is it possible to check if a "promise" has been "deliver"ed to without blocking?

[Sunil S Nandihalli]

Hello Everybody,

 Let us say I have something like

(def s (promise))

.

.

.

.

now can I check if the promise hase been delivered ..

Thanks 
Sunil.

  

[Laurent PETIT]

Nope.

here's the source:

Clojure classpath initialized by cljr.

user=> (source promise)

(defn promise

  "Alpha - subject to change.

  Returns a promise object that can be read with deref/@, and set,

  once only, with deliver. Calls to deref/@ prior to delivery will

  block. All subsequent derefs will return the same delivered value

  without blocking."

  {:added "1.1"}

  []

  (let [d (java.util.concurrent.CountDownLatch. 1)

        v (atom nil)]

    (reify 

     clojure.lang.IDeref

      (deref [_] (.await d) @v)

     clojure.lang.IFn

      (invoke [this x]

        (locking d

          (if (pos? (.getCount d))

            (do (reset! v x)

                (.countDown d)

                this)

            (throw (IllegalStateException. "Multiple deliver calls to a promise"))))))))

2010/9/14 Sunil S Nandihalli <sunil.na...@gmail.com>

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[Meikel Brandmeyer]

See also here: http://groups.google.com/group/clojure-dev/browse_thread/thread/bbf34a823f3081d6

[Hubert Iwaniuk]

Hi Sunil,

Before it gets to clojure.core you could use it like that:
http://github.com/neotyk/http.async.client/blob/master/src/http/async/client/util.clj#L21

Cheers,
Hubert.

[Sunil S Nandihalli]

Thanks Hubert,
 That is exactly what I was looking for.
Sunil.

--
************************************************
Sunil S Nandihalli,
Manager and Technical Lead,
GridPro India Operations,
Program Development Co. LLC India Branch
Bangalore.
ph: 9980520430

[Hubert Iwaniuk]

Glad I could help,
Hubert.