Hi,
Hopefully this is the right place for this. This with Boost 1.81.0 It looks like boost::adjacency_list's in_edge_iterator, out_edge_iterator, and for bidirectional graphs also edge_iterator all are only input iterators.
This seems a bit restrictive, and is regardless of the type of EdgeList template parameter. For example, this code (which seems a relatively reasonable thing to want to do) doesn't work:
https://godbolt.org/z/n3PdEYo49
It doesn't work because transform_view doesn't define iterator_category if the iterator is not at least a forward iterator (I'm a bit confused as to why that is, but that's not a boost-related thing).
I did some digging and found out why the iterator is always an input iterator:
The iterators are defined as following:
template < class BaseIter, class VertexDescriptor, class EdgeDescriptor,
class Difference >
struct in_edge_iter
: iterator_adaptor< in_edge_iter< BaseIter, VertexDescriptor,
EdgeDescriptor, Difference >,
BaseIter, EdgeDescriptor, use_default, EdgeDescriptor, Difference >
{
// ....
};
EdgeDescriptor is passed in as the reference type, but it is not a reference so the iterator adaptor always chooses input_iterator_tag for the iterator_category.
Does anyone know of a workaround, or know if this is the desired behavior for edge iterators? Am I missing something obvious here?
Thank you very much,
Nicolas Morales