sieve.clj

(ns orbits.core
  (:require [clojure.core.async :as async :refer [<! >! <!! chan go-loop]]))

(defn print-primes [ch]
  (dorun (repeatedly 35 #(println (<!! ch)))))

(defn gen-candidates [ch]
  (go-loop [i 2]
    (>! ch i)
    (recur (inc i)))
  ch)

(defn sift [m x y z]
  (update m (+ x y) #(cons z %)))

(defn gen-primes [ints ch]
  (go-loop [multiples {}]
    (let [x (<! ints)]
      (if (contains? multiples x)
        (recur 
         (dissoc
          (reduce
            #(sift % x %2 %2)
            multiples
            (multiples x))
          x))
        (do
          (>! ch x)
          (recur (sift multiples x x x))))))
  ch)

(defn -main []
  (print-primes 
   (gen-primes
    (gen-candidates (chan))
    (chan))))