Re: [Haskell-cafe] Data.Map - visiting tree nodes withi a given key range ?

You can roll your own indexKeyRange using the Data.Map.Internal module which exposes the (currently used) Map implementation. Also note that if the list of values in range is to be consumed immediately, you might want to go for a fold-based function: foldlWithRange :: (a -> k -> b -> a) -> (a,a) -> b -> Map k a -> b Olaf