TRAVERSALS FOR ALL OCCASIONS
summary
Traverse generalizes sequence so a T[F[A]] becomes an F[T[A]] and the talk shows concrete instances that make that work in production: using Cats’ parTraverse and EitherT/IO to turn a list of HTTP requests into an IO[Either[NonEmptyList[Error], List[User]]] that runs requests in parallel and accumulates errors, adding about ten Traverse helpers to Cats. It demonstrates Validated for commutative error accumulation (useful for unordered containers like Spark RDDs), non‑empty traversals, flatTraverse and when each actually succeeds or short‑circuits.
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chapters (16)
- 0:00Introduction
- 0:38Motivation
- 1:53Teaser
- 2:37Traverse
- 10:20NonEmpty Traverse
- 12:15NonEmpty List Traverse
- 13:15NonEmpty Map Traverse
- 18:30Commutative Applicative
- 20:27AnyS
- 21:36Flat Traverse
- 22:50Flat Traverse Example
- 23:26Parallel Types
- 27:43Other traversals
- 28:00Instants list
- 28:55Silly function
- 29:29Summary
