gistfile1.scm

;; The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.

;; Find the sum of all the primes below two million.

(defn is-prime [n]
  (loop [d (int (Math/sqrt n))]
    (if (= d 1)
      true
      (if (= 0 (rem n d))
        false
        (recur (dec d))))))

(time (loop [n 2, acc 0]
  (if (> n 2000000)
    acc
    (if (is-prime n)
      (recur (inc n) (+ acc n))
      (recur (inc n) acc)))))

; "Elapsed time: 134703.35 msecs"
; 142913828922


;; Damn it Github, give me Clojure syntax hightlighting. Oh well. Scheme works ok.