C++ List::erase方法代码示例

//' rcpp_get_polygons
//'
//' Extracts all polygons from an overpass API query
//'
//' @param st Text contents of an overpass API query
//' @return A \code{SpatialLinesDataFrame} contains all polygons and associated data
// [[Rcpp::export]]
Rcpp::S4 rcpp_get_polygons (const std::string& st)
{
#ifdef DUMP_INPUT
    {
        std::ofstream dump ("./get-polygons.xml");
        if (dump.is_open())
        {
            dump.write (st.c_str(), st.size());
        }
    }
#endif

    XmlPolys xml (st);

    const std::map <osmid_t, Node>& nodes = xml.nodes ();
    const std::map <osmid_t, OneWay>& ways = xml.ways ();
    const std::vector <Relation>& rels = xml.relations ();

    int count = 0;
    float xmin = FLOAT_MAX, xmax = -FLOAT_MAX,
          ymin = FLOAT_MAX, ymax = -FLOAT_MAX;
    std::vector <float> lons, lats;
    std::unordered_set <std::string> idset; // see TODO below
    std::vector <std::string> colnames, rownames, polynames;
    std::set <std::string> varnames;
    Rcpp::List dimnames (0), dummy_list (0);
    Rcpp::NumericMatrix nmat (Rcpp::Dimension (0, 0));

    idset.clear ();

    colnames.push_back ("lon");
    colnames.push_back ("lat");
    varnames.insert ("name");
    // other varnames added below

    /*
     * NOTE: Nodes are first loaded into the 2 vectors of (lon, lat), and these
     * are then copied into nmat. This intermediate can be avoided by loading
     * directly into nmat using direct indexing rather than iterators, however
     * this does *NOT* make the routine any faster, and so the current version
     * which more safely uses iterators is kept instead.
     */

    Rcpp::Environment sp_env = Rcpp::Environment::namespace_env ("sp");
    Rcpp::Function Polygon = sp_env ["Polygon"];
    Rcpp::Language polygons_call ("new", "Polygons");
    Rcpp::S4 polygons;

    /*
     * Polygons are extracted from the XmlPolys class in three setps:
     *  1. Get the names of all polygons that are part of multipolygon relations
     *  2. Get the names of any remaining ways that are polygonal (start == end)
     *  3. From the resultant list, extract the actual polygonal ways
     *
     * NOTE: OSM polygons are stored as ways, and thus all objects in the class
     * xmlPolys are rightly referred to as ways. Here within this Rcpp function,
     * these are referred to as Polygons, but the iteration is over the actual
     * polygonal ways.
     */

    // Step#1
    std::set <osmid_t> the_ways; // Set will only insert unique values
    for (auto it = rels.begin (); it != rels.end (); ++it)
        for (auto itw = (*it).ways.begin (); itw != (*it).ways.end (); ++itw)
        {
            assert (ways.find (itw->first) != ways.end ());
            the_ways.insert (itw->first);
        }

    // Step#2
    //const std::map <osmid_t, OneWay>& ways = xml.ways ();
    for (auto it = ways.begin (); it != ways.end (); ++it)
    {
        if (the_ways.find ((*it).first) == the_ways.end ())
            if ((*it).second.nodes.begin () == (*it).second.nodes.end ())
                the_ways.insert ((*it).first);
    }
    // Step#2b - Erase any ways that contain no data (should not happen).
    for (auto it = the_ways.begin (); it != the_ways.end (); )
    {
        auto itw = ways.find (*it);
        if (itw->second.nodes.size () == 0)
            it = the_ways.erase (it);
        else
            ++it;
    }
    Rcpp::List polyList (the_ways.size ());

    // Step#3 - Extract and store the_ways
    for (auto it = the_ways.begin (); it != the_ways.end (); ++it)
    {
        auto itw = ways.find (*it);
        // Collect all unique keys
//.........这里部分代码省略.........