Hi List, I've uploaded a first version of EnumMap to hackage. EnumMap is a generalization of IntMap that constrains the key to Enum rather than forcing it to be Int. I have no idea what impact this has on performance, but it still passes all the tests that ship with IntMap. (My guess is that performance will be similar/identical unless I've missed something.) If this package competes in speed (especially with an Int key) with IntMap, I'd expect this could be merged into the containers package as an IntMap replacement. The source comments/copyright/license hasn't been changed since this is a derivative work of the original IntMap package. http://hackage.haskell.org/package/EnumMap Comments/benchmarks/criticism is appreciated. Merging this in with containers eventually would be more appreciated. :) John Van Enk