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

[Michael Albinus]

Pedro Andres Aranda Gutierrez <paaguti@gmail.com> writes:

Hi Pedro,

> 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.

There is the `null' function, which is what you need.

> /PA

Best regards, Michael.