Directly-reducible PoC in Clojure

tree-seq.clj

(defn nth' [coll n]
  (transduce (drop n) (completing #(reduced %2)) nil coll))

(defn tree-seq'
  [branch? children root]
    (eduction (take-while some?) (map first)
      (iterate (fn [[node pair]]
                 (when-some [[[node' & r] cont] (if (branch? node)
                                                  (if-some [cs (not-empty (children node))]
                                                    [cs pair]
                                                    pair)
                                                  pair)]
                   (if (some? r)
                     [node' [r cont]]
                     [node' cont])))
        [root nil])))

(time (dotimes [x 10000] (nth' (tree-seq seq? identity (repeat 10 (repeat 100 [1 2 (repeat 100 3)]))) 1000)))
;; "Elapsed time: 6161.53902 msecs"
      
(time (dotimes [x 10000] (nth' (tree-seq' seq? identity (repeat 10 (repeat 100 [1 2 (repeat 100 3)]))) 1000)))     
;; "Elapsed time: 2830.583306 msecs"      

I made a faster transducer version there: https://gist.github.com/green-coder/3adf11660b7b0ca83648c5be69de2a3b