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  1. // <forward_list.h> -*- C++ -*-
  2.  
  3. // Copyright (C) 2008-2015 Free Software Foundation, Inc.
  4. //
  5. // This file is part of the GNU ISO C++ Library.  This library is free
  6. // software; you can redistribute it and/or modify it under the
  7. // terms of the GNU General Public License as published by the
  8. // Free Software Foundation; either version 3, or (at your option)
  9. // any later version.
  10.  
  11. // This library is distributed in the hope that it will be useful,
  12. // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13. // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14. // GNU General Public License for more details.
  15.  
  16. // Under Section 7 of GPL version 3, you are granted additional
  17. // permissions described in the GCC Runtime Library Exception, version
  18. // 3.1, as published by the Free Software Foundation.
  19.  
  20. // You should have received a copy of the GNU General Public License and
  21. // a copy of the GCC Runtime Library Exception along with this program;
  22. // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23. // <http://www.gnu.org/licenses/>.
  24.  
  25. /** @file bits/forward_list.h
  26.  *  This is an internal header file, included by other library headers.
  27.  *  Do not attempt to use it directly. @headername{forward_list}
  28.  */
  29.  
  30. #ifndef _FORWARD_LIST_H
  31. #define _FORWARD_LIST_H 1
  32.  
  33. #pragma GCC system_header
  34.  
  35. #include <initializer_list>
  36. #include <bits/stl_iterator_base_types.h>
  37. #include <bits/stl_iterator.h>
  38. #include <bits/stl_algobase.h>
  39. #include <bits/stl_function.h>
  40. #include <bits/allocator.h>
  41. #include <ext/alloc_traits.h>
  42. #include <ext/aligned_buffer.h>
  43.  
  44. namespace std _GLIBCXX_VISIBILITY(default)
  45. {
  46. _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
  47.  
  48.   /**
  49.    *  @brief  A helper basic node class for %forward_list.
  50.    *          This is just a linked list with nothing inside it.
  51.    *          There are purely list shuffling utility methods here.
  52.    */
  53.   struct _Fwd_list_node_base
  54.   {
  55.     _Fwd_list_node_base() = default;
  56.  
  57.     _Fwd_list_node_base* _M_next = nullptr;
  58.  
  59.     _Fwd_list_node_base*
  60.     _M_transfer_after(_Fwd_list_node_base* __begin,
  61.                       _Fwd_list_node_base* __end) noexcept
  62.     {
  63.       _Fwd_list_node_base* __keep = __begin->_M_next;
  64.       if (__end)
  65.         {
  66.           __begin->_M_next = __end->_M_next;
  67.           __end->_M_next = _M_next;
  68.         }
  69.       else
  70.         __begin->_M_next = 0;
  71.       _M_next = __keep;
  72.       return __end;
  73.     }
  74.  
  75.     void
  76.     _M_reverse_after() noexcept
  77.     {
  78.       _Fwd_list_node_base* __tail = _M_next;
  79.       if (!__tail)
  80.         return;
  81.       while (_Fwd_list_node_base* __temp = __tail->_M_next)
  82.         {
  83.           _Fwd_list_node_base* __keep = _M_next;
  84.           _M_next = __temp;
  85.           __tail->_M_next = __temp->_M_next;
  86.           _M_next->_M_next = __keep;
  87.         }
  88.     }
  89.   };
  90.  
  91.   /**
  92.    *  @brief  A helper node class for %forward_list.
  93.    *          This is just a linked list with uninitialized storage for a
  94.    *          data value in each node.
  95.    *          There is a sorting utility method.
  96.    */
  97.   template<typename _Tp>
  98.     struct _Fwd_list_node
  99.     : public _Fwd_list_node_base
  100.     {
  101.       _Fwd_list_node() = default;
  102.  
  103.       __gnu_cxx::__aligned_buffer<_Tp> _M_storage;
  104.  
  105.       _Tp*
  106.       _M_valptr() noexcept
  107.       { return _M_storage._M_ptr(); }
  108.  
  109.       const _Tp*
  110.       _M_valptr() const noexcept
  111.       { return _M_storage._M_ptr(); }
  112.     };
  113.  
  114.   /**
  115.    *   @brief A forward_list::iterator.
  116.    *
  117.    *   All the functions are op overloads.
  118.    */
  119.   template<typename _Tp>
  120.     struct _Fwd_list_iterator
  121.     {
  122.       typedef _Fwd_list_iterator<_Tp>            _Self;
  123.       typedef _Fwd_list_node<_Tp>                _Node;
  124.  
  125.       typedef _Tp                                value_type;
  126.       typedef _Tp*                               pointer;
  127.       typedef _Tp&                               reference;
  128.       typedef ptrdiff_t                          difference_type;
  129.       typedef std::forward_iterator_tag          iterator_category;
  130.  
  131.       _Fwd_list_iterator() noexcept
  132.       : _M_node() { }
  133.  
  134.       explicit
  135.       _Fwd_list_iterator(_Fwd_list_node_base* __n) noexcept
  136.       : _M_node(__n) { }
  137.  
  138.       reference
  139.       operator*() const noexcept
  140.       { return *static_cast<_Node*>(this->_M_node)->_M_valptr(); }
  141.  
  142.       pointer
  143.       operator->() const noexcept
  144.       { return static_cast<_Node*>(this->_M_node)->_M_valptr(); }
  145.  
  146.       _Self&
  147.       operator++() noexcept
  148.       {
  149.         _M_node = _M_node->_M_next;
  150.         return *this;
  151.       }
  152.  
  153.       _Self
  154.       operator++(int) noexcept
  155.       {
  156.         _Self __tmp(*this);
  157.         _M_node = _M_node->_M_next;
  158.         return __tmp;
  159.       }
  160.  
  161.       bool
  162.       operator==(const _Self& __x) const noexcept
  163.       { return _M_node == __x._M_node; }
  164.  
  165.       bool
  166.       operator!=(const _Self& __x) const noexcept
  167.       { return _M_node != __x._M_node; }
  168.  
  169.       _Self
  170.       _M_next() const noexcept
  171.       {
  172.         if (_M_node)
  173.           return _Fwd_list_iterator(_M_node->_M_next);
  174.         else
  175.           return _Fwd_list_iterator(0);
  176.       }
  177.  
  178.       _Fwd_list_node_base* _M_node;
  179.     };
  180.  
  181.   /**
  182.    *   @brief A forward_list::const_iterator.
  183.    *
  184.    *   All the functions are op overloads.
  185.    */
  186.   template<typename _Tp>
  187.     struct _Fwd_list_const_iterator
  188.     {
  189.       typedef _Fwd_list_const_iterator<_Tp>      _Self;
  190.       typedef const _Fwd_list_node<_Tp>          _Node;
  191.       typedef _Fwd_list_iterator<_Tp>            iterator;
  192.  
  193.       typedef _Tp                                value_type;
  194.       typedef const _Tp*                         pointer;
  195.       typedef const _Tp&                         reference;
  196.       typedef ptrdiff_t                          difference_type;
  197.       typedef std::forward_iterator_tag          iterator_category;
  198.  
  199.       _Fwd_list_const_iterator() noexcept
  200.       : _M_node() { }
  201.  
  202.       explicit
  203.       _Fwd_list_const_iterator(const _Fwd_list_node_base* __n)  noexcept
  204.       : _M_node(__n) { }
  205.  
  206.       _Fwd_list_const_iterator(const iterator& __iter) noexcept
  207.       : _M_node(__iter._M_node) { }
  208.  
  209.       reference
  210.       operator*() const noexcept
  211.       { return *static_cast<_Node*>(this->_M_node)->_M_valptr(); }
  212.  
  213.       pointer
  214.       operator->() const noexcept
  215.       { return static_cast<_Node*>(this->_M_node)->_M_valptr(); }
  216.  
  217.       _Self&
  218.       operator++() noexcept
  219.       {
  220.         _M_node = _M_node->_M_next;
  221.         return *this;
  222.       }
  223.  
  224.       _Self
  225.       operator++(int) noexcept
  226.       {
  227.         _Self __tmp(*this);
  228.         _M_node = _M_node->_M_next;
  229.         return __tmp;
  230.       }
  231.  
  232.       bool
  233.       operator==(const _Self& __x) const noexcept
  234.       { return _M_node == __x._M_node; }
  235.  
  236.       bool
  237.       operator!=(const _Self& __x) const noexcept
  238.       { return _M_node != __x._M_node; }
  239.  
  240.       _Self
  241.       _M_next() const noexcept
  242.       {
  243.         if (this->_M_node)
  244.           return _Fwd_list_const_iterator(_M_node->_M_next);
  245.         else
  246.           return _Fwd_list_const_iterator(0);
  247.       }
  248.  
  249.       const _Fwd_list_node_base* _M_node;
  250.     };
  251.  
  252.   /**
  253.    *  @brief  Forward list iterator equality comparison.
  254.    */
  255.   template<typename _Tp>
  256.     inline bool
  257.     operator==(const _Fwd_list_iterator<_Tp>& __x,
  258.                const _Fwd_list_const_iterator<_Tp>& __y) noexcept
  259.     { return __x._M_node == __y._M_node; }
  260.  
  261.   /**
  262.    *  @brief  Forward list iterator inequality comparison.
  263.    */
  264.   template<typename _Tp>
  265.     inline bool
  266.     operator!=(const _Fwd_list_iterator<_Tp>& __x,
  267.                const _Fwd_list_const_iterator<_Tp>& __y) noexcept
  268.     { return __x._M_node != __y._M_node; }
  269.  
  270.   /**
  271.    *  @brief  Base class for %forward_list.
  272.    */
  273.   template<typename _Tp, typename _Alloc>
  274.     struct _Fwd_list_base
  275.     {
  276.     protected:
  277.       typedef __alloc_rebind<_Alloc, _Tp>                 _Tp_alloc_type;
  278.       typedef __alloc_rebind<_Alloc, _Fwd_list_node<_Tp>> _Node_alloc_type;
  279.       typedef __gnu_cxx::__alloc_traits<_Node_alloc_type> _Node_alloc_traits;
  280.  
  281.       struct _Fwd_list_impl
  282.       : public _Node_alloc_type
  283.       {
  284.         _Fwd_list_node_base _M_head;
  285.  
  286.         _Fwd_list_impl()
  287.         : _Node_alloc_type(), _M_head()
  288.         { }
  289.  
  290.         _Fwd_list_impl(const _Node_alloc_type& __a)
  291.         : _Node_alloc_type(__a), _M_head()
  292.         { }
  293.  
  294.         _Fwd_list_impl(_Node_alloc_type&& __a)
  295.         : _Node_alloc_type(std::move(__a)), _M_head()
  296.         { }
  297.       };
  298.  
  299.       _Fwd_list_impl _M_impl;
  300.  
  301.     public:
  302.       typedef _Fwd_list_iterator<_Tp>                 iterator;
  303.       typedef _Fwd_list_const_iterator<_Tp>           const_iterator;
  304.       typedef _Fwd_list_node<_Tp>                     _Node;
  305.  
  306.       _Node_alloc_type&
  307.       _M_get_Node_allocator() noexcept
  308.       { return *static_cast<_Node_alloc_type*>(&this->_M_impl); }
  309.  
  310.       const _Node_alloc_type&
  311.       _M_get_Node_allocator() const noexcept
  312.       { return *static_cast<const _Node_alloc_type*>(&this->_M_impl); }
  313.  
  314.       _Fwd_list_base()
  315.       : _M_impl() { }
  316.  
  317.       _Fwd_list_base(const _Node_alloc_type& __a)
  318.       : _M_impl(__a) { }
  319.  
  320.       _Fwd_list_base(_Fwd_list_base&& __lst, const _Node_alloc_type& __a);
  321.  
  322.       _Fwd_list_base(_Fwd_list_base&& __lst)
  323.       : _M_impl(std::move(__lst._M_get_Node_allocator()))
  324.       {
  325.         this->_M_impl._M_head._M_next = __lst._M_impl._M_head._M_next;
  326.         __lst._M_impl._M_head._M_next = 0;
  327.       }
  328.  
  329.       ~_Fwd_list_base()
  330.       { _M_erase_after(&_M_impl._M_head, 0); }
  331.  
  332.     protected:
  333.  
  334.       _Node*
  335.       _M_get_node()
  336.       {
  337.         auto __ptr = _Node_alloc_traits::allocate(_M_get_Node_allocator(), 1);
  338.         return std::__addressof(*__ptr);
  339.       }
  340.  
  341.       template<typename... _Args>
  342.         _Node*
  343.         _M_create_node(_Args&&... __args)
  344.         {
  345.           _Node* __node = this->_M_get_node();
  346.           __try
  347.             {
  348.               _Tp_alloc_type __a(_M_get_Node_allocator());
  349.               typedef allocator_traits<_Tp_alloc_type> _Alloc_traits;
  350.               ::new ((void*)__node) _Node;
  351.               _Alloc_traits::construct(__a, __node->_M_valptr(),
  352.                                        std::forward<_Args>(__args)...);
  353.             }
  354.           __catch(...)
  355.             {
  356.               this->_M_put_node(__node);
  357.               __throw_exception_again;
  358.             }
  359.           return __node;
  360.         }
  361.  
  362.       template<typename... _Args>
  363.         _Fwd_list_node_base*
  364.         _M_insert_after(const_iterator __pos, _Args&&... __args);
  365.  
  366.       void
  367.       _M_put_node(_Node* __p)
  368.       {
  369.         typedef typename _Node_alloc_traits::pointer _Ptr;
  370.         auto __ptr = std::pointer_traits<_Ptr>::pointer_to(*__p);
  371.         _Node_alloc_traits::deallocate(_M_get_Node_allocator(), __ptr, 1);
  372.       }
  373.  
  374.       _Fwd_list_node_base*
  375.       _M_erase_after(_Fwd_list_node_base* __pos);
  376.  
  377.       _Fwd_list_node_base*
  378.       _M_erase_after(_Fwd_list_node_base* __pos,
  379.                      _Fwd_list_node_base* __last);
  380.     };
  381.  
  382.   /**
  383.    *  @brief A standard container with linear time access to elements,
  384.    *  and fixed time insertion/deletion at any point in the sequence.
  385.    *
  386.    *  @ingroup sequences
  387.    *
  388.    *  @tparam _Tp  Type of element.
  389.    *  @tparam _Alloc  Allocator type, defaults to allocator<_Tp>.
  390.    *
  391.    *  Meets the requirements of a <a href="tables.html#65">container</a>, a
  392.    *  <a href="tables.html#67">sequence</a>, including the
  393.    *  <a href="tables.html#68">optional sequence requirements</a> with the
  394.    *  %exception of @c at and @c operator[].
  395.    *
  396.    *  This is a @e singly @e linked %list.  Traversal up the
  397.    *  %list requires linear time, but adding and removing elements (or
  398.    *  @e nodes) is done in constant time, regardless of where the
  399.    *  change takes place.  Unlike std::vector and std::deque,
  400.    *  random-access iterators are not provided, so subscripting ( @c
  401.    *  [] ) access is not allowed.  For algorithms which only need
  402.    *  sequential access, this lack makes no difference.
  403.    *
  404.    *  Also unlike the other standard containers, std::forward_list provides
  405.    *  specialized algorithms %unique to linked lists, such as
  406.    *  splicing, sorting, and in-place reversal.
  407.    */
  408.   template<typename _Tp, typename _Alloc = allocator<_Tp> >
  409.     class forward_list : private _Fwd_list_base<_Tp, _Alloc>
  410.     {
  411.     private:
  412.       typedef _Fwd_list_base<_Tp, _Alloc>                  _Base;
  413.       typedef _Fwd_list_node<_Tp>                          _Node;
  414.       typedef _Fwd_list_node_base                          _Node_base;
  415.       typedef typename _Base::_Tp_alloc_type               _Tp_alloc_type;
  416.       typedef typename _Base::_Node_alloc_type             _Node_alloc_type;
  417.       typedef typename _Base::_Node_alloc_traits           _Node_alloc_traits;
  418.       typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type>    _Alloc_traits;
  419.  
  420.     public:
  421.       // types:
  422.       typedef _Tp                                          value_type;
  423.       typedef typename _Alloc_traits::pointer              pointer;
  424.       typedef typename _Alloc_traits::const_pointer        const_pointer;
  425.       typedef value_type&                                  reference;
  426.       typedef const value_type&                            const_reference;
  427.  
  428.       typedef _Fwd_list_iterator<_Tp>                      iterator;
  429.       typedef _Fwd_list_const_iterator<_Tp>                const_iterator;
  430.       typedef std::size_t                                  size_type;
  431.       typedef std::ptrdiff_t                               difference_type;
  432.       typedef _Alloc                                       allocator_type;
  433.  
  434.       // 23.3.4.2 construct/copy/destroy:
  435.  
  436.       /**
  437.        *  @brief  Creates a %forward_list with no elements.
  438.        *  @param  __al  An allocator object.
  439.        */
  440.       explicit
  441.       forward_list(const _Alloc& __al = _Alloc())
  442.       : _Base(_Node_alloc_type(__al))
  443.       { }
  444.  
  445.       /**
  446.        *  @brief  Copy constructor with allocator argument.
  447.        *  @param  __list  Input list to copy.
  448.        *  @param  __al    An allocator object.
  449.        */
  450.       forward_list(const forward_list& __list, const _Alloc& __al)
  451.       : _Base(_Node_alloc_type(__al))
  452.       { _M_range_initialize(__list.begin(), __list.end()); }
  453.  
  454.       /**
  455.        *  @brief  Move constructor with allocator argument.
  456.        *  @param  __list  Input list to move.
  457.        *  @param  __al    An allocator object.
  458.        */
  459.       forward_list(forward_list&& __list, const _Alloc& __al)
  460.       noexcept(_Node_alloc_traits::_S_always_equal())
  461.       : _Base(std::move(__list), _Node_alloc_type(__al))
  462.       { }
  463.  
  464.       /**
  465.        *  @brief  Creates a %forward_list with default constructed elements.
  466.        *  @param  __n   The number of elements to initially create.
  467.        *  @param  __al  An allocator object.
  468.        *
  469.        *  This constructor creates the %forward_list with @a __n default
  470.        *  constructed elements.
  471.        */
  472.       explicit
  473.       forward_list(size_type __n, const _Alloc& __al = _Alloc())
  474.       : _Base(_Node_alloc_type(__al))
  475.       { _M_default_initialize(__n); }
  476.  
  477.       /**
  478.        *  @brief  Creates a %forward_list with copies of an exemplar element.
  479.        *  @param  __n      The number of elements to initially create.
  480.        *  @param  __value  An element to copy.
  481.        *  @param  __al     An allocator object.
  482.        *
  483.        *  This constructor fills the %forward_list with @a __n copies of
  484.        *  @a __value.
  485.        */
  486.       forward_list(size_type __n, const _Tp& __value,
  487.                    const _Alloc& __al = _Alloc())
  488.       : _Base(_Node_alloc_type(__al))
  489.       { _M_fill_initialize(__n, __value); }
  490.  
  491.       /**
  492.        *  @brief  Builds a %forward_list from a range.
  493.        *  @param  __first  An input iterator.
  494.        *  @param  __last   An input iterator.
  495.        *  @param  __al     An allocator object.
  496.        *
  497.        *  Create a %forward_list consisting of copies of the elements from
  498.        *  [@a __first,@a __last).  This is linear in N (where N is
  499.        *  distance(@a __first,@a __last)).
  500.        */
  501.       template<typename _InputIterator,
  502.                typename = std::_RequireInputIter<_InputIterator>>
  503.         forward_list(_InputIterator __first, _InputIterator __last,
  504.                      const _Alloc& __al = _Alloc())
  505.         : _Base(_Node_alloc_type(__al))
  506.         { _M_range_initialize(__first, __last); }
  507.  
  508.       /**
  509.        *  @brief  The %forward_list copy constructor.
  510.        *  @param  __list  A %forward_list of identical element and allocator
  511.        *                  types.
  512.        */
  513.       forward_list(const forward_list& __list)
  514.       : _Base(_Node_alloc_traits::_S_select_on_copy(
  515.                 __list._M_get_Node_allocator()))
  516.       { _M_range_initialize(__list.begin(), __list.end()); }
  517.  
  518.       /**
  519.        *  @brief  The %forward_list move constructor.
  520.        *  @param  __list  A %forward_list of identical element and allocator
  521.        *                  types.
  522.        *
  523.        *  The newly-created %forward_list contains the exact contents of @a
  524.        *  __list. The contents of @a __list are a valid, but unspecified
  525.        *  %forward_list.
  526.        */
  527.       forward_list(forward_list&& __list) noexcept
  528.       : _Base(std::move(__list)) { }
  529.  
  530.       /**
  531.        *  @brief  Builds a %forward_list from an initializer_list
  532.        *  @param  __il  An initializer_list of value_type.
  533.        *  @param  __al  An allocator object.
  534.        *
  535.        *  Create a %forward_list consisting of copies of the elements
  536.        *  in the initializer_list @a __il.  This is linear in __il.size().
  537.        */
  538.       forward_list(std::initializer_list<_Tp> __il,
  539.                    const _Alloc& __al = _Alloc())
  540.       : _Base(_Node_alloc_type(__al))
  541.       { _M_range_initialize(__il.begin(), __il.end()); }
  542.  
  543.       /**
  544.        *  @brief  The forward_list dtor.
  545.        */
  546.       ~forward_list() noexcept
  547.       { }
  548.  
  549.       /**
  550.        *  @brief  The %forward_list assignment operator.
  551.        *  @param  __list  A %forward_list of identical element and allocator
  552.        *                types.
  553.        *
  554.        *  All the elements of @a __list are copied, but unlike the copy
  555.        *  constructor, the allocator object is not copied.
  556.        */
  557.       forward_list&
  558.       operator=(const forward_list& __list);
  559.  
  560.       /**
  561.        *  @brief  The %forward_list move assignment operator.
  562.        *  @param  __list  A %forward_list of identical element and allocator
  563.        *                types.
  564.        *
  565.        *  The contents of @a __list are moved into this %forward_list
  566.        *  (without copying, if the allocators permit it).
  567.        *  @a __list is a valid, but unspecified %forward_list
  568.        */
  569.       forward_list&
  570.       operator=(forward_list&& __list)
  571.       noexcept(_Node_alloc_traits::_S_nothrow_move())
  572.       {
  573.         constexpr bool __move_storage =
  574.           _Node_alloc_traits::_S_propagate_on_move_assign()
  575.           || _Node_alloc_traits::_S_always_equal();
  576.         _M_move_assign(std::move(__list),
  577.                        integral_constant<bool, __move_storage>());
  578.         return *this;
  579.       }
  580.  
  581.       /**
  582.        *  @brief  The %forward_list initializer list assignment operator.
  583.        *  @param  __il  An initializer_list of value_type.
  584.        *
  585.        *  Replace the contents of the %forward_list with copies of the
  586.        *  elements in the initializer_list @a __il.  This is linear in
  587.        *  __il.size().
  588.        */
  589.       forward_list&
  590.       operator=(std::initializer_list<_Tp> __il)
  591.       {
  592.         assign(__il);
  593.         return *this;
  594.       }
  595.  
  596.       /**
  597.        *  @brief  Assigns a range to a %forward_list.
  598.        *  @param  __first  An input iterator.
  599.        *  @param  __last   An input iterator.
  600.        *
  601.        *  This function fills a %forward_list with copies of the elements
  602.        *  in the range [@a __first,@a __last).
  603.        *
  604.        *  Note that the assignment completely changes the %forward_list and
  605.        *  that the number of elements of the resulting %forward_list is the
  606.        *  same as the number of elements assigned.  Old data is lost.
  607.        */
  608.       template<typename _InputIterator,
  609.                typename = std::_RequireInputIter<_InputIterator>>
  610.         void
  611.         assign(_InputIterator __first, _InputIterator __last)
  612.         {
  613.           typedef is_assignable<_Tp, decltype(*__first)> __assignable;
  614.           _M_assign(__first, __last, __assignable());
  615.         }
  616.  
  617.       /**
  618.        *  @brief  Assigns a given value to a %forward_list.
  619.        *  @param  __n  Number of elements to be assigned.
  620.        *  @param  __val  Value to be assigned.
  621.        *
  622.        *  This function fills a %forward_list with @a __n copies of the
  623.        *  given value.  Note that the assignment completely changes the
  624.        *  %forward_list, and that the resulting %forward_list has __n
  625.        *  elements.  Old data is lost.
  626.        */
  627.       void
  628.       assign(size_type __n, const _Tp& __val)
  629.       { _M_assign_n(__n, __val, is_copy_assignable<_Tp>()); }
  630.  
  631.       /**
  632.        *  @brief  Assigns an initializer_list to a %forward_list.
  633.        *  @param  __il  An initializer_list of value_type.
  634.        *
  635.        *  Replace the contents of the %forward_list with copies of the
  636.        *  elements in the initializer_list @a __il.  This is linear in
  637.        *  il.size().
  638.        */
  639.       void
  640.       assign(std::initializer_list<_Tp> __il)
  641.       { assign(__il.begin(), __il.end()); }
  642.  
  643.       /// Get a copy of the memory allocation object.
  644.       allocator_type
  645.       get_allocator() const noexcept
  646.       { return allocator_type(this->_M_get_Node_allocator()); }
  647.  
  648.       // 23.3.4.3 iterators:
  649.  
  650.       /**
  651.        *  Returns a read/write iterator that points before the first element
  652.        *  in the %forward_list.  Iteration is done in ordinary element order.
  653.        */
  654.       iterator
  655.       before_begin() noexcept
  656.       { return iterator(&this->_M_impl._M_head); }
  657.  
  658.       /**
  659.        *  Returns a read-only (constant) iterator that points before the
  660.        *  first element in the %forward_list.  Iteration is done in ordinary
  661.        *  element order.
  662.        */
  663.       const_iterator
  664.       before_begin() const noexcept
  665.       { return const_iterator(&this->_M_impl._M_head); }
  666.  
  667.       /**
  668.        *  Returns a read/write iterator that points to the first element
  669.        *  in the %forward_list.  Iteration is done in ordinary element order.
  670.        */
  671.       iterator
  672.       begin() noexcept
  673.       { return iterator(this->_M_impl._M_head._M_next); }
  674.  
  675.       /**
  676.        *  Returns a read-only (constant) iterator that points to the first
  677.        *  element in the %forward_list.  Iteration is done in ordinary
  678.        *  element order.
  679.        */
  680.       const_iterator
  681.       begin() const noexcept
  682.       { return const_iterator(this->_M_impl._M_head._M_next); }
  683.  
  684.       /**
  685.        *  Returns a read/write iterator that points one past the last
  686.        *  element in the %forward_list.  Iteration is done in ordinary
  687.        *  element order.
  688.        */
  689.       iterator
  690.       end() noexcept
  691.       { return iterator(0); }
  692.  
  693.       /**
  694.        *  Returns a read-only iterator that points one past the last
  695.        *  element in the %forward_list.  Iteration is done in ordinary
  696.        *  element order.
  697.        */
  698.       const_iterator
  699.       end() const noexcept
  700.       { return const_iterator(0); }
  701.  
  702.       /**
  703.        *  Returns a read-only (constant) iterator that points to the
  704.        *  first element in the %forward_list.  Iteration is done in ordinary
  705.        *  element order.
  706.        */
  707.       const_iterator
  708.       cbegin() const noexcept
  709.       { return const_iterator(this->_M_impl._M_head._M_next); }
  710.  
  711.       /**
  712.        *  Returns a read-only (constant) iterator that points before the
  713.        *  first element in the %forward_list.  Iteration is done in ordinary
  714.        *  element order.
  715.        */
  716.       const_iterator
  717.       cbefore_begin() const noexcept
  718.       { return const_iterator(&this->_M_impl._M_head); }
  719.  
  720.       /**
  721.        *  Returns a read-only (constant) iterator that points one past
  722.        *  the last element in the %forward_list.  Iteration is done in
  723.        *  ordinary element order.
  724.        */
  725.       const_iterator
  726.       cend() const noexcept
  727.       { return const_iterator(0); }
  728.  
  729.       /**
  730.        *  Returns true if the %forward_list is empty.  (Thus begin() would
  731.        *  equal end().)
  732.        */
  733.       bool
  734.       empty() const noexcept
  735.       { return this->_M_impl._M_head._M_next == 0; }
  736.  
  737.       /**
  738.        *  Returns the largest possible number of elements of %forward_list.
  739.        */
  740.       size_type
  741.       max_size() const noexcept
  742.       { return _Node_alloc_traits::max_size(this->_M_get_Node_allocator()); }
  743.  
  744.       // 23.3.4.4 element access:
  745.  
  746.       /**
  747.        *  Returns a read/write reference to the data at the first
  748.        *  element of the %forward_list.
  749.        */
  750.       reference
  751.       front()
  752.       {
  753.         _Node* __front = static_cast<_Node*>(this->_M_impl._M_head._M_next);
  754.         return *__front->_M_valptr();
  755.       }
  756.  
  757.       /**
  758.        *  Returns a read-only (constant) reference to the data at the first
  759.        *  element of the %forward_list.
  760.        */
  761.       const_reference
  762.       front() const
  763.       {
  764.         _Node* __front = static_cast<_Node*>(this->_M_impl._M_head._M_next);
  765.         return *__front->_M_valptr();
  766.       }
  767.  
  768.       // 23.3.4.5 modifiers:
  769.  
  770.       /**
  771.        *  @brief  Constructs object in %forward_list at the front of the
  772.        *          list.
  773.        *  @param  __args  Arguments.
  774.        *
  775.        *  This function will insert an object of type Tp constructed
  776.        *  with Tp(std::forward<Args>(args)...) at the front of the list
  777.        *  Due to the nature of a %forward_list this operation can
  778.        *  be done in constant time, and does not invalidate iterators
  779.        *  and references.
  780.        */
  781.       template<typename... _Args>
  782.         void
  783.         emplace_front(_Args&&... __args)
  784.         { this->_M_insert_after(cbefore_begin(),
  785.                                 std::forward<_Args>(__args)...); }
  786.  
  787.       /**
  788.        *  @brief  Add data to the front of the %forward_list.
  789.        *  @param  __val  Data to be added.
  790.        *
  791.        *  This is a typical stack operation.  The function creates an
  792.        *  element at the front of the %forward_list and assigns the given
  793.        *  data to it.  Due to the nature of a %forward_list this operation
  794.        *  can be done in constant time, and does not invalidate iterators
  795.        *  and references.
  796.        */
  797.       void
  798.       push_front(const _Tp& __val)
  799.       { this->_M_insert_after(cbefore_begin(), __val); }
  800.  
  801.       /**
  802.        *
  803.        */
  804.       void
  805.       push_front(_Tp&& __val)
  806.       { this->_M_insert_after(cbefore_begin(), std::move(__val)); }
  807.  
  808.       /**
  809.        *  @brief  Removes first element.
  810.        *
  811.        *  This is a typical stack operation.  It shrinks the %forward_list
  812.        *  by one.  Due to the nature of a %forward_list this operation can
  813.        *  be done in constant time, and only invalidates iterators/references
  814.        *  to the element being removed.
  815.        *
  816.        *  Note that no data is returned, and if the first element's data
  817.        *  is needed, it should be retrieved before pop_front() is
  818.        *  called.
  819.        */
  820.       void
  821.       pop_front()
  822.       { this->_M_erase_after(&this->_M_impl._M_head); }
  823.  
  824.       /**
  825.        *  @brief  Constructs object in %forward_list after the specified
  826.        *          iterator.
  827.        *  @param  __pos  A const_iterator into the %forward_list.
  828.        *  @param  __args  Arguments.
  829.        *  @return  An iterator that points to the inserted data.
  830.        *
  831.        *  This function will insert an object of type T constructed
  832.        *  with T(std::forward<Args>(args)...) after the specified
  833.        *  location.  Due to the nature of a %forward_list this operation can
  834.        *  be done in constant time, and does not invalidate iterators
  835.        *  and references.
  836.        */
  837.       template<typename... _Args>
  838.         iterator
  839.         emplace_after(const_iterator __pos, _Args&&... __args)
  840.         { return iterator(this->_M_insert_after(__pos,
  841.                                           std::forward<_Args>(__args)...)); }
  842.  
  843.       /**
  844.        *  @brief  Inserts given value into %forward_list after specified
  845.        *          iterator.
  846.        *  @param  __pos  An iterator into the %forward_list.
  847.        *  @param  __val  Data to be inserted.
  848.        *  @return  An iterator that points to the inserted data.
  849.        *
  850.        *  This function will insert a copy of the given value after
  851.        *  the specified location.  Due to the nature of a %forward_list this
  852.        *  operation can be done in constant time, and does not
  853.        *  invalidate iterators and references.
  854.        */
  855.       iterator
  856.       insert_after(const_iterator __pos, const _Tp& __val)
  857.       { return iterator(this->_M_insert_after(__pos, __val)); }
  858.  
  859.       /**
  860.        *
  861.        */
  862.       iterator
  863.       insert_after(const_iterator __pos, _Tp&& __val)
  864.       { return iterator(this->_M_insert_after(__pos, std::move(__val))); }
  865.  
  866.       /**
  867.        *  @brief  Inserts a number of copies of given data into the
  868.        *          %forward_list.
  869.        *  @param  __pos  An iterator into the %forward_list.
  870.        *  @param  __n  Number of elements to be inserted.
  871.        *  @param  __val  Data to be inserted.
  872.        *  @return  An iterator pointing to the last inserted copy of
  873.        *           @a val or @a pos if @a n == 0.
  874.        *
  875.        *  This function will insert a specified number of copies of the
  876.        *  given data after the location specified by @a pos.
  877.        *
  878.        *  This operation is linear in the number of elements inserted and
  879.        *  does not invalidate iterators and references.
  880.        */
  881.       iterator
  882.       insert_after(const_iterator __pos, size_type __n, const _Tp& __val);
  883.  
  884.       /**
  885.        *  @brief  Inserts a range into the %forward_list.
  886.        *  @param  __pos  An iterator into the %forward_list.
  887.        *  @param  __first  An input iterator.
  888.        *  @param  __last   An input iterator.
  889.        *  @return  An iterator pointing to the last inserted element or
  890.        *           @a __pos if @a __first == @a __last.
  891.        *
  892.        *  This function will insert copies of the data in the range
  893.        *  [@a __first,@a __last) into the %forward_list after the
  894.        *  location specified by @a __pos.
  895.        *
  896.        *  This operation is linear in the number of elements inserted and
  897.        *  does not invalidate iterators and references.
  898.        */
  899.       template<typename _InputIterator,
  900.                typename = std::_RequireInputIter<_InputIterator>>
  901.         iterator
  902.         insert_after(const_iterator __pos,
  903.                      _InputIterator __first, _InputIterator __last);
  904.  
  905.       /**
  906.        *  @brief  Inserts the contents of an initializer_list into
  907.        *          %forward_list after the specified iterator.
  908.        *  @param  __pos  An iterator into the %forward_list.
  909.        *  @param  __il  An initializer_list of value_type.
  910.        *  @return  An iterator pointing to the last inserted element
  911.        *           or @a __pos if @a __il is empty.
  912.        *
  913.        *  This function will insert copies of the data in the
  914.        *  initializer_list @a __il into the %forward_list before the location
  915.        *  specified by @a __pos.
  916.        *
  917.        *  This operation is linear in the number of elements inserted and
  918.        *  does not invalidate iterators and references.
  919.        */
  920.       iterator
  921.       insert_after(const_iterator __pos, std::initializer_list<_Tp> __il)
  922.       { return insert_after(__pos, __il.begin(), __il.end()); }
  923.  
  924.       /**
  925.        *  @brief  Removes the element pointed to by the iterator following
  926.        *          @c pos.
  927.        *  @param  __pos  Iterator pointing before element to be erased.
  928.        *  @return  An iterator pointing to the element following the one
  929.        *           that was erased, or end() if no such element exists.
  930.        *
  931.        *  This function will erase the element at the given position and
  932.        *  thus shorten the %forward_list by one.
  933.        *
  934.        *  Due to the nature of a %forward_list this operation can be done
  935.        *  in constant time, and only invalidates iterators/references to
  936.        *  the element being removed.  The user is also cautioned that
  937.        *  this function only erases the element, and that if the element
  938.        *  is itself a pointer, the pointed-to memory is not touched in
  939.        *  any way.  Managing the pointer is the user's responsibility.
  940.        */
  941.       iterator
  942.       erase_after(const_iterator __pos)
  943.       { return iterator(this->_M_erase_after(const_cast<_Node_base*>
  944.                                              (__pos._M_node))); }
  945.  
  946.       /**
  947.        *  @brief  Remove a range of elements.
  948.        *  @param  __pos  Iterator pointing before the first element to be
  949.        *                 erased.
  950.        *  @param  __last  Iterator pointing to one past the last element to be
  951.        *                  erased.
  952.        *  @return  @ __last.
  953.        *
  954.        *  This function will erase the elements in the range
  955.        *  @a (__pos,__last) and shorten the %forward_list accordingly.
  956.        *
  957.        *  This operation is linear time in the size of the range and only
  958.        *  invalidates iterators/references to the element being removed.
  959.        *  The user is also cautioned that this function only erases the
  960.        *  elements, and that if the elements themselves are pointers, the
  961.        *  pointed-to memory is not touched in any way.  Managing the pointer
  962.        *  is the user's responsibility.
  963.        */
  964.       iterator
  965.       erase_after(const_iterator __pos, const_iterator __last)
  966.       { return iterator(this->_M_erase_after(const_cast<_Node_base*>
  967.                                              (__pos._M_node),
  968.                                              const_cast<_Node_base*>
  969.                                              (__last._M_node))); }
  970.  
  971.       /**
  972.        *  @brief  Swaps data with another %forward_list.
  973.        *  @param  __list  A %forward_list of the same element and allocator
  974.        *                  types.
  975.        *
  976.        *  This exchanges the elements between two lists in constant
  977.        *  time.  Note that the global std::swap() function is
  978.        *  specialized such that std::swap(l1,l2) will feed to this
  979.        *  function.
  980.        */
  981.       void
  982.       swap(forward_list& __list)
  983.       noexcept(_Node_alloc_traits::_S_nothrow_swap())
  984.       {
  985.         std::swap(this->_M_impl._M_head._M_next,
  986.                   __list._M_impl._M_head._M_next);
  987.         _Node_alloc_traits::_S_on_swap(this->_M_get_Node_allocator(),
  988.                                        __list._M_get_Node_allocator());
  989.       }
  990.  
  991.       /**
  992.        *  @brief Resizes the %forward_list to the specified number of
  993.        *         elements.
  994.        *  @param __sz Number of elements the %forward_list should contain.
  995.        *
  996.        *  This function will %resize the %forward_list to the specified
  997.        *  number of elements.  If the number is smaller than the
  998.        *  %forward_list's current number of elements the %forward_list
  999.        *  is truncated, otherwise the %forward_list is extended and the
  1000.        *  new elements are default constructed.
  1001.        */
  1002.       void
  1003.       resize(size_type __sz);
  1004.  
  1005.       /**
  1006.        *  @brief Resizes the %forward_list to the specified number of
  1007.        *         elements.
  1008.        *  @param __sz Number of elements the %forward_list should contain.
  1009.        *  @param __val Data with which new elements should be populated.
  1010.        *
  1011.        *  This function will %resize the %forward_list to the specified
  1012.        *  number of elements.  If the number is smaller than the
  1013.        *  %forward_list's current number of elements the %forward_list
  1014.        *  is truncated, otherwise the %forward_list is extended and new
  1015.        *  elements are populated with given data.
  1016.        */
  1017.       void
  1018.       resize(size_type __sz, const value_type& __val);
  1019.  
  1020.       /**
  1021.        *  @brief  Erases all the elements.
  1022.        *
  1023.        *  Note that this function only erases
  1024.        *  the elements, and that if the elements themselves are
  1025.        *  pointers, the pointed-to memory is not touched in any way.
  1026.        *  Managing the pointer is the user's responsibility.
  1027.        */
  1028.       void
  1029.       clear() noexcept
  1030.       { this->_M_erase_after(&this->_M_impl._M_head, 0); }
  1031.  
  1032.       // 23.3.4.6 forward_list operations:
  1033.  
  1034.       /**
  1035.        *  @brief  Insert contents of another %forward_list.
  1036.        *  @param  __pos  Iterator referencing the element to insert after.
  1037.        *  @param  __list  Source list.
  1038.        *
  1039.        *  The elements of @a list are inserted in constant time after
  1040.        *  the element referenced by @a pos.  @a list becomes an empty
  1041.        *  list.
  1042.        *
  1043.        *  Requires this != @a x.
  1044.        */
  1045.       void
  1046.       splice_after(const_iterator __pos, forward_list&& __list)
  1047.       {
  1048.         if (!__list.empty())
  1049.           _M_splice_after(__pos, __list.before_begin(), __list.end());
  1050.       }
  1051.  
  1052.       void
  1053.       splice_after(const_iterator __pos, forward_list& __list)
  1054.       { splice_after(__pos, std::move(__list)); }
  1055.  
  1056.       /**
  1057.        *  @brief  Insert element from another %forward_list.
  1058.        *  @param  __pos  Iterator referencing the element to insert after.
  1059.        *  @param  __list  Source list.
  1060.        *  @param  __i   Iterator referencing the element before the element
  1061.        *                to move.
  1062.        *
  1063.        *  Removes the element in list @a list referenced by @a i and
  1064.        *  inserts it into the current list after @a pos.
  1065.        */
  1066.       void
  1067.       splice_after(const_iterator __pos, forward_list&& __list,
  1068.                    const_iterator __i);
  1069.  
  1070.       void
  1071.       splice_after(const_iterator __pos, forward_list& __list,
  1072.                    const_iterator __i)
  1073.       { splice_after(__pos, std::move(__list), __i); }
  1074.  
  1075.       /**
  1076.        *  @brief  Insert range from another %forward_list.
  1077.        *  @param  __pos  Iterator referencing the element to insert after.
  1078.        *  @param  __list  Source list.
  1079.        *  @param  __before  Iterator referencing before the start of range
  1080.        *                    in list.
  1081.        *  @param  __last  Iterator referencing the end of range in list.
  1082.        *
  1083.        *  Removes elements in the range (__before,__last) and inserts them
  1084.        *  after @a __pos in constant time.
  1085.        *
  1086.        *  Undefined if @a __pos is in (__before,__last).
  1087.        *  @{
  1088.        */
  1089.       void
  1090.       splice_after(const_iterator __pos, forward_list&&,
  1091.                    const_iterator __before, const_iterator __last)
  1092.       { _M_splice_after(__pos, __before, __last); }
  1093.  
  1094.       void
  1095.       splice_after(const_iterator __pos, forward_list&,
  1096.                    const_iterator __before, const_iterator __last)
  1097.       { _M_splice_after(__pos, __before, __last); }
  1098.       // @}
  1099.  
  1100.       /**
  1101.        *  @brief  Remove all elements equal to value.
  1102.        *  @param  __val  The value to remove.
  1103.        *
  1104.        *  Removes every element in the list equal to @a __val.
  1105.        *  Remaining elements stay in list order.  Note that this
  1106.        *  function only erases the elements, and that if the elements
  1107.        *  themselves are pointers, the pointed-to memory is not
  1108.        *  touched in any way.  Managing the pointer is the user's
  1109.        *  responsibility.
  1110.        */
  1111.       void
  1112.       remove(const _Tp& __val);
  1113.  
  1114.       /**
  1115.        *  @brief  Remove all elements satisfying a predicate.
  1116.        *  @param  __pred  Unary predicate function or object.
  1117.        *
  1118.        *  Removes every element in the list for which the predicate
  1119.        *  returns true.  Remaining elements stay in list order.  Note
  1120.        *  that this function only erases the elements, and that if the
  1121.        *  elements themselves are pointers, the pointed-to memory is
  1122.        *  not touched in any way.  Managing the pointer is the user's
  1123.        *  responsibility.
  1124.        */
  1125.       template<typename _Pred>
  1126.         void
  1127.         remove_if(_Pred __pred);
  1128.  
  1129.       /**
  1130.        *  @brief  Remove consecutive duplicate elements.
  1131.        *
  1132.        *  For each consecutive set of elements with the same value,
  1133.        *  remove all but the first one.  Remaining elements stay in
  1134.        *  list order.  Note that this function only erases the
  1135.        *  elements, and that if the elements themselves are pointers,
  1136.        *  the pointed-to memory is not touched in any way.  Managing
  1137.        *  the pointer is the user's responsibility.
  1138.        */
  1139.       void
  1140.       unique()
  1141.       { unique(std::equal_to<_Tp>()); }
  1142.  
  1143.       /**
  1144.        *  @brief  Remove consecutive elements satisfying a predicate.
  1145.        *  @param  __binary_pred  Binary predicate function or object.
  1146.        *
  1147.        *  For each consecutive set of elements [first,last) that
  1148.        *  satisfy predicate(first,i) where i is an iterator in
  1149.        *  [first,last), remove all but the first one.  Remaining
  1150.        *  elements stay in list order.  Note that this function only
  1151.        *  erases the elements, and that if the elements themselves are
  1152.        *  pointers, the pointed-to memory is not touched in any way.
  1153.        *  Managing the pointer is the user's responsibility.
  1154.        */
  1155.       template<typename _BinPred>
  1156.         void
  1157.         unique(_BinPred __binary_pred);
  1158.  
  1159.       /**
  1160.        *  @brief  Merge sorted lists.
  1161.        *  @param  __list  Sorted list to merge.
  1162.        *
  1163.        *  Assumes that both @a list and this list are sorted according to
  1164.        *  operator<().  Merges elements of @a __list into this list in
  1165.        *  sorted order, leaving @a __list empty when complete.  Elements in
  1166.        *  this list precede elements in @a __list that are equal.
  1167.        */
  1168.       void
  1169.       merge(forward_list&& __list)
  1170.       { merge(std::move(__list), std::less<_Tp>()); }
  1171.  
  1172.       void
  1173.       merge(forward_list& __list)
  1174.       { merge(std::move(__list)); }
  1175.  
  1176.       /**
  1177.        *  @brief  Merge sorted lists according to comparison function.
  1178.        *  @param  __list  Sorted list to merge.
  1179.        *  @param  __comp Comparison function defining sort order.
  1180.        *
  1181.        *  Assumes that both @a __list and this list are sorted according to
  1182.        *  comp.  Merges elements of @a __list into this list
  1183.        *  in sorted order, leaving @a __list empty when complete.  Elements
  1184.        *  in this list precede elements in @a __list that are equivalent
  1185.        *  according to comp().
  1186.        */
  1187.       template<typename _Comp>
  1188.         void
  1189.         merge(forward_list&& __list, _Comp __comp);
  1190.  
  1191.       template<typename _Comp>
  1192.         void
  1193.         merge(forward_list& __list, _Comp __comp)
  1194.         { merge(std::move(__list), __comp); }
  1195.  
  1196.       /**
  1197.        *  @brief  Sort the elements of the list.
  1198.        *
  1199.        *  Sorts the elements of this list in NlogN time.  Equivalent
  1200.        *  elements remain in list order.
  1201.        */
  1202.       void
  1203.       sort()
  1204.       { sort(std::less<_Tp>()); }
  1205.  
  1206.       /**
  1207.        *  @brief  Sort the forward_list using a comparison function.
  1208.        *
  1209.        *  Sorts the elements of this list in NlogN time.  Equivalent
  1210.        *  elements remain in list order.
  1211.        */
  1212.       template<typename _Comp>
  1213.         void
  1214.         sort(_Comp __comp);
  1215.  
  1216.       /**
  1217.        *  @brief  Reverse the elements in list.
  1218.        *
  1219.        *  Reverse the order of elements in the list in linear time.
  1220.        */
  1221.       void
  1222.       reverse() noexcept
  1223.       { this->_M_impl._M_head._M_reverse_after(); }
  1224.  
  1225.     private:
  1226.       // Called by the range constructor to implement [23.3.4.2]/9
  1227.       template<typename _InputIterator>
  1228.         void
  1229.         _M_range_initialize(_InputIterator __first, _InputIterator __last);
  1230.  
  1231.       // Called by forward_list(n,v,a), and the range constructor when it
  1232.       // turns out to be the same thing.
  1233.       void
  1234.       _M_fill_initialize(size_type __n, const value_type& __value);
  1235.  
  1236.       // Called by splice_after and insert_after.
  1237.       iterator
  1238.       _M_splice_after(const_iterator __pos, const_iterator __before,
  1239.                       const_iterator __last);
  1240.  
  1241.       // Called by forward_list(n).
  1242.       void
  1243.       _M_default_initialize(size_type __n);
  1244.  
  1245.       // Called by resize(sz).
  1246.       void
  1247.       _M_default_insert_after(const_iterator __pos, size_type __n);
  1248.  
  1249.       // Called by operator=(forward_list&&)
  1250.       void
  1251.       _M_move_assign(forward_list&& __list, std::true_type) noexcept
  1252.       {
  1253.         clear();
  1254.         std::swap(this->_M_impl._M_head._M_next,
  1255.                   __list._M_impl._M_head._M_next);
  1256.         std::__alloc_on_move(this->_M_get_Node_allocator(),
  1257.                              __list._M_get_Node_allocator());
  1258.       }
  1259.  
  1260.       // Called by operator=(forward_list&&)
  1261.       void
  1262.       _M_move_assign(forward_list&& __list, std::false_type)
  1263.       {
  1264.         if (__list._M_get_Node_allocator() == this->_M_get_Node_allocator())
  1265.           _M_move_assign(std::move(__list), std::true_type());
  1266.         else
  1267.           // The rvalue's allocator cannot be moved, or is not equal,
  1268.           // so we need to individually move each element.
  1269.           this->assign(std::__make_move_if_noexcept_iterator(__list.begin()),
  1270.                        std::__make_move_if_noexcept_iterator(__list.end()));
  1271.       }
  1272.  
  1273.       // Called by assign(_InputIterator, _InputIterator) if _Tp is
  1274.       // CopyAssignable.
  1275.       template<typename _InputIterator>
  1276.         void
  1277.         _M_assign(_InputIterator __first, _InputIterator __last, true_type)
  1278.         {
  1279.           auto __prev = before_begin();
  1280.           auto __curr = begin();
  1281.           auto __end = end();
  1282.           while (__curr != __end && __first != __last)
  1283.             {
  1284.               *__curr = *__first;
  1285.               ++__prev;
  1286.               ++__curr;
  1287.               ++__first;
  1288.             }
  1289.           if (__first != __last)
  1290.             insert_after(__prev, __first, __last);
  1291.           else if (__curr != __end)
  1292.             erase_after(__prev, __end);
  1293.         }
  1294.  
  1295.       // Called by assign(_InputIterator, _InputIterator) if _Tp is not
  1296.       // CopyAssignable.
  1297.       template<typename _InputIterator>
  1298.         void
  1299.         _M_assign(_InputIterator __first, _InputIterator __last, false_type)
  1300.         {
  1301.           clear();
  1302.           insert_after(cbefore_begin(), __first, __last);
  1303.         }
  1304.  
  1305.       // Called by assign(size_type, const _Tp&) if Tp is CopyAssignable
  1306.       void
  1307.       _M_assign_n(size_type __n, const _Tp& __val, true_type)
  1308.       {
  1309.         auto __prev = before_begin();
  1310.         auto __curr = begin();
  1311.         auto __end = end();
  1312.         while (__curr != __end && __n > 0)
  1313.           {
  1314.             *__curr = __val;
  1315.             ++__prev;
  1316.             ++__curr;
  1317.             --__n;
  1318.           }
  1319.         if (__n > 0)
  1320.           insert_after(__prev, __n, __val);
  1321.         else if (__curr != __end)
  1322.           erase_after(__prev, __end);
  1323.       }
  1324.  
  1325.       // Called by assign(size_type, const _Tp&) if Tp is non-CopyAssignable
  1326.       void
  1327.       _M_assign_n(size_type __n, const _Tp& __val, false_type)
  1328.       {
  1329.         clear();
  1330.         insert_after(cbefore_begin(), __n, __val);
  1331.       }
  1332.     };
  1333.  
  1334.   /**
  1335.    *  @brief  Forward list equality comparison.
  1336.    *  @param  __lx  A %forward_list
  1337.    *  @param  __ly  A %forward_list of the same type as @a __lx.
  1338.    *  @return  True iff the elements of the forward lists are equal.
  1339.    *
  1340.    *  This is an equivalence relation.  It is linear in the number of
  1341.    *  elements of the forward lists.  Deques are considered equivalent
  1342.    *  if corresponding elements compare equal.
  1343.    */
  1344.   template<typename _Tp, typename _Alloc>
  1345.     bool
  1346.     operator==(const forward_list<_Tp, _Alloc>& __lx,
  1347.                const forward_list<_Tp, _Alloc>& __ly);
  1348.  
  1349.   /**
  1350.    *  @brief  Forward list ordering relation.
  1351.    *  @param  __lx  A %forward_list.
  1352.    *  @param  __ly  A %forward_list of the same type as @a __lx.
  1353.    *  @return  True iff @a __lx is lexicographically less than @a __ly.
  1354.    *
  1355.    *  This is a total ordering relation.  It is linear in the number of
  1356.    *  elements of the forward lists.  The elements must be comparable
  1357.    *  with @c <.
  1358.    *
  1359.    *  See std::lexicographical_compare() for how the determination is made.
  1360.    */
  1361.   template<typename _Tp, typename _Alloc>
  1362.     inline bool
  1363.     operator<(const forward_list<_Tp, _Alloc>& __lx,
  1364.               const forward_list<_Tp, _Alloc>& __ly)
  1365.     { return std::lexicographical_compare(__lx.cbegin(), __lx.cend(),
  1366.                                           __ly.cbegin(), __ly.cend()); }
  1367.  
  1368.   /// Based on operator==
  1369.   template<typename _Tp, typename _Alloc>
  1370.     inline bool
  1371.     operator!=(const forward_list<_Tp, _Alloc>& __lx,
  1372.                const forward_list<_Tp, _Alloc>& __ly)
  1373.     { return !(__lx == __ly); }
  1374.  
  1375.   /// Based on operator<
  1376.   template<typename _Tp, typename _Alloc>
  1377.     inline bool
  1378.     operator>(const forward_list<_Tp, _Alloc>& __lx,
  1379.               const forward_list<_Tp, _Alloc>& __ly)
  1380.     { return (__ly < __lx); }
  1381.  
  1382.   /// Based on operator<
  1383.   template<typename _Tp, typename _Alloc>
  1384.     inline bool
  1385.     operator>=(const forward_list<_Tp, _Alloc>& __lx,
  1386.                const forward_list<_Tp, _Alloc>& __ly)
  1387.     { return !(__lx < __ly); }
  1388.  
  1389.   /// Based on operator<
  1390.   template<typename _Tp, typename _Alloc>
  1391.     inline bool
  1392.     operator<=(const forward_list<_Tp, _Alloc>& __lx,
  1393.                const forward_list<_Tp, _Alloc>& __ly)
  1394.     { return !(__ly < __lx); }
  1395.  
  1396.   /// See std::forward_list::swap().
  1397.   template<typename _Tp, typename _Alloc>
  1398.     inline void
  1399.     swap(forward_list<_Tp, _Alloc>& __lx,
  1400.          forward_list<_Tp, _Alloc>& __ly)
  1401.     { __lx.swap(__ly); }
  1402.  
  1403. _GLIBCXX_END_NAMESPACE_CONTAINER
  1404. } // namespace std
  1405.  
  1406. #endif // _FORWARD_LIST_H
  1407.