Hi, may I warm up an old subject? I would appreciate if at least the Map and the Set module could be added to the base package, soon! DData.Set and the current Data.Set can be merged together (as Sven Panne mentioned earlier). Data.FiniteMap and Data.Map should co-exist for a while. The current Data.FiniteMap and Data.Set have various missing functions and instances. It would make sense to add Data.Bag also (but I don't use Bags currently) (I also don't care about Seq, Queue and Int-specializations.) The last proposal was made by JP Bernardy: http://users.skynet.be/jyp/DData/doc Daan wanted to look into it. My experiments (with large maps) wrt. performance (and memory consumption with and without optimization) of both Map and FiniteMap implementations revealed differences, but no crucial ones. "FiniteMap Int a" performs better than "Map Int a", but not as good as "IntMap a", but the differences are unimportant for us. (We would need a pure HashMap with O(1) lookup while extending the Map) Christian