From: Tomas Hlavaty <tom@logand.com>
To: Thomas Koch <thomas@koch.ro>,
"emacs-devel@gnu.org" <emacs-devel@gnu.org>
Subject: Re: continuation passing in Emacs vs. JUST-THIS-ONE
Date: Mon, 27 Mar 2023 01:50:51 +0200 [thread overview]
Message-ID: <87wn332ht0.fsf@logand.com> (raw)
In-Reply-To: <627090382.312345.1678539189382@office.mailbox.org>
On Sat 11 Mar 2023 at 14:53, Thomas Koch <thomas@koch.ro> wrote:
> While I don't know elisp, I unfortunately had to do JavaScript. Like
> Emacs, JS is single-threaded. While I share the sentiment about JS,
> there are still things to learn from it, e.g. event driven
> programming.
I guess you mean async & await as opposed to callback hell.
I think that the essence of async & await is to teleport a value from
one place to another. It has nothing to do with asynchronicity. It
just happens that this is useful with asynchronous code where it is
convenient to teleport a value from under one stack (or thread) of
execution to under the current stack (or thread) of execution.
(await <- 2) to the current place
(async
...
(yield 42))) <- 1) teleport 42
=> 42
async is just a syntactic sugar to lexically provide the
necessary facilities to make this teleportation work. Thanks to
lexical binding and lisp macros, this is easy work for the lisp
compiler:
(defun await (future)
(let (z)
(while (eq 'EAGAIN (setq z (funcall future)))
(sit-for 0.2))
z))
(defmacro async (&rest body)
(declare (indent 0))
(let ((z (gensym))
(e (gensym)))
`(let (,e (,z 'EAGAIN))
(cl-flet ((yield (x) (setq ,z x))
(fail (string &rest args) (setq ,e (cons string args))))
,@body)
(lambda () (if ,e (apply #'error ,e) ,z)))))
Doing it this way brings great flexibility in what the three dots in the
sketch above can be: synchronous code in the current thread of
execution, asynchronous process with its filter or sentinel callback,
another thread or maybe a timer loop like in javascript.
prev parent reply other threads:[~2023-03-26 23:50 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
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 [this message]
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