Range adaptors

| Home | Libraries | People | FAQ | More

#### Range adaptors

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

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

    // Boost.Range
    #include <boost/range.hpp>
    // adaptors
    #include <boost/range/adaptor/indexed.hpp>
    #include <boost/range/adaptor/transformed.hpp>

    // a container
    #include <vector>

    // just for output
    #include <iostream>

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

    // Define a function object converting a value_type of indexed Range into std::pair<>.
    // This is a generic implementation but of course it'd be possible to use some
    // specific types. One could also take Value as template parameter and access
    // first_type and second_type members, etc.
    template <typename First, typename Second>
    struct pair_maker
    {
        typedef std::pair<First, Second> result_type;
        template<typename T>
        inline result_type operator()(T const& v) const
        {
            return result_type(v.value(), v.index());
        }
    };

    int main()
    {
        typedef bg::model::point<float, 2, bg::cs::cartesian> point;
        typedef bg::model::box<point> box;

        typedef std::vector<box> container;
        typedef container::size_type size_type;

        typedef std::pair<box, size_type> value;

        // create a container of boxes
        container boxes;
        for ( size_type i = 0 ; i < 10 ; ++i )
        {
            // add a box into the container
            box b(point(i + 0.0f, i + 0.0f), point(i + 0.5f, i + 0.5f));
            boxes.push_back(b);
        }

        // create the rtree passing a Range
        bgi::rtree< value, bgi::quadratic<16> >
            rtree(boxes | boost::adaptors::indexed()
                        | boost::adaptors::transformed(pair_maker<box, size_type>()));

        // print the number of values using boxes[0] as indexable
        std::cout << rtree.count(boxes[0]) << std::endl;

        return 0;
    }

##### Expected results

    1