Ah, very nice. I had not seen the alt! macro in use but upon close look
it is just what I need when using the :default option. My go-loop macro
now only requires the single stop channel:
(defmacro go-loop [bindings & body]
(let [stop (first bindings)]
`(let [~stop (chan)]
(go (while (alt! ~stop false :default :keep-going)
~@body))
~stop)))
Thanks for the tip!
On 7/17/13 2:26 PM, Jonas wrote:
You can also use the alt! macro:
(let [stop (chan)]
(go (loop []
(println "Hello World!")
(alt!
(timeout 1000) (do (println "I'm done sleeping...")
(recur))
stop :ok)))
(<!! (timeout 10000))
(>!! stop :now)
(println "We're done."))
On Wednesday, July 17, 2013 10:31:50 PM UTC+3, David Nolen wrote:
Why not the following?
(let [stop (chan)]
(go (loop []
(println "Hello World!")
(let [[v c]] (alts! [(timeout 10000) stop])]
(if (= c stop)
:done
(do (println "I'm done sleeping, going to recur now...")
(recur)))))))
On Wed, Jul 17, 2013 at 2:47 PM, Ben Mabey <b...@benmabey.com
<javascript:>> wrote:
Hi all,
In a number of places where I'm trying core.async I have run
across the pattern of having a loop inside a go block with
some timeouts in the loop body. Contrived example:
(go
(while true
(println "Hello World!")
(<! (timeout 10000))
(println "I'm done sleeping, going to recur now...")))
In situations like these I almost always want to be able to
stop the loop and prematurely stop the timeouts. Using alt!
we can easily handle the need of stopping the timeout.
Stopping the overall loop is easy as well but I can't seem to
do it without the use of an atom. Here are some macros I've
come up with using a channel, an atom, and an additional go block:
https://gist.github.com/bmabey/6023231
<https://gist.github.com/bmabey/6023231>
Is there a better way to do this that doesn't involve an atom?
If we had a `closed?` fn for channels one could write:
(let [stop (chan)]
(go
(while (not (closed? stop))
(println "Hello World!")
(alts! [(timeout 10000) stop])
(println "I'm done sleeping, going to recur now...")))
stop)
This seems ideal and a good use case for adding some sort of
function to detect termination. Thoughts?
Thanks,
Ben
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