Hi - I started off writing the following piece of monadic code: let drawModal :: Control -> ManagerM () drawModal c = do -- details omitted -- Prolog style coding... drawModals :: [Control] -> ManagerM () drawModals [] = return () drawModals (c:cs) = do drawModals cs drawModal c drawModals cs then it struck me that I should have not bothered with drawModals and instead should just have used: mapM_ drawModal (reverse cs) However, while this looks more elegant, it is less efficient? In other words, how much optimization can one assume when writing Haskell code? I'm trying to get a rough idea so I can decide whether to write helper functions such as drawModals in future or whether I should always just use the most elegant code instead. Any ideas? Thanks, Brian.