sieve.clj

gistfile1.clj

(set! *unchecked-math* true)

(defmacro iloop [[b t n] & body]
  `(loop [~@b]
     (when ~t
       ~@body
       (recur ~n))))

(defn count-primes [^long n]
  (let [c (inc n)
        ^java.util.BitSet prime? (java.util.BitSet. c)]
    (.set prime? 2 n)
    (iloop [(i 2) (<= (* i i) n) (inc i)]
           (if (.get prime? i)
             (iloop [(j i) (<= (* i j) n) (inc j)]
                    (.clear prime? (* i j)))))
    (.cardinality prime?)))

Nice :D