Lazify `ap` about missionary HOT 2 OPEN

I was curious if this might be related (or not)...

(defn take-none [f]
  (m/eduction (take 0) f))

(defn echo [f]
  (m/ap
   (let [v (m/?> f)]
     (prn 'produce v)
     v)))

(m/?
 (m/reduce (fn [_ _]) nil
   (take-none (echo (m/seed (range))))))

produce 0
produce 1

The echo/seed combination gets two values ahead of the consumer before being cancelled.

Now let's add in another layer:

(defn copy [f]
  (m/ap (m/?> f)))

... (take-none (copy (echo (m/seed (range)))))

produce 0
produce 1
produce 2

... (take-none (copy (copy (echo (m/seed (range))))))

produce 0
produce 1
produce 2
produce 3

Each added copy buffers an additional value, so each copy we add causes the producer to get an additional value ahead of the consumer.

Suppose this issue was implemented. In copy, the branch doesn't contain an asynchronous operator (it doesn't do anything but return), so the continuation would be evaluated lazily... and would that mean that copy would no longer buffer an additional value in a pipeline like it does now?

from missionary.

yes, when this issue is solved copy will be semantically equivalent to identity.

from missionary.