{-# Language MultiParamTypeClasses , FunctionalDependencies , DefaultSignatures #-}

module Unfoldable where
import Unfoldable_r
import State

----
-- Unfold for Stream

class Unfoldable0 f where
 unfoldr0 :: s -> State0 s a -> f a
 default unfoldr0 :: Unfoldable1 f => s -> State0 s a -> f a
 unfoldr0 s f = unfoldr1 s (fmap Just . f)

----
-- Unfold for Linear

class Unfoldable0 f => Unfoldable1 f where
 unfoldr1 :: s -> State1 s a -> f a
 default unfoldr1 :: Unfoldable f => s -> State1 s a -> f a
 unfoldr1 s f = unfoldr s (sequence . f)

----
-- Unfold for Stack

class Unfoldable1 f => Unfoldable f where
 unfoldr :: s -> State s a -> f a