Add an introduction and formatting for the combineLatest algorithm into a proposal.

[phausler]

Read the full proposal here.

[tcldr]

Excited to see this included. One comment:

The Naming part of the proposal mentions "withLatestFrom" as alternative naming. However, this is a quite different algorithm. Unlike, say CombineLatest2, which takes publisher A and publisher B, and emits when either A or B updates, withLatestFrom only emits when B updates. This can be useful for getting a snapshot of a frequently emitting sequence, say accelerometer data, on the occurrence of an infrequently emitting sequence, say a screen tap. e.g:

for await (tap, acceleration) in screenTaps.withLatestFrom(accelerometer) {
    // do something only on screen tap, with last emitted data from accelerometer
}

I'd love to see a proposal for this operator, too.

Also, what is the home for discussions on evolution proposals for Swift Algorithms? I couldn't find a CombineLatest thread in the swift forums and I don't see any discussions on the Issues board. The package readme mentions GitHub or Swift Forums, but isn't specific.

[phausler]

I haven't posted them to the forums yet; was planning on doing that Monday. Per an additional algorithm - that is definitely something we should talk about but I want to get through the stuff we have first and then discuss the others with a bit more dedicated focus. But if you want to take that on we can park that as a pitch until then and get it queued up as an item to cover.

[tcldr]

Lovely, makes sense. Thanks, Philippe.

[phausler]

For those wanting to follow along and post feedback on the algorithm itself: https://forums.swift.org/t/swift-async-algorithms-proposal-combinelatest/59042

[twittemb]

Excited to see this included. One comment:

The Naming part of the proposal mentions "withLatestFrom" as alternative naming. However, this is a quite different algorithm. Unlike, say CombineLatest2, which takes publisher A and publisher B, and emits when either A or B updates, withLatestFrom only emits when B updates. This can be useful for getting a snapshot of a frequently emitting sequence, say accelerometer data, on the occurrence of an infrequently emitting sequence, say a screen tap. e.g:

for await (tap, acceleration) in screenTaps.withLatestFrom(accelerometer) {
    // do something only on screen tap, with last emitted data from accelerometer
}

I'd love to see a proposal for this operator, too.

Also, what is the home for discussions on evolution proposals for Swift Algorithms? I couldn't find a CombineLatest thread in the swift forums and I don't see any discussions on the Issues board. The package readme mentions GitHub or Swift Forums, but isn't specific.

Hi,

If I may, there is already a proposal for withLatestFrom (temporarily named zipLatestFrom). The PR is here and the pitch is here

[twittemb]

Hi @phausler

From what I can see, on the one hand the implementation of CombineLatest3 is just a shortcut on two CombineLatest2. On the other hand, the implementations of Merge3 and Zip3 are done from scratch. Why not reusing two Merge2 and Zip2 ? is there is performance overhead in doing this ?

Thanks.