[Boost-users] [BGL] Can't set non-const edge_descriptor = const edge_descriptor

I have struct edge_properties { Traits::edge_descriptor ePredecessor; } some_function ( const Graph g ) { e = edge(vertex_a, vertex_b, g).first; //fails here g[e].ePredecessor = e; } compiler gives ./Includes/Utilities.cpp:451: error: passing ‘const boost::detail::edge_desc_impl’ as ‘this’ argument of ‘boost::detail::edge_desc_impl& boost::detail::edge_desc_impl::operator=(const boost::detail::edge_desc_impl&)’ discards qualifiers make: *** [pl] Error 1 My guess is that e is returned as a const but g[e].ePredecessor is declared a variable. How can I fix this? Thanks John