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Re: Any disadvantages of using put/get instead of defvar?
From: |
Tassilo Horn |
Subject: |
Re: Any disadvantages of using put/get instead of defvar? |
Date: |
Fri, 21 Feb 2014 12:56:06 +0100 |
User-agent: |
Gnus/5.13001 (Ma Gnus v0.10) Emacs/24.3.50 (gnu/linux) |
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