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diff --git a/boost/poly_collection/detail/base_model.hpp b/boost/poly_collection/detail/base_model.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_BASE_MODEL_HPP
+#define BOOST_POLY_COLLECTION_DETAIL_BASE_MODEL_HPP
+
+#if defined(_MSC_VER)
+#pragma once
+#endif
+
+#include <boost/core/addressof.hpp>
+#include <boost/poly_collection/detail/is_final.hpp>
+#include <boost/poly_collection/detail/packed_segment.hpp>
+#include <boost/poly_collection/detail/stride_iterator.hpp>
+#include <memory>
+#include <type_traits>
+#include <typeinfo>
+#include <utility>
+
+namespace boost{
+
+namespace poly_collection{
+
+namespace detail{
+
+/* model for base_collection */
+
+template<typename Base>
+struct base_model
+{
+  using value_type=Base;
+  template<typename Derived>
+  using is_subtype=std::is_base_of<Base,Derived>;
+  template<typename T>
+  using is_terminal=is_final<T>; //TODO: should we say !is_polymorhpic||is_final?
+
+private:
+  template<typename T>
+  using enable_if_not_terminal=
+    typename std::enable_if<!is_terminal<T>::value>::type*;
+  template<typename T>
+  using enable_if_terminal=
+    typename std::enable_if<is_terminal<T>::value>::type*;
+
+public:
+  template<typename T,enable_if_not_terminal<T> =nullptr>
+  static const std::type_info& subtypeid(const T& x){return typeid(x);}
+
+  template<typename T,enable_if_terminal<T> =nullptr>
+  static const std::type_info& subtypeid(const T&){return typeid(T);}
+
+  template<typename T,enable_if_not_terminal<T> =nullptr>
+  static void* subaddress(T& x)
+  {
+    return dynamic_cast<void*>(boost::addressof(x));
+  }
+
+  template<typename T,enable_if_not_terminal<T> =nullptr>
+  static const void* subaddress(const T& x)
+  {
+    return dynamic_cast<const void*>(boost::addressof(x));
+  }
+
+  template<typename T,enable_if_terminal<T> =nullptr>
+  static void* subaddress(T& x){return boost::addressof(x);}
+
+  template<typename T,enable_if_terminal<T> =nullptr>
+  static const void* subaddress(const T& x){return boost::addressof(x);}
+
+  using base_iterator=stride_iterator<Base>;
+  using const_base_iterator=stride_iterator<const Base>;
+  using base_sentinel=Base*;
+  using const_base_sentinel=const Base*;
+  template<typename Derived>
+  using iterator=Derived*;
+  template<typename Derived>
+  using const_iterator=const Derived*;
+  using segment_backend=detail::segment_backend<base_model>;
+  template<typename Derived,typename Allocator>
+  using segment_backend_implementation=packed_segment<
+    base_model,
+    Derived,
+    typename std::allocator_traits<Allocator>::template rebind_alloc<Derived>
+  >;
+  using segment_backend_unique_ptr=
+    typename segment_backend::segment_backend_unique_ptr;
+
+  static base_iterator nonconst_iterator(const_base_iterator it)
+  {
+    return {
+      const_cast<value_type*>(static_cast<const value_type*>(it)),
+      it.stride()
+    };
+  }
+
+  template<typename T>
+  static iterator<T> nonconst_iterator(const_iterator<T> it)
+  {
+    return const_cast<iterator<T>>(it);
+  }
+
+  template<typename Derived,typename Allocator>
+  static segment_backend_unique_ptr make(const Allocator& al)
+  {
+    return segment_backend_implementation<Derived,Allocator>::new_(al,al);
+  }
+
+private:
+  template<typename,typename,typename>
+  friend class packed_segment;
+
+  template<typename Derived>
+  static const Base* value_ptr(const Derived* p)noexcept
+  {
+    return p;
+  }
+};
+
+} /* namespace poly_collection::detail */
+
+} /* namespace poly_collection */
+
+} /* namespace boost */
+
+#endif