I find myself writing things like, splitListOn :: Eq a => a -> [a] -> [[a]] splitListOn delimiter = unfoldr splitter . (delimiter :) where splitter [] = Nothing splitter xs = Just (span (/= delimiter) (tail xs)) This is a sort of intersperse-opposite, in that... myId delimiter = concat . intersperse [delimiter] . splitListBy delimiter ...myId foo turns into a sort of id for lists of the correct type. With this, and other things, I always have a feeling that it's probably in the standard library somewhere but I didn't notice - maybe because it's abstracted out of recognition, just like "sequence" does Cartesian products for us, but not so that I noticed right away. Is there a good place to put these things - little things that feel like that maybe they're already in the standard library, and maybe they should be? I'd hate to be unknowingly reinventing the wheel all the time. I don't see an obviously-appropriate page for these on the Haskell Wiki, but maybe I missed it, or maybe I should create one. -- Mark