[Haskell-cafe] Re: ANNOUNCE: fixpoint 0.1

Roman Leshchinskiy wrote:

apfelmus wrote:

...

Making f an associacted type synonym / fundep instead of a associated data type is still worth it, since we can use it for Mu f

But alas, this breaks hylomorphisms:

hylo :: Fixpoint t => (Pre t s -> s) -> (p -> Pre t p) -> p -> s

If Pre is a type function, there is no way to infer t.

Ah, right. But unlike size , this is unambiguous since t can (and probably should) be fused away: hylo :: Functor f => (f s -> s) -> (p -> f p) -> p -> s hylo f g = f . fmap (hylo f g) . g Regards, apfelmus