Specializing insert_range for aux::map_tag

Taking advantage of the fact that order of insertion doesn't really
matter for associative sequences.
Comparing to the default implementation, which at any rate does work for
associative sequences, this specialization essencially avoids
reinserting every element of Sequence into a new sequence, besides the
fact no joint_view nor iterator_range needs to be instantiated.

include/boost/mpl/map/aux_/insert_range_impl.hpp

@@ -0,0 +1,41 @@
+
+#ifndef BOOST_MPL_MAP_AUX_INSERT_RANGE_IMPL_HPP_INCLUDED
+#define BOOST_MPL_MAP_AUX_INSERT_RANGE_IMPL_HPP_INCLUDED
+
+// Copyright Bruno Dutra 2015
+//
+// 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)
+//
+// See http://www.boost.org/libs/mpl for documentation.
+
+// $Id$
+// $Date$
+// $Revision$
+
+#include <boost/mpl/insert_range_fwd.hpp>
+#include <boost/mpl/map/aux_/tag.hpp>
+#include <boost/mpl/placeholders.hpp>
+#include <boost/mpl/fold.hpp>
+#include <boost/mpl/insert.hpp>
+
+namespace boost { namespace mpl {
+
+template<>
+struct insert_range_impl< aux::map_tag >
+{
+    template<
+          typename Sequence
+        , typename /*Pos*/
+        , typename Range
+        >
+    struct apply
+        : fold<Range, Sequence, insert<_1, _2> >
+    {
+    };
+};
+
+}}
+
+#endif // BOOST_MPL_MAP_AUX_INSERT_RANGE_IMPL_HPP_INCLUDED

include/boost/mpl/map/map0.hpp

@@ -19,6 +19,7 @@
 #include <boost/mpl/map/aux_/at_impl.hpp>
 //#include <boost/mpl/map/aux_/O1_size.hpp>
 #include <boost/mpl/map/aux_/insert_impl.hpp>
+#include <boost/mpl/map/aux_/insert_range_impl.hpp>
 #include <boost/mpl/map/aux_/erase_impl.hpp>
 #include <boost/mpl/map/aux_/erase_key_impl.hpp>
 #include <boost/mpl/map/aux_/has_key_impl.hpp>