gistfile1.hs

class Strategy s where
    storeOutput :: s -> Ports -> IO ()
    nextInput :: s -> IO Ports
    isDone :: s -> Bool
    failed :: s -> Bool

run :: Strategy s => s -> IO [Ports]
run world = let loop = do w' = next world
                          if isDone w'
                             then fetch w'
                             else loop w' in loop world