2024-07-21 missionary | Clojure Slack Archive

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awb99 2024-07-21T17:41:53.849679Z

I have issue in splitting seqs on a flow: ; RAW (def raw-order-flow (m/seed '([1 2 3] [4 5]))) (m/? (m/reduce conj raw-order-flow)) ; helper fn (defn split-seq-flow [s] (m/ap (loop [s s] (m/amb (first s) (let [s (rest s)] (when (seq s) (recur s))))))) (def order-flow (m/ap (let [data (m/?> raw-order-flow)] (m/?> (split-seq-flow data))))) (m/? (m/reduce conj order-flow)) ;; => [1 2 3 nil 4 5 nil] There should no be any nil There. I want the Output to be [1 2 3 4 5]. Whatever I do with amb .. either I get nothing back or it add the last recursion which produces nil.

2024-07-21T18:37:33.865249Z

with m/eduction and a transducer

(m/? (m/reduce conj (m/eduction cat (m/seed [[1 2 3] [4 5]]))))

2024-07-21T18:53:54.385859Z

trying to code eduction cat behavior

(defn concat* [coll-flow]
  (m/ap
   (when-let [coll (m/?> coll-flow)]
     (loop [coll coll]
       (if (seq coll)
         (m/amb (first coll) (recur (rest coll)))
         (m/amb))))))

;; works with empty seq & nil values
(m/? (m/reduce conj
              (concat* (m/seed [[1 2] [] [4] [nil] [5]]))))
;; res: [1 2 4 nil 5]

awb99 2024-07-22T02:12:08.073359Z

@kawas thanks! Your concat* fn also loop-recurs. So the way how it us written must be another answer. I tried something like that.. but either got no outgoing data pushed. Or I would get a compile exception saying in ap recur needs to be the last form.

Hendrik 2024-07-22T05:38:09.158819Z

If you do not recur, then „(when …)“ returns nil. And you get (amb (first s) nil). but what you need is a (amb) without any arguments if rest is nil. (amb) won’t produce any value. You need something like this: (if (seq s) (amb ( first s) (recur (rest s))) (amb)) Sorry for bad formatting, I am on mobile

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