adding fusion docs and tests

[SVN r34920]

example/extension/detail/size_impl.hpp

@@ -0,0 +1,34 @@
+/*=============================================================================
+    Copyright (c) 2001-2006 Joel de Guzman
+    Copyright (c) 2005-2006 Dan Marsden
+
+    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(BOOST_FUSION_SIZE_IMPL_20060223_2033)
+#define BOOST_FUSION_SIZE_IMPL_20060223_2033
+
+#include <boost/mpl/int.hpp>
+
+namespace boost { namespace fusion {
+
+    struct example_sequence_tag;
+
+    namespace extension
+    {
+        template<typename Tag>
+        struct size_impl;
+
+        template<>
+        struct size_impl<example_sequence_tag>
+        {
+            template<typename Sequence>
+            struct apply
+                : mpl::int_<2>
+            {};
+        };
+    }
+}}
+
+#endif