diff --git a/include/boost/container/flat_map.hpp b/include/boost/container/flat_map.hpp
index 18a3c5e..0142500 100644
--- a/include/boost/container/flat_map.hpp
+++ b/include/boost/container/flat_map.hpp
@@ -264,21 +264,21 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    key_compare key_comp() const
-      { return container_detail::force<key_compare>(m_flat_tree.key_comp()); }
+      { return container_detail::force_copy<key_compare>(m_flat_tree.key_comp()); }
 
    //! <b>Effects</b>: Returns an object of value_compare constructed out
    //!   of the comparison object.
    //!
    //! <b>Complexity</b>: Constant.
    value_compare value_comp() const
-      { return value_compare(container_detail::force<key_compare>(m_flat_tree.key_comp())); }
+      { return value_compare(container_detail::force_copy<key_compare>(m_flat_tree.key_comp())); }
 
    //! <b>Effects</b>: Returns a copy of the Allocator that
    //!   was passed to the object's constructor.
    //!
    //! <b>Complexity</b>: Constant.
    allocator_type get_allocator() const
-      { return container_detail::force<allocator_type>(m_flat_tree.get_allocator()); }
+      { return container_detail::force_copy<allocator_type>(m_flat_tree.get_allocator()); }
 
    const stored_allocator_type &get_stored_allocator() const
       { return container_detail::force<stored_allocator_type>(m_flat_tree.get_stored_allocator()); }
@@ -300,7 +300,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    const_iterator begin() const
-      { return container_detail::force<const_iterator>(m_flat_tree.begin()); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.begin()); }
 
    //! <b>Effects</b>: Returns an iterator to the end of the container.
    //!
@@ -316,7 +316,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    const_iterator end() const
-      { return container_detail::force<const_iterator>(m_flat_tree.end()); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.end()); }
 
    //! <b>Effects</b>: Returns a reverse_iterator pointing to the beginning
    //! of the reversed container.
@@ -325,7 +325,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    reverse_iterator rbegin()
-      { return container_detail::force<reverse_iterator>(m_flat_tree.rbegin()); }
+      { return container_detail::force_copy<reverse_iterator>(m_flat_tree.rbegin()); }
 
    //! <b>Effects</b>: Returns a const_reverse_iterator pointing to the beginning
    //! of the reversed container.
@@ -334,7 +334,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    const_reverse_iterator rbegin() const
-      { return container_detail::force<const_reverse_iterator>(m_flat_tree.rbegin()); }
+      { return container_detail::force_copy<const_reverse_iterator>(m_flat_tree.rbegin()); }
 
    //! <b>Effects</b>: Returns a reverse_iterator pointing to the end
    //! of the reversed container.
@@ -343,7 +343,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    reverse_iterator rend()
-      { return container_detail::force<reverse_iterator>(m_flat_tree.rend()); }
+      { return container_detail::force_copy<reverse_iterator>(m_flat_tree.rend()); }
 
    //! <b>Effects</b>: Returns a const_reverse_iterator pointing to the end
    //! of the reversed container.
@@ -352,7 +352,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    const_reverse_iterator rend() const
-      { return container_detail::force<const_reverse_iterator>(m_flat_tree.rend()); }
+      { return container_detail::force_copy<const_reverse_iterator>(m_flat_tree.rend()); }
 
    //! <b>Effects</b>: Returns a const_iterator to the first element contained in the container.
    //!
@@ -360,7 +360,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    const_iterator cbegin() const
-      { return container_detail::force<const_iterator>(m_flat_tree.cbegin()); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.cbegin()); }
 
    //! <b>Effects</b>: Returns a const_iterator to the end of the container.
    //!
@@ -368,7 +368,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    const_iterator cend() const
-      { return container_detail::force<const_iterator>(m_flat_tree.cend()); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.cend()); }
 
    //! <b>Effects</b>: Returns a const_reverse_iterator pointing to the beginning
    //! of the reversed container.
@@ -377,7 +377,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    const_reverse_iterator crbegin() const
-      { return container_detail::force<const_reverse_iterator>(m_flat_tree.crbegin()); }
+      { return container_detail::force_copy<const_reverse_iterator>(m_flat_tree.crbegin()); }
 
    //! <b>Effects</b>: Returns a const_reverse_iterator pointing to the end
    //! of the reversed container.
@@ -386,7 +386,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Constant.
    const_reverse_iterator crend() const
-      { return container_detail::force<const_reverse_iterator>(m_flat_tree.crend()); }
+      { return container_detail::force_copy<const_reverse_iterator>(m_flat_tree.crend()); }
 
    //! <b>Effects</b>: Returns true if the container contains no elements.
    //!
@@ -477,7 +477,7 @@ class flat_map
    //!
    //! <b>Note</b>: If an element is inserted it might invalidate elements.
    std::pair<iterator,bool> insert(const value_type& x)
-      { return container_detail::force<std::pair<iterator,bool> >(
+      { return container_detail::force_copy<std::pair<iterator,bool> >(
          m_flat_tree.insert_unique(container_detail::force<impl_value_type>(x))); }
 
    //! <b>Effects</b>: Inserts a new value_type move constructed from the pair if and
@@ -492,7 +492,7 @@ class flat_map
    //!
    //! <b>Note</b>: If an element is inserted it might invalidate elements.
    std::pair<iterator,bool> insert(BOOST_RV_REF(value_type) x)
-   {  return container_detail::force<std::pair<iterator,bool> >(
+   {  return container_detail::force_copy<std::pair<iterator,bool> >(
       m_flat_tree.insert_unique(boost::move(container_detail::force<impl_value_type>(x)))); }
 
    //! <b>Effects</b>: Inserts a new value_type move constructed from the pair if and
@@ -508,7 +508,7 @@ class flat_map
    //! <b>Note</b>: If an element is inserted it might invalidate elements.
    std::pair<iterator,bool> insert(BOOST_RV_REF(movable_value_type) x)
    {
-      return container_detail::force<std::pair<iterator,bool> >
+      return container_detail::force_copy<std::pair<iterator,bool> >
       (m_flat_tree.insert_unique(boost::move(x)));
    }
 
@@ -524,8 +524,11 @@ class flat_map
    //!
    //! <b>Note</b>: If an element is inserted it might invalidate elements.
    iterator insert(const_iterator position, const value_type& x)
-      { return container_detail::force_copy<iterator>(
-         m_flat_tree.insert_unique(container_detail::force<impl_const_iterator>(position), container_detail::force<impl_value_type>(x))); }
+   {
+      return container_detail::force_copy<iterator>(
+         m_flat_tree.insert_unique( container_detail::force_copy<impl_const_iterator>(position)
+                                  , container_detail::force<impl_value_type>(x)));
+   }
 
    //! <b>Effects</b>: Inserts an element move constructed from x in the container.
    //!   p is a hint pointing to where the insert should start to search.
@@ -539,7 +542,7 @@ class flat_map
    iterator insert(const_iterator position, BOOST_RV_REF(value_type) x)
    {
       return container_detail::force_copy<iterator>
-         (m_flat_tree.insert_unique( container_detail::force<impl_const_iterator>(position)
+         (m_flat_tree.insert_unique( container_detail::force_copy<impl_const_iterator>(position)
                                    , boost::move(container_detail::force<impl_value_type>(x))));
    }
 
@@ -555,7 +558,7 @@ class flat_map
    iterator insert(const_iterator position, BOOST_RV_REF(movable_value_type) x)
    {
       return container_detail::force_copy<iterator>(
-         m_flat_tree.insert_unique(container_detail::force<impl_const_iterator>(position), boost::move(x)));
+         m_flat_tree.insert_unique(container_detail::force_copy<impl_const_iterator>(position), boost::move(x)));
    }
 
    //! <b>Requires</b>: first, last are not iterators into *this.
@@ -620,8 +623,11 @@ class flat_map
    //! <b>Note</b>: If an element is inserted it might invalidate elements.
    template <class... Args>
    iterator emplace_hint(const_iterator hint, Args&&... args)
-   {  return container_detail::force_copy<iterator>
-      (m_flat_tree.emplace_hint_unique(container_detail::force<impl_const_iterator>(hint), boost::forward<Args>(args)...)); }
+   {
+      return container_detail::force_copy<iterator>
+         (m_flat_tree.emplace_hint_unique( container_detail::force_copy<impl_const_iterator>(hint)
+                                         , boost::forward<Args>(args)...));
+   }
 
    #else //#ifdef BOOST_CONTAINER_PERFECT_FORWARDING
 
@@ -635,7 +641,7 @@ class flat_map
    iterator emplace_hint(const_iterator hint                                                       \
                          BOOST_PP_ENUM_TRAILING(n, BOOST_CONTAINER_PP_PARAM_LIST, _))              \
    {  return container_detail::force_copy<iterator>(m_flat_tree.emplace_hint_unique                \
-            (container_detail::force<impl_const_iterator>(hint)                                    \
+            (container_detail::force_copy<impl_const_iterator>(hint)                               \
                BOOST_PP_ENUM_TRAILING(n, BOOST_CONTAINER_PP_PARAM_FORWARD, _))); }                 \
    //!
    #define BOOST_PP_LOCAL_LIMITS (0, BOOST_CONTAINER_MAX_CONSTRUCTOR_PARAMETERS)
@@ -654,7 +660,10 @@ class flat_map
    //! <b>Note</b>: Invalidates elements with keys
    //!   not less than the erased element.
    iterator erase(const_iterator position)
-      { return container_detail::force_copy<iterator>(m_flat_tree.erase(container_detail::force<impl_const_iterator>(position))); }
+   {
+      return container_detail::force_copy<iterator>
+         (m_flat_tree.erase(container_detail::force_copy<impl_const_iterator>(position)));
+   }
 
    //! <b>Effects</b>: Erases all elements in the container with key equivalent to x.
    //!
@@ -674,8 +683,11 @@ class flat_map
    //! <b>Complexity</b>: Logarithmic search time plus erasure time
    //!   linear to the elements with bigger keys.
    iterator erase(const_iterator first, const_iterator last)
-      { return container_detail::force_copy<iterator>
-         (m_flat_tree.erase(container_detail::force<impl_const_iterator>(first), container_detail::force<impl_const_iterator>(last))); }
+   {
+      return container_detail::force_copy<iterator>(
+         m_flat_tree.erase( container_detail::force_copy<impl_const_iterator>(first)
+                          , container_detail::force_copy<impl_const_iterator>(last)));
+   }
 
    //! <b>Effects</b>: erase(a.begin(),a.end()).
    //!
@@ -706,7 +718,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Logarithmic.s
    const_iterator find(const key_type& x) const
-      { return container_detail::force<const_iterator>(m_flat_tree.find(x)); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.find(x)); }
 
    //! <b>Returns</b>: The number of elements with key equivalent to x.
    //!
@@ -726,7 +738,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Logarithmic
    const_iterator lower_bound(const key_type& x) const
-      {  return container_detail::force<const_iterator>(m_flat_tree.lower_bound(x)); }
+      {  return container_detail::force_copy<const_iterator>(m_flat_tree.lower_bound(x)); }
 
    //! <b>Returns</b>: An iterator pointing to the first element with key not less
    //!   than x, or end() if such an element is not found.
@@ -740,7 +752,7 @@ class flat_map
    //!
    //! <b>Complexity</b>: Logarithmic
    const_iterator upper_bound(const key_type& x) const
-      {  return container_detail::force<const_iterator>(m_flat_tree.upper_bound(x)); }
+      {  return container_detail::force_copy<const_iterator>(m_flat_tree.upper_bound(x)); }
 
    //! <b>Effects</b>: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).
    //!
@@ -1050,21 +1062,21 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    key_compare key_comp() const
-      { return container_detail::force<key_compare>(m_flat_tree.key_comp()); }
+      { return container_detail::force_copy<key_compare>(m_flat_tree.key_comp()); }
 
    //! <b>Effects</b>: Returns an object of value_compare constructed out
    //!   of the comparison object.
    //!
    //! <b>Complexity</b>: Constant.
    value_compare value_comp() const
-      { return value_compare(container_detail::force<key_compare>(m_flat_tree.key_comp())); }
+      { return value_compare(container_detail::force_copy<key_compare>(m_flat_tree.key_comp())); }
 
    //! <b>Effects</b>: Returns a copy of the Allocator that
    //!   was passed to the object's constructor.
    //!
    //! <b>Complexity</b>: Constant.
    allocator_type get_allocator() const
-      { return container_detail::force<allocator_type>(m_flat_tree.get_allocator()); }
+      { return container_detail::force_copy<allocator_type>(m_flat_tree.get_allocator()); }
 
    const stored_allocator_type &get_stored_allocator() const
       { return container_detail::force<stored_allocator_type>(m_flat_tree.get_stored_allocator()); }
@@ -1086,7 +1098,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    const_iterator begin() const
-      { return container_detail::force<const_iterator>(m_flat_tree.begin()); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.begin()); }
 
    //! <b>Effects</b>: Returns an iterator to the end of the container.
    //!
@@ -1102,7 +1114,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    const_iterator end() const
-      { return container_detail::force<const_iterator>(m_flat_tree.end()); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.end()); }
 
    //! <b>Effects</b>: Returns a reverse_iterator pointing to the beginning
    //! of the reversed container.
@@ -1111,7 +1123,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    reverse_iterator rbegin()
-      { return container_detail::force<reverse_iterator>(m_flat_tree.rbegin()); }
+      { return container_detail::force_copy<reverse_iterator>(m_flat_tree.rbegin()); }
 
    //! <b>Effects</b>: Returns a const_reverse_iterator pointing to the beginning
    //! of the reversed container.
@@ -1120,7 +1132,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    const_reverse_iterator rbegin() const
-      { return container_detail::force<const_reverse_iterator>(m_flat_tree.rbegin()); }
+      { return container_detail::force_copy<const_reverse_iterator>(m_flat_tree.rbegin()); }
 
    //! <b>Effects</b>: Returns a reverse_iterator pointing to the end
    //! of the reversed container.
@@ -1129,7 +1141,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    reverse_iterator rend()
-      { return container_detail::force<reverse_iterator>(m_flat_tree.rend()); }
+      { return container_detail::force_copy<reverse_iterator>(m_flat_tree.rend()); }
 
    //! <b>Effects</b>: Returns a const_reverse_iterator pointing to the end
    //! of the reversed container.
@@ -1138,7 +1150,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    const_reverse_iterator rend() const
-      { return container_detail::force<const_reverse_iterator>(m_flat_tree.rend()); }
+      { return container_detail::force_copy<const_reverse_iterator>(m_flat_tree.rend()); }
 
    //! <b>Effects</b>: Returns a const_iterator to the first element contained in the container.
    //!
@@ -1146,7 +1158,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    const_iterator cbegin() const
-      { return container_detail::force<const_iterator>(m_flat_tree.cbegin()); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.cbegin()); }
 
    //! <b>Effects</b>: Returns a const_iterator to the end of the container.
    //!
@@ -1154,7 +1166,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    const_iterator cend() const
-      { return container_detail::force<const_iterator>(m_flat_tree.cend()); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.cend()); }
 
    //! <b>Effects</b>: Returns a const_reverse_iterator pointing to the beginning
    //! of the reversed container.
@@ -1163,7 +1175,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    const_reverse_iterator crbegin() const
-      { return container_detail::force<const_reverse_iterator>(m_flat_tree.crbegin()); }
+      { return container_detail::force_copy<const_reverse_iterator>(m_flat_tree.crbegin()); }
 
    //! <b>Effects</b>: Returns a const_reverse_iterator pointing to the end
    //! of the reversed container.
@@ -1172,7 +1184,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Constant.
    const_reverse_iterator crend() const
-      { return container_detail::force<const_reverse_iterator>(m_flat_tree.crend()); }
+      { return container_detail::force_copy<const_reverse_iterator>(m_flat_tree.crend()); }
 
    //! <b>Effects</b>: Returns true if the container contains no elements.
    //!
@@ -1214,7 +1226,10 @@ class flat_multimap
    //!
    //! <b>Note</b>: If an element is inserted it might invalidate elements.
    iterator insert(const value_type& x)
-      { return container_detail::force_copy<iterator>(m_flat_tree.insert_equal(container_detail::force<impl_value_type>(x))); }
+   {
+      return container_detail::force_copy<iterator>(
+         m_flat_tree.insert_equal(container_detail::force<impl_value_type>(x)));
+   }
 
    //! <b>Effects</b>: Inserts a new value move-constructed from x and returns
    //!   the iterator pointing to the newly inserted element.
@@ -1248,8 +1263,11 @@ class flat_multimap
    //!
    //! <b>Note</b>: If an element is inserted it might invalidate elements.
    iterator insert(const_iterator position, const value_type& x)
-      { return container_detail::force_copy<iterator>
-         (m_flat_tree.insert_equal(container_detail::force<impl_const_iterator>(position), container_detail::force<impl_value_type>(x))); }
+   {
+      return container_detail::force_copy<iterator>
+         (m_flat_tree.insert_equal( container_detail::force_copy<impl_const_iterator>(position)
+                                  , container_detail::force<impl_value_type>(x)));
+   }
 
    //! <b>Effects</b>: Inserts a value move constructed from x in the container.
    //!   p is a hint pointing to where the insert should start to search.
@@ -1265,7 +1283,7 @@ class flat_multimap
    iterator insert(const_iterator position, BOOST_RV_REF(value_type) x)
    {
       return container_detail::force_copy<iterator>
-         (m_flat_tree.insert_equal(container_detail::force<impl_const_iterator>(position)
+         (m_flat_tree.insert_equal(container_detail::force_copy<impl_const_iterator>(position)
                                   , boost::move(x)));
    }
 
@@ -1283,7 +1301,7 @@ class flat_multimap
    iterator insert(const_iterator position, BOOST_RV_REF(impl_value_type) x)
    {
       return container_detail::force_copy<iterator>(
-         m_flat_tree.insert_equal(container_detail::force<impl_const_iterator>(position), boost::move(x)));
+         m_flat_tree.insert_equal(container_detail::force_copy<impl_const_iterator>(position), boost::move(x)));
    }
 
    //! <b>Requires</b>: first, last are not iterators into *this.
@@ -1344,7 +1362,7 @@ class flat_multimap
    iterator emplace_hint(const_iterator hint, Args&&... args)
    {
       return container_detail::force_copy<iterator>(m_flat_tree.emplace_hint_equal
-         (container_detail::force<impl_const_iterator>(hint), boost::forward<Args>(args)...));
+         (container_detail::force_copy<impl_const_iterator>(hint), boost::forward<Args>(args)...));
    }
 
    #else //#ifdef BOOST_CONTAINER_PERFECT_FORWARDING
@@ -1359,7 +1377,7 @@ class flat_multimap
    iterator emplace_hint(const_iterator hint                                                       \
                          BOOST_PP_ENUM_TRAILING(n, BOOST_CONTAINER_PP_PARAM_LIST, _))              \
    {  return container_detail::force_copy<iterator>(m_flat_tree.emplace_hint_equal                 \
-            (container_detail::force<impl_const_iterator>(hint)                                    \
+            (container_detail::force_copy<impl_const_iterator>(hint)                               \
                BOOST_PP_ENUM_TRAILING(n, BOOST_CONTAINER_PP_PARAM_FORWARD, _))); }                 \
    //!
    #define BOOST_PP_LOCAL_LIMITS (0, BOOST_CONTAINER_MAX_CONSTRUCTOR_PARAMETERS)
@@ -1378,7 +1396,10 @@ class flat_multimap
    //! <b>Note</b>: Invalidates elements with keys
    //!   not less than the erased element.
    iterator erase(const_iterator position)
-      { return container_detail::force_copy<iterator>(m_flat_tree.erase(container_detail::force<impl_const_iterator>(position))); }
+   {
+      return container_detail::force_copy<iterator>(
+         m_flat_tree.erase(container_detail::force_copy<impl_const_iterator>(position)));
+   }
 
    //! <b>Effects</b>: Erases all elements in the container with key equivalent to x.
    //!
@@ -1398,8 +1419,11 @@ class flat_multimap
    //! <b>Complexity</b>: Logarithmic search time plus erasure time
    //!   linear to the elements with bigger keys.
    iterator erase(const_iterator first, const_iterator last)
-      { return container_detail::force_copy<iterator>
-         (m_flat_tree.erase(container_detail::force<impl_const_iterator>(first), container_detail::force<impl_const_iterator>(last))); }
+   {
+      return container_detail::force_copy<iterator>
+         (m_flat_tree.erase( container_detail::force_copy<impl_const_iterator>(first)
+                           , container_detail::force_copy<impl_const_iterator>(last)));
+   }
 
    //! <b>Effects</b>: erase(a.begin(),a.end()).
    //!
@@ -1430,7 +1454,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Logarithmic.
    const_iterator find(const key_type& x) const
-      { return container_detail::force<const_iterator>(m_flat_tree.find(x)); }
+      { return container_detail::force_copy<const_iterator>(m_flat_tree.find(x)); }
 
    //! <b>Returns</b>: The number of elements with key equivalent to x.
    //!
@@ -1450,7 +1474,7 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Logarithmic
    const_iterator lower_bound(const key_type& x) const
-      {  return container_detail::force<const_iterator>(m_flat_tree.lower_bound(x));  }
+      {  return container_detail::force_copy<const_iterator>(m_flat_tree.lower_bound(x));  }
 
    //! <b>Returns</b>: An iterator pointing to the first element with key not less
    //!   than x, or end() if such an element is not found.
@@ -1464,20 +1488,20 @@ class flat_multimap
    //!
    //! <b>Complexity</b>: Logarithmic
    const_iterator upper_bound(const key_type& x) const
-      {  return container_detail::force<const_iterator>(m_flat_tree.upper_bound(x)); }
+      {  return container_detail::force_copy<const_iterator>(m_flat_tree.upper_bound(x)); }
 
    //! <b>Effects</b>: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).
    //!
    //! <b>Complexity</b>: Logarithmic
    std::pair<iterator,iterator> equal_range(const key_type& x)
-      {  return container_detail::force<std::pair<iterator,iterator> >(m_flat_tree.equal_range(x));   }
+      {  return container_detail::force_copy<std::pair<iterator,iterator> >(m_flat_tree.equal_range(x));   }
 
    //! <b>Effects</b>: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).
    //!
    //! <b>Complexity</b>: Logarithmic
    std::pair<const_iterator,const_iterator>
       equal_range(const key_type& x) const
-      {  return container_detail::force<std::pair<const_iterator,const_iterator> >(m_flat_tree.equal_range(x));   }
+      {  return container_detail::force_copy<std::pair<const_iterator,const_iterator> >(m_flat_tree.equal_range(x));   }
 
    //! <b>Effects</b>: Number of elements for which memory has been allocated.
    //!   capacity() is always greater than or equal to size().