Seven-3.2-1 created by guozengxin1 - https://repl.it/MwDl/2

Seven-3.2-1.clj

(defn recursive-sum [numbers]
  (if (empty? numbers)
      0
      (+ (first numbers) (recursive-sum (rest numbers)))))

(defn reduce-sum [numbers]
  (reduce (fn [acc x] (+ acc x)) 0 numbers))    

(defn sum [numbers]
  (reduce + numbers))

(def numbers (into [] (range 0 1000000)))
(time (sum numbers))
(time (sum numbers))

(ns sum.core
    (:require [clojure.core.reducers :as r]))
  
(defn parallel-sum [numbers]
  (r/fold + numbers))

(def numbers (into [] (range 0 1000000)))

(time (parallel-sum numbers))
(time (parallel-sum numbers))