Initial move from Spirit CVS

[SVN r34896]

include/boost/fusion/sequence/intrinsic/value_at_key.hpp

@@ -0,0 +1,38 @@
+/*=============================================================================
+    Copyright (c) 2001-2006 Joel de Guzman
+    Copyright (c) 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(FUSION_VALUE_AT_KEY_05052005_0229)
+#define FUSION_VALUE_AT_KEY_05052005_0229
+
+#include <boost/mpl/int.hpp>
+#include <boost/fusion/support/tag_of.hpp>
+
+namespace boost { namespace fusion
+{
+    namespace extension
+    {
+        template <typename Tag>
+        struct value_at_key_impl
+        {
+            template <typename Sequence, typename N>
+            struct apply;
+        };
+    }
+    
+    namespace result_of
+    {
+        template <typename Sequence, typename N>
+        struct value_at_key
+            : extension::value_at_key_impl<typename detail::tag_of<Sequence>::type>::
+                template apply<Sequence, N>
+        {};
+    }
+}}
+
+#endif
+