Implicit conversion to Parallel / deriving Parallel from Par?
Closed this issue · 6 comments
I hit this when trying to get the default instance of Parallel for Kleisli[F, A, ?] (assuming F[_] : Par) - the instance wasn't picked up.
It'd be great to have a way to automatically get the Parallel instance back into the implicit scope.
Currently trying to build a generic workaround (having a Par.Aux provide a Parallel), but it's a diverging implicit expansion because of implicit def fromParallel[F[_], G[_]](implicit P: Parallel[F, G]): Par.Aux[F, G] in object Par...
Okay, it seems to compile if the aux pattern isn't used:
implicit def parToParallel[F[_]](implicit par: Par[F]): Parallel[F, par.ParAux] = par.parallel
So I'm a bit confused. I have that in the package object. So you should have that if you do a bulk import of import cats.temp.par._
I had considered an implicits package but thought the import overhead would be too high.
In the test we have a compile test that ensures we can go back the other direction when desired.
Is this the functionality you are looking for or am I misunderstanding.
ah, well, guess I didn't look deep enough to find the thing in the package object :D
Works, closing. Thanks a lot for the whole thing :)