Is there a

collect

variant for

Flow

that allows to access the previous value, or null for initial value?

you need something like

windowed

that will emit Pair(null, first) element

Not yet. Create an issue with your use-case please.

not sure that such operator exists

you need to combine with itself but skipping one value, it's a classic zipping structure

that should really be something like

.publish { zip(flow, flow.skip(1), ::Pair) }

to avoid subscribing upstream twice

it'd work if

flow

there was

shared()

first too, right?

only if it's async so that's unsafe. if it's synchronous the entire stream will be consumed in the first subscription before

flow.skip(1)

is subscribed to yielding either two upstream subscriptions or no output

are we talking Rx or Kx?

i'm sorta talking about both since they're really the same thing