Concurrency - Revision history

Elvince: /* emacs-deferred */ example project

2017-04-13T13:24:49Z

emacs-deferred: example project

Elvince: /* emacs-async */ examples

2017-02-21T13:53:02Z

emacs-async: examples

Elvince: /* Emacs 25's Thread */ async/await

2017-02-06T16:06:33Z

Emacs 25's Thread: async/await

Elvince: add categories

2017-01-16T12:56:29Z

add categories

Elvince: init concurrency

2017-01-16T12:51:49Z

init concurrency

New page

How to write concurrent/asynchronous code in Emacs ?

== Async processes ==

Accept that you can do a lot with just multiple async processes – this is the NodeJs approach; a single Emacs can ask another process to do something and use ProcessSentinels and ProcessFilterFunctions to do quite a lot of processing apparently concurrently but really just in an event loop. As long as the ProcessFilterFunction is not too slow this is fine. Elnode takes this approach to making a scalable webserver in EmacsLisp.

== emacs-async ==

Spawn more Emacs processes to do work for you – JohnWiegley’s [https://github.com/jwiegley/emacs-async Async] takes this approach, Elnode has an alternative and Elpakit another alternative. No one has unified this approach yet.

Some async applications are provided as well with emacs-async:

* Dired-async
* smtp-mail-async
* async-bytecomp

Example code:

<source lang="lisp">
(async-start
;; What to do in the child process
(lambda ()
(message "This is a test")
(sleep-for 3)
222)

;; What to do when it finishes
(lambda (result)
(message "Async process done, result should be 222: %s" result)))
</source>

== emacs-deferred ==

Defer asynchronous tasks – this is what the [https://github.com/kiwanami/emacs-deferred emacs-deferred] library does. It provides facilities to manage asynchronous tasks. The API and implementations were translated from JSDeferred and Mochikit.Async in Javascript. concurrent.el is a higher level library for concurrency, based on `deferred.el’.

Example:

This is a basic deferred chain. This code puts some outputs into message buffer, and then require a number from minibuffer.

<source lang="lisp">
(deferred:$
(deferred:next
(lambda () (message "deferred start")))
(deferred:nextc it
(lambda ()
(message "chain 1")
1))
(deferred:nextc it
(lambda (x)
(message "chain 2 : %s" x)))
(deferred:nextc it
(lambda ()
(read-minibuffer "Input a number: ")))
(deferred:nextc it
(lambda (x)
(message "Got the number : %i" x)))
(deferred:error it
(lambda (err)
(message "Wrong input : %s" err))))
</source>

= Emacs 25's Thread =

Thread support has been added to Emacs.

See the discussion at http://thread.gmane.org/gmane.emacs.devel/120530/focus=122664 or the info manual at Thread.

← Older revision		Revision as of 12:56, 16 January 2017
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	See the discussion at http://thread.gmane.org/gmane.emacs.devel/120530/focus=122664 or the info manual at Thread.		See the discussion at http://thread.gmane.org/gmane.emacs.devel/120530/focus=122664 or the info manual at Thread.
		+
		+	[[Category:Emacs Lisp]]
		+	[[Category:Programming]]
		+	[[Category:Advanced]]

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        (message "Wrong input : %s" err))))
 </source>
 = Async/Await =

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       (message "Async process done, result should be 222: %s" result)))
 </source>
 == emacs-deferred ==