kawas <laurent.joi...@gmail.com> writes: Hi Laurent,
> (defn prime-factors [n] > (loop [f 2 n n res []] > (cond > (<= n 1) res > (zero? (rem n f)) (recur f (quot n f) (conj res f)) > :else (recur (inc f) n res)))) > > Problem 1 (solved): If you use (= n 1) in the first cond clause, the > function may not terminate because (= 1 1.0) may be false. But we all > know that :) Use (== n 1) instead. > Problem 2: Now compare theses function calls > (prime-factors (Math/pow 2 58)) > (prime-factors (bigdec (Math/pow 2 58))) > (prime-factors (bigint (bigdec (Math/pow 2 58)))) > > The last two function calls are really really slow. > - Is this only a problem of rem/quot slow on big numbers ? No, debugging it a bit it seems to be a bug in clojure.lang.Numbers.quotient() applied to BigDecs: user> (quot 1.4411518807585587E17 2) ;; correct with doubles 7.2057594037927936E16 user> (quot 1.4411518807585587E+17M 2) ;; wrong with BigDecs 72057594037927935M Please file a bug report about that. Bye, Tassilo -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
