Clojure Loop Function Only Returns Nil

Question

The function below splits the text variable into a sequence of characters that is steps long. The only problem is I can't figure out how to return the resulting list, which I need to compute its Shannon entropy for several values of step.

(defn split-text [text step]

  (loop [i 0 result []]
    (when (<= (+ i step) (count text))
      (recur (+ i step)
             (conj result (subs text i (+ i step)))))))

as the answer below says, you should return result in a false condition branch. You can also do something like this, to reduce code complexity: (defn split-text [text step] (map (partial apply str) (partition step text))) — leetwinski
– leetwinski, Commented May 6, 2020 at 8:53

bereal · Accepted Answer · 2020-05-06 06:40:33Z

1

You need to return the result from the loop:

(defn split-text [text step]
  (loop [i 0 result []]
    (if (> (+ i step) (count text))
      result  ;; <== here
      (recur (+ i step)
             (conj result (subs text i (+ i step)))))))

Also, the last chunk will be lost if it's less than step characters long. If you want to keep it:

(defn split-text [text step]
  (loop [tail text result []]
    (if (empty? tail)
      result
      (let [len (min step (count tail))]
        (recur (subs tail len)
               (conj result (subs tail 0 len)))))))

edited May 6, 2020 at 6:40

answered May 6, 2020 at 6:28

bereal

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1 Comment

Rayos Over a year ago

Thank you! This is exactly what I needed.

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