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diff --git a/boost/poly_collection/detail/iterator_traits.hpp b/boost/poly_collection/detail/iterator_traits.hpp
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+++ b/boost/poly_collection/detail/iterator_traits.hpp
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+/* Copyright 2016-2017 Joaquin M Lopez Munoz.
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * See http://www.boost.org/libs/poly_collection for library home page.
+ */
+
+#ifndef BOOST_POLY_COLLECTION_DETAIL_ITERATOR_TRAITS_HPP
+#define BOOST_POLY_COLLECTION_DETAIL_ITERATOR_TRAITS_HPP
+
+#if defined(_MSC_VER)
+#pragma once
+#endif
+
+#include <iterator>
+#include <type_traits>
+
+namespace boost{
+
+namespace poly_collection{
+
+namespace detail{
+
+/* (Internal) bunch of traits-grouped functions for const-preserving
+ * interoperatibility between iterators and local iterators of a
+ * poly_collection.
+ */
+
+template<typename Iterator>
+struct poly_collection_of /* to be specialized for iterator impls */
+{
+ using type=void;
+};
+
+namespace poly_collection_impl{
+
+template<typename Model,typename Allocator>
+class poly_collection;
+
+}
+
+template<typename PolyCollection>
+struct model_of;
+
+template<typename Model,typename Allocator>
+struct model_of<poly_collection_impl::poly_collection<Model,Allocator>>
+{
+  using type=Model;
+};
+
+template<typename Iterator>
+struct iterator_traits
+{
+  using container_type=typename poly_collection_of<Iterator>::type;
+  using is_const_iterator=typename std::is_const<
+    typename std::remove_reference<
+      typename std::iterator_traits<Iterator>::reference
+    >::type
+  >::type;
+  using iterator=typename std::conditional<
+    is_const_iterator::value,
+    typename container_type::const_iterator,   
+    typename container_type::iterator
+  >::type;
+  using base_segment_info_iterator=typename std::conditional<
+    is_const_iterator::value,
+    typename container_type::const_base_segment_info_iterator,   
+    typename container_type::base_segment_info_iterator
+  >::type;
+  using local_base_iterator=typename std::conditional<
+    is_const_iterator::value,
+    typename container_type::const_local_base_iterator,   
+    typename container_type::local_base_iterator
+  >::type;
+  template<typename T>
+  using local_iterator=typename std::conditional<
+    is_const_iterator::value,
+    typename container_type::template const_local_iterator<T>,   
+    typename container_type::template local_iterator<T>
+  >::type;
+
+  static base_segment_info_iterator
+  base_segment_info_iterator_from(iterator it)noexcept{return it.mapit;} 
+
+  static base_segment_info_iterator
+  base_segment_info_iterator_from(local_base_iterator it)noexcept
+    {return it.mapit;}
+
+  static base_segment_info_iterator
+  end_base_segment_info_iterator_from(iterator it)noexcept{return it.mapend;} 
+
+  static local_base_iterator
+  local_base_iterator_from(iterator it)noexcept
+  {
+    return {
+      it.mapit,
+      model_of<container_type>::type::nonconst_iterator(it.segpos)
+    };
+  }
+
+  static iterator 
+  iterator_from(
+    local_base_iterator lbit,base_segment_info_iterator mapend)noexcept
+  {
+    return {lbit.mapit,mapend.base(),lbit.base()};
+  }
+};
+
+} /* namespace poly_collection::detail */
+
+} /* namespace poly_collection */
+
+} /* namespace boost */
+
+#endif