module Control.Monad.Indexed.Cont where
import Control.Monad.Identity
import Control.Functor.Indexed
import Control.Monad.Indexed
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 Monad m => IxMonad (IxContT m) where
ireturn a = IxContT ($a)
ibind f c = IxContT $ \k -> runIxContT c $ \a -> runIxContT (f a) k
class IxMonad m => IxContMonad m where
reset :: m a o o -> m r r a
shift :: ((a -> m i i o) -> m r j j) -> m r o a
instance Monad m => IxContMonad (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, IxMonad, IxContMonad)
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