Boost C++ Libraries

#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>

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

template <typename Container>
class my_indexable
{
    typedef typename Container::size_type size_t;
    typedef typename Container::const_reference cref;
    Container const& container;

public:
    typedef cref result_type;
    explicit my_indexable(Container const& c) : container(c) {}
    result_type operator()(size_t i) const { return container[i]; }
};

int main()
{
    typedef bg::model::point<float, 2, bg::cs::cartesian> point;
    typedef bg::model::box<point> box;
    typedef std::vector<box>::size_type value;
    typedef bgi::rstar<16, 4> parameters;
    typedef my_indexable< std::vector<box> > indexable_getter;

    // boxes
    std::vector<box> boxes;

    // create some boxes
    for ( unsigned i = 0 ; i < 10 ; ++i )
    {
        // add a box
        boxes.push_back(box(point(i+0.0f, i+0.0f), point(i+0.5f, i+0.5f)));
    }

    // display boxes
    std::cout << "generated boxes:" << std::endl;
    BOOST_FOREACH(box const& b, boxes)
        std::cout << bg::wkt<box>(b) << std::endl;

    // create the rtree
    parameters params;
    indexable_getter ind(boxes);
    bgi::rtree<value, parameters, indexable_getter> rtree(params, ind);

    // fill the spatial index
    for ( size_t i = 0 ; i < boxes.size() ; ++i )
        rtree.insert(i);

    // 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));

    // note: in Boost.Geometry the WKT representation of a box is polygon

    // 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 i, result_s)
        std::cout << bg::wkt<box>(boxes[i]) << 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 i, result_n)
        std::cout << bg::wkt<box>(boxes[i]) << std::endl;

    return 0;
}

Expected results

generated boxes:
POLYGON((0 0,0 0.5,0.5 0.5,0.5 0,0 0))
POLYGON((1 1,1 1.5,1.5 1.5,1.5 1,1 1))
POLYGON((2 2,2 2.5,2.5 2.5,2.5 2,2 2))
POLYGON((3 3,3 3.5,3.5 3.5,3.5 3,3 3))
POLYGON((4 4,4 4.5,4.5 4.5,4.5 4,4 4))
POLYGON((5 5,5 5.5,5.5 5.5,5.5 5,5 5))
POLYGON((6 6,6 6.5,6.5 6.5,6.5 6,6 6))
POLYGON((7 7,7 7.5,7.5 7.5,7.5 7,7 7))
POLYGON((8 8,8 8.5,8.5 8.5,8.5 8,8 8))
POLYGON((9 9,9 9.5,9.5 9.5,9.5 9,9 9))
spatial query box:
POLYGON((0 0,0 5,5 5,5 0,0 0))
spatial query result:
POLYGON((0 0,0 0.5,0.5 0.5,0.5 0,0 0))
POLYGON((1 1,1 1.5,1.5 1.5,1.5 1,1 1))
POLYGON((2 2,2 2.5,2.5 2.5,2.5 2,2 2))
POLYGON((3 3,3 3.5,3.5 3.5,3.5 3,3 3))
POLYGON((4 4,4 4.5,4.5 4.5,4.5 4,4 4))
POLYGON((5 5,5 5.5,5.5 5.5,5.5 5,5 5))
knn query point:
POINT(0 0)
knn query result:
POLYGON((4 4,4 4.5,4.5 4.5,4.5 4,4 4))
POLYGON((3 3,3 3.5,3.5 3.5,3.5 3,3 3))
POLYGON((2 2,2 2.5,2.5 2.5,2.5 2,2 2))
POLYGON((0 0,0 0.5,0.5 0.5,0.5 0,0 0))
POLYGON((1 1,1 1.5,1.5 1.5,1.5 1,1 1))