Hi all, out of curiosity, I was thinking about a parallel fallback construction, how would you imple...

# arrow

[Davio]

Hi all, out of curiosity, I was thinking about a parallel fallback construction, how would you implement the following use case (with or without Arrow):
• In parallel, start N computations
• Have a preference / priority for the result of the first computation
• If the first computation fails or returns no result (null), use the result of the second (fallback) computation
• If the first computation succeeds, cancel the second computation and use the value of the first computation

[Alejandro Serrano.Mena]

you speak about N computations, but then you speak about "first" and "second". Do you mean here "first" as "the first one to finish" (then raceN is your friend) or literally there's a distinguished first one (in that case using await on the first one, and only if that one is null awaiting the rest would work)

[Davio]

Ah yes, I talked about N, but that is a theoretical thing, in my example I just assume 1 regular computation and 1 fallback computation, but started at the same time (to save on total time in case the fallback was needed)

[Davio]

So I guess I don't need Arrow for this, but can simply do

runBlocking { 
            val regularJob = async<String?> { "hello" }
            val fallbackJob = async { "world" }
            
            val result = regularJob.await() ?: fallbackJob.await()
        }

[Alejandro Serrano.Mena]

yes, I think this is the best approach