// showing only metafunction result_from_distance
template <typename Point1, typename Point2, typename typename CalculationType>
struct result_from_distance<strategy::distance::comparable::pythagoras<Point1, Point2, CalculationType> >
{
private :
    typedef strategy::distance::comparable::pythagoras<Point1, Point2, CalculationType> this_type;
public :
    template <typename T>
    static inline typename this_type::return_type apply(T const& value)
    {
        typename this_type::return_type const v = value;
        return v * v;
    }
};