What is the relationship between BGL's edge_descriptor and edge_iterator?

From: Jeff Holle (jeff.holle_at_[hidden])
Date: 2003-03-14 01:07:36

What is the relationship between an "edge_descriptor" and what an
edge_iterator dereferences?

I'm having problems coding the following:

myFunct(GraphT& g)
{
     typedef graph_traits<GraphT>::edge_descriptor Edge;
     typedef map< Edge, Edge_Datum> Edge_Data;
     Edge_Data edge_data;
     graph_traits<GraphT>::edge_iterator ei, ei_end;
     for(tie(ei,ei_end)=edges(graph);ei!=ei_end;++ei)
        edge_data.insert( make_pair(*ei, Edge_Data()));  << blows up here.
}