* Michael Snoyman
The problem is the following Sink, which counts how many even/odd Tokens are seen:
type SinkState = (Integer, Integer)
sink2 :: (Monad m) => SinkState -> Sink Token m SinkState sink2 state@(!evenCount, !oddCount) = do maybeToken <- await case maybeToken of Nothing -> return state (Just Even) -> sink2 (evenCount + 1, oddCount ) (Just Odd ) -> sink2 (evenCount , oddCount + 1)
Wow, talk about timing! What you've run into here is expensive monadic bindings. As it turns out, this is exactly what my blog post from last week[1] covered. You have three options to fix this:
1. Just upgrade to conduit 1.2.0, which I released a few hours ago, and uses the codensity transform to avoid the problem. (I just tested your code; you get constant memory usage under conduit 1.2.0, seemingly without any code change necessary.)
Interesting. From looking at sink2, it seems that it produces a good, right-associated bind tree. Am I missing something? And what occupies the memory in this case? Roman