Jeff Rose writes:
>Getting with a timeout versus without one is the difference of:
>
> ; blocking deref
> @p
>
> ; deref with 100ms timeout
> (.get (future @p) 100 TimeUnit/MILLISECONDS)
But the former just blocks on the promise being delivered, while the
latter creates an anonymous function, cr
It might be nice to have a built-in mechanism to get with a timeout.
Maybe (await-for ...) could be modified to work on both agents and
promises?
Note though, that getting a promise with a timeout doesn't require
explicitly closing over the promise. The anonymous function that is
created in the o
You're right. Here's a recursive example of what I was trying to do
with promise/deliver:
http://gist.github.com/284957
And with delay/force:
http://gist.github.com/284972
Nice comparison, thanks for sharing.
I suppose the one thing I like about promise/deliver is that
promises can be "w
On Sat, Jan 23, 2010 at 7:43 PM, Richard Newman wrote:
> Use futures and promises for parallelism or dataflow-style work. Use delay
> for non-parallel, synchronous delayed execution.
You're right. Here's a recursive example of what I was trying to do with
promise/deliver:
http://gist.github.co
delay/force definitely do not do what I'm describing. What we want
to is something like a continuation as mentioned by Chouser. We want
to block the thread of execution until some point in the future when
the values become available.
I'm not sure that what you described describes what you w
Jeff Rose writes:
> The future is used because they have a timeout feature when using the
> .get method.
Should there be a corresponding timeout-based `deref' function¹
("deref-within"?) for promises? Having to close a function over your
"@p" form and spawn a job on a separate thread seems like
In a library for communicating with networked programs and devices
using Open Sound Control (OSC) messages, I use promises in combination
with futures to provide synchronous callbacks with an optional
timeout. For example, you might send a status request message to a
device and you expect an immed
Baishampayan Ghose writes:
> It would be great if someone pointed out some example usage of
> promise/deliver.
I've used them in cases where I think I need a future, but I don't want
to wrap the future around some function just to catch and propagate its
result elsewhere. In Clojure, the `future
On Fri, Jan 22, 2010 at 11:41 AM, Laurent PETIT wrote:
> David,
>
> maybe I don't understand your example well, but anyway, here are my
> remarks / concerns:
>
> * You're example is not at all exempt from multithreading: you use
> futures, and in the real scenario, the calls to deliver would have
On Thu, Jan 21, 2010 at 6:19 AM, Baishampayan Ghose
wrote:
>
> It would be great if someone pointed out some example usage of
> promise/deliver.
I've used them to convert a callback-based (continuation-passing
style, if you will) API into a blocking one. The lib I was using
provides something y
David,
maybe I don't understand your example well, but anyway, here are my
remarks / concerns:
* You're example is not at all exempt from multithreading: you use
futures, and in the real scenario, the calls to deliver would have to
occur from a thread able to pull from or be notified by the prog
They are actually useful even outside the context of concurrency. For
example perhaps you have a recursive data structure that represents a series
of unit tests and unit test suites. You would like to do two things:
1. Render out the nested structure of the tests that will be executed for
the user
Promises (and dataflow programming in general) are really useful with
interacting with physical devices, especially robots. Suppose you
have a 200 ton press, with a safety sensor. You have the following
code:
(def is-it-safe? (promise))
(defn activate-press []
(if @is-it-safe?
(go!)))
(d
In a nutshell, those are the building blocks for the "dataflow
programming paradigm".
It's an easy way to make a computation done in thread A (and using a
pre-declared promise) block until thread B has delivered the promise
(given it its value).
The book CTM covers dataflow programming :
http://w
Hello,
I am trying to understand the use-cases of the new promise/deliver
feature in Clojure. I have tried using them, and they seem to be
pretty straight-forward to use, but unfortunately I haven't been able
to understand its use-cases.
It would be great if someone pointed out some example usage
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