this doesn’t work : `val (a: A, b: B) = parZip({ f...

# arrow

[Satyam Agarwal]

this doesn’t work :
val (a: A, b: B) = parZip({ funA() }, { funB() }, ::Pair)
but this works :
val (a: A, b: B) = parZip({ funA() }, { funB() }) { a, b -> a to b }
in v0.13.0

[Jannis]

Kotlin is unable do lift ::Pair from (A, B) -> Pair<A, B> to suspend (A, B) -> Pair<A, B>.
parZip(a, b, f) allows f to be suspend which rules out ::func in most cases afaik.
Imo { a, b -> a to b } could also be added as a default to use for all of the zipping operators when no combine function is given.

[simon.vergauwen]

(A, B) -> Pair<A, B> to suspend (A, B) -> Pair<A, B>

This has actually been fixed, the reason why ::Pair does no longer work is because there is a CoroutineScope receiver in the lambda.
The Kotlin compiler cannot ignore unused receivers since those look like (CoroutineScope, A, B) -> Pair<A, B> on the JVM.

[simon.vergauwen]

It's a bit annoying but it's the most precise/powerful signature.

[Jannis]

Ooo nice, I did not know that. Can we add overloads for that without adding ambiguity?

[simon.vergauwen]

Imo { a, b -> a to b } could also be added as a default to use for all of the zipping operators when no combine function is given.

You mean this? It can not be added without duplicating the full API

[Jannis]

parZip(a, b, f = { a, b -> a to b }) can not be added? With ambiguity I was referring to adding some way of doing parZip(a, b, f) where f has no CoroutineScope receiver.

[simon.vergauwen]

No, that cannot be added as default lambda

[Jannis]

because of the receiver? If so can't we just use the current context?

[Jannis]

Dunno really, probably just need to start intellij and see the error myself