Is it possible to relax constraint from `Monad` to `Applicative` in `Parallel` class?

[paluh]

I have an Applicative (which is not a Monad) and I have another Applicative which with additional constraints provides parallel apply for my initial type. It seems that this is the purpose of Parallel class - to define such a relation between types.
If I understand it correctly Parallel requires me to provide Monad instance for my "non parallel type". Why is this the case? Wouldn't it be enough to just require an Applicative instance?

[garyb]

I don't know if there is a good reason not to do this - it seems reasonable, but I guess the idea is if there's a Monad instance then it is required to behave sequentially due to ap = apply.

Any thoughts @paf31, @natefaubion?

[natefaubion]

Considering there are no laws...

[masaeedu]

Would you folks take a PR implementing this? Or would the resulting breakage be too large?