Ken,
Thanks for putting this together. As a newbie, this gives me a lot to
mull over. Can you explain the convention of a * at the end of a
function name?
On Nov 24, 12:39 am, Ken Wesson <kwess...@gmail.com> wrote:
> On Tue, Nov 23, 2010 at 11:45 PM, HiHeelHottie <hiheelhot...@gmail.com> wrote:
>
> > Does anybody know of an implementation for a priority queue that can
> > be used for scheduling events in the future? I would like to put a
> > map associated with a timestamp into the queue and be able to pull out
> > all maps at or before a given time in order.
>
> That's something you can slap together in a few minutes.
>
> user=> (def sched (ref (sorted-map )))
>
> (def jobber (agent nil))
>
> (defn schedule-job!* [time runnable]
> (dosync
> (alter sched assoc time runnable)))
>
> (defn- next-job-time []
> (key (first @sched)))
>
> (defn- do-next-job! []
> (dosync
> (when-let [[k v] (first @sched)]
> (alter sched dissoc k)
> (send-off jobber (fn [_] (v) nil)))))
>
> (defn- job-runner []
> (loop []
> (if-not (empty? @sched)
> (if (> (System/currentTimeMillis) (next-job-time))
> (do-next-job!)))
> (Thread/sleep 10)
> (recur)))
>
> (doto (Thread. job-runner)
> (.setDaemon true)
> (.start))
>
> (defn schedule-job-after!* [delay runnable]
> (schedule-job!* (+ (System/currentTimeMillis) delay) runnable))
>
> (defmacro schedule-job! [time & body]
> `(schedule-job!* ~time (fn [] ~...@body)))
>
> (defmacro schedule-job-after! [delay & body]
> `(schedule-job-after!* ~delay (fn [] ~...@body)))
>
> (schedule-job-after! 10000
> (println "foo"))
>
> (schedule-job-after! 30000
> (println "bar"))
>
> (schedule-job-after! 20000
> (println "baz"))
> {1290576825292
> #<user$eval2986$fn__2987 user$eval2986$fn__2...@1ef2fd3>,
> 1290576835296
> #<user$eval2994$fn__2995 user$eval2994$fn__2...@1d5e94f>,
> 1290576845294
> #<user$eval2990$fn__2991 user$eval2990$fn__2...@24b943>}
> user=>
> foo
> baz
> bar
>
> The last three lines will print at ten-second intervals and may not
> appear in the same console as your user=> prompt depending on how your
> REPL/IDE handles asynchronous printlns. With NetBeans they'll appear
> in *out* instead of Repl (for sure) and in slime in the inferior-lisp
> buffer (I think).
>
> This could be reworked to use java.util.Date but the basic
> architecture would remain the same.
>
> You'll need to (shutdown-agents) during shutdown of any application
> where you use this if you don't want the JVM to linger as a zombie
> process.
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
