Re: Any disadvantages of using put/get instead of defvar?

["Andreas Röhler" <andreas.roehler@easy-emacs.de>]

Am 21.02.2014 10:39, schrieb Tassilo Horn:
> 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.
>

BTW in earlier times a "let" was used.
IIUC the way to make a function-local value now is "defvar" inside?