[Haskell-cafe] class Ref...

Hi, I the paper of Magnu Carlsson I noticed small, interesting class: class Monad m => Ref m r | m -> r where newRef :: a -> m (r a) readRef :: r a -> m a writeRef :: r a -> a -> m () He defined it locally, but it seems to be very useful generalization of IORef and STRef. Is there something like this in standard libraries? I couldn't find it... :( Is there any reason why isn't it included? Another question: priority queue. In libraries bundled with ghc we have Data.Queue, but I couldn't find PriorityQueue. Is there somewhere an implementation that everybody uses, but is not in the library? Thanks! -- Gracjan