Question

I have two structs containing some fields: struct MyNodeData, and struct MyEdgeData. When I create a graph with VertexList as vecS, there is no problem to access the descriptor of vertices etc. For example:

typedef adjacency_list<setS, vecS, undirectedS, MyNodeData, MyEdgeData> Graph;

typedef Graph::vertex_descriptor MyNodeDataID;
typedef Graph::edge_descriptor MyEdgeDataID;
typedef graph_traits < Graph >::vertex_iterator VertexIterator;
typedef graph_traits < Graph >::edge_iterator EdgeIterator;
typedef graph_traits < Graph >::adjacency_iterator AdjacencyIterator;
typedef property_map < Graph, vertex_index_t >::type IndexMap;

Graph g;
const IndexMap index = get(vertex_index, g);

/* Puis après avoir ajouté des vertex et edges, je peux accéder par exemple à la liste des vertex comme suite: */
pair<VertexIterator, VertexIterator> vi;
for(vi = vertices(g); vi.first != vi.second; ++vi.first)
{
   cout << "vertex: " << index[*vi.first] << endl;
   // or: cout << "vertex: " << *vi.first << endl;
}

But I usually need to add/delete edges and vertices from my graph. So I want to use setS or listS as a VertexList, instead of vecS, since with vecS the indexes are invalidated when we delete one of them !
The problem is that if I define VertexList as setS or listS, I can not browse the list of vertices/edges and access there descriptors like I did before !

To make it short, my question is: Since an adjacency_list that uses listS or setS as the vertex container does not automatically provide this vertex_id property, how can I add it to the code above ?

Answer 1

Currently, you just need to provide an associative property map.

<...>
typedef Graph::vertex_descriptor NodeID;

typedef map<NodeID, size_t> IndexMap;
IndexMap mapIndex;
associative_property_map<IndexMap> propmapIndex(mapIndex);
<...>

// indexing all vertices
int i=0;
BGL_FORALL_VERTICES(v, g, Graph)
{
   put(propmapIndex, v, i++);
}