Hi there, I am new to BGL library. I am walking through the online tutorial and just finished the "10.2. Six Degrees of Kevin Bacon". As it is said at the end of the example: "Note that vertex descriptor objects can not always be used as indices into vectors or arrays such as bacon_number. This is valid with the adjacency_list class with VertexList=vecS, but not with other variations of adjacency_list. A more generic way to index based on vertices is to use the ID property map (vertex_index_t) in coordination with the iterator_property_map.". So I turn to have a look at the iterator_property_map page and its sample. First, this sample uses VertexList=vecS too. Second, I know this sample is using iterator_property_map to build a property map, but I think the property is still indexed by the edge descriptor objects. So what is the difference? Thanks. Zhiyu LI 2013-05-29 lizy10b