A Benchmark I modified to Clojure from: https://github.com/c-cube/hashset_benchs

gistfile1.txt

(ns hash-set-bench
  "A Benchmark I modified to Clojure from:
   https://github.com/c-cube/hashset_benchs")

(defn iterNeighbors [f [i j]]
  (f [(dec i) j])
  (f [(inc i) j])
  (f [i (dec j)])
  (f [i (inc j)]))

(defn nth* [n p]
  (loop [n n s1 #{p} s2 #{}]
    (if (= n 0)
      s1
      (let [s0 (atom #{})]
        (letfn [(add [p]
                     (when (not (or (contains? s1 p) (contains? s2 p)))
                       (reset! s0 (conj @s0 p))))]
               (doseq [p s1] (iterNeighbors add p))
               (recur (dec n) @s0 s1))))))

#_(printf "result is %d" (count (time (nth* 2000 [0 0]))))