From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Tomas Hlavaty <tom@logand.com>
Cc: Jim Porter <jporterbugs@gmail.com>,
Karthik Chikmagalur <karthikchikmagalur@gmail.com>,
"emacs-devel@gnu.org" <emacs-devel@gnu.org>
Subject: Re: continuation passing in Emacs vs. JUST-THIS-ONE
Date: Tue, 11 Apr 2023 16:22:18 -0400 [thread overview]
Message-ID: <jwvr0sqkwvo.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <874jpmfaw9.fsf@logand.com> (Tomas Hlavaty's message of "Tue, 11 Apr 2023 21:59:18 +0200")
>> The idea is to use `futur.el` *instead of* threads.
> What do you mean?
> I can see thread-join and thread-signal in futur.el.
It's only used to work around the current lack of an async version of
process-send-string.
> It is useful to acknowledge, that there are 3 different use-cases:
> a) asynchronous processes
> b) threads
> c) iter
I can't see how `iter` would be a use case for futures.
> My impression was that futur.el was trying to address a) and b) but now
> you say it does address a) only. That is rather limited.
Looking at existing code, iter and threads are virtually never used, so
from where I stand it seems to cover the 99% cases.
>>> No, the iter case does map directly to futures:
>>>
>>> (await
>>> (async-iter
>>> (let ((a (async-iter
>>> (message "a1")
>>> (await-iter (sleep-iter3 3))
>>> (message "a2")
>>> 1))
>>> (b (async-iter
>>> (message "b1")
>>> (let ((c (async-iter
>>> (message "c1")
>>> (await-iter (sleep-iter3 3))
>>> (message "c2")
>>> 2)))
>>> (message "b2")
>>> (+ 3 (await-iter c))))))
>>> (+ (await-iter a) (await-iter b)))))
>>
>> I must say I don't understand this example: in which sense is it using
>> "iter"? I don't see any `iter-yield`.
>
> await-iter and async-iter macros are using iter under the hood.
The point of `iter` is to provide something that will iterate through
a sequence of things. Here I don't see any form of iteration. You seem
to use your `iter`s just as (expensive) thunks (futures).
Maybe what you mean by "iter" is the use of CPS-translation
(implemented by `generator.el`)?
>> `futur.el` also "queues the continuations in the event loop".
>
> I get:
>
> futur.el:97:8: Warning: the function ‘funcall-later’ is not known to be
> defined.
Yup, it's defined in C currently. You can use
(unless (fboundp 'funcall-later)
(defun funcall-later (function &rest args)
;; FIXME: Not sure if `run-with-timer' preserves ordering between
;; different calls with the same target time.
(apply #'run-with-timer 0 nil function args)))
>> Of course. You could do something like
>>
>> (futur-let*
>> ((a (futur-let* ((_ <- (futur-process-make
>> :command '("sleep" "9"))))
>> 9))
>> (b (futur-let* ((_ <- (futur-process-make
>> :command '("sleep" "8"))))
>> 8))
>> (a-val <- a)
>> (b-val <- b))
>> (message "Result = %s" (+ a-val b-val))))
>
> So will futur.el take 9sec or 17sec?
9 secs, of course: the above creates 2 futures and emits the message
when they're both done. Since those futures are executed in
subprocesses, they execute concurrently.
>> Similarly the "intended return value" of a process will depend on what
>> the process does. In some cases it will be the stdout, but I see no
>> reason to restrict my fundamental function to such a choice.
> This overgeneralized thinking is beyond usefulness and harmfully leads
> to the problem of how to maintain state.
While I do like to over-generalize, in this case, there is no
generalization involved. The code is the simple result of a thin
wrapper around the existing `make-process` to make it obey the
`futur.el` API. So if it's overgeneralized, it's not my fault, it's
`make-process`s :-)
Stefan
next prev parent reply other threads:[~2023-04-11 20:22 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-11 12:53 continuation passing in Emacs vs. JUST-THIS-ONE Thomas Koch
2023-03-12 1:45 ` Jim Porter
2023-03-12 6:33 ` tomas
2023-03-14 6:39 ` Karthik Chikmagalur
2023-03-14 18:58 ` Jim Porter
2023-03-15 17:48 ` Stefan Monnier
2023-03-17 0:17 ` Tomas Hlavaty
2023-03-17 3:08 ` Stefan Monnier
2023-03-17 5:37 ` Jim Porter
2023-03-25 18:42 ` Tomas Hlavaty
2023-03-26 19:35 ` Tomas Hlavaty
2023-03-28 7:23 ` Tomas Hlavaty
2023-03-29 19:00 ` Stefan Monnier
2023-04-03 0:39 ` Tomas Hlavaty
2023-04-03 1:44 ` Emanuel Berg
2023-04-03 2:09 ` Stefan Monnier
2023-04-03 4:03 ` Po Lu
2023-04-03 4:51 ` Jim Porter
2023-04-10 21:47 ` Tomas Hlavaty
2023-04-11 2:53 ` Stefan Monnier
2023-04-11 19:59 ` Tomas Hlavaty
2023-04-11 20:22 ` Stefan Monnier [this message]
2023-04-11 23:07 ` Tomas Hlavaty
2023-04-12 6:13 ` Eli Zaretskii
2023-04-17 20:51 ` Tomas Hlavaty
2023-04-18 2:25 ` Eli Zaretskii
2023-04-18 5:01 ` Tomas Hlavaty
2023-04-18 10:35 ` Konstantin Kharlamov
2023-04-18 15:31 ` [External] : " Drew Adams
2023-03-29 18:47 ` Stefan Monnier
2023-04-17 3:46 ` Lynn Winebarger
2023-04-17 19:50 ` Stefan Monnier
2023-04-18 2:56 ` Lynn Winebarger
2023-04-18 3:48 ` Stefan Monnier
2023-04-22 2:48 ` Lynn Winebarger
2023-04-18 6:19 ` Jim Porter
2023-04-18 9:52 ` Po Lu
2023-04-18 12:38 ` Lynn Winebarger
2023-04-18 13:14 ` Stefan Monnier
2023-04-19 0:28 ` Basil L. Contovounesios
2023-04-19 2:59 ` Stefan Monnier
2023-04-19 13:25 ` [External] : " Drew Adams
2023-04-19 13:34 ` Robert Pluim
2023-04-19 14:19 ` Stefan Monnier
2023-04-21 1:33 ` Richard Stallman
2023-04-19 1:11 ` Po Lu
2023-04-17 21:00 ` Tomas Hlavaty
2023-03-14 3:58 ` Richard Stallman
2023-03-14 6:28 ` Jim Porter
2023-03-16 21:35 ` miha
2023-03-16 22:14 ` Jim Porter
2023-03-25 21:05 ` Tomas Hlavaty
2023-03-26 23:50 ` Tomas Hlavaty
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