On Sat, Apr 4, 2015 at 8:52 AM, Paul Roush <pro...@gmail.com> wrote: > I have 2 questions related to bigints. > > 1) I've read things suggesting Clojure auto-converts between int, long, > and bigint to prevent overflow. That isn't the behavior I've experienced. > Did something change from an older release of Clojure to more recent ones? >
Clojure 1.2 and earlier auto-promoted, if I recall correctly, but that has not been the case since Clojure 1.3, released in Sep 2011. You may have found something published before then. Clojure 1.3 and later do give a bigint result for integer arithmetic if any of the arguments are bigints, e.g. (+ 1N 1) => 2N > > 2) I found myself wanting to write a function that would use bigint math > vs not depending on whether I passed a bigint in as arg. Internally I > wanted to "seed" a reduce call with either 1 or 1N as appropriate. So I > wanted to write something like this (except I'd like it to work): > > (defn foo [n] > (cast (type n) 1)) > > ; (foo 3) => 1 > ; (foo 42N) => 1N > > The following works, but I'd like to understand if I can avoid the > conditional: > > (defn foo [n] > (if (= clojure.lang.BigInt (type n)) 1N 1)) > More commonly I have seen (instance? clojure.lang.BigInt n) rather than (= clojure.lang.BigInt (type n)), but I do not know any way to avoid the conditional here. I would ask that you consider whether you really do need this check, though, since if your argument is BigInt and is combined with any arithmetic operation with a local long value in the function, the result will be BigInt. Andy -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
