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  1. // <forward_list.h> -*- C++ -*-
  2.  
  3. // Copyright (C) 2008-2013 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 <memory>
  36. #if __cplusplus >= 201103L
  37. #include <initializer_list>
  38. #endif
  39.  
  40. namespace std _GLIBCXX_VISIBILITY(default)
  41. {
  42. _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
  43.  
  44.   /**
  45.    *  @brief  A helper basic node class for %forward_list.
  46.    *          This is just a linked list with nothing inside it.
  47.    *          There are purely list shuffling utility methods here.
  48.    */
  49.   struct _Fwd_list_node_base
  50.   {
  51.     _Fwd_list_node_base() = default;
  52.  
  53.     _Fwd_list_node_base* _M_next = nullptr;
  54.  
  55.     _Fwd_list_node_base*
  56.     _M_transfer_after(_Fwd_list_node_base* __begin,
  57.                       _Fwd_list_node_base* __end)
  58.     {
  59.       _Fwd_list_node_base* __keep = __begin->_M_next;
  60.       if (__end)
  61.         {
  62.           __begin->_M_next = __end->_M_next;
  63.           __end->_M_next = _M_next;
  64.         }
  65.       else
  66.         __begin->_M_next = 0;
  67.       _M_next = __keep;
  68.       return __end;
  69.     }
  70.  
  71.     void
  72.     _M_reverse_after() noexcept
  73.     {
  74.       _Fwd_list_node_base* __tail = _M_next;
  75.       if (!__tail)
  76.         return;
  77.       while (_Fwd_list_node_base* __temp = __tail->_M_next)
  78.         {
  79.           _Fwd_list_node_base* __keep = _M_next;
  80.           _M_next = __temp;
  81.           __tail->_M_next = __temp->_M_next;
  82.           _M_next->_M_next = __keep;
  83.         }
  84.     }
  85.   };
  86.  
  87.   /**
  88.    *  @brief  A helper node class for %forward_list.
  89.    *          This is just a linked list with uninitialized storage for a
  90.    *          data value in each node.
  91.    *          There is a sorting utility method.
  92.    */
  93.   template<typename _Tp>
  94.     struct _Fwd_list_node
  95.     : public _Fwd_list_node_base
  96.     {
  97.       _Fwd_list_node() = default;
  98.  
  99.       typename aligned_storage<sizeof(_Tp), alignment_of<_Tp>::value>::type
  100.         _M_storage;
  101.  
  102.       _Tp*
  103.       _M_valptr() noexcept
  104.       {
  105.         return static_cast<_Tp*>(static_cast<void*>(&_M_storage));
  106.       }
  107.  
  108.       const _Tp*
  109.       _M_valptr() const noexcept
  110.       {
  111.         return static_cast<const _Tp*>(static_cast<const void*>(&_M_storage));
  112.       }
  113.     };
  114.  
  115.   /**
  116.    *   @brief A forward_list::iterator.
  117.    *
  118.    *   All the functions are op overloads.
  119.    */
  120.   template<typename _Tp>
  121.     struct _Fwd_list_iterator
  122.     {
  123.       typedef _Fwd_list_iterator<_Tp>            _Self;
  124.       typedef _Fwd_list_node<_Tp>                _Node;
  125.  
  126.       typedef _Tp                                value_type;
  127.       typedef _Tp*                               pointer;
  128.       typedef _Tp&                               reference;
  129.       typedef ptrdiff_t                          difference_type;
  130.       typedef std::forward_iterator_tag          iterator_category;
  131.  
  132.       _Fwd_list_iterator()
  133.       : _M_node() { }
  134.  
  135.       explicit
  136.       _Fwd_list_iterator(_Fwd_list_node_base* __n)
  137.       : _M_node(__n) { }
  138.  
  139.       reference
  140.       operator*() const
  141.       { return *static_cast<_Node*>(this->_M_node)->_M_valptr(); }
  142.  
  143.       pointer
  144.       operator->() const
  145.       { return static_cast<_Node*>(this->_M_node)->_M_valptr(); }
  146.  
  147.       _Self&
  148.       operator++()
  149.       {
  150.         _M_node = _M_node->_M_next;
  151.         return *this;
  152.       }
  153.  
  154.       _Self
  155.       operator++(int)
  156.       {
  157.         _Self __tmp(*this);
  158.         _M_node = _M_node->_M_next;
  159.         return __tmp;
  160.       }
  161.  
  162.       bool
  163.       operator==(const _Self& __x) const
  164.       { return _M_node == __x._M_node; }
  165.  
  166.       bool
  167.       operator!=(const _Self& __x) const
  168.       { return _M_node != __x._M_node; }
  169.  
  170.       _Self
  171.       _M_next() const
  172.       {
  173.         if (_M_node)
  174.           return _Fwd_list_iterator(_M_node->_M_next);
  175.         else
  176.           return _Fwd_list_iterator(0);
  177.       }
  178.  
  179.       _Fwd_list_node_base* _M_node;
  180.     };
  181.  
  182.   /**
  183.    *   @brief A forward_list::const_iterator.
  184.    *
  185.    *   All the functions are op overloads.
  186.    */
  187.   template<typename _Tp>
  188.     struct _Fwd_list_const_iterator
  189.     {
  190.       typedef _Fwd_list_const_iterator<_Tp>      _Self;
  191.       typedef const _Fwd_list_node<_Tp>          _Node;
  192.       typedef _Fwd_list_iterator<_Tp>            iterator;
  193.  
  194.       typedef _Tp                                value_type;
  195.       typedef const _Tp*                         pointer;
  196.       typedef const _Tp&                         reference;
  197.       typedef ptrdiff_t                          difference_type;
  198.       typedef std::forward_iterator_tag          iterator_category;
  199.  
  200.       _Fwd_list_const_iterator()
  201.       : _M_node() { }
  202.  
  203.       explicit
  204.       _Fwd_list_const_iterator(const _Fwd_list_node_base* __n)
  205.       : _M_node(__n) { }
  206.  
  207.       _Fwd_list_const_iterator(const iterator& __iter)
  208.       : _M_node(__iter._M_node) { }
  209.  
  210.       reference
  211.       operator*() const
  212.       { return *static_cast<_Node*>(this->_M_node)->_M_valptr(); }
  213.  
  214.       pointer
  215.       operator->() const
  216.       { return static_cast<_Node*>(this->_M_node)->_M_valptr(); }
  217.  
  218.       _Self&
  219.       operator++()
  220.       {
  221.         _M_node = _M_node->_M_next;
  222.         return *this;
  223.       }
  224.  
  225.       _Self
  226.       operator++(int)
  227.       {
  228.         _Self __tmp(*this);
  229.         _M_node = _M_node->_M_next;
  230.         return __tmp;
  231.       }
  232.  
  233.       bool
  234.       operator==(const _Self& __x) const
  235.       { return _M_node == __x._M_node; }
  236.  
  237.       bool
  238.       operator!=(const _Self& __x) const
  239.       { return _M_node != __x._M_node; }
  240.  
  241.       _Self
  242.       _M_next() const
  243.       {
  244.         if (this->_M_node)
  245.           return _Fwd_list_const_iterator(_M_node->_M_next);
  246.         else
  247.           return _Fwd_list_const_iterator(0);
  248.       }
  249.  
  250.       const _Fwd_list_node_base* _M_node;
  251.     };
  252.  
  253.   /**
  254.    *  @brief  Forward list iterator equality comparison.
  255.    */
  256.   template<typename _Tp>
  257.     inline bool
  258.     operator==(const _Fwd_list_iterator<_Tp>& __x,
  259.                const _Fwd_list_const_iterator<_Tp>& __y)
  260.     { return __x._M_node == __y._M_node; }
  261.  
  262.   /**
  263.    *  @brief  Forward list iterator inequality comparison.
  264.    */
  265.   template<typename _Tp>
  266.     inline bool
  267.     operator!=(const _Fwd_list_iterator<_Tp>& __x,
  268.                const _Fwd_list_const_iterator<_Tp>& __y)
  269.     { return __x._M_node != __y._M_node; }
  270.  
  271.   /**
  272.    *  @brief  Base class for %forward_list.
  273.    */
  274.   template<typename _Tp, typename _Alloc>
  275.     struct _Fwd_list_base
  276.     {
  277.     protected:
  278.       typedef typename __gnu_cxx::__alloc_traits<_Alloc> _Alloc_traits;
  279.       typedef typename _Alloc_traits::template rebind<_Tp>::other
  280.         _Tp_alloc_type;
  281.  
  282.       typedef typename _Alloc_traits::template
  283.         rebind<_Fwd_list_node<_Tp>>::other _Node_alloc_type;
  284.  
  285.       typedef __gnu_cxx::__alloc_traits<_Node_alloc_type> _Node_alloc_traits;
  286.  
  287.       struct _Fwd_list_impl
  288.       : public _Node_alloc_type
  289.       {
  290.         _Fwd_list_node_base _M_head;
  291.  
  292.         _Fwd_list_impl()
  293.         : _Node_alloc_type(), _M_head()
  294.         { }
  295.  
  296.         _Fwd_list_impl(const _Node_alloc_type& __a)
  297.         : _Node_alloc_type(__a), _M_head()
  298.         { }
  299.  
  300.         _Fwd_list_impl(_Node_alloc_type&& __a)
  301.         : _Node_alloc_type(std::move(__a)), _M_head()
  302.         { }
  303.       };
  304.  
  305.       _Fwd_list_impl _M_impl;
  306.  
  307.     public:
  308.       typedef _Fwd_list_iterator<_Tp>                 iterator;
  309.       typedef _Fwd_list_const_iterator<_Tp>           const_iterator;
  310.       typedef _Fwd_list_node<_Tp>                     _Node;
  311.  
  312.       _Node_alloc_type&
  313.       _M_get_Node_allocator() noexcept
  314.       { return *static_cast<_Node_alloc_type*>(&this->_M_impl); }
  315.  
  316.       const _Node_alloc_type&
  317.       _M_get_Node_allocator() const noexcept
  318.       { return *static_cast<const _Node_alloc_type*>(&this->_M_impl); }
  319.  
  320.       _Fwd_list_base()
  321.       : _M_impl() { }
  322.  
  323.       _Fwd_list_base(const _Node_alloc_type& __a)
  324.       : _M_impl(__a) { }
  325.  
  326.       _Fwd_list_base(_Fwd_list_base&& __lst, const _Node_alloc_type& __a);
  327.  
  328.       _Fwd_list_base(_Fwd_list_base&& __lst)
  329.       : _M_impl(std::move(__lst._M_get_Node_allocator()))
  330.       {
  331.         this->_M_impl._M_head._M_next = __lst._M_impl._M_head._M_next;
  332.         __lst._M_impl._M_head._M_next = 0;
  333.       }
  334.  
  335.       ~_Fwd_list_base()
  336.       { _M_erase_after(&_M_impl._M_head, 0); }
  337.  
  338.     protected:
  339.  
  340.       _Node*
  341.       _M_get_node()
  342.       { return _Node_alloc_traits::allocate(_M_get_Node_allocator(), 1); }
  343.  
  344.       template<typename... _Args>
  345.         _Node*
  346.         _M_create_node(_Args&&... __args)
  347.         {
  348.           _Node* __node = this->_M_get_node();
  349.           __try
  350.             {
  351.               _Tp_alloc_type __a(_M_get_Node_allocator());
  352.               typedef allocator_traits<_Tp_alloc_type> _Alloc_traits;
  353.               ::new ((void*)__node) _Node();
  354.               _Alloc_traits::construct(__a, __node->_M_valptr(),
  355.                                        std::forward<_Args>(__args)...);
  356.             }
  357.           __catch(...)
  358.             {
  359.               this->_M_put_node(__node);
  360.               __throw_exception_again;
  361.             }
  362.           return __node;
  363.         }
  364.  
  365.       template<typename... _Args>
  366.         _Fwd_list_node_base*
  367.         _M_insert_after(const_iterator __pos, _Args&&... __args);
  368.  
  369.       void
  370.       _M_put_node(_Node* __p)
  371.       { _Node_alloc_traits::deallocate(_M_get_Node_allocator(), __p, 1); }
  372.  
  373.       _Fwd_list_node_base*
  374.       _M_erase_after(_Fwd_list_node_base* __pos);
  375.  
  376.       _Fwd_list_node_base*
  377.       _M_erase_after(_Fwd_list_node_base* __pos,
  378.                      _Fwd_list_node_base* __last);
  379.     };
  380.  
  381.   /**
  382.    *  @brief A standard container with linear time access to elements,
  383.    *  and fixed time insertion/deletion at any point in the sequence.
  384.    *
  385.    *  @ingroup sequences
  386.    *
  387.    *  @tparam _Tp  Type of element.
  388.    *  @tparam _Alloc  Allocator type, defaults to allocator<_Tp>.
  389.    *
  390.    *  Meets the requirements of a <a href="tables.html#65">container</a>, a
  391.    *  <a href="tables.html#67">sequence</a>, including the
  392.    *  <a href="tables.html#68">optional sequence requirements</a> with the
  393.    *  %exception of @c at and @c operator[].
  394.    *
  395.    *  This is a @e singly @e linked %list.  Traversal up the
  396.    *  %list requires linear time, but adding and removing elements (or
  397.    *  @e nodes) is done in constant time, regardless of where the
  398.    *  change takes place.  Unlike std::vector and std::deque,
  399.    *  random-access iterators are not provided, so subscripting ( @c
  400.    *  [] ) access is not allowed.  For algorithms which only need
  401.    *  sequential access, this lack makes no difference.
  402.    *
  403.    *  Also unlike the other standard containers, std::forward_list provides
  404.    *  specialized algorithms %unique to linked lists, such as
  405.    *  splicing, sorting, and in-place reversal.
  406.    */
  407.   template<typename _Tp, typename _Alloc = allocator<_Tp> >
  408.     class forward_list : private _Fwd_list_base<_Tp, _Alloc>
  409.     {
  410.     private:
  411.       typedef _Fwd_list_base<_Tp, _Alloc>                  _Base;
  412.       typedef _Fwd_list_node<_Tp>                          _Node;
  413.       typedef _Fwd_list_node_base                          _Node_base;
  414.       typedef typename _Base::_Tp_alloc_type               _Tp_alloc_type;
  415.       typedef typename _Base::_Node_alloc_type             _Node_alloc_type;
  416.       typedef typename _Base::_Node_alloc_traits           _Node_alloc_traits;
  417.       typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type>    _Alloc_traits;
  418.  
  419.     public:
  420.       // types:
  421.       typedef _Tp                                          value_type;
  422.       typedef typename _Alloc_traits::pointer              pointer;
  423.       typedef typename _Alloc_traits::const_pointer        const_pointer;
  424.       typedef typename _Alloc_traits::reference            reference;
  425.       typedef typename _Alloc_traits::const_reference      const_reference;
  426.  
  427.       typedef _Fwd_list_iterator<_Tp>                      iterator;
  428.       typedef _Fwd_list_const_iterator<_Tp>                const_iterator;
  429.       typedef std::size_t                                  size_type;
  430.       typedef std::ptrdiff_t                               difference_type;
  431.       typedef _Alloc                                       allocator_type;
  432.  
  433.       // 23.3.4.2 construct/copy/destroy:
  434.  
  435.       /**
  436.        *  @brief  Creates a %forward_list with no elements.
  437.        *  @param  __al  An allocator object.
  438.        */
  439.       explicit
  440.       forward_list(const _Alloc& __al = _Alloc())
  441.       : _Base(_Node_alloc_type(__al))
  442.       { }
  443.  
  444.       /**
  445.        *  @brief  Copy constructor with allocator argument.
  446.        *  @param  __list  Input list to copy.
  447.        *  @param  __al    An allocator object.
  448.        */
  449.       forward_list(const forward_list& __list, const _Alloc& __al)
  450.       : _Base(_Node_alloc_type(__al))
  451.       { _M_range_initialize(__list.begin(), __list.end()); }
  452.  
  453.       /**
  454.        *  @brief  Move constructor with allocator argument.
  455.        *  @param  __list  Input list to move.
  456.        *  @param  __al    An allocator object.
  457.        */
  458.       forward_list(forward_list&& __list, const _Alloc& __al)
  459.       noexcept(_Node_alloc_traits::_S_always_equal())
  460.       : _Base(std::move(__list), _Node_alloc_type(__al))
  461.       { }
  462.  
  463.       /**
  464.        *  @brief  Creates a %forward_list with default constructed elements.
  465.        *  @param  __n  The number of elements to initially create.
  466.        *
  467.        *  This constructor creates the %forward_list with @a __n default
  468.        *  constructed elements.
  469.        */
  470.       explicit
  471.       forward_list(size_type __n, const _Alloc& __al = _Alloc())
  472.       : _Base(_Node_alloc_type(__al))
  473.       { _M_default_initialize(__n); }
  474.  
  475.       /**
  476.        *  @brief  Creates a %forward_list with copies of an exemplar element.
  477.        *  @param  __n      The number of elements to initially create.
  478.        *  @param  __value  An element to copy.
  479.        *  @param  __al     An allocator object.
  480.        *
  481.        *  This constructor fills the %forward_list with @a __n copies of
  482.        *  @a __value.
  483.        */
  484.       forward_list(size_type __n, const _Tp& __value,
  485.                    const _Alloc& __al = _Alloc())
  486.       : _Base(_Node_alloc_type(__al))
  487.       { _M_fill_initialize(__n, __value); }
  488.  
  489.       /**
  490.        *  @brief  Builds a %forward_list from a range.
  491.        *  @param  __first  An input iterator.
  492.        *  @param  __last   An input iterator.
  493.        *  @param  __al     An allocator object.
  494.        *
  495.        *  Create a %forward_list consisting of copies of the elements from
  496.        *  [@a __first,@a __last).  This is linear in N (where N is
  497.        *  distance(@a __first,@a __last)).
  498.        */
  499.       template<typename _InputIterator,
  500.                typename = std::_RequireInputIter<_InputIterator>>
  501.         forward_list(_InputIterator __first, _InputIterator __last,
  502.                      const _Alloc& __al = _Alloc())
  503.         : _Base(_Node_alloc_type(__al))
  504.         { _M_range_initialize(__first, __last); }
  505.  
  506.       /**
  507.        *  @brief  The %forward_list copy constructor.
  508.        *  @param  __list  A %forward_list of identical element and allocator
  509.        *                  types.
  510.        */
  511.       forward_list(const forward_list& __list)
  512.       : _Base(_Node_alloc_traits::_S_select_on_copy(
  513.                 __list._M_get_Node_allocator()))
  514.       { _M_range_initialize(__list.begin(), __list.end()); }
  515.  
  516.       /**
  517.        *  @brief  The %forward_list move constructor.
  518.        *  @param  __list  A %forward_list of identical element and allocator
  519.        *                  types.
  520.        *
  521.        *  The newly-created %forward_list contains the exact contents of @a
  522.        *  __list. The contents of @a __list are a valid, but unspecified
  523.        *  %forward_list.
  524.        */
  525.       forward_list(forward_list&& __list) noexcept
  526.       : _Base(std::move(__list)) { }
  527.  
  528.       /**
  529.        *  @brief  Builds a %forward_list from an initializer_list
  530.        *  @param  __il  An initializer_list of value_type.
  531.        *  @param  __al  An allocator object.
  532.        *
  533.        *  Create a %forward_list consisting of copies of the elements
  534.        *  in the initializer_list @a __il.  This is linear in __il.size().
  535.        */
  536.       forward_list(std::initializer_list<_Tp> __il,
  537.                    const _Alloc& __al = _Alloc())
  538.       : _Base(_Node_alloc_type(__al))
  539.       { _M_range_initialize(__il.begin(), __il.end()); }
  540.  
  541.       /**
  542.        *  @brief  The forward_list dtor.
  543.        */
  544.       ~forward_list() noexcept
  545.       { }
  546.  
  547.       /**
  548.        *  @brief  The %forward_list assignment operator.
  549.        *  @param  __list  A %forward_list of identical element and allocator
  550.        *                types.
  551.        *
  552.        *  All the elements of @a __list are copied, but unlike the copy
  553.        *  constructor, the allocator object is not copied.
  554.        */
  555.       forward_list&
  556.       operator=(const forward_list& __list);
  557.  
  558.       /**
  559.        *  @brief  The %forward_list move assignment operator.
  560.        *  @param  __list  A %forward_list of identical element and allocator
  561.        *                types.
  562.        *
  563.        *  The contents of @a __list are moved into this %forward_list
  564.        *  (without copying, if the allocators permit it).
  565.        *  @a __list is a valid, but unspecified %forward_list
  566.        */
  567.       forward_list&
  568.       operator=(forward_list&& __list)
  569.       noexcept(_Node_alloc_traits::_S_nothrow_move())
  570.       {
  571.         constexpr bool __move_storage =
  572.           _Node_alloc_traits::_S_propagate_on_move_assign()
  573.           || _Node_alloc_traits::_S_always_equal();
  574.         _M_move_assign(std::move(__list),
  575.                        integral_constant<bool, __move_storage>());
  576.         return *this;
  577.       }
  578.  
  579.       /**
  580.        *  @brief  The %forward_list initializer list assignment operator.
  581.        *  @param  __il  An initializer_list of value_type.
  582.        *
  583.        *  Replace the contents of the %forward_list with copies of the
  584.        *  elements in the initializer_list @a __il.  This is linear in
  585.        *  __il.size().
  586.        */
  587.       forward_list&
  588.       operator=(std::initializer_list<_Tp> __il)
  589.       {
  590.         assign(__il);
  591.         return *this;
  592.       }
  593.  
  594.       /**
  595.        *  @brief  Assigns a range to a %forward_list.
  596.        *  @param  __first  An input iterator.
  597.        *  @param  __last   An input iterator.
  598.        *
  599.        *  This function fills a %forward_list with copies of the elements
  600.        *  in the range [@a __first,@a __last).
  601.        *
  602.        *  Note that the assignment completely changes the %forward_list and
  603.        *  that the number of elements of the resulting %forward_list is the
  604.        *  same as the number of elements assigned.  Old data is lost.
  605.        */
  606.       template<typename _InputIterator,
  607.                typename = std::_RequireInputIter<_InputIterator>>
  608.         void
  609.         assign(_InputIterator __first, _InputIterator __last)
  610.         {
  611.           typedef is_assignable<_Tp, decltype(*__first)> __assignable;
  612.           _M_assign(__first, __last, __assignable());
  613.         }
  614.  
  615.       /**
  616.        *  @brief  Assigns a given value to a %forward_list.
  617.        *  @param  __n  Number of elements to be assigned.
  618.        *  @param  __val  Value to be assigned.
  619.        *
  620.        *  This function fills a %forward_list with @a __n copies of the
  621.        *  given value.  Note that the assignment completely changes the
  622.        *  %forward_list, and that the resulting %forward_list has __n
  623.        *  elements.  Old data is lost.
  624.        */
  625.       void
  626.       assign(size_type __n, const _Tp& __val)
  627.       { _M_assign_n(__n, __val, is_copy_assignable<_Tp>()); }
  628.  
  629.       /**
  630.        *  @brief  Assigns an initializer_list to a %forward_list.
  631.        *  @param  __il  An initializer_list of value_type.
  632.        *
  633.        *  Replace the contents of the %forward_list with copies of the
  634.        *  elements in the initializer_list @a __il.  This is linear in
  635.        *  il.size().
  636.        */
  637.       void
  638.       assign(std::initializer_list<_Tp> __il)
  639.       { assign(__il.begin(), __il.end()); }
  640.  
  641.       /// Get a copy of the memory allocation object.
  642.       allocator_type
  643.       get_allocator() const noexcept
  644.       { return allocator_type(this->_M_get_Node_allocator()); }
  645.  
  646.       // 23.3.4.3 iterators:
  647.  
  648.       /**
  649.        *  Returns a read/write iterator that points before the first element
  650.        *  in the %forward_list.  Iteration is done in ordinary element order.
  651.        */
  652.       iterator
  653.       before_begin() noexcept
  654.       { return iterator(&this->_M_impl._M_head); }
  655.  
  656.       /**
  657.        *  Returns a read-only (constant) iterator that points before the
  658.        *  first element in the %forward_list.  Iteration is done in ordinary
  659.        *  element order.
  660.        */
  661.       const_iterator
  662.       before_begin() const noexcept
  663.       { return const_iterator(&this->_M_impl._M_head); }
  664.  
  665.       /**
  666.        *  Returns a read/write iterator that points to the first element
  667.        *  in the %forward_list.  Iteration is done in ordinary element order.
  668.        */
  669.       iterator
  670.       begin() noexcept
  671.       { return iterator(this->_M_impl._M_head._M_next); }
  672.  
  673.       /**
  674.        *  Returns a read-only (constant) iterator that points to the first
  675.        *  element in the %forward_list.  Iteration is done in ordinary
  676.        *  element order.
  677.        */
  678.       const_iterator
  679.       begin() const noexcept
  680.       { return const_iterator(this->_M_impl._M_head._M_next); }
  681.  
  682.       /**
  683.        *  Returns a read/write iterator that points one past the last
  684.        *  element in the %forward_list.  Iteration is done in ordinary
  685.        *  element order.
  686.        */
  687.       iterator
  688.       end() noexcept
  689.       { return iterator(0); }
  690.  
  691.       /**
  692.        *  Returns a read-only iterator that points one past the last
  693.        *  element in the %forward_list.  Iteration is done in ordinary
  694.        *  element order.
  695.        */
  696.       const_iterator
  697.       end() const noexcept
  698.       { return const_iterator(0); }
  699.  
  700.       /**
  701.        *  Returns a read-only (constant) iterator that points to the
  702.        *  first element in the %forward_list.  Iteration is done in ordinary
  703.        *  element order.
  704.        */
  705.       const_iterator
  706.       cbegin() const noexcept
  707.       { return const_iterator(this->_M_impl._M_head._M_next); }
  708.  
  709.       /**
  710.        *  Returns a read-only (constant) iterator that points before the
  711.        *  first element in the %forward_list.  Iteration is done in ordinary
  712.        *  element order.
  713.        */
  714.       const_iterator
  715.       cbefore_begin() const noexcept
  716.       { return const_iterator(&this->_M_impl._M_head); }
  717.  
  718.       /**
  719.        *  Returns a read-only (constant) iterator that points one past
  720.        *  the last element in the %forward_list.  Iteration is done in
  721.        *  ordinary element order.
  722.        */
  723.       const_iterator
  724.       cend() const noexcept
  725.       { return const_iterator(0); }
  726.  
  727.       /**
  728.        *  Returns true if the %forward_list is empty.  (Thus begin() would
  729.        *  equal end().)
  730.        */
  731.       bool
  732.       empty() const noexcept
  733.       { return this->_M_impl._M_head._M_next == 0; }
  734.  
  735.       /**
  736.        *  Returns the largest possible number of elements of %forward_list.
  737.        */
  738.       size_type
  739.       max_size() const noexcept
  740.       { return _Node_alloc_traits::max_size(this->_M_get_Node_allocator()); }
  741.  
  742.       // 23.3.4.4 element access:
  743.  
  744.       /**
  745.        *  Returns a read/write reference to the data at the first
  746.        *  element of the %forward_list.
  747.        */
  748.       reference
  749.       front()
  750.       {
  751.         _Node* __front = static_cast<_Node*>(this->_M_impl._M_head._M_next);
  752.         return *__front->_M_valptr();
  753.       }
  754.  
  755.       /**
  756.        *  Returns a read-only (constant) reference to the data at the first
  757.        *  element of the %forward_list.
  758.        */
  759.       const_reference
  760.       front() const
  761.       {
  762.         _Node* __front = static_cast<_Node*>(this->_M_impl._M_head._M_next);
  763.         return *__front->_M_valptr();
  764.       }
  765.  
  766.       // 23.3.4.5 modifiers:
  767.  
  768.       /**
  769.        *  @brief  Constructs object in %forward_list at the front of the
  770.        *          list.
  771.        *  @param  __args  Arguments.
  772.        *
  773.        *  This function will insert an object of type Tp constructed
  774.        *  with Tp(std::forward<Args>(args)...) at the front of the list
  775.        *  Due to the nature of a %forward_list this operation can
  776.        *  be done in constant time, and does not invalidate iterators
  777.        *  and references.
  778.        */
  779.       template<typename... _Args>
  780.         void
  781.         emplace_front(_Args&&... __args)
  782.         { this->_M_insert_after(cbefore_begin(),
  783.                                 std::forward<_Args>(__args)...); }
  784.  
  785.       /**
  786.        *  @brief  Add data to the front of the %forward_list.
  787.        *  @param  __val  Data to be added.
  788.        *
  789.        *  This is a typical stack operation.  The function creates an
  790.        *  element at the front of the %forward_list and assigns the given
  791.        *  data to it.  Due to the nature of a %forward_list this operation
  792.        *  can be done in constant time, and does not invalidate iterators
  793.        *  and references.
  794.        */
  795.       void
  796.       push_front(const _Tp& __val)
  797.       { this->_M_insert_after(cbefore_begin(), __val); }
  798.  
  799.       /**
  800.        *
  801.        */
  802.       void
  803.       push_front(_Tp&& __val)
  804.       { this->_M_insert_after(cbefore_begin(), std::move(__val)); }
  805.  
  806.       /**
  807.        *  @brief  Removes first element.
  808.        *
  809.        *  This is a typical stack operation.  It shrinks the %forward_list
  810.        *  by one.  Due to the nature of a %forward_list this operation can
  811.        *  be done in constant time, and only invalidates iterators/references
  812.        *  to the element being removed.
  813.        *
  814.        *  Note that no data is returned, and if the first element's data
  815.        *  is needed, it should be retrieved before pop_front() is
  816.        *  called.
  817.        */
  818.       void
  819.       pop_front()
  820.       { this->_M_erase_after(&this->_M_impl._M_head); }
  821.  
  822.       /**
  823.        *  @brief  Constructs object in %forward_list after the specified
  824.        *          iterator.
  825.        *  @param  __pos  A const_iterator into the %forward_list.
  826.        *  @param  __args  Arguments.
  827.        *  @return  An iterator that points to the inserted data.
  828.        *
  829.        *  This function will insert an object of type T constructed
  830.        *  with T(std::forward<Args>(args)...) after the specified
  831.        *  location.  Due to the nature of a %forward_list this operation can
  832.        *  be done in constant time, and does not invalidate iterators
  833.        *  and references.
  834.        */
  835.       template<typename... _Args>
  836.         iterator
  837.         emplace_after(const_iterator __pos, _Args&&... __args)
  838.         { return iterator(this->_M_insert_after(__pos,
  839.                                           std::forward<_Args>(__args)...)); }
  840.  
  841.       /**
  842.        *  @brief  Inserts given value into %forward_list after specified
  843.        *          iterator.
  844.        *  @param  __pos  An iterator into the %forward_list.
  845.        *  @param  __val  Data to be inserted.
  846.        *  @return  An iterator that points to the inserted data.
  847.        *
  848.        *  This function will insert a copy of the given value after
  849.        *  the specified location.  Due to the nature of a %forward_list this
  850.        *  operation can be done in constant time, and does not
  851.        *  invalidate iterators and references.
  852.        */
  853.       iterator
  854.       insert_after(const_iterator __pos, const _Tp& __val)
  855.       { return iterator(this->_M_insert_after(__pos, __val)); }
  856.  
  857.       /**
  858.        *
  859.        */
  860.       iterator
  861.       insert_after(const_iterator __pos, _Tp&& __val)
  862.       { return iterator(this->_M_insert_after(__pos, std::move(__val))); }
  863.  
  864.       /**
  865.        *  @brief  Inserts a number of copies of given data into the
  866.        *          %forward_list.
  867.        *  @param  __pos  An iterator into the %forward_list.
  868.        *  @param  __n  Number of elements to be inserted.
  869.        *  @param  __val  Data to be inserted.
  870.        *  @return  An iterator pointing to the last inserted copy of
  871.        *           @a val or @a pos if @a n == 0.
  872.        *
  873.        *  This function will insert a specified number of copies of the
  874.        *  given data after the location specified by @a pos.
  875.        *
  876.        *  This operation is linear in the number of elements inserted and
  877.        *  does not invalidate iterators and references.
  878.        */
  879.       iterator
  880.       insert_after(const_iterator __pos, size_type __n, const _Tp& __val);
  881.  
  882.       /**
  883.        *  @brief  Inserts a range into the %forward_list.
  884.        *  @param  __pos  An iterator into the %forward_list.
  885.        *  @param  __first  An input iterator.
  886.        *  @param  __last   An input iterator.
  887.        *  @return  An iterator pointing to the last inserted element or
  888.        *           @a __pos if @a __first == @a __last.
  889.        *
  890.        *  This function will insert copies of the data in the range
  891.        *  [@a __first,@a __last) into the %forward_list after the
  892.        *  location specified by @a __pos.
  893.        *
  894.        *  This operation is linear in the number of elements inserted and
  895.        *  does not invalidate iterators and references.
  896.        */
  897.       template<typename _InputIterator,
  898.                typename = std::_RequireInputIter<_InputIterator>>
  899.         iterator
  900.         insert_after(const_iterator __pos,
  901.                      _InputIterator __first, _InputIterator __last);
  902.  
  903.       /**
  904.        *  @brief  Inserts the contents of an initializer_list into
  905.        *          %forward_list after the specified iterator.
  906.        *  @param  __pos  An iterator into the %forward_list.
  907.        *  @param  __il  An initializer_list of value_type.
  908.        *  @return  An iterator pointing to the last inserted element
  909.        *           or @a __pos if @a __il is empty.
  910.        *
  911.        *  This function will insert copies of the data in the
  912.        *  initializer_list @a __il into the %forward_list before the location
  913.        *  specified by @a __pos.
  914.        *
  915.        *  This operation is linear in the number of elements inserted and
  916.        *  does not invalidate iterators and references.
  917.        */
  918.       iterator
  919.       insert_after(const_iterator __pos, std::initializer_list<_Tp> __il)
  920.       { return insert_after(__pos, __il.begin(), __il.end()); }
  921.  
  922.       /**
  923.        *  @brief  Removes the element pointed to by the iterator following
  924.        *          @c pos.
  925.        *  @param  __pos  Iterator pointing before element to be erased.
  926.        *  @return  An iterator pointing to the element following the one
  927.        *           that was erased, or end() if no such element exists.
  928.        *
  929.        *  This function will erase the element at the given position and
  930.        *  thus shorten the %forward_list by one.
  931.        *
  932.        *  Due to the nature of a %forward_list this operation can be done
  933.        *  in constant time, and only invalidates iterators/references to
  934.        *  the element being removed.  The user is also cautioned that
  935.        *  this function only erases the element, and that if the element
  936.        *  is itself a pointer, the pointed-to memory is not touched in
  937.        *  any way.  Managing the pointer is the user's responsibility.
  938.        */
  939.       iterator
  940.       erase_after(const_iterator __pos)
  941.       { return iterator(this->_M_erase_after(const_cast<_Node_base*>
  942.                                              (__pos._M_node))); }
  943.  
  944.       /**
  945.        *  @brief  Remove a range of elements.
  946.        *  @param  __pos  Iterator pointing before the first element to be
  947.        *                 erased.
  948.        *  @param  __last  Iterator pointing to one past the last element to be
  949.        *                  erased.
  950.        *  @return  @ __last.
  951.        *
  952.        *  This function will erase the elements in the range
  953.        *  @a (__pos,__last) and shorten the %forward_list accordingly.
  954.        *
  955.        *  This operation is linear time in the size of the range and only
  956.        *  invalidates iterators/references to the element being removed.
  957.        *  The user is also cautioned that this function only erases the
  958.        *  elements, and that if the elements themselves are pointers, the
  959.        *  pointed-to memory is not touched in any way.  Managing the pointer
  960.        *  is the user's responsibility.
  961.        */
  962.       iterator
  963.       erase_after(const_iterator __pos, const_iterator __last)
  964.       { return iterator(this->_M_erase_after(const_cast<_Node_base*>
  965.                                              (__pos._M_node),
  966.                                              const_cast<_Node_base*>
  967.                                              (__last._M_node))); }
  968.  
  969.       /**
  970.        *  @brief  Swaps data with another %forward_list.
  971.        *  @param  __list  A %forward_list of the same element and allocator
  972.        *                  types.
  973.        *
  974.        *  This exchanges the elements between two lists in constant
  975.        *  time.  Note that the global std::swap() function is
  976.        *  specialized such that std::swap(l1,l2) will feed to this
  977.        *  function.
  978.        */
  979.       void
  980.       swap(forward_list& __list)
  981.       noexcept(_Node_alloc_traits::_S_nothrow_swap())
  982.       {
  983.         std::swap(this->_M_impl._M_head._M_next,
  984.                   __list._M_impl._M_head._M_next);
  985.         _Node_alloc_traits::_S_on_swap(this->_M_get_Node_allocator(),
  986.                                        __list._M_get_Node_allocator());
  987.       }
  988.  
  989.       /**
  990.        *  @brief Resizes the %forward_list to the specified number of
  991.        *         elements.
  992.        *  @param __sz Number of elements the %forward_list should contain.
  993.        *
  994.        *  This function will %resize the %forward_list to the specified
  995.        *  number of elements.  If the number is smaller than the
  996.        *  %forward_list's current number of elements the %forward_list
  997.        *  is truncated, otherwise the %forward_list is extended and the
  998.        *  new elements are default constructed.
  999.        */
  1000.       void
  1001.       resize(size_type __sz);
  1002.  
  1003.       /**
  1004.        *  @brief Resizes the %forward_list to the specified number of
  1005.        *         elements.
  1006.        *  @param __sz Number of elements the %forward_list should contain.
  1007.        *  @param __val Data with which new elements should be populated.
  1008.        *
  1009.        *  This function will %resize the %forward_list to the specified
  1010.        *  number of elements.  If the number is smaller than the
  1011.        *  %forward_list's current number of elements the %forward_list
  1012.        *  is truncated, otherwise the %forward_list is extended and new
  1013.        *  elements are populated with given data.
  1014.        */
  1015.       void
  1016.       resize(size_type __sz, const value_type& __val);
  1017.  
  1018.       /**
  1019.        *  @brief  Erases all the elements.
  1020.        *
  1021.        *  Note that this function only erases
  1022.        *  the elements, and that if the elements themselves are
  1023.        *  pointers, the pointed-to memory is not touched in any way.
  1024.        *  Managing the pointer is the user's responsibility.
  1025.        */
  1026.       void
  1027.       clear() noexcept
  1028.       { this->_M_erase_after(&this->_M_impl._M_head, 0); }
  1029.  
  1030.       // 23.3.4.6 forward_list operations:
  1031.  
  1032.       /**
  1033.        *  @brief  Insert contents of another %forward_list.
  1034.        *  @param  __pos  Iterator referencing the element to insert after.
  1035.        *  @param  __list  Source list.
  1036.        *
  1037.        *  The elements of @a list are inserted in constant time after
  1038.        *  the element referenced by @a pos.  @a list becomes an empty
  1039.        *  list.
  1040.        *
  1041.        *  Requires this != @a x.
  1042.        */
  1043.       void
  1044.       splice_after(const_iterator __pos, forward_list&& __list)
  1045.       {
  1046.         if (!__list.empty())
  1047.           _M_splice_after(__pos, __list.before_begin(), __list.end());
  1048.       }
  1049.  
  1050.       void
  1051.       splice_after(const_iterator __pos, forward_list& __list)
  1052.       { splice_after(__pos, std::move(__list)); }
  1053.  
  1054.       /**
  1055.        *  @brief  Insert element from another %forward_list.
  1056.        *  @param  __pos  Iterator referencing the element to insert after.
  1057.        *  @param  __list  Source list.
  1058.        *  @param  __i   Iterator referencing the element before the element
  1059.        *                to move.
  1060.        *
  1061.        *  Removes the element in list @a list referenced by @a i and
  1062.        *  inserts it into the current list after @a pos.
  1063.        */
  1064.       void
  1065.       splice_after(const_iterator __pos, forward_list&& __list,
  1066.                    const_iterator __i);
  1067.  
  1068.       void
  1069.       splice_after(const_iterator __pos, forward_list& __list,
  1070.                    const_iterator __i)
  1071.       { splice_after(__pos, std::move(__list), __i); }
  1072.  
  1073.       /**
  1074.        *  @brief  Insert range from another %forward_list.
  1075.        *  @param  __pos  Iterator referencing the element to insert after.
  1076.        *  @param  __list  Source list.
  1077.        *  @param  __before  Iterator referencing before the start of range
  1078.        *                    in list.
  1079.        *  @param  __last  Iterator referencing the end of range in list.
  1080.        *
  1081.        *  Removes elements in the range (__before,__last) and inserts them
  1082.        *  after @a __pos in constant time.
  1083.        *
  1084.        *  Undefined if @a __pos is in (__before,__last).
  1085.        */
  1086.       void
  1087.       splice_after(const_iterator __pos, forward_list&&,
  1088.                    const_iterator __before, const_iterator __last)
  1089.       { _M_splice_after(__pos, __before, __last); }
  1090.  
  1091.       void
  1092.       splice_after(const_iterator __pos, forward_list&,
  1093.                    const_iterator __before, const_iterator __last)
  1094.       { _M_splice_after(__pos, __before, __last); }
  1095.  
  1096.       /**
  1097.        *  @brief  Remove all elements equal to value.
  1098.        *  @param  __val  The value to remove.
  1099.        *
  1100.        *  Removes every element in the list equal to @a __val.
  1101.        *  Remaining elements stay in list order.  Note that this
  1102.        *  function only erases the elements, and that if the elements
  1103.        *  themselves are pointers, the pointed-to memory is not
  1104.        *  touched in any way.  Managing the pointer is the user's
  1105.        *  responsibility.
  1106.        */
  1107.       void
  1108.       remove(const _Tp& __val);
  1109.  
  1110.       /**
  1111.        *  @brief  Remove all elements satisfying a predicate.
  1112.        *  @param  __pred  Unary predicate function or object.
  1113.        *
  1114.        *  Removes every element in the list for which the predicate
  1115.        *  returns true.  Remaining elements stay in list order.  Note
  1116.        *  that this function only erases the elements, and that if the
  1117.        *  elements themselves are pointers, the pointed-to memory is
  1118.        *  not touched in any way.  Managing the pointer is the user's
  1119.        *  responsibility.
  1120.        */
  1121.       template<typename _Pred>
  1122.         void
  1123.         remove_if(_Pred __pred);
  1124.  
  1125.       /**
  1126.        *  @brief  Remove consecutive duplicate elements.
  1127.        *
  1128.        *  For each consecutive set of elements with the same value,
  1129.        *  remove all but the first one.  Remaining elements stay in
  1130.        *  list order.  Note that this function only erases the
  1131.        *  elements, and that if the elements themselves are pointers,
  1132.        *  the pointed-to memory is not touched in any way.  Managing
  1133.        *  the pointer is the user's responsibility.
  1134.        */
  1135.       void
  1136.       unique()
  1137.       { unique(std::equal_to<_Tp>()); }
  1138.  
  1139.       /**
  1140.        *  @brief  Remove consecutive elements satisfying a predicate.
  1141.        *  @param  __binary_pred  Binary predicate function or object.
  1142.        *
  1143.        *  For each consecutive set of elements [first,last) that
  1144.        *  satisfy predicate(first,i) where i is an iterator in
  1145.        *  [first,last), remove all but the first one.  Remaining
  1146.        *  elements stay in list order.  Note that this function only
  1147.        *  erases the elements, and that if the elements themselves are
  1148.        *  pointers, the pointed-to memory is not touched in any way.
  1149.        *  Managing the pointer is the user's responsibility.
  1150.        */
  1151.       template<typename _BinPred>
  1152.         void
  1153.         unique(_BinPred __binary_pred);
  1154.  
  1155.       /**
  1156.        *  @brief  Merge sorted lists.
  1157.        *  @param  __list  Sorted list to merge.
  1158.        *
  1159.        *  Assumes that both @a list and this list are sorted according to
  1160.        *  operator<().  Merges elements of @a __list into this list in
  1161.        *  sorted order, leaving @a __list empty when complete.  Elements in
  1162.        *  this list precede elements in @a __list that are equal.
  1163.        */
  1164.       void
  1165.       merge(forward_list&& __list)
  1166.       { merge(std::move(__list), std::less<_Tp>()); }
  1167.  
  1168.       void
  1169.       merge(forward_list& __list)
  1170.       { merge(std::move(__list)); }
  1171.  
  1172.       /**
  1173.        *  @brief  Merge sorted lists according to comparison function.
  1174.        *  @param  __list  Sorted list to merge.
  1175.        *  @param  __comp Comparison function defining sort order.
  1176.        *
  1177.        *  Assumes that both @a __list and this list are sorted according to
  1178.        *  comp.  Merges elements of @a __list into this list
  1179.        *  in sorted order, leaving @a __list empty when complete.  Elements
  1180.        *  in this list precede elements in @a __list that are equivalent
  1181.        *  according to comp().
  1182.        */
  1183.       template<typename _Comp>
  1184.         void
  1185.         merge(forward_list&& __list, _Comp __comp);
  1186.  
  1187.       template<typename _Comp>
  1188.         void
  1189.         merge(forward_list& __list, _Comp __comp)
  1190.         { merge(std::move(__list), __comp); }
  1191.  
  1192.       /**
  1193.        *  @brief  Sort the elements of the list.
  1194.        *
  1195.        *  Sorts the elements of this list in NlogN time.  Equivalent
  1196.        *  elements remain in list order.
  1197.        */
  1198.       void
  1199.       sort()
  1200.       { sort(std::less<_Tp>()); }
  1201.  
  1202.       /**
  1203.        *  @brief  Sort the forward_list using a comparison function.
  1204.        *
  1205.        *  Sorts the elements of this list in NlogN time.  Equivalent
  1206.        *  elements remain in list order.
  1207.        */
  1208.       template<typename _Comp>
  1209.         void
  1210.         sort(_Comp __comp);
  1211.  
  1212.       /**
  1213.        *  @brief  Reverse the elements in list.
  1214.        *
  1215.        *  Reverse the order of elements in the list in linear time.
  1216.        */
  1217.       void
  1218.       reverse() noexcept
  1219.       { this->_M_impl._M_head._M_reverse_after(); }
  1220.  
  1221.     private:
  1222.       // Called by the range constructor to implement [23.3.4.2]/9
  1223.       template<typename _InputIterator>
  1224.         void
  1225.         _M_range_initialize(_InputIterator __first, _InputIterator __last);
  1226.  
  1227.       // Called by forward_list(n,v,a), and the range constructor when it
  1228.       // turns out to be the same thing.
  1229.       void
  1230.       _M_fill_initialize(size_type __n, const value_type& __value);
  1231.  
  1232.       // Called by splice_after and insert_after.
  1233.       iterator
  1234.       _M_splice_after(const_iterator __pos, const_iterator __before,
  1235.                       const_iterator __last);
  1236.  
  1237.       // Called by forward_list(n).
  1238.       void
  1239.       _M_default_initialize(size_type __n);
  1240.  
  1241.       // Called by resize(sz).
  1242.       void
  1243.       _M_default_insert_after(const_iterator __pos, size_type __n);
  1244.  
  1245.       // Called by operator=(forward_list&&)
  1246.       void
  1247.       _M_move_assign(forward_list&& __list, std::true_type) noexcept
  1248.       {
  1249.         clear();
  1250.         std::swap(this->_M_impl._M_head._M_next,
  1251.                   __list._M_impl._M_head._M_next);
  1252.         std::__alloc_on_move(this->_M_get_Node_allocator(),
  1253.                              __list._M_get_Node_allocator());
  1254.       }
  1255.  
  1256.       // Called by operator=(forward_list&&)
  1257.       void
  1258.       _M_move_assign(forward_list&& __list, std::false_type)
  1259.       {
  1260.         if (__list._M_get_Node_allocator() == this->_M_get_Node_allocator())
  1261.           _M_move_assign(std::move(__list), std::true_type());
  1262.         else
  1263.           // The rvalue's allocator cannot be moved, or is not equal,
  1264.           // so we need to individually move each element.
  1265.           this->assign(std::__make_move_if_noexcept_iterator(__list.begin()),
  1266.                        std::__make_move_if_noexcept_iterator(__list.end()));
  1267.       }
  1268.  
  1269.       // Called by assign(_InputIterator, _InputIterator) if _Tp is
  1270.       // CopyAssignable.
  1271.       template<typename _InputIterator>
  1272.         void
  1273.         _M_assign(_InputIterator __first, _InputIterator __last, true_type)
  1274.         {
  1275.           auto __prev = before_begin();
  1276.           auto __curr = begin();
  1277.           auto __end = end();
  1278.           while (__curr != __end && __first != __last)
  1279.             {
  1280.               *__curr = *__first;
  1281.               ++__prev;
  1282.               ++__curr;
  1283.               ++__first;
  1284.             }
  1285.           if (__first != __last)
  1286.             insert_after(__prev, __first, __last);
  1287.           else if (__curr != __end)
  1288.             erase_after(__prev, __end);
  1289.         }
  1290.  
  1291.       // Called by assign(_InputIterator, _InputIterator) if _Tp is not
  1292.       // CopyAssignable.
  1293.       template<typename _InputIterator>
  1294.         void
  1295.         _M_assign(_InputIterator __first, _InputIterator __last, false_type)
  1296.         {
  1297.           clear();
  1298.           insert_after(cbefore_begin(), __first, __last);
  1299.         }
  1300.  
  1301.       // Called by assign(size_type, const _Tp&) if Tp is CopyAssignable
  1302.       void
  1303.       _M_assign_n(size_type __n, const _Tp& __val, true_type)
  1304.       {
  1305.         auto __prev = before_begin();
  1306.         auto __curr = begin();
  1307.         auto __end = end();
  1308.         while (__curr != __end && __n > 0)
  1309.           {
  1310.             *__curr = __val;
  1311.             ++__prev;
  1312.             ++__curr;
  1313.             --__n;
  1314.           }
  1315.         if (__n > 0)
  1316.           insert_after(__prev, __n, __val);
  1317.         else if (__curr != __end)
  1318.           erase_after(__prev, __end);
  1319.       }
  1320.  
  1321.       // Called by assign(size_type, const _Tp&) if Tp is non-CopyAssignable
  1322.       void
  1323.       _M_assign_n(size_type __n, const _Tp& __val, false_type)
  1324.       {
  1325.         clear();
  1326.         insert_after(cbefore_begin(), __n, __val);
  1327.       }
  1328.     };
  1329.  
  1330.   /**
  1331.    *  @brief  Forward list equality comparison.
  1332.    *  @param  __lx  A %forward_list
  1333.    *  @param  __ly  A %forward_list of the same type as @a __lx.
  1334.    *  @return  True iff the elements of the forward lists are equal.
  1335.    *
  1336.    *  This is an equivalence relation.  It is linear in the number of
  1337.    *  elements of the forward lists.  Deques are considered equivalent
  1338.    *  if corresponding elements compare equal.
  1339.    */
  1340.   template<typename _Tp, typename _Alloc>
  1341.     bool
  1342.     operator==(const forward_list<_Tp, _Alloc>& __lx,
  1343.                const forward_list<_Tp, _Alloc>& __ly);
  1344.  
  1345.   /**
  1346.    *  @brief  Forward list ordering relation.
  1347.    *  @param  __lx  A %forward_list.
  1348.    *  @param  __ly  A %forward_list of the same type as @a __lx.
  1349.    *  @return  True iff @a __lx is lexicographically less than @a __ly.
  1350.    *
  1351.    *  This is a total ordering relation.  It is linear in the number of
  1352.    *  elements of the forward lists.  The elements must be comparable
  1353.    *  with @c <.
  1354.    *
  1355.    *  See std::lexicographical_compare() for how the determination is made.
  1356.    */
  1357.   template<typename _Tp, typename _Alloc>
  1358.     inline bool
  1359.     operator<(const forward_list<_Tp, _Alloc>& __lx,
  1360.               const forward_list<_Tp, _Alloc>& __ly)
  1361.     { return std::lexicographical_compare(__lx.cbegin(), __lx.cend(),
  1362.                                           __ly.cbegin(), __ly.cend()); }
  1363.  
  1364.   /// Based on operator==
  1365.   template<typename _Tp, typename _Alloc>
  1366.     inline bool
  1367.     operator!=(const forward_list<_Tp, _Alloc>& __lx,
  1368.                const forward_list<_Tp, _Alloc>& __ly)
  1369.     { return !(__lx == __ly); }
  1370.  
  1371.   /// Based on operator<
  1372.   template<typename _Tp, typename _Alloc>
  1373.     inline bool
  1374.     operator>(const forward_list<_Tp, _Alloc>& __lx,
  1375.               const forward_list<_Tp, _Alloc>& __ly)
  1376.     { return (__ly < __lx); }
  1377.  
  1378.   /// Based on operator<
  1379.   template<typename _Tp, typename _Alloc>
  1380.     inline bool
  1381.     operator>=(const forward_list<_Tp, _Alloc>& __lx,
  1382.                const forward_list<_Tp, _Alloc>& __ly)
  1383.     { return !(__lx < __ly); }
  1384.  
  1385.   /// Based on operator<
  1386.   template<typename _Tp, typename _Alloc>
  1387.     inline bool
  1388.     operator<=(const forward_list<_Tp, _Alloc>& __lx,
  1389.                const forward_list<_Tp, _Alloc>& __ly)
  1390.     { return !(__ly < __lx); }
  1391.  
  1392.   /// See std::forward_list::swap().
  1393.   template<typename _Tp, typename _Alloc>
  1394.     inline void
  1395.     swap(forward_list<_Tp, _Alloc>& __lx,
  1396.          forward_list<_Tp, _Alloc>& __ly)
  1397.     { __lx.swap(__ly); }
  1398.  
  1399. _GLIBCXX_END_NAMESPACE_CONTAINER
  1400. } // namespace std
  1401.  
  1402. #endif // _FORWARD_LIST_H
  1403.