text: #include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
  #include <CGAL/Triangulation_2.h>
  #include <CGAL/boost/graph/graph_traits_Triangulation_2.h>
  
  #include <CGAL/boost/graph/dijkstra_shortest_paths.h>
  #include <boost/graph/filtered_graph.hpp>
  #include <fstream>
  
  typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
  typedef K::Point_2 Point;
  
  typedef CGAL::Triangulation_2<K> Triangulation;
  
  // As we want to run Dijskra's shortest path algorithm we only
  // consider finite vertices and edges.
  
  template <typename T>
  struct Is_finite {
  
    const T* t_;
  
    Is_finite()
      : t_(NULL)
    {}
  
    Is_finite(const T& t)
      : t_(&t)
    { }
  
    template <typename VertexOrEdge>
    bool operator()(const VertexOrEdge& voe) const {
      return ! t_->is_infinite(voe);
    }
  };
  
  typedef Is_finite<Triangulation> Filter;
  typedef boost::filtered_graph<Triangulation,Filter,Filter> Finite_triangulation;
  typedef boost::graph_traits<Finite_triangulation>::vertex_descriptor vertex_descriptor;
  typedef boost::graph_traits<Finite_triangulation>::vertex_iterator vertex_iterator;
  
  typedef std::map<vertex_descriptor,int> VertexIndexMap;
  VertexIndexMap vertex_id_map;
  
  typedef boost::associative_property_map<VertexIndexMap> VertexIdPropertyMap;
  VertexIdPropertyMap vertex_index_pmap(vertex_id_map);
  
  int
  main(int argc,char* argv[])
  {
    const char* filename = (argc > 1) ? argv[1] : "data/points.xy";
    std::ifstream input(filename);
    Triangulation t;
    Filter is_finite(t);
    Finite_triangulation ft(t, is_finite, is_finite);
  
    Point p ;
    while(input >> p){
      t.insert(p);
    }
  
    vertex_iterator vit, ve;
    // Associate indices to the vertices
    int index = 0;
    // boost::tie assigns the first and second element of the std::pair
    // returned by boost::vertices to the variables vit and ve
    for(boost::tie(vit,ve)=boost::vertices(ft); vit!=ve; ++vit ){
      vertex_descriptor  vd = *vit;
      vertex_id_map[vd]= index++;
      }
  
    // Dijkstra's shortest path needs property maps for the predecessor and distance
    // We first declare a vector
    std::vector<vertex_descriptor> predecessor(boost::num_vertices(ft));
    // and then turn it into a property map
    boost::iterator_property_map<std::vector<vertex_descriptor>::iterator,
                                 VertexIdPropertyMap>
      predecessor_pmap(predecessor.begin(), vertex_index_pmap);
  
    std::vector<double> distance(boost::num_vertices(ft));
    boost::iterator_property_map<std::vector<double>::iterator,
                                 VertexIdPropertyMap>
      distance_pmap(distance.begin(), vertex_index_pmap);
  
    // start at an arbitrary vertex
    vertex_descriptor source = *boost::vertices(ft).first;
    std::cout << "\nStart dijkstra_shortest_paths at " << source->point() <<"\n";
  
    boost::dijkstra_shortest_paths(ft, source,
  				 distance_map(distance_pmap)
  				 .predecessor_map(predecessor_pmap)
  				 .vertex_index_map(vertex_index_pmap));
  
    for(boost::tie(vit,ve)=boost::vertices(ft); vit!=ve; ++vit ){
      vertex_descriptor vd = *vit;
      std::cout << vd->point() << " [" <<  vertex_id_map[vd] << "] ";
      std::cout << " has distance = "  << boost::get(distance_pmap,vd)
  	      << " and predecessor ";
      vd =  boost::get(predecessor_pmap,vd);
      std::cout << vd->point() << " [" <<  vertex_id_map[vd] << "]\n ";
    }
  
    return 0;
  }
  