the ContCatchT monad

ContCatchT.hs

newtype ContCatchT r e m a =
    ContCatchT { getContCatchT :: ((e -> m r) -> a -> m r) -> (e -> m r) -> m r }

instance Functor (ContCatchT r e m) where
    fmap f (ContCatchT k) =
        ContCatchT $ \c1 c2 -> k (\c3 -> c1 c3 . f) c2

instance Applicative (ContCatchT r e m) where
    pure x = ContCatchT $ \c1 c2 -> c1 c2 x
    ContCatchT cf <*> ContCatchT cx = ContCatchT
      $ \c1 c2 -> cf (\c3f f -> cx (\c3x -> c1 c3x . f) c3f) c2

instance Monad (ContCatchT r e m) where
    return = pure
    c >>= f = ContCatchT $ \c1 c2 ->
                getContCatchT c (\c3x x -> getContCatchT (f x) c1 c3x) c2

instance MonadIO m => MonadIO (ContCatchT r e m) where
  liftIO m = ContCatchT $ \k1 k2 -> liftIO m >>= k1 k2