Hi, Data.List exports strict versions of foldl an foldl1. I think it should also export these strict versions of scanl, scanl1 and mapAccumL: scanl' :: (a -> b -> a) -> a -> [b] -> [a] scanl' f q ls = q : (case ls of [] -> [] x:xs -> let q' = f q x in q' `seq` scanl f q' xs) scanl1' :: (a -> a -> a) -> [a] -> [a] scanl1' f (x:xs) = scanl' f x xs scanl1' _ [] = [] mapAccumL' :: (acc -> x -> (acc, y)) -> acc -> [x] -> (acc, [y]) mapAccumL' _ s [] = (s, []) mapAccumL' f s (x:xs) = (s'',y:ys) where (s', y ) = f s x (s'',ys) = s' `seq` mapAccumL' f s' xs Is there a good reason they're not included? Discussion deadline: 2 weeks (till Monday 26 November). Regards, Bas