Re: Arguing for a nilp function and where to put it

[Pedro Andres Aranda Gutierrez <paaguti@gmail.com>]

Hi Eli,

it might be that sometimes I'd like a bit more of logic...

When you want to check if a variable is an integer, you use integerp,
when you want to check if a variable is a string, you use stringp, etc.
so I was expecting, in pure logic and in the frenzy of real life, that
when you want to check if a variable is nil, you use nilp

So, null is an outlier... no problem, can live with that... intuition
failed me <blush>RTFM</blush>...
Anyway, thx
/PA

On Sat, 1 Apr 2023 at 08:09, Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: Pedro Andres Aranda Gutierrez <paaguti@gmail.com>
> > Date: Sat, 1 Apr 2023 07:37:44 +0200
> >
> > Use case for a nilp function:
> >
> > I have a buffer-local variable with a default value, and I want to
> > allow to (silently) set it to nil (and only to nil) from
> > .dir-locals.el or Local Variables.
> >
> > Currently I have
> >
> > (defun nilp(v) (unless v t))
> >
> > and I use it with
> >
> > (put '<variable> 'safe-local-variable #'nilp)
> >
> > which is much cleaner than
> >
> > (put '<variable> 'safe-local-variable (lambda (p) (unless p t)))
> >
> > every time I need it. I think other people may benefit from having
> > this simple function as part of Emacs and I'm not sure whether the
> > elisp form would be better than something more lower level like
> > integerp and in which file it would reside best.
>
> Why cannot you use the existing function 'null'?
>
> If 'null' doesn't fit the bill, please explain why.



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Georg Kreisler

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