On May 3, 2014, at 9:45 AM, Dave Tenny <[email protected]> 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*))
Inside the binding you can call set! if you must.
You can also just use 'def' to redefine the global binding. It says this:
"Using def to modify the root value of a var at other than the top level is
usually an indication that you are using the var as a mutable global, and is
considered bad style. Consider either using binding to provide a thread-local
value for the var, or putting a ref or agent in the var and using transactions
or actions for mutation." in the docs at http://clojure.org/special_forms#def
which is roughly what you did with the atom. But it'll work.
You can also just write it:
(def ^:dynamic *x* (atom 1))
which is a little less verbose.
Cheers,
Bob
>
>
> Is that the simplest way to map between the two language scenarios?
> Or is there something simpler, perhaps using some var-* apis or what have you?
>
>
>
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