[strategies][comparable distance] implement the class

comparable_distance_result

include/boost/geometry/strategies/comparable_distance_result.hpp

@@ -0,0 +1,63 @@
+// Boost.Geometry (aka GGL, Generic Geometry Library)
+
+// Copyright (c) 2014, Oracle and/or its affiliates.
+
+// Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
+
+// Licensed under the Boost Software License version 1.0.
+// http://www.boost.org/users/license.html
+
+#ifndef BOOST_GEOMETRY_STRATEGIES_COMPARABLE_DISTANCE_RESULT_HPP
+#define BOOST_GEOMETRY_STRATEGIES_COMPARABLE_DISTANCE_RESULT_HPP
+
+#include <boost/geometry/core/point_type.hpp>
+#include <boost/geometry/strategies/distance.hpp>
+
+#include <boost/geometry/algorithms/detail/distance/default_strategies.hpp>
+
+
+namespace boost { namespace geometry
+{
+
+/*!
+\brief Meta-function defining return type of comparable_distance function
+\ingroup distance
+*/
+template
+<
+    typename Geometry1,
+    typename Geometry2 = Geometry1,
+    typename Strategy = void
+>
+struct comparable_distance_result
+{
+    typedef typename strategy::distance::services::return_type
+        <
+            typename strategy::distance::services::comparable_type
+                <
+                    Strategy
+                >::type,
+            typename point_type<Geometry1>::type,
+            typename point_type<Geometry2>::type
+        >::type type;
+};
+
+
+template <typename Geometry1, typename Geometry2>
+struct comparable_distance_result<Geometry1, Geometry2, void>
+    : comparable_distance_result
+        <
+            Geometry1,
+            Geometry2,
+            typename detail::distance::default_strategy
+                <
+                    Geometry1, Geometry2
+                >::type
+        >
+{};
+
+
+}} // namespace boost::geometry
+
+
+#endif // BOOST_GEOMETRY_STRATEGIES_COMPARABLE_DISTANCE_RESULT_HPP