CODEWITHSUNDEEP
listemacs
feklee
feklee

Reputation: 7705

How do I partition a list into (sub-)lists of random length?

Input, by example (4 is the maximum length):

(my-partition-randomly '(a b c d e f g h i j k l) 4)

Output:

'((a b c) (d) (e f g h) (i j k) (l))

The code should run in the Emacs Lisp interpreter.

Upvotes: 1

Views: 113

Answers (1)

choroba
choroba

Reputation: 241988

My elisp-fu is weak, but I was able to write the following function:

(defun my-partition-randomly (list max-length) ""
       (let ((result '()))
         (while list
           (push (seq-take-while (lambda (x) x)
                                 (map 'list
                                      (lambda (x) (pop list))
                                      (number-sequence 1 (+ 1 (random max-length)))))
                 result))
         (reverse result)))

It extracts random initial sequences of the input list and adds them to result (the seq-take-while is needed not to include nils when the last subsequence wants to be longer than the remaining list). push adds elements to the left, so the result has to reversed.

Upvotes: 2

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