adding get_tag definition

test/Jamfile.v2

@@ -37,6 +37,7 @@ compile find_if.cpp ;
 compile fold.cpp ;
 run for_each.cpp ;
 compile front.cpp ;
+compile get_tag_def.cpp ;
 compile has_xxx.cpp ;
 compile identity.cpp ;
 compile if.cpp ;

test/get_tag_def.cpp

@@ -0,0 +1,32 @@
+
+// Copyright Sergey Krivonos 2017
+//
+// 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/get_tag.hpp>
+#include <boost/mpl/aux_/test.hpp>
+#include <boost/mpl/aux_/test/assert.hpp>
+#include <boost/type_traits/is_same.hpp>
+
+
+struct test_type_get_tag_def
+{
+    typedef int a_tag;
+};
+
+BOOST_MPL_GET_TAG_DEF(a_tag);
+
+MPL_TEST_CASE()
+{
+    MPL_ASSERT(( is_same<int, boost::mpl::get_a_tag<test_type_get_tag_def>::type> ));
+    MPL_ASSERT(( is_same<test_type_get_tag_def::a_tag, boost::mpl::get_a_tag<test_type_get_tag_def>::type> ));
+}