why not ref and dosync?
On Thu, May 16, 2013 at 2:45 PM, Phillip Lord
<phillip.l...@newcastle.ac.uk>wrote:
> 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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