I was trying to figure out how I could pass in a priority queue to a utility function of my Stoer–Wagner implementation that would also give me access to the "distances" that are associated to values in the priority queue. In short, I don't think that this is currently possible. But, I only need one method: something like `keys() const` on an updatable priority queue could return a readable property map with the key type being the value type of the queue and the value type being a `key_type` that is the distance type.
A small update: I had added another method `clear()` to the `UpdatableQueue` concept, but I don't think that I will need it. Attached is an updated version of `buffer_concepts.hpp`. Also attached is a patch for `boost/graph/detail/d_ary_heap.hpp`. After applying the patch, `boost::d_ary_heap_indirect` models `KeyedUpdatableQueue`. I am working on documentation pages for the `UpdatableQueue` and `KeyedUpdatableQueue` concepts.