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Re: Elisp: What does ''nil mean?
From: |
Thomas Gehrlein |
Subject: |
Re: Elisp: What does ''nil mean? |
Date: |
16 May 2003 18:16:15 +0200 |
User-agent: |
Gnus/5.09 (Gnus v5.9.0) Emacs/21.1 |
David Kastrup <dak@gnu.org> writes:
> Thomas Gehrlein <thomas.gehrlein@t-online.de> writes:
>
> > David Kastrup <dak@gnu.org> writes:
> >
> > > Thomas Gehrlein <thomas.gehrlein@t-online.de> writes:
> > >
> > > > The following line is from easy-menu-create-menu:
> > > >
> > > > ((eq keyword :active) (setq enable (or arg ''nil)))
> > > >
> > > > It is part of a (cond ...).
> > > >
> > > > What does "''nil" mean?
> > >
> > > The same as '(quote nil), an unevaluated list with the two members
> > > quote and nil.
> >
> > Is this the same as (quote (quote nil))?
>
> It is, like (quote nil), the result of evaluating (quote (quote nil)).
>
> > Why would you quote nil and not evaluate it?
>
> To make it different from nil, while evaluating to it eventually.
Thank you. I think now I understand.