vector iteration

foo.clj

(ns foo.bar
  (:require [criterium.core :as c])
  (:import [clojure.lang Indexed Counted]))

(defmacro c! [& form]
  `(c/with-progress-reporting (c/quick-bench (do ~@form))))

(defn fn1 [u]
  (dotimes [i (.count ^Counted u)]
    (.nth ^Indexed u (unchecked-int i))))

(defn fn2 [u]
  (doseq [x u]
    x))

(defn fn3 [u]
  (let [c (.count ^Counted u)]
    (loop [i (unchecked-dec c)]
      (if (== i 0)
        nil
        (let [x (.nth ^Indexed u (unchecked-int i))]
          (recur (unchecked-dec i)))))))

(def x (vec (range 1000)))

(c! (fn1 x))  ;; 2.42us
(c! (fn2 x))  ;; 1.26us
(c! (fn3 x))  ;; 2.41us