Patchwork unordered map design modification

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Submitter François Dumont
Date Oct. 27, 2012, 12:27 p.m.
Message ID <508BD329.409@gmail.com>
Download mbox | patch
Permalink /patch/194616/
State New
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François Dumont - Oct. 27, 2012, 12:27 p.m.
On 10/26/2012 10:41 AM, Paolo Carlini wrote:
> On 10/25/2012 10:15 PM, François Dumont wrote:
>> Here is the patch to apply the same modification applied to 
>> unordered_set and unordered_multiset. It also use default 
>> implementation for unordered_set/unordered_multiset copy/move 
>> constructor/assignment operators.
> Looks good to me, thanks! Before committing, please double check the 
> various comments vs the various observations Jon sent over the last time.
>
> Thanks again,
> Paolo.
>
Attached patch applied.

2012-10-27  François Dumont  <fdumont@gcc.gnu.org>

     * include/bits/unordered_map.h (unordered_map<>): Prefer
     aggreagation to inheritance with _Hashtable.
     (unordered_multimap<>): Likewise.
     * include/bits/unordered_set.h
     (unordered_set<>(const unordered_set&)):  Use default
     implementation.
     (unordered_set<>(unordered_set&&)): Likewise.
     (unordered_set<>::operator=(const unordered_set&)): Likewise.
     (unordered_set<>::operator=(unordered_set&&)): Likewise.
     (unordered_multiset<>(const unordered_multiset&)): Likewise.
     (unordered_multiset<>(unordered_multiset&&)): Likewise.
     (unordered_multiset<>::operator=(const unordered_multiset&)):
     Likewise.
(unordered_multiset<>::operator=(unordered_multiset&&)): Likewise.
     * include/debug/unordered_map (operator==): Adapt.
     * include/profile/unordered_map (operator==): Adapt.

I think I did consider all Jonathan remarks which was mostly to use as 
much as possible default implementations so benefit from noexcept 
qualification.

François

Patch

Index: include/profile/unordered_map
===================================================================
--- include/profile/unordered_map	(revision 192694)
+++ include/profile/unordered_map	(working copy)
@@ -330,7 +330,7 @@ 
     inline bool
     operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
 	       const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
-    { return __x._M_equal(__y); }
+    { return static_cast<const _GLIBCXX_STD_BASE&>(__x) == __y; }
 
   template<typename _Key, typename _Tp, typename _Hash,
 	   typename _Pred, typename _Alloc>
@@ -599,7 +599,7 @@ 
     inline bool
     operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
 	       const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
-    { return __x._M_equal(__y); }
+    { return static_cast<const _GLIBCXX_STD_BASE&>(__x) == __y; }
 
   template<typename _Key, typename _Tp, typename _Hash,
 	   typename _Pred, typename _Alloc>
Index: include/debug/unordered_map
===================================================================
--- include/debug/unordered_map	(revision 192694)
+++ include/debug/unordered_map	(working copy)
@@ -482,7 +482,7 @@ 
     inline bool
     operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
 	       const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
-    { return __x._M_equal(__y); }
+    { return __x._M_base() == __y._M_base(); }
 
   template<typename _Key, typename _Tp, typename _Hash,
 	   typename _Pred, typename _Alloc>
@@ -929,7 +929,7 @@ 
     inline bool
     operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
 	       const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
-    { return __x._M_equal(__y); }
+    { return __x._M_base() == __y._M_base(); }
 
   template<typename _Key, typename _Tp, typename _Hash,
 	   typename _Pred, typename _Alloc>
Index: include/bits/unordered_map.h
===================================================================
--- include/bits/unordered_map.h	(revision 192694)
+++ include/bits/unordered_map.h	(working copy)
@@ -95,41 +95,654 @@ 
 	   class _Pred = std::equal_to<_Key>,
 	   class _Alloc = std::allocator<std::pair<const _Key, _Tp> > >
     class unordered_map
-    : public __umap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc>
     {
-      typedef __umap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc>  _Base;
+      typedef __umap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc>  _Hashtable;
+      _Hashtable _M_h;
 
     public:
-      typedef typename _Base::value_type      value_type;
-      typedef typename _Base::size_type       size_type;
-      typedef typename _Base::hasher          hasher;
-      typedef typename _Base::key_equal       key_equal;
-      typedef typename _Base::allocator_type  allocator_type;
+      // typedefs:
+      //@{
+      /// Public typedefs.
+      typedef typename _Hashtable::key_type	key_type;
+      typedef typename _Hashtable::value_type	value_type;
+      typedef typename _Hashtable::mapped_type	mapped_type;
+      typedef typename _Hashtable::hasher	hasher;
+      typedef typename _Hashtable::key_equal	key_equal;
+      typedef typename _Hashtable::allocator_type allocator_type;
+      //@}
 
+      //@{
+      ///  Iterator-related typedefs.
+      typedef typename allocator_type::pointer		pointer;
+      typedef typename allocator_type::const_pointer	const_pointer;
+      typedef typename allocator_type::reference	reference;
+      typedef typename allocator_type::const_reference	const_reference;
+      typedef typename _Hashtable::iterator		iterator;
+      typedef typename _Hashtable::const_iterator	const_iterator;
+      typedef typename _Hashtable::local_iterator	local_iterator;
+      typedef typename _Hashtable::const_local_iterator	const_local_iterator;
+      typedef typename _Hashtable::size_type		size_type;
+      typedef typename _Hashtable::difference_type	difference_type;
+      //@}
+
+      //construct/destroy/copy
+
+      /**
+       *  @brief  Default constructor creates no elements.
+       *  @param __n  Initial number of buckets.
+       *  @param __hf  A hash functor.
+       *  @param __eql  A key equality functor.
+       *  @param __a  An allocator object.
+       */
       explicit
       unordered_map(size_type __n = 10,
 		    const hasher& __hf = hasher(),
 		    const key_equal& __eql = key_equal(),
 		    const allocator_type& __a = allocator_type())
-      : _Base(__n, __hf, __eql, __a)
+      : _M_h(__n, __hf, __eql, __a)
       { }
 
+      /**
+       *  @brief  Builds an %unordered_map from a range.
+       *  @param  __first  An input iterator.
+       *  @param  __last  An input iterator.
+       *  @param __n  Minimal initial number of buckets.
+       *  @param __hf  A hash functor.
+       *  @param __eql  A key equality functor.
+       *  @param __a  An allocator object.
+       *
+       *  Create an %unordered_map consisting of copies of the elements from
+       *  [__first,__last).  This is linear in N (where N is
+       *  distance(__first,__last)).
+       */
       template<typename _InputIterator>
 	unordered_map(_InputIterator __f, _InputIterator __l,
 		      size_type __n = 0,
 		      const hasher& __hf = hasher(),
 		      const key_equal& __eql = key_equal(),
 		      const allocator_type& __a = allocator_type())
-	: _Base(__f, __l, __n, __hf, __eql, __a)
+	: _M_h(__f, __l, __n, __hf, __eql, __a)
 	{ }
 
+      /// Copy constructor.
+      unordered_map(const unordered_map&) = default;
+
+      /// Move constrcutor.
+      unordered_map(unordered_map&&) = default;
+
+      /**
+       *  @brief  Builds an %unordered_map from an initializer_list.
+       *  @param  __l  An initializer_list.
+       *  @param __n  Minimal initial number of buckets.
+       *  @param __hf  A hash functor.
+       *  @param __eql  A key equality functor.
+       *  @param  __a  An allocator object.
+       *
+       *  Create an %unordered_map consisting of copies of the elements in the
+       *  list. This is linear in N (where N is @a __l.size()).
+       */
       unordered_map(initializer_list<value_type> __l,
 		    size_type __n = 0,
 		    const hasher& __hf = hasher(),
 		    const key_equal& __eql = key_equal(),
 		    const allocator_type& __a = allocator_type())
-      : _Base(__l.begin(), __l.end(), __n, __hf, __eql, __a)
+	: _M_h(__l, __n, __hf, __eql, __a)
       { }
+
+      /// Copy assignment operator.
+      unordered_map&
+      operator=(const unordered_map&) = default;
+
+      /// Move assignment operator.
+      unordered_map&
+      operator=(unordered_map&&) = default;
+
+      /**
+       *  @brief  %Unordered_map list assignment operator.
+       *  @param  __l  An initializer_list.
+       *
+       *  This function fills an %unordered_map with copies of the elements in
+       *  the initializer list @a __l.
+       *
+       *  Note that the assignment completely changes the %unordered_map and
+       *  that the resulting %unordered_map's size is the same as the number
+       *  of elements assigned.  Old data may be lost.
+       */
+      unordered_map&
+      operator=(initializer_list<value_type> __l)
+      {
+	_M_h = __l;
+	return *this;
+      }
+
+      ///  Returns the allocator object with which the %unordered_map was
+      ///  constructed.
+      allocator_type
+      get_allocator() const noexcept
+      { return _M_h.get_allocator(); }
+
+      // size and capacity:
+
+      ///  Returns true if the %unordered_map is empty.
+      bool
+      empty() const noexcept
+      { return _M_h.empty(); }
+
+      ///  Returns the size of the %unordered_map.
+      size_type
+      size() const noexcept
+      { return _M_h.size(); }
+
+      ///  Returns the maximum size of the %unordered_map.
+      size_type
+      max_size() const noexcept
+      { return _M_h.max_size(); }
+
+      // iterators.
+
+      /**
+       *  Returns a read/write iterator that points to the first element in the
+       *  %unordered_map.
+       */
+      iterator
+      begin() noexcept
+      { return _M_h.begin(); }
+
+      //@{
+      /**
+       *  Returns a read-only (constant) iterator that points to the first
+       *  element in the %unordered_map.
+       */
+      const_iterator
+      begin() const noexcept
+      { return _M_h.begin(); }
+
+      const_iterator
+      cbegin() const noexcept
+      { return _M_h.begin(); }
+      //@}
+
+      /**
+       *  Returns a read/write iterator that points one past the last element in
+       *  the %unordered_map.
+       */
+      iterator
+      end() noexcept
+      { return _M_h.end(); }
+
+      //@{
+      /**
+       *  Returns a read-only (constant) iterator that points one past the last
+       *  element in the %unordered_map.
+       */
+      const_iterator
+      end() const noexcept
+      { return _M_h.end(); }
+
+      const_iterator
+      cend() const noexcept
+      { return _M_h.end(); }
+      //@}
+
+      // modifiers.
+
+      /**
+       *  @brief Attempts to build and insert a std::pair into the %unordered_map.
+       *
+       *  @param __args  Arguments used to generate a new pair instance (see
+       *	        std::piecewise_contruct for passing arguments to each
+       *	        part of the pair constructor).
+       *
+       *  @return  A pair, of which the first element is an iterator that points
+       *           to the possibly inserted pair, and the second is a bool that
+       *           is true if the pair was actually inserted.
+       *
+       *  This function attempts to build and insert a (key, value) %pair into
+       *  the %unordered_map.
+       *  An %unordered_map relies on unique keys and thus a %pair is only
+       *  inserted if its first element (the key) is not already present in the
+       *  %unordered_map.
+       *
+       *  Insertion requires amortized constant time.
+       */
+      template<typename... _Args>
+	std::pair<iterator, bool>
+	emplace(_Args&&... __args)
+	{ return _M_h.emplace(std::forward<_Args>(__args)...); }
+
+      /**
+       *  @brief Attempts to build and insert a std::pair into the %unordered_map.
+       *
+       *  @param  __pos  An iterator that serves as a hint as to where the pair
+       *                should be inserted.
+       *  @param  __args  Arguments used to generate a new pair instance (see
+       *	         std::piecewise_contruct for passing arguments to each
+       *	         part of the pair constructor).
+       *  @return An iterator that points to the element with key of the
+       *          std::pair built from @a __args (may or may not be that
+       *          std::pair).
+       *
+       *  This function is not concerned about whether the insertion took place,
+       *  and thus does not return a boolean like the single-argument emplace()
+       *  does.
+       *  Note that the first parameter is only a hint and can potentially
+       *  improve the performance of the insertion process. A bad hint would
+       *  cause no gains in efficiency.
+       *
+       *  See
+       *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt07ch17.html
+       *  for more on @a hinting.
+       *
+       *  Insertion requires amortized constant time.
+       */
+      template<typename... _Args>
+	iterator
+	emplace_hint(const_iterator __pos, _Args&&... __args)
+	{ return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); }
+
+      //@{
+      /**
+       *  @brief Attempts to insert a std::pair into the %unordered_map.
+
+       *  @param __x Pair to be inserted (see std::make_pair for easy
+       *	     creation of pairs).
+       *
+       *  @return  A pair, of which the first element is an iterator that 
+       *           points to the possibly inserted pair, and the second is 
+       *           a bool that is true if the pair was actually inserted.
+       *
+       *  This function attempts to insert a (key, value) %pair into the
+       *  %unordered_map. An %unordered_map relies on unique keys and thus a
+       *  %pair is only inserted if its first element (the key) is not already
+       *  present in the %unordered_map.
+       *
+       *  Insertion requires amortized constant time.
+       */
+      std::pair<iterator, bool>
+      insert(const value_type& __x)
+      { return _M_h.insert(__x); }
+
+      template<typename _Pair>
+	std::pair<iterator, bool>
+	insert(_Pair&& __x)
+	{ return _M_h.insert(std::move(__x)); }
+      //@}
+
+      //@{
+      /**
+       *  @brief Attempts to insert a std::pair into the %unordered_map.
+       *  @param  __hint  An iterator that serves as a hint as to where the
+       *                 pair should be inserted.
+       *  @param  __x  Pair to be inserted (see std::make_pair for easy creation
+       *               of pairs).
+       *  @return An iterator that points to the element with key of
+       *           @a __x (may or may not be the %pair passed in).
+       *
+       *  This function is not concerned about whether the insertion took place,
+       *  and thus does not return a boolean like the single-argument insert()
+       *  does.  Note that the first parameter is only a hint and can
+       *  potentially improve the performance of the insertion process.  A bad
+       *  hint would cause no gains in efficiency.
+       *
+       *  See
+       *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt07ch17.html
+       *  for more on @a hinting.
+       *
+       *  Insertion requires amortized constant time.
+       */
+      iterator
+      insert(const_iterator __hint, const value_type& __x)
+      { return _M_h.insert(__hint, __x); }
+
+      template<typename _Pair>
+	iterator
+	insert(const_iterator __hint, _Pair&& __x)
+	{ return _M_h.insert(__hint, std::move(__x)); }
+      //@}
+
+      /**
+       *  @brief A template function that attempts to insert a range of
+       *  elements.
+       *  @param  __first  Iterator pointing to the start of the range to be
+       *                   inserted.
+       *  @param  __last  Iterator pointing to the end of the range.
+       *
+       *  Complexity similar to that of the range constructor.
+       */
+      template<typename _InputIterator>
+	void
+	insert(_InputIterator __first, _InputIterator __last)
+	{ _M_h.insert(__first, __last); }
+
+      /**
+       *  @brief Attempts to insert a list of elements into the %unordered_map.
+       *  @param  __l  A std::initializer_list<value_type> of elements
+       *               to be inserted.
+       *
+       *  Complexity similar to that of the range constructor.
+       */
+      void
+      insert(initializer_list<value_type> __l)
+      { _M_h.insert(__l); }
+
+      //@{
+      /**
+       *  @brief Erases an element from an %unordered_map.
+       *  @param  __position  An iterator pointing to the element to be erased.
+       *  @return An iterator pointing to the element immediately following
+       *          @a __position prior to the element being erased. If no such
+       *          element exists, end() is returned.
+       *
+       *  This function erases an element, pointed to by the given iterator,
+       *  from an %unordered_map.
+       *  Note that this function only erases the element, and that if the
+       *  element is itself a pointer, the pointed-to memory is not touched in
+       *  any way.  Managing the pointer is the user's responsibility.
+       */
+      iterator
+      erase(const_iterator __position)
+      { return _M_h.erase(__position); }
+
+      // LWG 2059.
+      iterator
+      erase(iterator __it)
+      { return _M_h.erase(__it); }
+      //@}
+
+      /**
+       *  @brief Erases elements according to the provided key.
+       *  @param  __x  Key of element to be erased.
+       *  @return  The number of elements erased.
+       *
+       *  This function erases all the elements located by the given key from
+       *  an %unordered_map. For an %unordered_map the result of this function
+       *  can only be 0 (not present) or 1 (present).
+       *  Note that this function only erases the element, and that if the
+       *  element is itself a pointer, the pointed-to memory is not touched in
+       *  any way.  Managing the pointer is the user's responsibility.
+       */
+      size_type
+      erase(const key_type& __x)
+      { return _M_h.erase(__x); }
+
+      /**
+       *  @brief Erases a [__first,__last) range of elements from an
+       *  %unordered_map.
+       *  @param  __first  Iterator pointing to the start of the range to be
+       *                  erased.
+       *  @param __last  Iterator pointing to the end of the range to
+       *                be erased.
+       *  @return The iterator @a __last.
+       *
+       *  This function erases a sequence of elements from an %unordered_map.
+       *  Note that this function only erases the elements, and that if
+       *  the element is itself a pointer, the pointed-to memory is not touched
+       *  in any way.  Managing the pointer is the user's responsibility.
+       */
+      iterator
+      erase(const_iterator __first, const_iterator __last)
+      { return _M_h.erase(__first, __last); }
+
+      /**
+       *  Erases all elements in an %unordered_map.
+       *  Note that this function only erases the elements, and that if the
+       *  elements themselves are pointers, the pointed-to memory is not touched
+       *  in any way.  Managing the pointer is the user's responsibility.
+       */
+      void
+      clear() noexcept
+      { _M_h.clear(); }
+
+      /**
+       *  @brief  Swaps data with another %unordered_map.
+       *  @param  __x  An %unordered_map of the same element and allocator
+       *  types.
+       *
+       *  This exchanges the elements between two %unordered_map in constant time.
+       *  Note that the global std::swap() function is specialized such that
+       *  std::swap(m1,m2) will feed to this function.
+       */
+      void
+      swap(unordered_map& __x)
+      { _M_h.swap(__x._M_h); }
+
+      // observers.
+
+      ///  Returns the hash functor object with which the %unordered_map was
+      ///  constructed.
+      hasher
+      hash_function() const
+      { return _M_h.hash_function(); }
+
+      ///  Returns the key comparison object with which the %unordered_map was
+      ///  constructed.
+      key_equal
+      key_eq() const
+      { return _M_h.key_eq(); }
+
+      // lookup.
+
+      //@{
+      /**
+       *  @brief Tries to locate an element in an %unordered_map.
+       *  @param  __x  Key to be located.
+       *  @return  Iterator pointing to sought-after element, or end() if not
+       *           found.
+       *
+       *  This function takes a key and tries to locate the element with which
+       *  the key matches.  If successful the function returns an iterator
+       *  pointing to the sought after element.  If unsuccessful it returns the
+       *  past-the-end ( @c end() ) iterator.
+       */
+      iterator
+      find(const key_type& __x)
+      { return _M_h.find(__x); }
+
+      const_iterator
+      find(const key_type& __x) const
+      { return _M_h.find(__x); }
+      //@}
+
+      /**
+       *  @brief  Finds the number of elements.
+       *  @param  __x  Key to count.
+       *  @return  Number of elements with specified key.
+       *
+       *  This function only makes sense for %unordered_multimap; for
+       *  %unordered_map the result will either be 0 (not present) or 1
+       *  (present).
+       */
+      size_type
+      count(const key_type& __x) const
+      { return _M_h.count(__x); }
+
+      //@{
+      /**
+       *  @brief Finds a subsequence matching given key.
+       *  @param  __x  Key to be located.
+       *  @return  Pair of iterators that possibly points to the subsequence
+       *           matching given key.
+       *
+       *  This function probably only makes sense for %unordered_multimap.
+       */
+      std::pair<iterator, iterator>
+      equal_range(const key_type& __x)
+      { return _M_h.equal_range(__x); }
+
+      std::pair<const_iterator, const_iterator>
+      equal_range(const key_type& __x) const
+      { return _M_h.equal_range(__x); }
+      //@}
+
+      //@{
+      /**
+       *  @brief  Subscript ( @c [] ) access to %unordered_map data.
+       *  @param  __k  The key for which data should be retrieved.
+       *  @return  A reference to the data of the (key,data) %pair.
+       *
+       *  Allows for easy lookup with the subscript ( @c [] )operator.  Returns
+       *  data associated with the key specified in subscript.  If the key does
+       *  not exist, a pair with that key is created using default values, which
+       *  is then returned.
+       *
+       *  Lookup requires constant time.
+       */
+      mapped_type&
+      operator[](const key_type& __k)
+      { return _M_h[__k]; }
+
+      mapped_type&
+      operator[](key_type&& __k)
+      { return _M_h[std::move(__k)]; }
+      //@}
+
+      //@{
+      /**
+       *  @brief  Access to %unordered_map data.
+       *  @param  __k  The key for which data should be retrieved.
+       *  @return  A reference to the data whose key is equal to @a __k, if
+       *           such a data is present in the %unordered_map.
+       *  @throw  std::out_of_range  If no such data is present.
+       */
+      mapped_type&
+      at(const key_type& __k)
+      { return _M_h.at(__k); }
+
+      const mapped_type&
+      at(const key_type& __k) const
+      { return _M_h.at(__k); }
+      //@}
+
+      // bucket interface.
+
+      /// Returns the number of buckets of the %unordered_map.
+      size_type
+      bucket_count() const noexcept
+      { return _M_h.bucket_count(); }
+
+      /// Returns the maximum number of buckets of the %unordered_map.
+      size_type
+      max_bucket_count() const noexcept
+      { return _M_h.max_bucket_count(); }
+
+      /*
+       * @brief  Returns the number of elements in a given bucket.
+       * @param  __n  A bucket index.
+       * @return  The number of elements in the bucket.
+       */
+      size_type
+      bucket_size(size_type __n) const
+      { return _M_h.bucket_size(__n); }
+
+      /*
+       * @brief  Returns the bucket index of a given element.
+       * @param  __key  A key instance.
+       * @return  The key bucket index.
+       */
+      size_type
+      bucket(const key_type& __key) const
+      { return _M_h.bucket(__key); }
+      
+      /**
+       *  @brief  Returns a read/write iterator pointing to the first bucket
+       *         element.
+       *  @param  __n The bucket index.
+       *  @return  A read/write local iterator.
+       */
+      local_iterator
+      begin(size_type __n)
+      { return _M_h.begin(__n); }
+
+      //@{
+      /**
+       *  @brief  Returns a read-only (constant) iterator pointing to the first
+       *         bucket element.
+       *  @param  __n The bucket index.
+       *  @return  A read-only local iterator.
+       */
+      const_local_iterator
+      begin(size_type __n) const
+      { return _M_h.begin(__n); }
+
+      const_local_iterator
+      cbegin(size_type __n) const
+      { return _M_h.cbegin(__n); }
+      //@}
+
+      /**
+       *  @brief  Returns a read/write iterator pointing to one past the last
+       *         bucket elements.
+       *  @param  __n The bucket index.
+       *  @return  A read/write local iterator.
+       */
+      local_iterator
+      end(size_type __n)
+      { return _M_h.end(__n); }
+
+      //@{
+      /**
+       *  @brief  Returns a read-only (constant) iterator pointing to one past
+       *         the last bucket elements.
+       *  @param  __n The bucket index.
+       *  @return  A read-only local iterator.
+       */
+      const_local_iterator
+      end(size_type __n) const
+      { return _M_h.end(__n); }
+
+      const_local_iterator
+      cend(size_type __n) const
+      { return _M_h.cend(__n); }
+      //@}
+
+      // hash policy.
+
+      /// Returns the average number of elements per bucket.
+      float
+      load_factor() const noexcept
+      { return _M_h.load_factor(); }
+
+      /// Returns a positive number that the %unordered_map tries to keep the
+      /// load factor less than or equal to.
+      float
+      max_load_factor() const noexcept
+      { return _M_h.max_load_factor(); }
+
+      /**
+       *  @brief  Change the %unordered_map maximum load factor.
+       *  @param  __z The new maximum load factor.
+       */
+      void
+      max_load_factor(float __z)
+      { _M_h.max_load_factor(__z); }
+
+      /**
+       *  @brief  May rehash the %unordered_map.
+       *  @param  __n The new number of buckets.
+       *
+       *  Rehash will occur only if the new number of buckets respect the
+       *  %unordered_map maximum load factor.
+       */
+      void
+      rehash(size_type __n)
+      { _M_h.rehash(__n); }
+
+      /**
+       *  @brief  Prepare the %unordered_map for a specified number of
+       *          elements.
+       *  @param  __n Number of elements required.
+       *
+       *  Same as rehash(ceil(n / max_load_factor())).
+       */
+      void
+      reserve(size_type __n)
+      { _M_h.reserve(__n); }
+
+      template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1,
+	       typename _Alloc1>
+        friend bool
+      operator==(const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&,
+		 const unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&);
     };
 
   /**
@@ -159,41 +772,595 @@ 
 	   class _Pred = std::equal_to<_Key>,
 	   class _Alloc = std::allocator<std::pair<const _Key, _Tp> > >
     class unordered_multimap
-    : public __ummap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc>
     {
-      typedef __ummap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc>  _Base;
+      typedef __ummap_hashtable<_Key, _Tp, _Hash, _Pred, _Alloc>  _Hashtable;
+      _Hashtable _M_h;
 
     public:
-      typedef typename _Base::value_type      value_type;
-      typedef typename _Base::size_type       size_type;
-      typedef typename _Base::hasher          hasher;
-      typedef typename _Base::key_equal       key_equal;
-      typedef typename _Base::allocator_type  allocator_type;
+      // typedefs:
+      //@{
+      /// Public typedefs.
+      typedef typename _Hashtable::key_type	key_type;
+      typedef typename _Hashtable::value_type	value_type;
+      typedef typename _Hashtable::mapped_type	mapped_type;
+      typedef typename _Hashtable::hasher	hasher;
+      typedef typename _Hashtable::key_equal	key_equal;
+      typedef typename _Hashtable::allocator_type allocator_type;
+      //@}
 
+      //@{
+      ///  Iterator-related typedefs.
+      typedef typename allocator_type::pointer		pointer;
+      typedef typename allocator_type::const_pointer	const_pointer;
+      typedef typename allocator_type::reference	reference;
+      typedef typename allocator_type::const_reference	const_reference;
+      typedef typename _Hashtable::iterator		iterator;
+      typedef typename _Hashtable::const_iterator	const_iterator;
+      typedef typename _Hashtable::local_iterator	local_iterator;
+      typedef typename _Hashtable::const_local_iterator	const_local_iterator;
+      typedef typename _Hashtable::size_type		size_type;
+      typedef typename _Hashtable::difference_type	difference_type;
+      //@}
+
+      //construct/destroy/copy
+
+      /**
+       *  @brief  Default constructor creates no elements.
+       *  @param __n  Initial number of buckets.
+       *  @param __hf  A hash functor.
+       *  @param __eql  A key equality functor.
+       *  @param __a  An allocator object.
+       */
       explicit
       unordered_multimap(size_type __n = 10,
 			 const hasher& __hf = hasher(),
 			 const key_equal& __eql = key_equal(),
 			 const allocator_type& __a = allocator_type())
-      : _Base(__n, __hf, __eql, __a)
+      : _M_h(__n, __hf, __eql, __a)
       { }
 
+      /**
+       *  @brief  Builds an %unordered_multimap from a range.
+       *  @param  __first  An input iterator.
+       *  @param  __last  An input iterator.
+       *  @param __n  Minimal initial number of buckets.
+       *  @param __hf  A hash functor.
+       *  @param __eql  A key equality functor.
+       *  @param __a  An allocator object.
+       *
+       *  Create an %unordered_multimap consisting of copies of the elements
+       *  from [__first,__last).  This is linear in N (where N is
+       *  distance(__first,__last)).
+       */
       template<typename _InputIterator>
 	unordered_multimap(_InputIterator __f, _InputIterator __l,
 			   size_type __n = 0,
 			   const hasher& __hf = hasher(),
 			   const key_equal& __eql = key_equal(),
 			   const allocator_type& __a = allocator_type())
-	: _Base(__f, __l, __n, __hf, __eql, __a)
+	: _M_h(__f, __l, __n, __hf, __eql, __a)
 	{ }
 
+      /// Copy constructor.
+      unordered_multimap(const unordered_multimap&) = default;
+
+      /// Move constrcutor.
+      unordered_multimap(unordered_multimap&&) = default;
+
+      /**
+       *  @brief  Builds an %unordered_multimap from an initializer_list.
+       *  @param  __l  An initializer_list.
+       *  @param __n  Minimal initial number of buckets.
+       *  @param __hf  A hash functor.
+       *  @param __eql  A key equality functor.
+       *  @param  __a  An allocator object.
+       *
+       *  Create an %unordered_multimap consisting of copies of the elements in
+       *  the list. This is linear in N (where N is @a __l.size()).
+       */
       unordered_multimap(initializer_list<value_type> __l,
 			 size_type __n = 0,
 			 const hasher& __hf = hasher(),
 			 const key_equal& __eql = key_equal(),
 			 const allocator_type& __a = allocator_type())
-      : _Base(__l.begin(), __l.end(), __n, __hf, __eql, __a)
+	: _M_h(__l, __n, __hf, __eql, __a)
       { }
+
+      /// Copy assignment operator.
+      unordered_multimap&
+      operator=(const unordered_multimap&) = default;
+
+      /// Move assignment operator.
+      unordered_multimap&
+      operator=(unordered_multimap&&) = default;
+
+      /**
+       *  @brief  %Unordered_multimap list assignment operator.
+       *  @param  __l  An initializer_list.
+       *
+       *  This function fills an %unordered_multimap with copies of the elements
+       *  in the initializer list @a __l.
+       *
+       *  Note that the assignment completely changes the %unordered_multimap
+       *  and that the resulting %unordered_multimap's size is the same as the
+       *  number of elements assigned.  Old data may be lost.
+       */
+      unordered_multimap&
+      operator=(initializer_list<value_type> __l)
+      {
+	_M_h = __l;
+	return *this;
+      }
+
+      ///  Returns the allocator object with which the %unordered_multimap was
+      ///  constructed.
+      allocator_type
+      get_allocator() const noexcept
+      { return _M_h.get_allocator(); }
+
+      // size and capacity:
+
+      ///  Returns true if the %unordered_multimap is empty.
+      bool
+      empty() const noexcept
+      { return _M_h.empty(); }
+
+      ///  Returns the size of the %unordered_multimap.
+      size_type
+      size() const noexcept
+      { return _M_h.size(); }
+
+      ///  Returns the maximum size of the %unordered_multimap.
+      size_type
+      max_size() const noexcept
+      { return _M_h.max_size(); }
+
+      // iterators.
+
+      /**
+       *  Returns a read/write iterator that points to the first element in the
+       *  %unordered_multimap.
+       */
+      iterator
+      begin() noexcept
+      { return _M_h.begin(); }
+
+      //@{
+      /**
+       *  Returns a read-only (constant) iterator that points to the first
+       *  element in the %unordered_multimap.
+       */
+      const_iterator
+      begin() const noexcept
+      { return _M_h.begin(); }
+
+      const_iterator
+      cbegin() const noexcept
+      { return _M_h.begin(); }
+      //@}
+
+      /**
+       *  Returns a read/write iterator that points one past the last element in
+       *  the %unordered_multimap.
+       */
+      iterator
+      end() noexcept
+      { return _M_h.end(); }
+
+      //@{
+      /**
+       *  Returns a read-only (constant) iterator that points one past the last
+       *  element in the %unordered_multimap.
+       */
+      const_iterator
+      end() const noexcept
+      { return _M_h.end(); }
+
+      const_iterator
+      cend() const noexcept
+      { return _M_h.end(); }
+      //@}
+
+      // modifiers.
+
+      /**
+       *  @brief Attempts to build and insert a std::pair into the
+       *  %unordered_multimap.
+       *
+       *  @param __args  Arguments used to generate a new pair instance (see
+       *	        std::piecewise_contruct for passing arguments to each
+       *	        part of the pair constructor).
+       *
+       *  @return  An iterator that points to the inserted pair.
+       *
+       *  This function attempts to build and insert a (key, value) %pair into
+       *  the %unordered_multimap.
+       *
+       *  Insertion requires amortized constant time.
+       */
+      template<typename... _Args>
+	iterator
+	emplace(_Args&&... __args)
+	{ return _M_h.emplace(std::forward<_Args>(__args)...); }
+
+      /**
+       *  @brief Attempts to build and insert a std::pair into the %unordered_multimap.
+       *
+       *  @param  __pos  An iterator that serves as a hint as to where the pair
+       *                should be inserted.
+       *  @param  __args  Arguments used to generate a new pair instance (see
+       *	         std::piecewise_contruct for passing arguments to each
+       *	         part of the pair constructor).
+       *  @return An iterator that points to the element with key of the
+       *          std::pair built from @a __args.
+       *
+       *  Note that the first parameter is only a hint and can potentially
+       *  improve the performance of the insertion process. A bad hint would
+       *  cause no gains in efficiency.
+       *
+       *  See
+       *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt07ch17.html
+       *  for more on @a hinting.
+       *
+       *  Insertion requires amortized constant time.
+       */
+      template<typename... _Args>
+	iterator
+	emplace_hint(const_iterator __pos, _Args&&... __args)
+	{ return _M_h.emplace_hint(__pos, std::forward<_Args>(__args)...); }
+
+      //@{
+      /**
+       *  @brief Inserts a std::pair into the %unordered_multimap.
+       *  @param __x Pair to be inserted (see std::make_pair for easy
+       *	     creation of pairs).
+       *
+       *  @return  An iterator that points to the inserted pair.
+       *
+       *  Insertion requires amortized constant time.
+       */
+      iterator
+      insert(const value_type& __x)
+      { return _M_h.insert(__x); }
+
+      template<typename _Pair>
+	iterator
+	insert(_Pair&& __x)
+	{ return _M_h.insert(std::move(__x)); }
+      //@}
+
+      //@{
+      /**
+       *  @brief Inserts a std::pair into the %unordered_multimap.
+       *  @param  __hint  An iterator that serves as a hint as to where the
+       *                 pair should be inserted.
+       *  @param  __x  Pair to be inserted (see std::make_pair for easy creation
+       *               of pairs).
+       *  @return An iterator that points to the element with key of
+       *           @a __x (may or may not be the %pair passed in).
+       *
+       *  Note that the first parameter is only a hint and can potentially
+       *  improve the performance of the insertion process.  A bad hint would
+       *  cause no gains in efficiency.
+       *
+       *  See
+       *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt07ch17.html
+       *  for more on @a hinting.
+       *
+       *  Insertion requires amortized constant time.
+       */
+      iterator
+      insert(const_iterator __hint, const value_type& __x)
+      { return _M_h.insert(__hint, __x); }
+
+      template<typename _Pair>
+	iterator
+	insert(const_iterator __hint, _Pair&& __x)
+	{ return _M_h.insert(__hint, std::move(__x)); }
+      //@}
+
+      /**
+       *  @brief A template function that attempts to insert a range of
+       *  elements.
+       *  @param  __first  Iterator pointing to the start of the range to be
+       *                   inserted.
+       *  @param  __last  Iterator pointing to the end of the range.
+       *
+       *  Complexity similar to that of the range constructor.
+       */
+      template<typename _InputIterator>
+	void
+	insert(_InputIterator __first, _InputIterator __last)
+	{ _M_h.insert(__first, __last); }
+
+      /**
+       *  @brief Attempts to insert a list of elements into the
+       *  %unordered_multimap.
+       *  @param  __l  A std::initializer_list<value_type> of elements
+       *               to be inserted.
+       *
+       *  Complexity similar to that of the range constructor.
+       */
+      void
+      insert(initializer_list<value_type> __l)
+      { _M_h.insert(__l); }
+
+      //@{
+      /**
+       *  @brief Erases an element from an %unordered_multimap.
+       *  @param  __position  An iterator pointing to the element to be erased.
+       *  @return An iterator pointing to the element immediately following
+       *          @a __position prior to the element being erased. If no such
+       *          element exists, end() is returned.
+       *
+       *  This function erases an element, pointed to by the given iterator,
+       *  from an %unordered_multimap.
+       *  Note that this function only erases the element, and that if the
+       *  element is itself a pointer, the pointed-to memory is not touched in
+       *  any way.  Managing the pointer is the user's responsibility.
+       */
+      iterator
+      erase(const_iterator __position)
+      { return _M_h.erase(__position); }
+
+      // LWG 2059.
+      iterator
+      erase(iterator __it)
+      { return _M_h.erase(__it); }
+      //@}
+
+      /**
+       *  @brief Erases elements according to the provided key.
+       *  @param  __x  Key of elements to be erased.
+       *  @return  The number of elements erased.
+       *
+       *  This function erases all the elements located by the given key from
+       *  an %unordered_multimap.
+       *  Note that this function only erases the element, and that if the
+       *  element is itself a pointer, the pointed-to memory is not touched in
+       *  any way.  Managing the pointer is the user's responsibility.
+       */
+      size_type
+      erase(const key_type& __x)
+      { return _M_h.erase(__x); }
+
+      /**
+       *  @brief Erases a [__first,__last) range of elements from an
+       *  %unordered_multimap.
+       *  @param  __first  Iterator pointing to the start of the range to be
+       *                  erased.
+       *  @param __last  Iterator pointing to the end of the range to
+       *                be erased.
+       *  @return The iterator @a __last.
+       *
+       *  This function erases a sequence of elements from an
+       *  %unordered_multimap.
+       *  Note that this function only erases the elements, and that if
+       *  the element is itself a pointer, the pointed-to memory is not touched
+       *  in any way.  Managing the pointer is the user's responsibility.
+       */
+      iterator
+      erase(const_iterator __first, const_iterator __last)
+      { return _M_h.erase(__first, __last); }
+
+      /**
+       *  Erases all elements in an %unordered_multimap.
+       *  Note that this function only erases the elements, and that if the
+       *  elements themselves are pointers, the pointed-to memory is not touched
+       *  in any way.  Managing the pointer is the user's responsibility.
+       */
+      void
+      clear() noexcept
+      { _M_h.clear(); }
+
+      /**
+       *  @brief  Swaps data with another %unordered_multimap.
+       *  @param  __x  An %unordered_multimap of the same element and allocator
+       *  types.
+       *
+       *  This exchanges the elements between two %unordered_multimap in
+       *  constant time.
+       *  Note that the global std::swap() function is specialized such that
+       *  std::swap(m1,m2) will feed to this function.
+       */
+      void
+      swap(unordered_multimap& __x)
+      { _M_h.swap(__x._M_h); }
+
+      // observers.
+
+      ///  Returns the hash functor object with which the %unordered_multimap
+      ///  was constructed.
+      hasher
+      hash_function() const
+      { return _M_h.hash_function(); }
+
+      ///  Returns the key comparison object with which the %unordered_multimap
+      ///  was constructed.
+      key_equal
+      key_eq() const
+      { return _M_h.key_eq(); }
+
+      // lookup.
+
+      //@{
+      /**
+       *  @brief Tries to locate an element in an %unordered_multimap.
+       *  @param  __x  Key to be located.
+       *  @return  Iterator pointing to sought-after element, or end() if not
+       *           found.
+       *
+       *  This function takes a key and tries to locate the element with which
+       *  the key matches.  If successful the function returns an iterator
+       *  pointing to the sought after element.  If unsuccessful it returns the
+       *  past-the-end ( @c end() ) iterator.
+       */
+      iterator
+      find(const key_type& __x)
+      { return _M_h.find(__x); }
+
+      const_iterator
+      find(const key_type& __x) const
+      { return _M_h.find(__x); }
+      //@}
+
+      /**
+       *  @brief  Finds the number of elements.
+       *  @param  __x  Key to count.
+       *  @return  Number of elements with specified key.
+       */
+      size_type
+      count(const key_type& __x) const
+      { return _M_h.count(__x); }
+
+      //@{
+      /**
+       *  @brief Finds a subsequence matching given key.
+       *  @param  __x  Key to be located.
+       *  @return  Pair of iterators that possibly points to the subsequence
+       *           matching given key.
+       */
+      std::pair<iterator, iterator>
+      equal_range(const key_type& __x)
+      { return _M_h.equal_range(__x); }
+
+      std::pair<const_iterator, const_iterator>
+      equal_range(const key_type& __x) const
+      { return _M_h.equal_range(__x); }
+      //@}
+
+      // bucket interface.
+
+      /// Returns the number of buckets of the %unordered_multimap.
+      size_type
+      bucket_count() const noexcept
+      { return _M_h.bucket_count(); }
+
+      /// Returns the maximum number of buckets of the %unordered_multimap.
+      size_type
+      max_bucket_count() const noexcept
+      { return _M_h.max_bucket_count(); }
+
+      /*
+       * @brief  Returns the number of elements in a given bucket.
+       * @param  __n  A bucket index.
+       * @return  The number of elements in the bucket.
+       */
+      size_type
+      bucket_size(size_type __n) const
+      { return _M_h.bucket_size(__n); }
+
+      /*
+       * @brief  Returns the bucket index of a given element.
+       * @param  __key  A key instance.
+       * @return  The key bucket index.
+       */
+      size_type
+      bucket(const key_type& __key) const
+      { return _M_h.bucket(__key); }
+      
+      /**
+       *  @brief  Returns a read/write iterator pointing to the first bucket
+       *         element.
+       *  @param  __n The bucket index.
+       *  @return  A read/write local iterator.
+       */
+      local_iterator
+      begin(size_type __n)
+      { return _M_h.begin(__n); }
+
+      //@{
+      /**
+       *  @brief  Returns a read-only (constant) iterator pointing to the first
+       *         bucket element.
+       *  @param  __n The bucket index.
+       *  @return  A read-only local iterator.
+       */
+      const_local_iterator
+      begin(size_type __n) const
+      { return _M_h.begin(__n); }
+
+      const_local_iterator
+      cbegin(size_type __n) const
+      { return _M_h.cbegin(__n); }
+      //@}
+
+      /**
+       *  @brief  Returns a read/write iterator pointing to one past the last
+       *         bucket elements.
+       *  @param  __n The bucket index.
+       *  @return  A read/write local iterator.
+       */
+      local_iterator
+      end(size_type __n)
+      { return _M_h.end(__n); }
+
+      //@{
+      /**
+       *  @brief  Returns a read-only (constant) iterator pointing to one past
+       *         the last bucket elements.
+       *  @param  __n The bucket index.
+       *  @return  A read-only local iterator.
+       */
+      const_local_iterator
+      end(size_type __n) const
+      { return _M_h.end(__n); }
+
+      const_local_iterator
+      cend(size_type __n) const
+      { return _M_h.cend(__n); }
+      //@}
+
+      // hash policy.
+
+      /// Returns the average number of elements per bucket.
+      float
+      load_factor() const noexcept
+      { return _M_h.load_factor(); }
+
+      /// Returns a positive number that the %unordered_multimap tries to keep
+      /// the load factor less than or equal to.
+      float
+      max_load_factor() const noexcept
+      { return _M_h.max_load_factor(); }
+
+      /**
+       *  @brief  Change the %unordered_multimap maximum load factor.
+       *  @param  __z The new maximum load factor.
+       */
+      void
+      max_load_factor(float __z)
+      { _M_h.max_load_factor(__z); }
+
+      /**
+       *  @brief  May rehash the %unordered_multimap.
+       *  @param  __n The new number of buckets.
+       *
+       *  Rehash will occur only if the new number of buckets respect the
+       *  %unordered_multimap maximum load factor.
+       */
+      void
+      rehash(size_type __n)
+      { _M_h.rehash(__n); }
+
+      /**
+       *  @brief  Prepare the %unordered_multimap for a specified number of
+       *          elements.
+       *  @param  __n Number of elements required.
+       *
+       *  Same as rehash(ceil(n / max_load_factor())).
+       */
+      void
+      reserve(size_type __n)
+      { _M_h.reserve(__n); }
+
+      template<typename _Key1, typename _Tp1, typename _Hash1, typename _Pred1,
+	       typename _Alloc1>
+        friend bool
+	operator==(const unordered_multimap<_Key1, _Tp1,
+					    _Hash1, _Pred1, _Alloc1>&,
+		   const unordered_multimap<_Key1, _Tp1,
+					    _Hash1, _Pred1, _Alloc1>&);
     };
 
   template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
@@ -212,7 +1379,7 @@ 
     inline bool
     operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
 	       const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
-    { return __x._M_equal(__y); }
+    { return __x._M_h._M_equal(__y._M_h); }
 
   template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
     inline bool
@@ -224,7 +1391,7 @@ 
     inline bool
     operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
 	       const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __y)
-    { return __x._M_equal(__y); }
+    { return __x._M_h._M_equal(__y._M_h); }
 
   template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
     inline bool
Index: include/bits/unordered_set.h
===================================================================
--- include/bits/unordered_set.h	(revision 192695)
+++ include/bits/unordered_set.h	(working copy)
@@ -158,29 +158,11 @@ 
 	: _M_h(__f, __l, __n, __hf, __eql, __a)
 	{ }
 
-      /**
-       *  @brief  %Unordered_set copy constructor.
-       *  @param  __x  An %unordered_set of identical element and allocator
-       *  types.
-       *
-       *  The newly-created %unordered_set uses a copy of the allocation object
-       *  used by @a __x.
-       */
-      unordered_set(const unordered_set& __x)
-	: _M_h(__x._M_h) { }
+      /// Copy constructor.
+      unordered_set(const unordered_set&) = default;
 
-     /**
-       *  @brief %Unordered_set move constructor
-       *  @param __x  An %unordered_set of identical element and allocator
-       *  types.
-       *
-       *  The newly-created %unordered_set contains the exact contents of @a
-       *  __x. The contents of @a __x are a valid, but unspecified
-       *  %unordered_set.
-       */
-      unordered_set(unordered_set&& __x)
-	: _M_h(std::move(__x._M_h))
-      { }
+      /// Move constructor.
+      unordered_set(unordered_set&&) = default;
 
       /**
        *  @brief  Builds an %unordered_set from an initializer_list.
@@ -201,35 +183,13 @@ 
 	: _M_h(__l, __n, __hf, __eql, __a)
       { }
 
-      /**
-       *  @brief  %Unordered_set assignment operator.
-       *  @param  __x  An %unordered_set of identical element and allocator
-       *  types.
-       *
-       *  All the elements of @a __x are copied, but unlike the copy
-       *  constructor, the allocator object is not copied.
-       */
+      /// Copy assignment operator.
       unordered_set&
-      operator=(const unordered_set& __x)
-      {
-	_M_h = __x._M_h;
-	return *this;
-      }
+      operator=(const unordered_set&) = default;
 
-      /**
-       *  @brief %Unordered_set move assignment operator.
-       *  @param __x  An %unordered_set of identical element and allocator
-       *  types.
-       *
-       *  The contents of @a __x are moved into this %unordered_set (without
-       *  copying). @a __x is a valid, but unspecified %unordered_set.
-       */
+      /// Move assignment operator.
       unordered_set&
-      operator=(unordered_set&& __x)
-      {
-	_M_h = std::move(__x._M_h);
-	return *this;
-      }
+      operator=(unordered_set&&) = default;
 
       /**
        *  @brief  %Unordered_set list assignment operator.
@@ -330,7 +290,8 @@ 
        *
        *  This function attempts to build and insert an element into the
        *  %unordered_set. An %unordered_set relies on unique keys and thus an
-       *  element is only inserted if it is not already present in the %set.
+       *  element is only inserted if it is not already present in the
+       *  %unordered_set.
        *
        *  Insertion requires amortized constant time.
        */
@@ -802,29 +763,11 @@ 
 	: _M_h(__f, __l, __n, __hf, __eql, __a)
 	{ }
 
-      /**
-       *  @brief  %Unordered_multiset copy constructor.
-       *  @param  __x  An %unordered_multiset of identical element and allocator
-       *  types.
-       *
-       *  The newly-created %unordered_multiset uses a copy of the allocation object
-       *  used by @a __x.
-       */
-      unordered_multiset(const unordered_multiset& __x)
-	: _M_h(__x._M_h) { }
+      /// Copy constructor.
+      unordered_multiset(const unordered_multiset&) = default;
 
-     /**
-       *  @brief %Unordered_multiset move constructor
-       *  @param __x  An %unordered_multiset of identical element and allocator
-       *  types.
-       *
-       *  The newly-created %unordered_multiset contains the exact contents of
-       *  @a __x. The contents of @a __x are a valid, but unspecified
-       *  %unordered_multiset.
-       */
-      unordered_multiset(unordered_multiset&& __x)
-	: _M_h(std::move(__x._M_h))
-      { }
+      /// Move constructor.
+      unordered_multiset(unordered_multiset&&) = default;
 
       /**
        *  @brief  Builds an %unordered_multiset from an initializer_list.
@@ -845,36 +788,13 @@ 
 	: _M_h(__l, __n, __hf, __eql, __a)
       { }
 
-      /**
-       *  @brief  %Unordered_multiset assignment operator.
-       *  @param  __x  An %unordered_multiset of identical element and allocator
-       *  types.
-       *
-       *  All the elements of @a __x are copied, but unlike the copy
-       *  constructor, the allocator object is not copied.
-       */
+      /// Copy assignment operator.
       unordered_multiset&
-      operator=(const unordered_multiset& __x)
-      {
-	_M_h = __x._M_h;
-	return *this;
-      }
+      operator=(const unordered_multiset&) = default;
 
-      /**
-       *  @brief %Unordered_multiset move assignment operator.
-       *  @param __x  An %unordered_multiset of identical element and allocator
-       *  types.
-       *
-       *  The contents of @a __x are moved into this %unordered_multiset
-       *  (without copying). @a __x is a valid, but unspecified
-       *  %unordered_multiset.
-       */
+      /// Move assignment operator.
       unordered_multiset&
-      operator=(unordered_multiset&& __x)
-      {
-	_M_h = std::move(__x._M_h);
-	return *this;
-      }
+      operator=(unordered_multiset&& __x) = default;
 
       /**
        *  @brief  %Unordered_multiset list assignment operator.