On 20 June 2010 02:13, David Nolen <dnolen.li...@gmail.com> wrote: > On Sat, Jun 19, 2010 at 4:10 PM, Michał Marczyk > <michal.marc...@gmail.com> wrote: >> (defn fact [n] >> (loop [n n r 1] >> (if (zero? n) >> r >> (recur (dec n) (* r n))))) > Huh? That doesn't look like it's going to work at all. > 1) 1 is primitive, we know that, accept it > 2) we don't know the type of n, what will (* r n) be? > 3) BOOM!
Yes, I know what's going on, after reading through this rather lengthy thread and participating in / listening in on a number of exchanges on #clojure. I still find the notion that this code "doesn't look like it's going to work at all" to be fairly surprising. (Also, I'd rather not refactor a private loop so that it becomes exposed to the outside world (presumably to be instructed to ignore the binary overload), but that is beside the point. The (num ...) hint is a simple enough solution, which incidentally I'd be able to live with if things were not to go the way I prefer.) I wanted to address the pre-BOOM points above, though: 1) With the other approach being proposed, this would read something like "1 is primitive in primitive contexts, but will get boxed if used as an initialiser for an unhinted local". That's rather a significant improvement over the stylistically matching description of the 1.2-master (& 1.1) state of affairs (which I'll omit from here while noting that apparently acceptance was pretty low on that). I'm very happy to see Clojure moving forward w.r.t. the way in which top numeric performance can be achieved; that leaves plenty of room for doubting whether it should be the outright default. So, how about we address this point...? 2) That is in fact precisely the reason why I find it odd to presume that we know the desired type of r based on the literal alone. The question I wanted to pose when posting that factorial example was this: Should basic arithmetic work with no explicit hints / casts / primed ops / whatever -- or not necessarily? This seems like a valid question to me. If the answer is "not necessarily", I'll probably be able to get used to the idea; if it is "yes", or at least "hopefully", then perhaps there's something left to tweak / change etc. Note that if there was a way to have primitive-by-default arithmetic, yet also have naive arithmetic code work without hinting, this would be orthogonal to the issue of the choice of default. (In fact, it could affect my personal preference, or at least the degree to which I care about it.) Sincerely, Michał -- 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
