- hoisted enable_equality, enable_comparison and is_native_fusion_sequence to fusion::traits namespace

- added SFINAE-enable
(http://article.gmane.org/gmane.comp.parsers.spirit.devel/3902)

[SVN r68225]

include/boost/fusion/sequence/comparison/enable_comparison.hpp

@@ -0,0 +1,40 @@
+/*=============================================================================
+    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_ENABLE_COMPARISON_09232005_1958)
+#define FUSION_ENABLE_COMPARISON_09232005_1958
+
+#include <boost/mpl/or.hpp>
+#include <boost/mpl/and.hpp>
+#include <boost/mpl/not.hpp>
+#include <boost/mpl/equal_to.hpp>
+#include <boost/fusion/support/sequence_base.hpp>
+#include <boost/fusion/support/is_sequence.hpp>
+#include <boost/fusion/sequence/intrinsic/size.hpp>
+#include <boost/type_traits/is_convertible.hpp>
+
+namespace boost { namespace fusion { namespace traits
+{
+    template <typename Sequence, typename Enable = void>
+    struct is_native_fusion_sequence
+      : is_convertible<Sequence, detail::from_sequence_convertible_type>
+    {};
+
+    template <typename Seq1, typename Seq2, typename Enable = void>
+    struct enable_equality
+        : mpl::or_<traits::is_sequence<Seq1>, traits::is_sequence<Seq2> >
+    {};
+
+    template <typename Seq1, typename Seq2, typename Enable = void>
+    struct enable_comparison
+        : mpl::and_<
+            mpl::or_<traits::is_sequence<Seq1>, traits::is_sequence<Seq2> >
+          , mpl::equal_to<result_of::size<Seq1>, result_of::size<Seq2> >
+        >
+    {};
+}}}
+
+#endif