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diff --git a/boost/fusion/iterator/distance.hpp b/boost/fusion/iterator/distance.hpp
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+/*=============================================================================
+    Copyright (c) 2001-2011 Joel de Guzman
+
+    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)
+==============================================================================*/
+#if !defined(FUSION_DISTANCE_09172005_0721)
+#define FUSION_DISTANCE_09172005_0721
+
+#include <boost/fusion/iterator/detail/distance.hpp>
+#include <boost/fusion/support/category_of.hpp>
+
+#include <boost/mpl/int.hpp>
+#include <boost/mpl/assert.hpp>
+#include <boost/type_traits/is_same.hpp>
+
+#include <boost/fusion/support/tag_of.hpp>
+
+namespace boost { namespace fusion
+{
+    struct random_access_traversal_tag;
+
+    // Special tags:
+    struct iterator_facade_tag; // iterator facade tag
+    struct boost_array_iterator_tag; // boost::array iterator tag
+    struct mpl_iterator_tag; // mpl sequence iterator tag
+    struct std_pair_iterator_tag; // std::pair iterator tag
+
+    namespace extension
+    {
+        template <typename Tag>
+        struct distance_impl
+        {
+            // default implementation
+            template <typename First, typename Last>
+            struct apply : distance_detail::linear_distance<First, Last> 
+            {};
+        };
+
+        template <>
+        struct distance_impl<iterator_facade_tag>
+        {
+            template <typename First, typename Last>
+            struct apply : First::template distance<First, Last> {};
+        };
+
+        template <>
+        struct distance_impl<boost_array_iterator_tag>;
+
+        template <>
+        struct distance_impl<mpl_iterator_tag>;
+
+        template <>
+        struct distance_impl<std_pair_iterator_tag>;
+    }
+
+    namespace result_of
+    {
+        template <typename First, typename Last>
+        struct distance
+          : extension::distance_impl<typename detail::tag_of<First>::type>::
+                template apply<First, Last>
+        {
+            typedef typename extension::distance_impl<typename detail::tag_of<First>::type>:: 
+            template apply<First, Last>::type distance_application;
+            BOOST_STATIC_CONSTANT(int, value = distance_application::value);
+        };
+    }
+        
+    template <typename First, typename Last>
+    inline typename result_of::distance<First, Last>::type
+    distance(First const& a, Last const& b)
+    {
+        return result_of::distance<First, Last>::call(a,b);
+    }
+}}
+
+#endif