i made a lazy prime number seive, and it seems to work for a while:
(defn natural [] (iterate #(+ % 1) 1))
(def primes
;;takes a sorted set of counters and a seq of numbers to filter
((fn sieve [in-counters checked]
;;first part of the cons is the first in said seq. hurray!
(lazy-cons (first checked)
;;this bit takes the set of counters, and the unchecked seq
(loop [counts in-counters
unchecked (rest checked)]
(let [count (first counts)
[c p] count
u (first unchecked)]
;;if first in seq = a counter, composite -> try next
in seq
(cond (= c u) (recur counts
(rest unchecked))
;;if the counter is smaller, increment it and
try again
(< c u) (recur (conj (disj counts
count)
[(+ c p) p])
unchecked)
;;if the counter is bigger, first in seq is prime
(> c u) (sieve (conj counts
[(* u u) u])
unchecked))))))
;;feed it a set with 2's counter and a seq from 2
(sorted-set [4 2])
(rest (natural))))
i tried it out with:
(doseq [p primes] (println p))
here's the tail end of it:
46301
46307
46309
46327
46337
java.lang.RuntimeException: java.lang.ClassCastException:
java.lang.Integer cannot be cast to java.lang.Long (NO_SOURCE_FILE:0)
any ideas what's going on here?
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