Hi there,
The :default option is for a *value* that should be returned if none of the
channels are available. The expression is evaluated *before* the
async/alts! call happens (just like normal parameters).
I think you are misunderstanding alts!. It should be used like this
(let [[val ch] (async/alts! [[inner-chan e]] :default :default)]
(if (= :default val)
(println "inner-chan was not ready")
(if val
(println "did the put to inner-chan")
(println "inner-chan is closed"))))
I hope that helps. Let me know if you have any more questions.
Eric
On Thursday, August 14, 2014 11:03:01 AM UTC-5, dgrnbrg wrote:
>
> When I use alts!, it seems that both the put and :default action run every
> time. I've included the code sample below:
>
> (let [inner-chan (async/chan (async/buffer 1000))
> mult (async/mult inner-chan)
> (async/thread
> (while true
> (let [e (.take linked-blocking-queue)]
> (async/alts!
> [[inner-chan e]] (println "did the put")
> :default (println "failed to put")
> :priority true)))))
>
>
> Elsewhere in the code, I tap the mult before I start putting elements onto
> the linked-blocking-queue. For every element I put onto the LBQ, I see both
> messages: "did the put" and "failed to put". What is going on here?
>
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