Monad?

src/GoodList.hs

@@ -19,6 +19,13 @@ instance Applicative GoodList where
   (Singleton f)    <*> x = fmap f x
   (Multiple a b c) <*> x = append (append (fmap a x) (b <*> x)) (fmap c x)
 
+-- Needs to be proven
+instance Monad GoodList where
+  return = pure
+  Empty          >>= _ = Empty
+  Singleton x    >>= f = f x
+  Multiple a b c >>= f = append (append (f a) (b >>= f)) (f c)
+
 instance Semigroup (GoodList a) where
   (<>) = append
 
@@ -34,7 +41,6 @@ instance Show a => Show (GoodList a) where
       show' (Multiple a Empty c) = show a ++ ", " ++ show c
       show' (Multiple a b c)     = show a ++ ", " ++ show' b ++ ", " ++ show c
 
-
 singleton :: a -> GoodList a
 singleton = Singleton