gistfile1.hs

class Strategy s where
    store :: s -> Ports -> IO ()
    fetch :: s -> IO [Ports]
    isDone :: Ports -> Bool
    updatePorts :: Ports -> IO Ports
    next :: s -> s

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