Add runningFold function to Flow

[jakobulbrich]

Kotlin supports the following functions on Collections

• reduce and runningReduce
• fold and runningFold

whereas Flows only support

• reduce and runningReduce
• fold and ???

Turns out the function is called scan, which is not consistent with the known naming scheme and hard to find. The scan function also exists for Collections but only acts as an alias for runningFold there.

It would be helpful to also add the runningFold function to Flows.

[pacher]

Well, just to be fair, coming from RxJava it is much easier to find scan than runningFold, also for Collections :)

[qwwdfsad]

Thanks for pointing it out!

Well, just to be fair, coming from RxJava it is much easier to find scan than runningFold

Indeed! This alias exists for better discoverability for people who came from reactive frameworks.
But we weren't really happy with the name scan. It doesn't have any reasonable rationale now, the name came from APL where \ operator with the same semantics was called scan , probably due to similarity to "scanning line".

[pacher]

True, the name scan was puzzling at first in rx, but it is nice and short and we are quite used to it now.
What I mean is please keep it as an alias to runningFold, I would prefer keep using scan despite the lack of reasonable rationale ;-)

[sebastianharder]

@qwwdfsad the KDoc of runningFold refers to the scan function.