yes I mean I/O. There are no stateful transducers (as in 'distinct' or 'partition'), I know that this doesn't work well on pipelines. In this case only map with a function that does I/O.

what is by the way, the 'recommended' way of doing I/O on items that pass through core.async channels? a thread loop? pipeline-blocking?

pipeline-blocking executes xf in (thread ...), so it's OK to do I/O there

as I understand it's a purpose of pipeline-blocking: to execute I/O with parallelism n

also it's possible to use pipeline-async but call I/O in thread manually

pipeline-async is a good fit for libraries which already deal with thread pools internally to do their I/O.