From: Tassilo Horn <tsdh@gnu.org>
To: "Andreas Röhler" <andreas.roehler@easy-emacs.de>
Cc: help-gnu-emacs@gnu.org
Subject: Re: Any disadvantages of using put/get instead of defvar?
Date: Fri, 21 Feb 2014 12:56:06 +0100 [thread overview]
Message-ID: <87wqgofzmx.fsf@thinkpad-t61.fritz.box> (raw)
In-Reply-To: <530721AC.2050500@easy-emacs.de> ("Andreas \=\?utf-8\?Q\?R\=C3\=B6h\?\= \=\?utf-8\?Q\?ler\=22's\?\= message of "Fri, 21 Feb 2014 10:51:40 +0100")
Andreas Röhler <andreas.roehler@easy-emacs.de> writes:
>> 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.
>>
>
> BTW in earlier times a "let" was used.
> IIUC the way to make a function-local value now is "defvar" inside?
No, not at all. `defvar' creates a global variable, no matter where
it's called. Oleh's goal was just to keep a global variable and
function together, because that function is the only one using the
variable.
Another way would be
(progn
(defvar bar-foo 0)
(defun bar ()
;; do stuff with bar-foo
))
which has the possible benefit that bar-foo is defined as soon as the
file is loaded instead being undefined until the first `bar' call. And
the wrapping in a `progn' probably reduces the chance that you move
`bar' somewhere and forget `bar-foo'.
Bye,
Tassilo
next prev parent reply other threads:[~2014-02-21 11:56 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
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 [this message]
[not found] ` <mailman.15678.1392983787.10748.help-gnu-emacs@gnu.org>
2014-02-21 13:45 ` Helmut Eller
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