If you don't want the overhead introduced by an atom or (maybe, I'm not sure) by local vars, you can just instanciate a mutable object. The simplest being just an array of Objects with just one element. This can be achieved without java interop by using make-array , aset, aget ...
A laaaaasst resort trick, of course. HTH, -- Laurent 2009/7/10 J. McConnell <jdo...@gmail.com>: > > On Thu, Jul 9, 2009 at 7:56 PM, Conrad<drc...@gmail.com> wrote: >> >> I'm trying to optimize an inner loop and need a variable that mutates >> to make this work. It does NOT need to be a thread-safe variable. >> What's the best way to create a "plain ol' mutating variable" in >> Clojure? I know I can always use an Atom, but I was wondering if >> there's a more low-level way (besides using the java interop, since I >> may still want this variable to be dynamically typed.) > > You can try with-local-vars. I'm not sure of the performance > characteristics of this versus using an atom, but it certainly feels > more imperative: > > user=> (doc with-local-vars) > ------------------------- > clojure.core/with-local-vars > ([name-vals-vec & body]) > Macro > varbinding=> symbol init-expr > > Executes the exprs in a context in which the symbols are bound to > vars with per-thread bindings to the init-exprs. The symbols refer > to the var objects themselves, and must be accessed with var-get and > var-set > nil > user=> (with-local-vars [i 0 j 0] > (doseq [k (range 10)] > (println "i * j =" (* (var-get i) (var-get j))) > (var-set i (inc (var-get i))) > (var-set j (dec (var-get j))))) > i * j = 0 > i * j = -1 > i * j = -4 > i * j = -9 > i * j = -16 > i * j = -25 > i * j = -36 > i * j = -49 > i * j = -64 > i * j = -81 > nil > > HTH, > > - J. > > > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
