Hello there, I started using Boost graph library recently for one of my projects.I was trying to implement dijkstra's shortest path algorithm with the help of the following function, dijkstra_shortest_paths (G, vertex(a, G), distance_map(make_iterator_property_map(distance.begin(), vertex_id, distance[0])). predecessor_map(make_iterator_property_map(parent.begin(), vertex_id, parent[0])). visitor(make_dijkstra_visitor(copy_graph(G_copy, on_examine_edge())))); But while comparing the definition of the function as in http://www.boost.org/doc/libs/1_55_0/libs/graph/doc/dijkstra_shortest_paths...., to the above written function,it doesnt make sense, especially the third argument of the above written function.Can anyone help me with this? Thanks in advance.