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Re: truth of %nil

From: Mark H Weaver
Subject: Re: truth of %nil
Date: Sun, 30 Aug 2009 10:15:19 -0400

On Sun, Aug 30, 2009 at 12:13:59PM +0100, Neil Jerram wrote:
> Mark H Weaver <address@hidden> writes:
> > This numbering has the nice properties that 0 is #f.
> Just to be clear: will this mean that (SCM_BOOL_F == 0) ?  As things
> stand I don't think it will, because SCM_MAKIFLAG shifts and adds
> 0x04.

Yes, that's correct.  SCM_BOOL_F is 4.  What I should have said above
is that #f is IFLAG number 0.

> > Also, you may have noticed that I've been using the term "lisp"
> > instead of "elisp".  This is because guile may support other lisps in
> > the future, and they will also need the same %nil handling.  (For that
> > matter, we could even use %nil to implement an "old scheme" language
> > which treats '() as false.)  With this in mind, should SCM_ELISP_NIL
> > be renamed to SCM_LISP_NIL?
> Yes, that sounds like a good argument to me - i.e. I can't see any
> reason why the special-case-ness of Elisp shouldn't apply equally to
> other Lisps - so please do rename "ELISP" things to "LISP", where this
> argument supports that.

Sounds good!


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