module State where

type State   s a = s -> (a, s)
type CoState s a = (a, s) -> s

hyloState :: State s a -> (CoState b a) -> s ->  b
hyloState f c = go
   where
     go = c . fmap go . f
-- (\(x,q') -> c (x,go q')) . f

--

type SafeState   s a = s -> (a, Maybe s)
type CoSafeState s a = (a, Maybe s) -> s

hyloSafeState :: SafeState s a -> (CoSafeState b a) -> s ->  b
hyloSafeState f c = go
 where
     go = c . fmap (fmap go) . f

--

type StateSafe   s a = s -> Maybe (a, s)
type CoStateSafe s a = Maybe (a, s) -> s

hyloStateSafe :: StateSafe s a -> (CoStateSafe b a) -> s -> b
hyloStateSafe f c = go
 where
  go = c . fmap (fmap go) . f