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juergenhoetzel/gist:964676

Forked from swannodette/gist:962877
Created May 10, 2011 15:20
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sieve.clj
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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?)))
@swannodette
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Nice :D

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