On Tue, Aug 03, 2010 at 10:59:45PM +0200, Daniel Peebles wrote: > > Deletion in Data.Map does not always preserve the balance of a tree. I've filed a ticket here: http://hackage.haskell.org/trac/ghc/ticket/4242 It would be useful if people familiar with the library could comment as to whether setting delta to 4 would be the right fix. Thanks Ian