From: Barry OReilly <gundaetiapo@gmail.com>
To: help-gnu-emacs <help-gnu-emacs@gnu.org>
Subject: Re: Returning variable "references" under lexical binding
Date: Tue, 21 May 2013 10:41:51 -0400 [thread overview]
Message-ID: <CAFM41H2UAzGJE-SjdmL1HDhj5fh-9fceNeCLMkU6C78zYseQEg@mail.gmail.com> (raw)
>> Why not
>>
>> (defun start-my-timer ()
>> (let ((timer (make-timer ...))
>> ...
>> timer))
>> (defun cancel-my-timer (timer)
>> (cancel-timer timer))
>
> Because start-my-timer sets up callbacks that may repeatedly change the
> value of the "timer" variable:
But you said:
> I want my routine to return an object that can be used to cancel the
> most recently set timer.
How is the above start-my-timer inadequate then?
> (defun start-my-timer ()
> (let (timer)
> ;; ... (setq timer (make-timer ...)) ...
> (lambda () timer)))
>
> (defun cancel-my-timer (timer)
> (cancel-timer (funcall timer)))
Each invocation of this start-my-timer will return a different closure.
Whether start-my-timer returns a timer or a closure, you still have to keep
track of which one to pass to cancel-my-timer. So the use of closures
doesn't facilitate anything that I can see.
next reply other threads:[~2013-05-21 14:41 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-21 14:41 Barry OReilly [this message]
-- strict thread matches above, loose matches on Subject: below --
2013-05-20 20:35 Returning variable "references" under lexical binding Sean McAfee
2013-05-21 1:18 ` Barry Margolin
2013-05-21 3:18 ` Stefan Monnier
[not found] ` <mailman.112.1369106352.22516.help-gnu-emacs@gnu.org>
2013-05-21 5:39 ` Sean McAfee
2013-05-21 12:54 ` Stefan Monnier
2013-05-21 14:23 ` Barry Margolin
2013-05-21 16:38 ` Sean McAfee
2013-05-21 18:06 ` Barry Margolin
2013-05-21 22:43 ` Sean McAfee
2013-05-23 1:01 ` Stefan Monnier
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