Recursive nesting in Python and Clojure

Readme.md

https://twitter.com/ftrain/status/267503513477713920

gistfile1.py

# N.B. destroys the list; pass a copy if you want to retain the original!
def matryoshka(dolls, depth=1):
    out = []
    while(len(dolls) > 0):
        if dolls[0] == depth:
            out.append(dolls.pop(0))
        elif dolls[0] > depth:
            out.append(matryoshka(dolls, depth+1))
        else:
            break
    return out

matryoshka([1,2,3,3,4,4,2,1])
#[1, [2, [3, 3, [4, 4]], 2], 1]

matryoshka.clj

(defn matryoshka [dolls depth]
  (let [[head body] (split-with (partial > (+ 1 depth)) dolls)
        [body tail] (split-with (partial < depth) body)]
    (concat head (if (not= body ()) (list (matryoshka body (+ 1 depth)))) tail)))

(matryoshka dolls 1)
;; (1 (2 (3 3 (4 4)) 2) 1)