Why does `combine(flows, transform)` not call `transform` if `flows` is empty? Is that intended? See...

# flow

[Alexander Maryanovsky]

Why does combine(flows, transform) not call transform if flows is empty? Is that intended? Seems like it would be more natural to call it with an empty array.

[ephemient]

I don't think so. the transform should only be called when there are emissions, and there are none here

[Alexander Maryanovsky]

My use-case is that I have a list of flows of Int, and I need to return a flow of their sum.

[Alexander Maryanovsky]

combine(flows, Array<Int>::sum) seems like an intuitive solution that fails when flows is empty.

[ephemient]

combine(List(n) { flowOf(*Array(m) { 0 }) }, transform)

the way I see it: in general, this can call transform anywhere in n..n*(m-1)+1 times. when n=0, 0 times is a reasonable ourcome

[Alexander Maryanovsky]

On the other hand

combine(List(n){ flowOf(0) }, transform)

calls transform exactly once for every value of n except 0

[Nick Allen]

combine(List(n){ flowOf(0) }, transform)

also receives emitted most recent values (which is what it operates on) for every n except 0.

[ephemient]

combine(List(n) { flowOf() }, transform)

calls transform 0 times for any value of n, including 0