Gregory Crosswhite
Okay, where that unpost button when I need it... :-)
So, I hadn't noticed that the script that I copied and pasted didn't even compile because I was pressing "up enter" at the console to run it, but had forgotten that I was now working with a script with a new name and so all I was doing was running a different script over and over again! Doh. :-)
Happens. =)
Anyway, okay, I see your point now. The following script *does* work.
import Data.List
import Control.Monad import Control.Monad.IO.Class import Control.Monad.Trans.Cont
goto :: Monad m => ContT r m r -> ContT r m a goto (ContT m) = ContT $ \_ -> m return
myComp :: ContT () IO () myComp = do input <- liftIO $ putStrLn "Print something (y/n)?" >> getLine unless ("y" `isPrefixOf` input) $ goto exit liftIO $ putStrLn "Something."
input <- liftIO $ putStrLn "Print more (y/n)?" >> getLine unless ("y" `isPrefixOf` input) $ goto exit liftIO $ putStrLn "More."
where exit = do liftIO $ putStrLn "Ok, I'm exiting." return ()
main :: IO () main = runContT myComp return
*HOWEVER*, if we replace main with
main = runContT myComp (const $ putStrLn "I can't wait to print this string!")
Then the program will be eternally disappointed because it will never actually get to print that string at the end.
It should print the string, if the computation isn't aborted, i.e. if the last continuation, which you specify as an argument to runContT is reached. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/