Hey Haskell, So for a fairly inane reason, I ended up taking a couple of minutes and writing a program that would spit out, to the console, the number of lines in a file. Off the top of my head, I came up with this which worked fine with files that had 100k lines: main = do path <- liftM head $ getArgs h <- openFile path ReadMode n <- execStateT (countLines h) 0 print n untilM :: Monad m => (a -> m Bool) -> (a -> m ()) -> a -> m () untilM cond action val = do truthy <- cond val if truthy then return () else action val >> (untilM cond action val) countLines :: Handle -> StateT Int IO () countLines = untilM (\h -> lift $ hIsEOF h) (\h -> do lift $ hGetLine h modify (+1)) If this makes anyone cringe or cry "you're doing it wrong", I'd actually like to hear it. I never really share my projects, so I don't know how idiosyncratic my style is.