Jim <jimpil1...@gmail.com> writes:

> On 16/05/13 11:33, Phillip Lord wrote:
>> And if it is okay to use set!
>> on*warn-on-reflection*, why is it not okay to allow me, as the library
>> developer, to define similar properties for my library which work in a
>> similar way.
>
> well, nothing stops you from providing bindings at the main entry point of
> your library, much in the same way that Clojure does...then consumers can use
> set! as you expect. That said, I wouldn't go down that road simply because it
> gives that 'global-state' smell...


I don't have a main entry point. And, yes, I want global-state for
exactly the same reason that Clojure does. I have a process that
produces logging output, and I want the user to be able to define
where that output goes. Basically, the same as doing:

(set! *out* some-sensible-value)

but different because I also want to be able to choose between a
GUI output, and text.

So, I guess, my two options are:


(def
  ^{:dynamic true}
  *can-we-change-it* (atom "John"))

(println @*can-we-change-it*)

(reset! *can-we-change-it* "Paul")

(println @*can-we-change-it*)

(binding [*can-we-change-it*
          (atom "George")]
  (println @*can-we-change-it*))


(println @*can-we-change-it*)



(def
  ^{:dynamic true}
  *can-we-change-this-one* "Mick")

(println *can-we-change-this-one*)

(alter-var-root #'*can-we-change-this-one*
                (fn [x] "Keith"))

(println *can-we-change-this-one*)

(binding [*can-we-change-this-one*
          "Bill"]
  (println *can-we-change-this-one*))

(println *can-we-change-this-one*)



Of which, I think, the former is the best option, although it's going to
break my existing code which uses binding forms.

Phil

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