If I have a `Flow<Int>` , say 1, 20, 30, 35,...

# coroutines

[dimsuz]

If I have a Flow<Int> , say 1, 20, 30, 35, how could I produce a flow which "samples" this flow and counts the difference between last elements emitted in chunked time windows?

for example sampleTime=20ms if 1,20, 30 got emitted in 20ms since start and then only one item 35 got emitted in next 20 ms, I would get 29,5 (30-1,35-30 ) out.

Should I combine sample with map with timestamps? Would be grateful for direction.

Or should I write a fully custom "transform" function instead of trying to combine existing ones?

[bezrukov]

I feel built-in sample fun does almost what you want, except calculating the diff in the first window, but you can wrap it to onEach+drop(1) to take the first value into a separate window. But in this case it won't emit anything if original flow contains only a single element.

Technically, you need https://github.com/Kotlin/kotlinx.coroutines/issues/1302 chunked with timeout + scan over it

[dimsuz]

Yep, I felt like "scan" also should come into play here. Thanks, I'll play with this!