// Boost.Geometry (aka GGL, Generic Geometry Library)

// Copyright (c) 2007-2011 Barend Gehrels, Amsterdam, the Netherlands.
// Copyright (c) 2008-2011 Bruno Lalande, Paris, France.
// Copyright (c) 2009-2011 Mateusz Loskot, London, UK.

// Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
// (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.

// 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)

#ifndef BOOST_GEOMETRY_ALGORITHMS_COMPARABLE_DISTANCE_HPP
#define BOOST_GEOMETRY_ALGORITHMS_COMPARABLE_DISTANCE_HPP


#include <boost/geometry/algorithms/distance.hpp>


namespace boost { namespace geometry
{


/*!
\brief \brief_calc2{comparable distance measurement}
\ingroup distance
\details The free function comparable_distance does not necessarily calculate the distance,
    but it calculates a distance measure such that two distances are comparable to each other.
    For example: for the Cartesian coordinate system, Pythagoras is used but the square root
    is not taken, which makes it faster and the results of two point pairs can still be 
    compared to each other.
\tparam Geometry1 first geometry type
\tparam Geometry2 second geometry type
\param geometry1 \param_geometry
\param geometry2 \param_geometry
\return \return_calc{comparable distance}

\qbk{[include reference/algorithms/comparable_distance.qbk]}
 */
template <typename Geometry1, typename Geometry2>
inline typename default_distance_result<Geometry1, Geometry2>::type comparable_distance(
                Geometry1 const& geometry1, Geometry2 const& geometry2)
{
    concept::check<Geometry1 const>();
    concept::check<Geometry2 const>();

    typedef typename point_type<Geometry1>::type point1_type;
    typedef typename point_type<Geometry2>::type point2_type;

    // Define a point-point-distance-strategy
    // for either the normal case, either the reversed case

    typedef typename strategy::distance::services::comparable_type
        <
            typename boost::mpl::if_c
                <
                    geometry::reverse_dispatch
                        <Geometry1, Geometry2>::type::value,
                    typename strategy::distance::services::default_strategy
                            <point_tag, point2_type, point1_type>::type,
                    typename strategy::distance::services::default_strategy
                            <point_tag, point1_type, point2_type>::type
                >::type
        >::type strategy_type;

    return distance(geometry1, geometry2, strategy_type());
}


}} // namespace boost::geometry


#endif // BOOST_GEOMETRY_ALGORITHMS_COMPARABLE_DISTANCE_HPP
