From: Eli Zaretskii <eliz@gnu.org>
To: Pedro Andres Aranda Gutierrez <paaguti@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Arguing for a nilp function and where to put it
Date: Sat, 01 Apr 2023 09:10:02 +0300 [thread overview]
Message-ID: <831ql416bp.fsf@gnu.org> (raw)
In-Reply-To: <CAO48Bk_E7XSLB7X_Q8T5M7gifUBF=-50cGUNjRfVLbkhVyRykg@mail.gmail.com> (message from Pedro Andres Aranda Gutierrez on Sat, 1 Apr 2023 07:37:44 +0200)
> 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.
next prev parent reply other threads:[~2023-04-01 6:10 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-01 5:37 Arguing for a nilp function and where to put it Pedro Andres Aranda Gutierrez
2023-04-01 6:01 ` tomas
2023-04-01 6:07 ` Michael Albinus
2023-04-01 6:10 ` Eli Zaretskii [this message]
2023-04-01 7:09 ` Pedro Andres Aranda Gutierrez
2023-04-02 21:28 ` Roland Winkler
2023-04-03 3:02 ` Richard Stallman
2023-04-03 3:34 ` Emanuel Berg
2023-04-03 12:46 ` Andreas Schwab
2023-04-03 18:48 ` Roland Winkler
2023-04-03 23:44 ` Emanuel Berg
2023-04-04 2:56 ` Richard Stallman
2023-04-05 7:24 ` Emanuel Berg
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