Initial move from Spirit CVS

[SVN r34896]

include/boost/fusion/iterator/distance.hpp

@@ -0,0 +1,58 @@
+/*=============================================================================
+    Copyright (c) 2001-2006 Joel de Guzman
+
+    Use, modification and distribution is subject to 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;
+
+    namespace extension
+    {
+        template <typename Tag>
+        struct distance_impl
+        {
+            // default implementation
+            template <typename First, typename Last>
+            struct apply : distance_detail::linear_distance<First, Last> 
+            {
+                typedef typename traits::category_of<First>::type first_category;
+                typedef typename traits::category_of<Last>::type last_category;
+                BOOST_MPL_ASSERT((is_same<first_category, last_category>));
+                BOOST_MPL_ASSERT_NOT((is_same<first_category, random_access_traversal_tag>));
+            };
+        };
+    }
+
+    namespace result_of
+    {
+        template <typename First, typename Last>
+        struct distance
+            : extension::distance_impl<typename detail::tag_of<First>::type>:: 
+                template apply<First, Last>
+        {};
+    }
+        
+    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