From: Tassilo Horn <tsdh@gnu.org>
To: Oleh <ohwoeowho@gmail.com>
Cc: help-gnu-emacs@gnu.org
Subject: Re: Any disadvantages of using put/get instead of defvar?
Date: Fri, 21 Feb 2014 10:39:30 +0100 [thread overview]
Message-ID: <87bny0x0rx.fsf@thinkpad-t61.fritz.box> (raw)
In-Reply-To: <CAA01p3rVJDD9k6yHZHpyST516KNbibfQf5=MnUmtCJxfMF6FPg@mail.gmail.com> (Oleh's message of "Fri, 21 Feb 2014 10:12:44 +0100")
Oleh <ohwoeowho@gmail.com> writes:
>>> The situation is that I have a function that uses one global variable.
>>> It's for sure that no other function will want this variable. In an
>>> effort to have all code in one place I want to move from:
>>>
>>> (defvar bar-foo 1)
>>> (defun bar ()
>>> ;; use bar-foo here
>>> )
>>>
>>> to:
>>>
>>> (defun bar ()
>>> (let ((foo (or (get 'bar 'foo) 1)))
>>> ;; use foo here
>>> ))
>>>
>>> So the advantage is that I can move and rename the function without
>>> worry that the function/variable coupling will break, because now
>>> everything is inside one function.
>>
>> You could also define the variable inside the function, i.e., that's a
>> buffer-local counter:
>>
>> (defun counter ()
>> (defvar counter-var 1)
>> (setq-local counter-var (1+ counter-var)))
>>
>
> Thanks, Tassilo,
>
> But doesn't `defvar` introduce overhead this way?
Well, I've measured my counter above versus a version using symbol
properties as you suggest:
(defun bar ()
(let ((foo (or (get 'bar 'foo) 1)))
(put 'bar 'foo (1+ foo))))
My counter is way faster although it uses defvar and setq-local, so that
overhead is still small compared to looking up/putting a symbol
property.
Bye,
Tassilo
next prev parent reply other threads:[~2014-02-21 9:39 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-20 17:04 Any disadvantages of using put/get instead of defvar? Oleh
2014-02-20 22:24 ` Tassilo Horn
2014-02-21 1:40 ` Stefan Monnier
2014-02-21 10:29 ` Nicolas Richard
2014-02-21 13:57 ` Stefan Monnier
2014-02-21 11:49 ` Tassilo Horn
2014-02-21 14:41 ` Stefan Monnier
2014-02-21 9:12 ` Oleh
2014-02-21 9:39 ` Tassilo Horn [this message]
2014-02-21 9:44 ` Oleh
2014-02-21 9:51 ` Andreas Röhler
2014-02-21 9:56 ` Sebastian Wiesner
2014-02-21 11:56 ` Tassilo Horn
[not found] ` <mailman.15678.1392983787.10748.help-gnu-emacs@gnu.org>
2014-02-21 13:45 ` Helmut Eller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/emacs/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87bny0x0rx.fsf@thinkpad-t61.fritz.box \
--to=tsdh@gnu.org \
--cc=help-gnu-emacs@gnu.org \
--cc=ohwoeowho@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).