So loop really doesn't seem to help here, but I couldn't find another way either to feed outputs back into the system. What I need is: Either A B ~> Either C B -> A ~> C

Does such a thing exist? At this point you don't really have enough structure to define such a feedback loop. Since you have streams of different rates, you need to find some common ground to merge them. The path taken by Reactive is to assign a timestamp to events, and ensure that merging preserves time ordering. Of course you'll immediately run into the problem of simultaneous occurrences, and it depends on the context how you want to resolve them.

Also, what you're trying to achieve looks similar to Peakachu, so you might want to check it out, especially the Program abstraction [1]. It even has a feedback combinator with a slightly different signature. Gergely [1] http://hackage.haskell.org/packages/archive/peakachu/0.3.0/doc/html/FRP-Peak... -- http://www.fastmail.fm - mmm... Fastmail...