n < __base::size())
1811        __erase_to_end(__base::begin() + __n);
1812}
1813
1814template <class _Tp, class _Allocator>
1815void
1816deque<_Tp, _Allocator>::resize(size_type __n, const value_type& __v)
1817{
1818    if (__n > __base::size())
1819        __append(__n - __base::size(), __v);
1820    else if (__n < __base::size())
1821        __erase_to_end(__base::begin() + __n);
1822}
1823
1824template <class _Tp, class _Allocator>
1825void
1826deque<_Tp, _Allocator>::shrink_to_fit() _NOEXCEPT
1827{
1828    allocator_type& __a = __base::__alloc();
1829    if (empty())
1830    {
1831        while (__base::__map_.size() > 0)
1832        {
1833            __alloc_traits::deallocate(__a, __base::__map_.back(), __base::__block_size);
1834            __base::__map_.pop_back();
1835        }
1836        __base::__start_ = 0;
1837    }
1838    else
1839    {
1840      __maybe_remove_front_spare(/*__keep_one=*/false);
1841      __maybe_remove_back_spare(/*__keep_one=*/false);
1842    }
1843    __base::__map_.shrink_to_fit();
1844}
1845
1846template <class _Tp, class _Allocator>
1847inline
1848typename deque<_Tp, _Allocator>::reference
1849deque<_Tp, _Allocator>::operator[](size_type __i) _NOEXCEPT
1850{
1851    size_type __p = __base::__start_ + __i;
1852    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
1853}
1854
1855template <class _Tp, class _Allocator>
1856inline
1857typename deque<_Tp, _Allocator>::const_reference
1858deque<_Tp, _Allocator>::operator[](size_type __i) const _NOEXCEPT
1859{
1860    size_type __p = __base::__start_ + __i;
1861    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
1862}
1863
1864template <class _Tp, class _Allocator>
1865inline
1866typename deque<_Tp, _Allocator>::reference
1867deque<_Tp, _Allocator>::at(size_type __i)
1868{
1869    if (__i >= __base::size())
1870        __base::__throw_out_of_range();
1871    size_type __p = __base::__start_ + __i;
1872    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
1873}
1874
1875template <class _Tp, class _Allocator>
1876inline
1877typename deque<_Tp, _Allocator>::const_reference
1878deque<_Tp, _Allocator>::at(size_type __i) const
1879{
1880    if (__i >= __base::size())
1881        __base::__throw_out_of_range();
1882    size_type __p = __base::__start_ + __i;
1883    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
1884}
1885
1886template <class _Tp, class _Allocator>
1887inline
1888typename deque<_Tp, _Allocator>::reference
1889deque<_Tp, _Allocator>::front() _NOEXCEPT
1890{
1891    return *(*(__base::__map_.begin() + __base::__start_ / __base::__block_size)
1892                                      + __base::__start_ % __base::__block_size);
1893}
1894
1895template <class _Tp, class _Allocator>
1896inline
1897typename deque<_Tp, _Allocator>::const_reference
1898deque<_Tp, _Allocator>::front() const _NOEXCEPT
1899{
1900    return *(*(__base::__map_.begin() + __base::__start_ / __base::__block_size)
1901                                      + __base::__start_ % __base::__block_size);
1902}
1903
1904template <class _Tp, class _Allocator>
1905inline
1906typename deque<_Tp, _Allocator>::reference
1907deque<_Tp, _Allocator>::back() _NOEXCEPT
1908{
1909    size_type __p = __base::size() + __base::__start_ - 1;
1910    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
1911}
1912
1913template <class _Tp, class _Allocator>
1914inline
1915typename deque<_Tp, _Allocator>::const_reference
1916deque<_Tp, _Allocator>::back() const _NOEXCEPT
1917{
1918    size_type __p = __base::size() + __base::__start_ - 1;
1919    return *(*(__base::__map_.begin() + __p / __base::__block_size) + __p % __base::__block_size);
1920}
1921
1922template <class _Tp, class _Allocator>
1923void
1924deque<_Tp, _Allocator>::push_back(const value_type& __v)
1925{
1926    allocator_type& __a = __base::__alloc();
1927    if (__back_spare() == 0)
1928        __add_back_capacity();
1929    // __back_spare() >= 1
1930    __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), __v);
1931    ++__base::size();
1932}
1933
1934template <class _Tp, class _Allocator>
1935void
1936deque<_Tp, _Allocator>::push_front(const value_type& __v)
1937{
1938    allocator_type& __a = __base::__alloc();
1939    if (__front_spare() == 0)
1940        __add_front_capacity();
1941    // __front_spare() >= 1
1942    __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), __v);
1943    --__base::__start_;
1944    ++__base::size();
1945}
1946
1947#ifndef _LIBCPP_CXX03_LANG
1948template <class _Tp, class _Allocator>
1949void
1950deque<_Tp, _Allocator>::push_back(value_type&& __v)
1951{
1952    allocator_type& __a = __base::__alloc();
1953    if (__back_spare() == 0)
1954        __add_back_capacity();
1955    // __back_spare() >= 1
1956    __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::move(__v));
1957    ++__base::size();
1958}
1959
1960template <class _Tp, class _Allocator>
1961template <class... _Args>
1962#if _LIBCPP_STD_VER > 14
1963typename deque<_Tp, _Allocator>::reference
1964#else
1965void
1966#endif
1967deque<_Tp, _Allocator>::emplace_back(_Args&&... __args)
1968{
1969    allocator_type& __a = __base::__alloc();
1970    if (__back_spare() == 0)
1971        __add_back_capacity();
1972    // __back_spare() >= 1
1973    __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()),
1974                              _VSTD::forward<_Args>(__args)...);
1975    ++__base::size();
1976#if _LIBCPP_STD_VER > 14
1977    return *--__base::end();
1978#endif
1979}
1980
1981template <class _Tp, class _Allocator>
1982void
1983deque<_Tp, _Allocator>::push_front(value_type&& __v)
1984{
1985    allocator_type& __a = __base::__alloc();
1986    if (__front_spare() == 0)
1987        __add_front_capacity();
1988    // __front_spare() >= 1
1989    __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::move(__v));
1990    --__base::__start_;
1991    ++__base::size();
1992}
1993
1994
1995template <class _Tp, class _Allocator>
1996template <class... _Args>
1997#if _LIBCPP_STD_VER > 14
1998typename deque<_Tp, _Allocator>::reference
1999#else
2000void
2001#endif
2002deque<_Tp, _Allocator>::emplace_front(_Args&&... __args)
2003{
2004    allocator_type& __a = __base::__alloc();
2005    if (__front_spare() == 0)
2006        __add_front_capacity();
2007    // __front_spare() >= 1
2008    __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::forward<_Args>(__args)...);
2009    --__base::__start_;
2010    ++__base::size();
2011#if _LIBCPP_STD_VER > 14
2012    return *__base::begin();
2013#endif
2014}
2015
2016template <class _Tp, class _Allocator>
2017typename deque<_Tp, _Allocator>::iterator
2018deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v)
2019{
2020    size_type __pos = __p - __base::begin();
2021    size_type __to_end = __base::size() - __pos;
2022    allocator_type& __a = __base::__alloc();
2023    if (__pos < __to_end)
2024    {   // insert by shifting things backward
2025        if (__front_spare() == 0)
2026            __add_front_capacity();
2027        // __front_spare() >= 1
2028        if (__pos == 0)
2029        {
2030            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::move(__v));
2031            --__base::__start_;
2032            ++__base::size();
2033        }
2034        else
2035        {
2036            iterator __b = __base::begin();
2037            iterator __bm1 = _VSTD::prev(__b);
2038            __alloc_traits::construct(__a, _VSTD::addressof(*__bm1), _VSTD::move(*__b));
2039            --__base::__start_;
2040            ++__base::size();
2041            if (__pos > 1)
2042                __b = _VSTD::move(_VSTD::next(__b), __b + __pos, __b);
2043            *__b = _VSTD::move(__v);
2044        }
2045    }
2046    else
2047    {   // insert by shifting things forward
2048        if (__back_spare() == 0)
2049            __add_back_capacity();
2050        // __back_capacity >= 1
2051        size_type __de = __base::size() - __pos;
2052        if (__de == 0)
2053        {
2054            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::move(__v));
2055            ++__base::size();
2056        }
2057        else
2058        {
2059            iterator __e = __base::end();
2060            iterator __em1 = _VSTD::prev(__e);
2061            __alloc_traits::construct(__a, _VSTD::addressof(*__e), _VSTD::move(*__em1));
2062            ++__base::size();
2063            if (__de > 1)
2064                __e = _VSTD::move_backward(__e - __de, __em1, __e);
2065            *--__e = _VSTD::move(__v);
2066        }
2067    }
2068    return __base::begin() + __pos;
2069}
2070
2071template <class _Tp, class _Allocator>
2072template <class... _Args>
2073typename deque<_Tp, _Allocator>::iterator
2074deque<_Tp, _Allocator>::emplace(const_iterator __p, _Args&&... __args)
2075{
2076    size_type __pos = __p - __base::begin();
2077    size_type __to_end = __base::size() - __pos;
2078    allocator_type& __a = __base::__alloc();
2079    if (__pos < __to_end)
2080    {   // insert by shifting things backward
2081        if (__front_spare() == 0)
2082            __add_front_capacity();
2083        // __front_spare() >= 1
2084        if (__pos == 0)
2085        {
2086            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::forward<_Args>(__args)...);
2087            --__base::__start_;
2088            ++__base::size();
2089        }
2090        else
2091        {
2092            __temp_value<value_type, _Allocator> __tmp(this->__alloc(), _VSTD::forward<_Args>(__args)...);
2093            iterator __b = __base::begin();
2094            iterator __bm1 = _VSTD::prev(__b);
2095            __alloc_traits::construct(__a, _VSTD::addressof(*__bm1), _VSTD::move(*__b));
2096            --__base::__start_;
2097            ++__base::size();
2098            if (__pos > 1)
2099                __b = _VSTD::move(_VSTD::next(__b), __b + __pos, __b);
2100            *__b = _VSTD::move(__tmp.get());
2101        }
2102    }
2103    else
2104    {   // insert by shifting things forward
2105        if (__back_spare() == 0)
2106            __add_back_capacity();
2107        // __back_capacity >= 1
2108        size_type __de = __base::size() - __pos;
2109        if (__de == 0)
2110        {
2111            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::forward<_Args>(__args)...);
2112            ++__base::size();
2113        }
2114        else
2115        {
2116            __temp_value<value_type, _Allocator> __tmp(this->__alloc(), _VSTD::forward<_Args>(__args)...);
2117            iterator __e = __base::end();
2118            iterator __em1 = _VSTD::prev(__e);
2119            __alloc_traits::construct(__a, _VSTD::addressof(*__e), _VSTD::move(*__em1));
2120            ++__base::size();
2121            if (__de > 1)
2122                __e = _VSTD::move_backward(__e - __de, __em1, __e);
2123            *--__e = _VSTD::move(__tmp.get());
2124        }
2125    }
2126    return __base::begin() + __pos;
2127}
2128
2129#endif  // _LIBCPP_CXX03_LANG
2130
2131
2132template <class _Tp, class _Allocator>
2133typename deque<_Tp, _Allocator>::iterator
2134deque<_Tp, _Allocator>::insert(const_iterator __p, const value_type& __v)
2135{
2136    size_type __pos = __p - __base::begin();
2137    size_type __to_end = __base::size() - __pos;
2138    allocator_type& __a = __base::__alloc();
2139    if (__pos < __to_end)
2140    {   // insert by shifting things backward
2141        if (__front_spare() == 0)
2142            __add_front_capacity();
2143        // __front_spare() >= 1
2144        if (__pos == 0)
2145        {
2146            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), __v);
2147            --__base::__start_;
2148            ++__base::size();
2149        }
2150        else
2151        {
2152            const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
2153            iterator __b = __base::begin();
2154            iterator __bm1 = _VSTD::prev(__b);
2155            if (__vt == pointer_traits<const_pointer>::pointer_to(*__b))
2156                __vt = pointer_traits<const_pointer>::pointer_to(*__bm1);
2157            __alloc_traits::construct(__a, _VSTD::addressof(*__bm1), _VSTD::move(*__b));
2158            --__base::__start_;
2159            ++__base::size();
2160            if (__pos > 1)
2161                __b = __move_and_check(_VSTD::next(__b), __b + __pos, __b, __vt);
2162            *__b = *__vt;
2163        }
2164    }
2165    else
2166    {   // insert by shifting things forward
2167        if (__back_spare() == 0)
2168            __add_back_capacity();
2169        // __back_capacity >= 1
2170        size_type __de = __base::size() - __pos;
2171        if (__de == 0)
2172        {
2173            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), __v);
2174            ++__base::size();
2175        }
2176        else
2177        {
2178            const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
2179            iterator __e = __base::end();
2180            iterator __em1 = _VSTD::prev(__e);
2181            if (__vt == pointer_traits<const_pointer>::pointer_to(*__em1))
2182                __vt = pointer_traits<const_pointer>::pointer_to(*__e);
2183            __alloc_traits::construct(__a, _VSTD::addressof(*__e), _VSTD::move(*__em1));
2184            ++__base::size();
2185            if (__de > 1)
2186                __e = __move_backward_and_check(__e - __de, __em1, __e, __vt);
2187            *--__e = *__vt;
2188        }
2189    }
2190    return __base::begin() + __pos;
2191}
2192
2193template <class _Tp, class _Allocator>
2194typename deque<_Tp, _Allocator>::iterator
2195deque<_Tp, _Allocator>::insert(const_iterator __p, size_type __n, const value_type& __v)
2196{
2197    size_type __pos = __p - __base::begin();
2198    size_type __to_end = __base::size() - __pos;
2199    allocator_type& __a = __base::__alloc();
2200    if (__pos < __to_end)
2201    {   // insert by shifting things backward
2202        if (__n > __front_spare())
2203            __add_front_capacity(__n - __front_spare());
2204        // __n <= __front_spare()
2205        iterator __old_begin = __base::begin();
2206        iterator __i = __old_begin;
2207        if (__n > __pos)
2208        {
2209            for (size_type __m = __n - __pos; __m; --__m, --__base::__start_, ++__base::size())
2210                __alloc_traits::construct(__a, _VSTD::addressof(*--__i), __v);
2211            __n = __pos;
2212        }
2213        if (__n > 0)
2214        {
2215            const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
2216            iterator __obn = __old_begin + __n;
2217            __move_construct_backward_and_check(__old_begin, __obn, __i, __vt);
2218            if (__n < __pos)
2219                __old_begin = __move_and_check(__obn, __old_begin + __pos, __old_begin, __vt);
2220            _VSTD::fill_n(__old_begin, __n, *__vt);
2221        }
2222    }
2223    else
2224    {   // insert by shifting things forward
2225        size_type __back_capacity = __back_spare();
2226        if (__n > __back_capacity)
2227            __add_back_capacity(__n - __back_capacity);
2228        // __n <= __back_capacity
2229        iterator __old_end = __base::end();
2230        iterator __i = __old_end;
2231        size_type __de = __base::size() - __pos;
2232        if (__n > __de)
2233        {
2234            for (size_type __m = __n - __de; __m; --__m, ++__i, ++__base::size())
2235                __alloc_traits::construct(__a, _VSTD::addressof(*__i), __v);
2236            __n = __de;
2237        }
2238        if (__n > 0)
2239        {
2240            const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
2241            iterator __oen = __old_end - __n;
2242            __move_construct_and_check(__oen, __old_end, __i, __vt);
2243            if (__n < __de)
2244                __old_end = __move_backward_and_check(__old_end - __de, __oen, __old_end, __vt);
2245            _VSTD::fill_n(__old_end - __n, __n, *__vt);
2246        }
2247    }
2248    return __base::begin() + __pos;
2249}
2250
2251template <class _Tp, class _Allocator>
2252template <class _InputIter>
2253typename deque<_Tp, _Allocator>::iterator
2254deque<_Tp, _Allocator>::insert(const_iterator __p, _InputIter __f, _InputIter __l,
2255                               typename enable_if<__is_cpp17_input_iterator<_InputIter>::value
2256                                               &&!__is_cpp17_forward_iterator<_InputIter>::value>::type*)
2257{
2258    __split_buffer<value_type, allocator_type&> __buf(__base::__alloc());
2259    __buf.__construct_at_end(__f, __l);
2260    typedef typename __split_buffer<value_type, allocator_type&>::iterator __bi;
2261    return insert(__p, move_iterator<__bi>(__buf.begin()), move_iterator<__bi>(__buf.end()));
2262}
2263
2264template <class _Tp, class _Allocator>
2265template <class _ForwardIterator>
2266typename deque<_Tp, _Allocator>::iterator
2267deque<_Tp, _Allocator>::insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l,
2268                               typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value
2269                                               &&!__is_cpp17_bidirectional_iterator<_ForwardIterator>::value>::type*)
2270{
2271    size_type __n = _VSTD::distance(__f, __l);
2272    __split_buffer<value_type, allocator_type&> __buf(__n, 0, __base::__alloc());
2273    __buf.__construct_at_end(__f, __l);
2274    typedef typename __split_buffer<value_type, allocator_type&>::iterator __fwd;
2275    return insert(__p, move_iterator<__fwd>(__buf.begin()), move_iterator<__fwd>(__buf.end()));
2276}
2277
2278template <class _Tp, class _Allocator>
2279template <class _BiIter>
2280typename deque<_Tp, _Allocator>::iterator
2281deque<_Tp, _Allocator>::insert(const_iterator __p, _BiIter __f, _BiIter __l,
2282                               typename enable_if<__is_cpp17_bidirectional_iterator<_BiIter>::value>::type*)
2283{
2284    size_type __n = _VSTD::distance(__f, __l);
2285    size_type __pos = __p - __base::begin();
2286    size_type __to_end = __base::size() - __pos;
2287    allocator_type& __a = __base::__alloc();
2288    if (__pos < __to_end)
2289    {   // insert by shifting things backward
2290        if (__n > __front_spare())
2291            __add_front_capacity(__n - __front_spare());
2292        // __n <= __front_spare()
2293        iterator __old_begin = __base::begin();
2294        iterator __i = __old_begin;
2295        _BiIter __m = __f;
2296        if (__n > __pos)
2297        {
2298            __m = __pos < __n / 2 ? _VSTD::prev(__l, __pos) : _VSTD::next(__f, __n - __pos);
2299            for (_BiIter __j = __m; __j != __f; --__base::__start_, ++__base::size())
2300                __alloc_traits::construct(__a, _VSTD::addressof(*--__i), *--__j);
2301            __n = __pos;
2302        }
2303        if (__n > 0)
2304        {
2305            iterator __obn = __old_begin + __n;
2306            for (iterator __j = __obn; __j != __old_begin;)
2307            {
2308                __alloc_traits::construct(__a, _VSTD::addressof(*--__i), _VSTD::move(*--__j));
2309                --__base::__start_;
2310                ++__base::size();
2311            }
2312            if (__n < __pos)
2313                __old_begin = _VSTD::move(__obn, __old_begin + __pos, __old_begin);
2314            _VSTD::copy(__m, __l, __old_begin);
2315        }
2316    }
2317    else
2318    {   // insert by shifting things forward
2319        size_type __back_capacity = __back_spare();
2320        if (__n > __back_capacity)
2321            __add_back_capacity(__n - __back_capacity);
2322        // __n <= __back_capacity
2323        iterator __old_end = __base::end();
2324        iterator __i = __old_end;
2325        _BiIter __m = __l;
2326        size_type __de = __base::size() - __pos;
2327        if (__n > __de)
2328        {
2329            __m = __de < __n / 2 ? _VSTD::next(__f, __de) : _VSTD::prev(__l, __n - __de);
2330            for (_BiIter __j = __m; __j != __l; ++__i, (void) ++__j, ++__base::size())
2331                __alloc_traits::construct(__a, _VSTD::addressof(*__i), *__j);
2332            __n = __de;
2333        }
2334        if (__n > 0)
2335        {
2336            iterator __oen = __old_end - __n;
2337            for (iterator __j = __oen; __j != __old_end; ++__i, ++__j, ++__base::size())
2338                __alloc_traits::construct(__a, _VSTD::addressof(*__i), _VSTD::move(*__j));
2339            if (__n < __de)
2340                __old_end = _VSTD::move_backward(__old_end - __de, __oen, __old_end);
2341            _VSTD::copy_backward(__f, __m, __old_end);
2342        }
2343    }
2344    return __base::begin() + __pos;
2345}
2346
2347template <class _Tp, class _Allocator>
2348template <class _InpIter>
2349void
2350deque<_Tp, _Allocator>::__append(_InpIter __f, _InpIter __l,
2351                                 typename enable_if<__is_cpp17_input_iterator<_InpIter>::value &&
2352                                                   !__is_cpp17_forward_iterator<_InpIter>::value>::type*)
2353{
2354    for (; __f != __l; ++__f)
2355#ifdef _LIBCPP_CXX03_LANG
2356        push_back(*__f);
2357#else
2358        emplace_back(*__f);
2359#endif
2360}
2361
2362template <class _Tp, class _Allocator>
2363template <class _ForIter>
2364void
2365deque<_Tp, _Allocator>::__append(_ForIter __f, _ForIter __l,
2366                                 typename enable_if<__is_cpp17_forward_iterator<_ForIter>::value>::type*)
2367{
2368    size_type __n = _VSTD::distance(__f, __l);
2369    allocator_type& __a = __base::__alloc();
2370    size_type __back_capacity = __back_spare();
2371    if (__n > __back_capacity)
2372        __add_back_capacity(__n - __back_capacity);
2373    // __n <= __back_capacity
2374    for (__deque_block_range __br : __deque_range(__base::end(), __base::end() + __n)) {
2375      _ConstructTransaction __tx(this, __br);
2376      for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_, (void)++__f) {
2377        __alloc_traits::construct(__a, std::__to_address(__tx.__pos_), *__f);
2378      }
2379    }
2380}
2381
2382template <class _Tp, class _Allocator>
2383void
2384deque<_Tp, _Allocator>::__append(size_type __n)
2385{
2386    allocator_type& __a = __base::__alloc();
2387    size_type __back_capacity = __back_spare();
2388    if (__n > __back_capacity)
2389        __add_back_capacity(__n - __back_capacity);
2390    // __n <= __back_capacity
2391    for (__deque_block_range __br : __deque_range(__base::end(), __base::end() + __n)) {
2392      _ConstructTransaction __tx(this, __br);
2393      for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) {
2394        __alloc_traits::construct(__a, std::__to_address(__tx.__pos_));
2395      }
2396    }
2397}
2398
2399template <class _Tp, class _Allocator>
2400void
2401deque<_Tp, _Allocator>::__append(size_type __n, const value_type& __v)
2402{
2403    allocator_type& __a = __base::__alloc();
2404    size_type __back_capacity = __back_spare();
2405    if (__n > __back_capacity)
2406        __add_back_capacity(__n - __back_capacity);
2407    // __n <= __back_capacity
2408    for (__deque_block_range __br : __deque_range(__base::end(), __base::end() + __n)) {
2409      _ConstructTransaction __tx(this, __br);
2410      for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) {
2411        __alloc_traits::construct(__a, std::__to_address(__tx.__pos_), __v);
2412      }
2413    }
2414
2415}
2416
2417// Create front capacity for one block of elements.
2418// Strong guarantee.  Either do it or don't touch anything.
2419template <class _Tp, class _Allocator>
2420void
2421deque<_Tp, _Allocator>::__add_front_capacity()
2422{
2423    allocator_type& __a = __base::__alloc();
2424    if (__back_spare() >= __base::__block_size)
2425    {
2426        __base::__start_ += __base::__block_size;
2427        pointer __pt = __base::__map_.back();
2428        __base::__map_.pop_back();
2429        __base::__map_.push_front(__pt);
2430    }
2431    // Else if __base::__map_.size() < __base::__map_.capacity() then we need to allocate 1 buffer
2432    else if (__base::__map_.size() < __base::__map_.capacity())
2433    {   // we can put the new buffer into the map, but don't shift things around
2434        // until all buffers are allocated.  If we throw, we don't need to fix
2435        // anything up (any added buffers are undetectible)
2436        if (__base::__map_.__front_spare() > 0)
2437            __base::__map_.push_front(__alloc_traits::allocate(__a, __base::__block_size));
2438        else
2439        {
2440            __base::__map_.push_back(__alloc_traits::allocate(__a, __base::__block_size));
2441            // Done allocating, reorder capacity
2442            pointer __pt = __base::__map_.back();
2443            __base::__map_.pop_back();
2444            __base::__map_.push_front(__pt);
2445        }
2446        __base::__start_ = __base::__map_.size() == 1 ?
2447                               __base::__block_size / 2 :
2448                               __base::__start_ + __base::__block_size;
2449    }
2450    // Else need to allocate 1 buffer, *and* we need to reallocate __map_.
2451    else
2452    {
2453        __split_buffer<pointer, typename __base::__pointer_allocator&>
2454            __buf(max<size_type>(2 * __base::__map_.capacity(), 1),
2455                  0, __base::__map_.__alloc());
2456
2457        typedef __allocator_destructor<_Allocator> _Dp;
2458        unique_ptr<pointer, _Dp> __hold(
2459            __alloc_traits::allocate(__a, __base::__block_size),
2460                _Dp(__a, __base::__block_size));
2461        __buf.push_back(__hold.get());
2462        __hold.release();
2463
2464        for (typename __base::__map_pointer __i = __base::__map_.begin();
2465                __i != __base::__map_.end(); ++__i)
2466            __buf.push_back(*__i);
2467        _VSTD::swap(__base::__map_.__first_, __buf.__first_);
2468        _VSTD::swap(__base::__map_.__begin_, __buf.__begin_);
2469        _VSTD::swap(__base::__map_.__end_, __buf.__end_);
2470        _VSTD::swap(__base::__map_.__end_cap(), __buf.__end_cap());
2471        __base::__start_ = __base::__map_.size() == 1 ?
2472                               __base::__block_size / 2 :
2473                               __base::__start_ + __base::__block_size;
2474    }
2475}
2476
2477// Create front capacity for __n elements.
2478// Strong guarantee.  Either do it or don't touch anything.
2479template <class _Tp, class _Allocator>
2480void
2481deque<_Tp, _Allocator>::__add_front_capacity(size_type __n)
2482{
2483    allocator_type& __a = __base::__alloc();
2484    size_type __nb = __recommend_blocks(__n + __base::__map_.empty());
2485    // Number of unused blocks at back:
2486    size_type __back_capacity = __back_spare() / __base::__block_size;
2487    __back_capacity = _VSTD::min(__back_capacity, __nb);  // don't take more than you need
2488    __nb -= __back_capacity;  // number of blocks need to allocate
2489    // If __nb == 0, then we have sufficient capacity.
2490    if (__nb == 0)
2491    {
2492        __base::__start_ += __base::__block_size * __back_capacity;
2493        for (; __back_capacity > 0; --__back_capacity)
2494        {
2495            pointer __pt = __base::__map_.back();
2496            __base::__map_.pop_back();
2497            __base::__map_.push_front(__pt);
2498        }
2499    }
2500    // Else if __nb <= __map_.capacity() - __map_.size() then we need to allocate __nb buffers
2501    else if (__nb <= __base::__map_.capacity() - __base::__map_.size())
2502    {   // we can put the new buffers into the map, but don't shift things around
2503        // until all buffers are allocated.  If we throw, we don't need to fix
2504        // anything up (any added buffers are undetectible)
2505        for (; __nb > 0; --__nb, __base::__start_ += __base::__block_size - (__base::__map_.size() == 1))
2506        {
2507            if (__base::__map_.__front_spare() == 0)
2508                break;
2509            __base::__map_.push_front(__alloc_traits::allocate(__a, __base::__block_size));
2510        }
2511        for (; __nb > 0; --__nb, ++__back_capacity)
2512            __base::__map_.push_back(__alloc_traits::allocate(__a, __base::__block_size));
2513        // Done allocating, reorder capacity
2514        __base::__start_ += __back_capacity * __base::__block_size;
2515        for (; __back_capacity > 0; --__back_capacity)
2516        {
2517            pointer __pt = __base::__map_.back();
2518            __base::__map_.pop_back();
2519            __base::__map_.push_front(__pt);
2520        }
2521    }
2522    // Else need to allocate __nb buffers, *and* we need to reallocate __map_.
2523    else
2524    {
2525        size_type __ds = (__nb + __back_capacity) * __base::__block_size - __base::__map_.empty();
2526        __split_buffer<pointer, typename __base::__pointer_allocator&>
2527            __buf(max<size_type>(2* __base::__map_.capacity(),
2528                                 __nb + __base::__map_.size()),
2529                  0, __base::__map_.__alloc());
2530#ifndef _LIBCPP_NO_EXCEPTIONS
2531        try
2532        {
2533#endif  // _LIBCPP_NO_EXCEPTIONS
2534            for (; __nb > 0; --__nb)
2535                __buf.push_back(__alloc_traits::allocate(__a, __base::__block_size));
2536#ifndef _LIBCPP_NO_EXCEPTIONS
2537        }
2538        catch (...)
2539        {
2540            for (typename __base::__map_pointer __i = __buf.begin();
2541                    __i != __buf.end(); ++__i)
2542                __alloc_traits::deallocate(__a, *__i, __base::__block_size);
2543            throw;
2544        }
2545#endif  // _LIBCPP_NO_EXCEPTIONS
2546        for (; __back_capacity > 0; --__back_capacity)
2547        {
2548            __buf.push_back(__base::__map_.back());
2549            __base::__map_.pop_back();
2550        }
2551        for (typename __base::__map_pointer __i = __base::__map_.begin();
2552                __i != __base::__map_.end(); ++__i)
2553            __buf.push_back(*__i);
2554        _VSTD::swap(__base::__map_.__first_, __buf.__first_);
2555        _VSTD::swap(__base::__map_.__begin_, __buf.__begin_);
2556        _VSTD::swap(__base::__map_.__end_, __buf.__end_);
2557        _VSTD::swap(__base::__map_.__end_cap(), __buf.__end_cap());
2558        __base::__start_ += __ds;
2559    }
2560}
2561
2562// Create back capacity for one block of elements.
2563// Strong guarantee.  Either do it or don't touch anything.
2564template <class _Tp, class _Allocator>
2565void
2566deque<_Tp, _Allocator>::__add_back_capacity()
2567{
2568    allocator_type& __a = __base::__alloc();
2569    if (__front_spare() >= __base::__block_size)
2570    {
2571        __base::__start_ -= __base::__block_size;
2572        pointer __pt = __base::__map_.front();
2573        __base::__map_.pop_front();
2574        __base::__map_.push_back(__pt);
2575    }
2576    // Else if __nb <= __map_.capacity() - __map_.size() then we need to allocate __nb buffers
2577    else if (__base::__map_.size() < __base::__map_.capacity())
2578    {   // we can put the new buffer into the map, but don't shift things around
2579        // until it is allocated.  If we throw, we don't need to fix
2580        // anything up (any added buffers are undetectible)
2581        if (__base::__map_.__back_spare() != 0)
2582            __base::__map_.push_back(__alloc_traits::allocate(__a, __base::__block_size));
2583        else
2584        {
2585            __base::__map_.push_front(__alloc_traits::allocate(__a, __base::__block_size));
2586            // Done allocating, reorder capacity
2587            pointer __pt = __base::__map_.front();
2588            __base::__map_.pop_front();
2589            __base::__map_.push_back(__pt);
2590        }
2591    }
2592    // Else need to allocate 1 buffer, *and* we need to reallocate __map_.
2593    else
2594    {
2595        __split_buffer<pointer, typename __base::__pointer_allocator&>
2596            __buf(max<size_type>(2* __base::__map_.capacity(), 1),
2597                  __base::__map_.size(),
2598                  __base::__map_.__alloc());
2599
2600        typedef __allocator_destructor<_Allocator> _Dp;
2601        unique_ptr<pointer, _Dp> __hold(
2602            __alloc_traits::allocate(__a, __base::__block_size),
2603                _Dp(__a, __base::__block_size));
2604        __buf.push_back(__hold.get());
2605        __hold.release();
2606
2607        for (typename __base::__map_pointer __i = __base::__map_.end();
2608                __i != __base::__map_.begin();)
2609            __buf.push_front(*--__i);
2610        _VSTD::swap(__base::__map_.__first_, __buf.__first_);
2611        _VSTD::swap(__base::__map_.__begin_, __buf.__begin_);
2612        _VSTD::swap(__base::__map_.__end_, __buf.__end_);
2613        _VSTD::swap(__base::__map_.__end_cap(), __buf.__end_cap());
2614    }
2615}
2616
2617// Create back capacity for __n elements.
2618// Strong guarantee.  Either do it or don't touch anything.
2619template <class _Tp, class _Allocator>
2620void
2621deque<_Tp, _Allocator>::__add_back_capacity(size_type __n)
2622{
2623    allocator_type& __a = __base::__alloc();
2624    size_type __nb = __recommend_blocks(__n + __base::__map_.empty());
2625    // Number of unused blocks at front:
2626    size_type __front_capacity = __front_spare() / __base::__block_size;
2627    __front_capacity = _VSTD::min(__front_capacity, __nb);  // don't take more than you need
2628    __nb -= __front_capacity;  // number of blocks need to allocate
2629    // If __nb == 0, then we have sufficient capacity.
2630    if (__nb == 0)
2631    {
2632        __base::__start_ -= __base::__block_size * __front_capacity;
2633        for (; __front_capacity > 0; --__front_capacity)
2634        {
2635            pointer __pt = __base::__map_.front();
2636            __base::__map_.pop_front();
2637            __base::__map_.push_back(__pt);
2638        }
2639    }
2640    // Else if __nb <= __map_.capacity() - __map_.size() then we need to allocate __nb buffers
2641    else if (__nb <= __base::__map_.capacity() - __base::__map_.size())
2642    {   // we can put the new buffers into the map, but don't shift things around
2643        // until all buffers are allocated.  If we throw, we don't need to fix
2644        // anything up (any added buffers are undetectible)
2645        for (; __nb > 0; --__nb)
2646        {
2647            if (__base::__map_.__back_spare() == 0)
2648                break;
2649            __base::__map_.push_back(__alloc_traits::allocate(__a, __base::__block_size));
2650        }
2651        for (; __nb > 0; --__nb, ++__front_capacity, __base::__start_ +=
2652                                 __base::__block_size - (__base::__map_.size() == 1))
2653            __base::__map_.push_front(__alloc_traits::allocate(__a, __base::__block_size));
2654        // Done allocating, reorder capacity
2655        __base::__start_ -= __base::__block_size * __front_capacity;
2656        for (; __front_capacity > 0; --__front_capacity)
2657        {
2658            pointer __pt = __base::__map_.front();
2659            __base::__map_.pop_front();
2660            __base::__map_.push_back(__pt);
2661        }
2662    }
2663    // Else need to allocate __nb buffers, *and* we need to reallocate __map_.
2664    else
2665    {
2666        size_type __ds = __front_capacity * __base::__block_size;
2667        __split_buffer<pointer, typename __base::__pointer_allocator&>
2668            __buf(max<size_type>(2* __base::__map_.capacity(),
2669                                 __nb + __base::__map_.size()),
2670                  __base::__map_.size() - __front_capacity,
2671                  __base::__map_.__alloc());
2672#ifndef _LIBCPP_NO_EXCEPTIONS
2673        try
2674        {
2675#endif  // _LIBCPP_NO_EXCEPTIONS
2676            for (; __nb > 0; --__nb)
2677                __buf.push_back(__alloc_traits::allocate(__a, __base::__block_size));
2678#ifndef _LIBCPP_NO_EXCEPTIONS
2679        }
2680        catch (...)
2681        {
2682            for (typename __base::__map_pointer __i = __buf.begin();
2683                    __i != __buf.end(); ++__i)
2684                __alloc_traits::deallocate(__a, *__i, __base::__block_size);
2685            throw;
2686        }
2687#endif  // _LIBCPP_NO_EXCEPTIONS
2688        for (; __front_capacity > 0; --__front_capacity)
2689        {
2690            __buf.push_back(__base::__map_.front());
2691            __base::__map_.pop_front();
2692        }
2693        for (typename __base::__map_pointer __i = __base::__map_.end();
2694                __i != __base::__map_.begin();)
2695            __buf.push_front(*--__i);
2696        _VSTD::swap(__base::__map_.__first_, __buf.__first_);
2697        _VSTD::swap(__base::__map_.__begin_, __buf.__begin_);
2698        _VSTD::swap(__base::__map_.__end_, __buf.__end_);
2699        _VSTD::swap(__base::__map_.__end_cap(), __buf.__end_cap());
2700        __base::__start_ -= __ds;
2701    }
2702}
2703
2704template <class _Tp, class _Allocator>
2705void
2706deque<_Tp, _Allocator>::pop_front()
2707{
2708    allocator_type& __a = __base::__alloc();
2709    __alloc_traits::destroy(__a, __to_address(*(__base::__map_.begin() +
2710                                                    __base::__start_ / __base::__block_size) +
2711                                                    __base::__start_ % __base::__block_size));
2712    --__base::size();
2713    ++__base::__start_;
2714    __maybe_remove_front_spare();
2715}
2716
2717template <class _Tp, class _Allocator>
2718void
2719deque<_Tp, _Allocator>::pop_back()
2720{
2721    _LIBCPP_ASSERT(!empty(), "deque::pop_back called for empty deque");
2722    allocator_type& __a = __base::__alloc();
2723    size_type __p = __base::size() + __base::__start_ - 1;
2724    __alloc_traits::destroy(__a, __to_address(*(__base::__map_.begin() +
2725                                                    __p / __base::__block_size) +
2726                                                    __p % __base::__block_size));
2727    --__base::size();
2728    __maybe_remove_back_spare();
2729}
2730
2731// move assign [__f, __l) to [__r, __r + (__l-__f)).
2732// If __vt points into [__f, __l), then subtract (__f - __r) from __vt.
2733template <class _Tp, class _Allocator>
2734typename deque<_Tp, _Allocator>::iterator
2735deque<_Tp, _Allocator>::__move_and_check(iterator __f, iterator __l, iterator __r,
2736                                         const_pointer& __vt)
2737{
2738    // as if
2739    //   for (; __f != __l; ++__f, ++__r)
2740    //       *__r = _VSTD::move(*__f);
2741    difference_type __n = __l - __f;
2742    while (__n > 0)
2743    {
2744        pointer __fb = __f.__ptr_;
2745        pointer __fe = *__f.__m_iter_ + __base::__block_size;
2746        difference_type __bs = __fe - __fb;
2747        if (__bs > __n)
2748        {
2749            __bs = __n;
2750            __fe = __fb + __bs;
2751        }
2752        if (__fb <= __vt && __vt < __fe)
2753            __vt = (const_iterator(static_cast<__map_const_pointer>(__f.__m_iter_), __vt) -= __f - __r).__ptr_;
2754        __r = _VSTD::move(__fb, __fe, __r);
2755        __n -= __bs;
2756        __f += __bs;
2757    }
2758    return __r;
2759}
2760
2761// move assign [__f, __l) to [__r - (__l-__f), __r) backwards.
2762// If __vt points into [__f, __l), then add (__r - __l) to __vt.
2763template <class _Tp, class _Allocator>
2764typename deque<_Tp, _Allocator>::iterator
2765deque<_Tp, _Allocator>::__move_backward_and_check(iterator __f, iterator __l, iterator __r,
2766                                                  const_pointer& __vt)
2767{
2768    // as if
2769    //   while (__f != __l)
2770    //       *--__r = _VSTD::move(*--__l);
2771    difference_type __n = __l - __f;
2772    while (__n > 0)
2773    {
2774        --__l;
2775        pointer __lb = *__l.__m_iter_;
2776        pointer __le = __l.__ptr_ + 1;
2777        difference_type __bs = __le - __lb;
2778        if (__bs > __n)
2779        {
2780            __bs = __n;
2781            __lb = __le - __bs;
2782        }
2783        if (__lb <= __vt && __vt < __le)
2784            __vt = (const_iterator(static_cast<__map_const_pointer>(__l.__m_iter_), __vt) += __r - __l - 1).__ptr_;
2785        __r = _VSTD::move_backward(__lb, __le, __r);
2786        __n -= __bs;
2787        __l -= __bs - 1;
2788    }
2789    return __r;
2790}
2791
2792// move construct [__f, __l) to [__r, __r + (__l-__f)).
2793// If __vt points into [__f, __l), then add (__r - __f) to __vt.
2794template <class _Tp, class _Allocator>
2795void
2796deque<_Tp, _Allocator>::__move_construct_and_check(iterator __f, iterator __l,
2797                                                   iterator __r, const_pointer& __vt)
2798{
2799    allocator_type& __a = __base::__alloc();
2800    // as if
2801    //   for (; __f != __l; ++__r, ++__f, ++__base::size())
2802    //       __alloc_traits::construct(__a, _VSTD::addressof(*__r), _VSTD::move(*__f));
2803    difference_type __n = __l - __f;
2804    while (__n > 0)
2805    {
2806        pointer __fb = __f.__ptr_;
2807        pointer __fe = *__f.__m_iter_ + __base::__block_size;
2808        difference_type __bs = __fe - __fb;
2809        if (__bs > __n)
2810        {
2811            __bs = __n;
2812            __fe = __fb + __bs;
2813        }
2814        if (__fb <= __vt && __vt < __fe)
2815            __vt = (const_iterator(static_cast<__map_const_pointer>(__f.__m_iter_), __vt) += __r - __f).__ptr_;
2816        for (; __fb != __fe; ++__fb, ++__r, ++__base::size())
2817            __alloc_traits::construct(__a, _VSTD::addressof(*__r), _VSTD::move(*__fb));
2818        __n -= __bs;
2819        __f += __bs;
2820    }
2821}
2822
2823// move construct [__f, __l) to [__r - (__l-__f), __r) backwards.
2824// If __vt points into [__f, __l), then subtract (__l - __r) from __vt.
2825template <class _Tp, class _Allocator>
2826void
2827deque<_Tp, _Allocator>::__move_construct_backward_and_check(iterator __f, iterator __l,
2828                                                            iterator __r, const_pointer& __vt)
2829{
2830    allocator_type& __a = __base::__alloc();
2831    // as if
2832    //   for (iterator __j = __l; __j != __f;)
2833    //   {
2834    //       __alloc_traitsconstruct(__a, _VSTD::addressof(*--__r), _VSTD::move(*--__j));
2835    //       --__base::__start_;
2836    //       ++__base::size();
2837    //   }
2838    difference_type __n = __l - __f;
2839    while (__n > 0)
2840    {
2841        --__l;
2842        pointer __lb = *__l.__m_iter_;
2843        pointer __le = __l.__ptr_ + 1;
2844        difference_type __bs = __le - __lb;
2845        if (__bs > __n)
2846        {
2847            __bs = __n;
2848            __lb = __le - __bs;
2849        }
2850        if (__lb <= __vt && __vt < __le)
2851            __vt = (const_iterator(static_cast<__map_const_pointer>(__l.__m_iter_), __vt) -= __l - __r + 1).__ptr_;
2852        while (__le != __lb)
2853        {
2854            __alloc_traits::construct(__a, _VSTD::addressof(*--__r), _VSTD::move(*--__le));
2855            --__base::__start_;
2856            ++__base::size();
2857        }
2858        __n -= __bs;
2859        __l -= __bs - 1;
2860    }
2861}
2862
2863template <class _Tp, class _Allocator>
2864typename deque<_Tp, _Allocator>::iterator
2865deque<_Tp, _Allocator>::erase(const_iterator __f)
2866{
2867    iterator __b = __base::begin();
2868    difference_type __pos = __f - __b;
2869    iterator __p = __b + __pos;
2870    allocator_type& __a = __base::__alloc();
2871    if (static_cast<size_t>(__pos) <= (__base::size() - 1) / 2)
2872    {   // erase from front
2873        _VSTD::move_backward(__b, __p, _VSTD::next(__p));
2874        __alloc_traits::destroy(__a, _VSTD::addressof(*__b));
2875        --__base::size();
2876        ++__base::__start_;
2877        __maybe_remove_front_spare();
2878    }
2879    else
2880    {   // erase from back
2881        iterator __i = _VSTD::move(_VSTD::next(__p), __base::end(), __p);
2882        __alloc_traits::destroy(__a, _VSTD::addressof(*__i));
2883        --__base::size();
2884        __maybe_remove_back_spare();
2885    }
2886    return __base::begin() + __pos;
2887}
2888
2889template <class _Tp, class _Allocator>
2890typename deque<_Tp, _Allocator>::iterator
2891deque<_Tp, _Allocator>::erase(const_iterator __f, const_iterator __l)
2892{
2893    difference_type __n = __l - __f;
2894    iterator __b = __base::begin();
2895    difference_type __pos = __f - __b;
2896    iterator __p = __b + __pos;
2897    if (__n > 0)
2898    {
2899        allocator_type& __a = __base::__alloc();
2900        if (static_cast<size_t>(__pos) <= (__base::size() - __n) / 2)
2901        {   // erase from front
2902            iterator __i = _VSTD::move_backward(__b, __p, __p + __n);
2903            for (; __b != __i; ++__b)
2904                __alloc_traits::destroy(__a, _VSTD::addressof(*__b));
2905            __base::size() -= __n;
2906            __base::__start_ += __n;
2907            while (__maybe_remove_front_spare()) {
2908            }
2909        }
2910        else
2911        {   // erase from back
2912            iterator __i = _VSTD::move(__p + __n, __base::end(), __p);
2913            for (iterator __e = __base::end(); __i != __e; ++__i)
2914                __alloc_traits::destroy(__a, _VSTD::addressof(*__i));
2915            __base::size() -= __n;
2916            while (__maybe_remove_back_spare()) {
2917            }
2918        }
2919    }
2920    return __base::begin() + __pos;
2921}
2922
2923template <class _Tp, class _Allocator>
2924void
2925deque<_Tp, _Allocator>::__erase_to_end(const_iterator __f)
2926{
2927    iterator __e = __base::end();
2928    difference_type __n = __e - __f;
2929    if (__n > 0)
2930    {
2931        allocator_type& __a = __base::__alloc();
2932        iterator __b = __base::begin();
2933        difference_type __pos = __f - __b;
2934        for (iterator __p = __b + __pos; __p != __e; ++__p)
2935            __alloc_traits::destroy(__a, _VSTD::addressof(*__p));
2936        __base::size() -= __n;
2937        while (__maybe_remove_back_spare()) {
2938        }
2939    }
2940}
2941
2942template <class _Tp, class _Allocator>
2943inline
2944void
2945deque<_Tp, _Allocator>::swap(deque& __c)
2946#if _LIBCPP_STD_VER >= 14
2947        _NOEXCEPT
2948#else
2949        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
2950                    __is_nothrow_swappable<allocator_type>::value)
2951#endif
2952{
2953    __base::swap(__c);
2954}
2955
2956template <class _Tp, class _Allocator>
2957inline
2958void
2959deque<_Tp, _Allocator>::clear() _NOEXCEPT
2960{
2961    __base::clear();
2962}
2963
2964template <class _Tp, class _Allocator>
2965inline _LIBCPP_INLINE_VISIBILITY
2966bool
2967operator==(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y)
2968{
2969    const typename deque<_Tp, _Allocator>::size_type __sz = __x.size();
2970    return __sz == __y.size() && _VSTD::equal(__x.begin(), __x.end(), __y.begin());
2971}
2972
2973template <class _Tp, class _Allocator>
2974inline _LIBCPP_INLINE_VISIBILITY
2975bool
2976operator!=(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y)
2977{
2978    return !(__x == __y);
2979}
2980
2981template <class _Tp, class _Allocator>
2982inline _LIBCPP_INLINE_VISIBILITY
2983bool
2984operator< (const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y)
2985{
2986    return _VSTD::lexicographical_compare(__x.begin(), __x.end(), __y.begin(), __y.end());
2987}
2988
2989template <class _Tp, class _Allocator>
2990inline _LIBCPP_INLINE_VISIBILITY
2991bool
2992operator> (const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y)
2993{
2994    return __y < __x;
2995}
2996
2997template <class _Tp, class _Allocator>
2998inline _LIBCPP_INLINE_VISIBILITY
2999bool
3000operator>=(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y)
3001{
3002    return !(__x < __y);
3003}
3004
3005template <class _Tp, class _Allocator>
3006inline _LIBCPP_INLINE_VISIBILITY
3007bool
3008operator<=(const deque<_Tp, _Allocator>& __x, const deque<_Tp, _Allocator>& __y)
3009{
3010    return !(__y < __x);
3011}
3012
3013template <class _Tp, class _Allocator>
3014inline _LIBCPP_INLINE_VISIBILITY
3015void
3016swap(deque<_Tp, _Allocator>& __x, deque<_Tp, _Allocator>& __y)
3017    _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y)))
3018{
3019    __x.swap(__y);
3020}
3021
3022#if _LIBCPP_STD_VER > 17
3023template <class _Tp, class _Allocator, class _Up>
3024inline _LIBCPP_INLINE_VISIBILITY
3025void erase(deque<_Tp, _Allocator>& __c, const _Up& __v)
3026{ __c.erase(_VSTD::remove(__c.begin(), __c.end(), __v), __c.end()); }
3027
3028template <class _Tp, class _Allocator, class _Predicate>
3029inline _LIBCPP_INLINE_VISIBILITY
3030void erase_if(deque<_Tp, _Allocator>& __c, _Predicate __pred)
3031{ __c.erase(_VSTD::remove_if(__c.begin(), __c.end(), __pred), __c.end()); }
3032#endif
3033
3034
3035_LIBCPP_END_NAMESPACE_STD
3036
3037_LIBCPP_POP_MACROS
3038
3039#endif  // _LIBCPP_DEQUE
3040