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   1 // Boost.Geometry Index
   2 //
   3 // squared distance between point and centroid of the box or point
   4 //
   5 // Copyright (c) 2011-2014 Adam Wulkiewicz, Lodz, Poland.
   6 //
   7 // Use, modification and distribution is subject to the Boost Software License,
   8 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   9 // http://www.boost.org/LICENSE_1_0.txt)
  10
  11 #ifndef BOOST_GEOMETRY_INDEX_DETAIL_ALGORITHMS_COMPARABLE_DISTANCE_CENTROID_HPP
  12 #define BOOST_GEOMETRY_INDEX_DETAIL_ALGORITHMS_COMPARABLE_DISTANCE_CENTROID_HPP
  13
  14 #include <boost/geometry/index/detail/algorithms/sum_for_indexable.hpp>
  15 #include <boost/geometry/index/detail/algorithms/diff_abs.hpp>
  16
  17 namespace boost { namespace geometry { namespace index { namespace detail {
  18
  19 struct comparable_distance_centroid_tag {};
  20
  21 template <
  22     typename Point,
  23     typename PointIndexable,
  24     size_t N>
  25 struct sum_for_indexable<Point, PointIndexable, point_tag, comparable_distance_centroid_tag, N>
  26 {
  27     typedef typename geometry::default_comparable_distance_result<Point, PointIndexable>::type result_type;
  28
  29     inline static result_type apply(Point const& pt, PointIndexable const& i)
  30     {
  31         return geometry::comparable_distance(pt, i);
  32     }
  33 };
  34
  35 template <
  36     typename Point,
  37     typename BoxIndexable,
  38     size_t DimensionIndex>
  39 struct sum_for_indexable_dimension<Point, BoxIndexable, box_tag, comparable_distance_centroid_tag, DimensionIndex>
  40 {
  41     typedef typename geometry::default_comparable_distance_result<Point, BoxIndexable>::type result_type;
  42
  43     inline static result_type apply(Point const& pt, BoxIndexable const& i)
  44     {
  45         typedef typename coordinate_type<Point>::type point_coord_t;
  46         typedef typename coordinate_type<BoxIndexable>::type indexable_coord_t;
  47
  48         point_coord_t pt_c = geometry::get<DimensionIndex>(pt);
  49         indexable_coord_t ind_c_min = geometry::get<geometry::min_corner, DimensionIndex>(i);
  50         indexable_coord_t ind_c_max = geometry::get<geometry::max_corner, DimensionIndex>(i);
  51
  52         indexable_coord_t ind_c_avg = ind_c_min + (ind_c_max - ind_c_min) / 2;
  53         // TODO: awulkiew - is (ind_c_min + ind_c_max) / 2 safe?
  54
  55         result_type diff = detail::diff_abs(ind_c_avg, pt_c);
  56
  57         return diff * diff;
  58     }
  59 };
  60
  61 template <typename Point, typename Indexable>
  62 typename geometry::default_comparable_distance_result<Point, Indexable>::type
  63 comparable_distance_centroid(Point const& pt, Indexable const& i)
  64 {
  65     return detail::sum_for_indexable<
  66         Point,
  67         Indexable,
  68         typename tag<Indexable>::type,
  69         detail::comparable_distance_centroid_tag,
  70         dimension<Indexable>::value
  71     >::apply(pt, i);
  72 }
  73
  74 }}}} // namespace boost::geometry::index::detail
  75
  76 #endif // #define BOOST_GEOMETRY_INDEX_DETAIL_ALGORITHMS_COMPARABLE_DISTANCE_CENTROID_HPP
  77