On Wed, 27 Oct 2010, langermatze wrote:
I tried this:
typedef boost::adjacency_list<boost::vecS, boost::vecS, boost::bidirectionalS> Graph; typedef typename boost::graph_traits<Graph>::degree_size_type (*FuncPtrType)(typename boost::graph_traits<Graph>::vertex_descriptor, const Graph &);
FuncPtrType funcPtr = boost::in_degree<Graph>;
The error I'm getting: error: no matches converting function ‘in_degree’ to type ‘size_t (*)(long unsigned int, const class boost::adjacency_list<boost::vecS, boost::vecS, boost::bidirectionalS, boost::no_property, boost::no_property, boost::no_property, boost::listS>&)’ /usr/include/boost/graph/detail/adjacency_list.hpp:1058: error: candidates are: template<class Config> typename Config::degree_size_type boost::in_degree(typename Config::vertex_descriptor, const boost::undirected_graph_helper<C>&) /usr/include/boost/graph/detail/adjacency_list.hpp:1649: error: template<class Config> typename Config::degree_size_type boost::in_degree(typename Config::vertex_descriptor, const boost::directed_edges_helper<Config>&)
Sounds reasonable since the signature of in_degree is way more complex than my function pointer signature. I couldn't find a way to get the correct Config template for my Graph class, that's why I tried to pass the Graph class itself but apparently that's not how it works.
I also tried casting which ends up in the "improper use of overloaded function" error that you mentioned:
FuncPtrType funcPtr = static_cast<FuncPtrType>(boost::in_degree<Graph>);
error: invalid static_cast from type ‘<unresolved overloaded function type>’ to type ‘size_t (*)(long unsigned int, const boost::adjacency_list<boost::vecS, boost::vecS, boost::bidirectionalS, boost::no_property, boost::no_property, boost::no_property, boost::listS>&)’
As for your concerns about efficiency, I'd ultimately use the function pointer as an additional template for the visitor which then shouldn't affect code efficiency at all but avoid code duplication only.
If you're doing that, you might as well make your own function objects (that are not function pointers) that call in_degree and/or out_degree directly in their operator()() implementations. That will be faster and avoid the casting problems you are having. -- Jeremiah Willcock