Thank you Meikel, I was aware of the nil issue but it's good that you
made that explicit.
I got rid of the 'symbol per your suggestion, and factored the closure
to take the stream as an input:
(defn init-features [stream]
(let [feature-stream (ref stream)]
(dosync (ref-set feature-stream stream))
(fn []
(dosync
(let [f (first @feature-stream)]
(alter feature-stream rest)
f)))))
It's amazing to me how concise this is. I'm really loving Clojure! I
kinda miss typing 'lambda' instead of 'fn' or '#(', but I suppose a
macro can fix that. Must have been done already :)
On Jan 29, 1:42 am, Meikel Brandmeyer <[email protected]> wrote:
> Hi,
>
> On Jan 29, 5:05 am, free_variation <[email protected]> wrote:
>
>
>
> > You people are terrific, thanks so much.
>
> > I basically went with what Michal and Konrad worked out:
>
> > (let [feature-stream (ref nil)]
> > (defn init-features [stream]
> > (dosync (ref-set feature-stream stream))
> > 'ready)
> > (defn get-feature []
> > (dosync
> > (let [f (first @feature-stream)]
> > (alter feature-stream rest)
> > f))))
>
> > Works like a charm. Are the ref to nil (as initial value) and the
> > constructor-like "init-features" in the closure idiomatic to Clojure?
> > I realize I'm writing scheme here :)
>
> Please note, that you cannot distinguish a nil in the stream from an
> exhausted stream. That's the reason I returned the whole seq in my
> solution and not only the first element. Maybe this doesn't apply in
> your case, but you should keep it in mind for other occasions.
>
> For the idiomatic question (and personal taste): Use :keywords instead
> of 'quoted-symbols. I would not hard-wire the ref. I would make it
> explicit as an argument. You can spice this more general function for
> convenience with partial.
>
> Sincerely
> Meikel
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