On Jun 18, 5:45 am, David Nolen <dnolen.li...@gmail.com> wrote: > On Fri, Jun 18, 2010 at 6:47 AM, Carson <c.sci.b...@gmail.com> wrote: > > (defn fact [n] (if (zero? n) 1 (* n (fact (dec n))))) > > (defn twice-fact [n] (fact (fact n))) > > (defn bad-twice-fact [n] (fact (-> n fact range last inc))) > > Not only is it contrived, under the proposal, this implementation of fact is > broken. It needs to be fixed to: > > (defn fact [n] (if (zero? n) 1N (* n (fact (dec n))))) > > With that change bad-twice-fact is not actually bad.
I appreciate what you're saying, and the example above is not broken. Recall from here: On Jun 17, 8:00 pm, Rich Hickey <richhic...@gmail.com> wrote: ... > Certainly one could write a version of fact > that hardwired bigints as you showed. But you need not - here's the > original naive definition: > > (defn fact [n] > (if (zero? n) 1 (* n (fact (dec n))))) > > Such logic that doesn't specify one of the components (in this case, > n) is still polymorphic, as are operations with mixed components. So > the power is in the hands of the supplier of n: > > user=> (fact 10) > 3628800 > > user=> (fact 40) > java.lang.ArithmeticException: integer overflow > > user=> (fact 40N) > 815915283247897734345611269596115894272000000000N > > I think you can always write code in this way, such that it will work > with any of the numeric types, without dictating. I believe the example (which I have tried on the num branch) shows providing a BigInt argument does not always make things safe. That is all. Carson > As Christophe Grand has mentioned one of the main things that is be > complained about from the BigInt supporters *is already a problem* in > Clojure. Nothing new to see here. > > Finally having actually tried out the new branches, this is a good change > for me. I'd like to hear more from the BigInt crowd about whether getting > their code to work with the new branches is actually causing problems. > > So far it just seems like talk. -- 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
