BGL: subgraph<..> Problems

1. How to create a subgraph from a given simple boost graph type? 2. Why are modell subgraph not the same concept as the underlying graph type? Why are not all non-member function defined for the only graph modell adjacence_list<> also available for subgraph? 3. I've defined something like class NG { public: typedef boost::property

vertex_SPIterator_Prop; // GridSP_type::iterator

typedef Default::Graph::Subgraph::Undirected Graph; ... }; where struct Default { ..... template<class VertexProperties=boost::no_property, class EdgeProperties=boost::no_property, class GraphProperties=boost::no_property, class EdgeList=boost::hash_setS, class VertexList=boost::listS > struct Graph { ........ struct Subgraph { typedef typename boost::subgraph < boost::adjacency_list, boost::property

,GraphProperties> > Undirected; }; .... };

and then i'm doing somewhere else { vertex_descriptor v=boost::add_vertex( theGraph); IteratorMap[Prop ] =v; boost::put( boost::vertex_all_t() , theGraph, v, Prop); return v; } I get a nice error with MSVC 6.5 d:\matthias\programmieren\boost\boost\graph\subgraph.hpp(751): error C2679: Binaerer Operator '=': Kein Operator definiert, der einen rechtsseitigen Operator vom Typ 'const _Ht_iter>>,_Nonconst_trait............ (no operator= defined for the type conversion used in put pmap[k] = val;) But using a simple adjacence_list<..> instead of the subgraph< adjacence_list<...> this mess compiles fine. What am i doing wrong? Are there better ways to create a property map containing (const) iterators, that don't modell STL::RandomAccesIterator? Matthias