Suppose I have a task I want to do to each line of a file, accumulate a result and output it, I can write main = do stuff <- getContents print $ foldl process_line initial_value (lines stuff) ie, it's obviously a fold I can't see a way of doing the same thing directly on the IO: I'd like to write something similar to main = do res <- foldX process_line initial_value getLine print res foldM almost does it: main = do res <- foldM process initial_value (repeat getLine) print res process a g = do line <- g return (process_line a line) but that goes on forever (or some fixed amount if (replicate n/repeat)) I feel this ought to be straightforward -- the structure is obviously some sort of fold, but I shouldn't have to use a list -- so I must be missing something obvious. What is it? Jón -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk 31 Chalmers Road jf@cl.cam.ac.uk Cambridge CB1 3SZ +44 1223 570179 (after 14:00 only, please!)