Why isn't BoundedEnum constraint used in defaultSucc and defaultPred?

[safareli]

current implementation for defaultSucc and defaultPred is taking toEnum and fromEnum as arguments:

defaultSucc :: forall a. (Int -> Maybe a) -> (a -> Int) -> a -> Maybe a
defaultSucc toEnum' fromEnum' a = toEnum' (fromEnum' a + 1)

defaultPred :: forall a. (Int -> Maybe a) -> (a -> Int) -> a -> Maybe a
defaultPred toEnum' fromEnum' a = toEnum' (fromEnum' a - 1)

When it could also be implemented like this:

defaultSucc :: ∀ a. BoundedEnum a => a -> Maybe a
defaultSucc = toEnum <<< (_ + 1) <<< fromEnum

defaultPred :: ∀ a. BoundedEnum a => a -> Maybe a
defaultPred = toEnum <<< (_ - 1) <<< fromEnum

so why is it like that?

[garyb]

You would only be able to use it to provide the default Enum implementation for BoundedEnums then.

[safareli]

ah makes sense.