Hi guys, playing around with different ways of creating primes. The
following implementation is probably not very efficient, but it does
seem to be correct. The problem is that when run it gives a
java.lang.StackOverflowError.
(defn primes[num]
(let [possible (range 2 num)]
(loop [current 2 rst possible]
(if-not current rst
(recur
(first (filter #(< current %) rst))
(remove
(fn [el] (and
(> el current)
(= (rem el current) 0)))
rst))))))
(primes 20)
=> (2 3 5 7 11 13 17 19)
(primes 80000)
=> (2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83
89 97 101 103 107 109 113 127 131 137 139 149 151 157 ......)
(primes 90000)
=> java.lang.StackOverflowError
It seems there is quite a tight loop that is responsible for the overflow:
....
at clojure.core$filter$fn__3718.invoke(core.clj:2130)
at clojure.lang.LazySeq.sval(LazySeq.java:42)
at clojure.lang.LazySeq.seq(LazySeq.java:56)
at clojure.lang.RT.seq(RT.java:450)
at clojure.core$seq.invoke(core.clj:122)
at clojure.core$filter$fn__3718.invoke(core.clj:2130)
at clojure.lang.LazySeq.sval(LazySeq.java:42)
at clojure.lang.LazySeq.seq(LazySeq.java:56)
at clojure.lang.RT.seq(RT.java:450)
at clojure.core$seq.invoke(core.clj:122)
at clojure.core$filter$fn__3718.invoke(core.clj:2130)
....
What am I doing wrong here, will filter/remove or something else give
StackOverflowError when used incorrectly?
Cheers,
Alf
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