A priority search queue efficiently supports the opperations of both a
search tree and a priority queue. A 'Binding' is a product of a key and
a priority.  Bindings can be inserted, deleted, modified and queried in
logarithmic time, and the binding with the least priority can be
retrieved in constant time.  A queue can be built from a list of
bindings, sorted by keys, in linear time.

WWW: http://hackage.haskell.org/package/PSQueue