On Sat, Oct 17, 2009 at 3:32 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'. In this case, most often the name parameter will just be a symbol, but it's generally a good idea to avoid reoccurrences of the same macro argument in the macro expansion, except when it's needed. In this case the test and body expression *should* be multiply evaluated for the semantics of a looping construct to occur, though. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
