Since collatz is defined for integer math, I would argue that the use of "quot" instead of "/" isn't a workaround at all -- "quot" is the right function for the job, and better communicates what the code is doing.
That said, Mark is certainly right that we want feedback on the numeric support in 1.3. Please switch to it if you can. Stu > On Thu, Oct 7, 2010 at 12:29 PM, Jarl Haggerty <fictivela...@gmail.com> wrote: >> I'm using clojure 1.2 > > OK, I stand corrected. Stuart's right. The problem is that you're > getting mixed numeric types. > When you do (collatz 113383) the sequence eventually hits > 2482111348 > which is a Long, not an Integer. > When you divide by 2, > (/ 249211348 2) you should get back an Integer, but instead, you get > back a Long. > This continues until eventually you're bouncing back and forth between > 1, 2, and 4 which are Longs rather than Integers, and thus aren't > being found in your hash map. > > My understanding is that Clojure 1.2 is supposed to auto-reduce all > arithmetic operations specifically to avoid situations like this. > Therefore, I believe it is a bug that (/ 249211348 2) returns a Long > rather than an Integer. > > Unfortunately, I don't know whether anyone is likely to fix it, since > Clojure 1.3 is pursuing an entirely different arithmetic strategy. > > The quickest fix for your particular situation is to use quot > (quotient) rather than /, since quot properly auto-reduces. > Another workaround (for example, if you don't know in advance that the > first operand is divisible by the second) is to call > clojure.lang.Numbers/reduce after each division. > > -- > 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 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
