creating branch for fusion 2.1

[SVN r40232]

include/boost/fusion/container/map/detail/lookup_key.hpp

@@ -0,0 +1,99 @@
+/*=============================================================================
+    Copyright (c) 2001-2006 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_LOOKUP_KEY_07222005_1248)
+#define FUSION_LOOKUP_KEY_07222005_1248
+
+#include <boost/mpl/int.hpp>
+#include <boost/type_traits/add_const.hpp>
+#include <boost/type_traits/add_reference.hpp>
+#include <boost/fusion/support/detail/unknown_key.hpp>
+
+namespace boost { namespace fusion 
+{
+    struct void_;    
+}}
+
+namespace boost { namespace fusion { namespace detail 
+{
+    template <typename T>
+    struct map_data_type
+    {
+        typedef typename 
+            add_reference<
+                typename T::second_type
+            >::type 
+        type;
+    };
+
+    template <>
+    struct map_data_type<void_>
+    {
+        typedef void_& type;
+    };
+
+    template <typename T>
+    struct map_const_data_type
+    {
+        typedef typename 
+            add_reference<
+                typename add_const<
+                    typename T::second_type
+                >::type
+            >::type 
+        type;
+    };
+
+    template <>
+    struct map_const_data_type<void_>
+    {
+        typedef void_ const& type;
+    };
+
+    template <typename T>
+    struct map_value_type
+    {
+        typedef typename T::second_type type;
+    };
+
+    template <>
+    struct map_value_type<void_>
+    {
+        typedef void_ type;
+    };
+
+    template <typename T, int index>
+    struct map_key_type
+    {
+        typedef typename T::first_type type;
+    };
+
+    template <int index>
+    struct map_key_type<void_, index>
+    {
+        typedef unknown_key<index> type;
+    };
+
+    template <int index, typename RT, typename Key, typename Vector>
+    struct map_lookup_key
+    {
+        static RT
+        call(Vector& vec)
+        {
+            return vec.at_impl(mpl::int_<index>()).second;
+        }
+    };
+
+    template <int index, typename Vector>
+    struct map_lookup_key<index, void_&, unknown_key<index>, Vector>
+    {
+        static void_&
+        call(Vector& vec); // intentionally undefined
+    };
+}}} 
+
+#endif
+