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Re: truth of %nil

From: Neil Jerram
Subject: Re: truth of %nil
Date: Sun, 30 Aug 2009 12:13:59 +0100
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/22.2 (gnu/linux)

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

Just checking this because Ludovic said recently that (SCM_BOOL_F ==
0) would have nice properties for BDW-GC.

> 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.


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