On Dec 2, 9:10 am, Konrad Kułakowski (kony) <[email protected]>
wrote:
> Recently I need something which works as "inverse of interleave"
>
> I did something like that:
>
> (defn unravel [expr-list]
> (loop [flist () slist () tic-tac 0 olist expr-list]
> (let [item (first olist)]
> (if (= item nil)
> (list flist slist)
> (if (= tic-tac 0)
> (recur (concat flist (list item))
> slist 1 (rest olist))
> (recur flist (concat slist (list
> item)) 0 (rest olist)))))))
>
> Test:
>
> (def dl (interleave (iterate inc 1) ["A" "B" "C" "D" "E"]))
> (unravel dl)
>
> And the "classic" question is it possible to do it simple, more in a
> "functional manner", without explicit looping?
How about this?
(defn skip [coll n]
(lazy-seq
(when-let [s (seq coll)]
(cons (first s) (skip (drop n (next s)) n)))))
(defn unravel [coll n]
(for [i (range n)]
(skip (drop i coll) (dec n))))
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