On Oct 17, 10:32 am, Timothy Pratley <timothyprat...@gmail.com> wrote: > > But name is multiply evaluated. This might be preferable: > > Hi John, > > Could you explain this a bit more for me? I can understand if the > condition is duplicated that is unnecessary calculation but don't > appreciate the issue with the binding name... both versions of the > macro seem to expand to identical code: > user=> (macroexpand-1 '(while-let [a nil] (foo))) > (clojure.core/loop [] (clojure.core/let [a nil] (clojure.core/when a > (foo) (recur)))) > So my naive view was they would have identical behaviour/performance. > I've heard this come up before but never understood or been able to > find any reference about this 'issue'.
I don't think the multiple evaluation matters in this case, since it's the name parameter, which will in all sane cases be a simple symbol. gensyms are needed when multiple evaluation could cause side-effects or an expensive function to be computed multiple times, which is not the case here. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
