Add Traverse.traverseM #1020
Add Traverse.traverseM #1020
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| * A traverse followed by flattening the inner result. | ||
| */ | ||
| def traverseM[G[_], A, B](fa: F[A])(f: A => G[F[B]])(implicit G: Applicative[G], F: FlatMap[F]): G[F[B]] = | ||
| G.map(traverse(fa)(f))(F.flatten) |
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We got F (FlatMap[F]) as an Applicative[F], but we could also use the Traverse itself : G.map(traverse(fa)(f)(this))(F.flatten).
I am not sure if there is a reason to choose one over the other ?
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I think the version that you currently have is probably better, because Applicative.traverse ends up delegating through to Traverse.traverse anyway.
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Should this be called traverseA ? Consistent with replicateA. I think the M suffix is usually used when it has a Monad constraint.
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@adelbertc The Applicative[G] is required on traverse also. Here I think of the M as "monadic", referring to the FlatMap[F]. I guess we could call it traverseF instead, though that runs the risk of being confused with Functor.
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I was not really sure about the M. traverseA seems a bit strange because we need FlatMap. traverseF could also be confusing with the flatMapF and mapF on (some) monad transformers.
Maybe we can call it traverseFlatten ?
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Oh I totally did not see the FlatMap requirement.. the size of my screen stopped right at Applicative so I assumed that was all there was. I am good with traverseM in that case
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👍 thanks! |
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I have added
Traverse.traverseMand added some examples to thetraversesyntax.