Sometimes you do want a mutable thing with thread-local binding, noir does
this for it's mutable session-flash stuff:
https://github.com/noir-clojure/lib-noir/blob/master/src/noir/session.clj#L95
I don't really recommend the approach, but I could see it being convenient.
On Mon, May 5, 2014 at 1:38 PM, John Gabriele <jmg3...@gmail.com> wrote:
> On Saturday, May 3, 2014 10:53:40 AM UTC-4, Bob Hutchison wrote:
>>
>>
>> On May 3, 2014, at 9:45 AM, Dave Tenny <dave....@gmail.com> wrote:
>>
>> I'm still struggling with how to write the most readable, simple clojure
>> code
>> to deal with dynamically bindings.
>>
>> What is the graceful clojure equivalent of common lisp special variables
>> for the following scenario.
>>
>> If I were writing common lisp I'd just do something like (pardon if my
>> lisp is rusty here):
>>
>> (defvar *x* 1)
>> ... do stuff with *x* ...
>> (setq *x* 2)
>> ... do stuff with *x* ...
>> (let ((*x* 3)) (do stuff with *x*...)
>> ;; do stuff with *x* that's currently at 2
>>
>>
>> The way I'm tempted to do this in clojure is
>>
>> (def ^{:dynamic true} *x* (atom 1))
>> ... do stuff with @*x* ...
>> (reset! *x* 2)
>> ... do stuff with @*x* ...
>> (binding [*x* (atom 3)] (do stuff with @*x*))
>>
>>
>> You can also just write it:
>>
>> (def ^:dynamic *x* (atom 1))
>>
>> which is a little less verbose.
>>
>>
> My understanding is that it's more common to *either*
>
> * use `(def ^:dynamic *x* 1)`, *or*
> * use `(def x (atom 1))`,
>
> but not both at the same time.
>
> That is to say, either you specifically want at dynamic var which you can
> change via a `binding`, or else you just want a global mutable (the atom).
>
> Would love to be corrected if I'm wrong though.
>
> -- John
>
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