Hm... this way you have to setup a ref and a transaction, but its local: user=> (let [a (ref 0)] (dosync (ref-set a 1))) 1 user=> a java.lang.Exception: Unable to resolve symbol: a in this context (NO_SOURCE_FILE:0) -Ralf On Mon, Dec 1, 2008 at 10:07 PM, jim <[EMAIL PROTECTED]> wrote:
> > The rule of thumb I used when I started with Clojure was if I'm > tempted to use a def inside a function, I'm doing something wrong. > Now, I'm not even tempted. > > (def mut-local) > (defn f [] > (binding [mut-local 0] > (set! mut-local 1) > mut-local)) > > Is the same as what you wrote. > > Functional programming is a totally different mind set than imperative > programming. You might pick up "The Little Schemer" and "The Seasoned > Schemer". They do a good job of changing your perspective. > > Jim > > On Dec 1, 2:55 pm, puzzler <[EMAIL PROTECTED]> wrote: > > I'm often copying "classic algorithms" from various sources, and it is > > true that it can take some thought to do a functional conversion. > > Sometimes, it's easier to just go ahead and use mutable local > > variables. Fortunately, Clojure lets you do mutability if needed. > > > > But I'm still unclear on the best way to do that. To simulate mutable > > locals, would you use refs or vars? My own instinct would be to use > > vars for a temporary mutable local, and refs for something that the > > closure has to remember (like memoization). > > > > Here's how I think you could do a mutable local: > > (defn f [] > > (def mut-local) > > (binding [mut-local 0] > > (set! mut-local 1) > > mut-local)) > > > > (f) should yield 1 > > > > The flaw with this approach is that def actually creates a global > > var. It remains unbound, but the fact that the function ends up > > having a global effect is less than satisfying. > > > > Better ways? > > > --~--~---------~--~----~------------~-------~--~----~ 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 To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
