mean5 :: Fractional a => Circuit a a mean5 = proc value -> do rec (lastTot, lastN) <- delay (0,0) -< (tot, n) let (tot, n) = (lastTot + value, lastN + 1) let mean = tot / n returnA -< mean

So I ask: what's the sour version of `mean5`?

The translation is very similar to the one for 'mfix', except that you need to account for the side channel in the input: mean5 = loop $ proc (value, ~(tot', n')) -> do (lastTot, lastN) <- delay (0,0) -< (tot', n') let (tot, n) = (lastTot + value, lastN + 1) id -< (tot / n, (tot, n)) You need the values 'tot' and 'n' to be in scope as input to the 'delay' action. To achieve that you literally just return them as the second output component, and 'loop' will feed them back as the second input component. That's how they get in scope for 'delay's input. This is not the exact way it's desugared (which is probably a lot uglier), but it's equivalent and should give you an intuition for how 'loop' works. I'm not entirely sure the lazy pattern is necessary or even possible. If it's possible, it's probably also necessary. Greets ertes