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scalascala-catsfs2cats-effect

How to convert a `List[IO[Unit]]` into `Stream[IO,Unit]`

I have a List[IO[Unit]] which consists of distinct works encoded in IO. I would like to convert it into Stream[IO,Unit]

Currently, what I have done is this

val works: List[IO[Unit]]
works.map(work => Stream.eval(work)).reduceLeft((left, right) => left ++ right)

Is there a better way?

Solution

  • I suggest doing one of those:

    Stream.emits(works).flatMap(Stream.eval) // or
Stream.emits(works).evalMap(x => x) // which is the same, or
Stream(works: _*).evalMap(x => x) // which is also the same

    There's a difference vs. doing Stream.evals on a works.sequence in that you lose the fact that your effect is made of different parts. That will surface itself if you run stream partially, e.g. by doing:

    stream.take(3).compile.drain

    If you do not sequence, it will only run first 3 elements from works. If you do, it will run all of them.

    From other options proposed by Luis Miguel, only the unfoldEval one preserves the separation, but it's probably an overkill.