Re: Elisp: What does ''nil mean?

[Thomas Gehrlein]

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.