module Control.Monad.Indexed.Cont where
import Control.Monad.Identity
import Control.Monad.Indexed
class IxMonad m => IxMonadCont m where
reset :: m a o o -> m r r a
shift :: (forall i. (a -> m i i o) -> m r j j) -> m r o a
newtype IxContT m r o a = IxContT { runIxContT :: (a -> m o) -> m r }
runIxContT_ :: Monad m => IxContT m r a a -> m r
runIxContT_ m = runIxContT m return
instance IxFunctor (IxContT m) where
imap f m = IxContT $ \c -> runIxContT m (c . f)
instance IxPointed (IxContT m) where
ireturn a = IxContT ($a)
instance Monad m => IxApplicative (IxContT m) where
iap = iapIxMonad
instance Monad m => IxMonad (IxContT m) where
ibind f c = IxContT $ \k -> runIxContT c $ \a -> runIxContT (f a) k
instance Monad m => IxMonadCont (IxContT m) where
reset e = IxContT $ \k -> runIxContT e return >>= k
shift e = IxContT $ \k -> e (\a -> IxContT (\k' -> k a >>= k')) `runIxContT` return
newtype IxCont r o a = IxCont (IxContT Identity r o a)
deriving (IxFunctor, IxPointed, IxApplicative, IxMonad, IxMonadCont)
runIxCont :: IxCont r o a -> (a -> o) -> r
runIxCont (IxCont k) f = runIdentity $ runIxContT k (return . f)
runIxCont_ :: IxCont r a a -> r
runIxCont_ m = runIxCont m id