Hello. I'm trying to understand the FRP (by implementing FRP system on my own) and I think I'm slowly getting it. 1. How to interpret ArrowLoop? I have two possible implementations: type RunSF a = a Dynamic () data SF a b c = SF (a (Dynamic, b, RunSF, Set Unique) (c, Set Unique, SF a b c)) (...) instance ArrowLoop (SF a) where loop (SF f) = loop' f undefined where loop' g d = proc (dyn, b, r, s) -> do ((c, d'), s, g') <- g <- (dyn, (b, d), r, s) returnA -< (c, s, loop' g' d') instance ArrowLoop a => ArrowLoop (SF a) where loop (SF f) = SF $! proc (d, b, r, s) -> do rec ((c, d), s, f') <- f -< (d, (b, d), r, s) returnA -< (c, s, loop f') Since the first is not unlike ArrayCircuit from arrays I guess second one but I'm not quite sure. 2. Why there is no ArrowIO in arrows? I.e. class Arrow a => ArrowIO a where liftAIO :: Kleisli IO b c -> a b c (possibly class Arrow a => ArrowST a where liftAST :: Kleisli ST b c -> a b c ) 3. Why switch is needed? How to interpret switch with current continuation? I think switch is equivalent to ArrowChoice but do I miss something? Regards