Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

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Specializing index::indexable function object - storing shared pointers in the rtree

#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point.hpp>
#include <boost/geometry/geometries/box.hpp>

#include <boost/geometry/index/rtree.hpp>

#include <cmath>
#include <vector>
#include <iostream>
#include <boost/foreach.hpp>
#include <boost/shared_ptr.hpp>

namespace bg = boost::geometry;
namespace bgi = boost::geometry::index;

namespace boost { namespace geometry { namespace index {

template <typename Box>
struct indexable< boost::shared_ptr<Box> >
{
    typedef boost::shared_ptr<Box> V;

    typedef Box const& result_type;
    result_type operator()(V const& v) const { return *v; }
};

}}} // namespace boost::geometry::index

int main(void)
{
    typedef bg::model::point<float, 2, bg::cs::cartesian> point;
    typedef bg::model::box<point> box;
    typedef boost::shared_ptr<box> shp;
    typedef shp value;

    // create the rtree using default constructor
    bgi::rtree< value, bgi::linear<16, 4> > rtree;

    std::cout << "filling index with boxes shared pointers:" << std::endl;

    // fill the spatial index
    for ( unsigned i = 0 ; i < 10 ; ++i )
    {
        // create a box
        shp b(new box(point(i, i), point(i+0.5f, i+0.5f)));

        // display new box
        std::cout << bg::wkt<box>(*b) << std::endl;

        // insert new value
        rtree.insert(b);
    }

    // find values intersecting some area defined by a box
    box query_box(point(0, 0), point(5, 5));
    std::vector<value> result_s;
    rtree.query(bgi::intersects(query_box), std::back_inserter(result_s));

    // find 5 nearest values to a point
    std::vector<value> result_n;
    rtree.query(bgi::nearest(point(0, 0), 5), std::back_inserter(result_n));

    // display results
    std::cout << "spatial query box:" << std::endl;
    std::cout << bg::wkt<box>(query_box) << std::endl;
    std::cout << "spatial query result:" << std::endl;
    BOOST_FOREACH(value const& v, result_s)
        std::cout << bg::wkt<box>(*v) << std::endl;

    std::cout << "knn query point:" << std::endl;
    std::cout << bg::wkt<point>(point(0, 0)) << std::endl;
    std::cout << "knn query result:" << std::endl;
    BOOST_FOREACH(value const& v, result_n)
        std::cout << bg::wkt<box>(*v) << std::endl;

    return 0;
}


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