[boost] null vertex, edge descriptors

From: Tim Culver (tim.gmane_at_[hidden])
Date: 2002-09-16 16:01:19

I read an archived discussion of vertex and edge descriptors, but I'm 
not sure I understood it.  Is this the proper way to handle these:

typedef adjacency_list<listS, listS, ...> Graph;
typedef graph_traits<Graph>::vertex_descriptor Vdesc;
typedef graph_traits<Graph>::edge_descriptor Edesc;

Vdesc find_vertex(Graph& g) {
   Vdesc v, v_end;
   for (tie(v, v_end)=g.vertices(); v!=v_end; v++)
     if (my criterion)
       return v;
   return Vdesc();
}

   Vdesc v = find_vertex(g);
   if (v != Vdesc()) {
     // found
   } else {
     // not found
   }

1. Is this correct as written?  (Semantically, I mean--does it do what I 
obviously want it to do?)

2. Is this still correct if I change both listS to vecS?

Thanks,
Tim