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Re: A value for "nothing"


From: tomas
Subject: Re: A value for "nothing"
Date: Mon, 27 Aug 2018 10:04:15 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

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On Sun, Aug 26, 2018 at 04:07:13PM -0400, Mark H Weaver wrote:

[...]

> It's true that Guile historically has a special object distinct from all
> other objects, which (if #f #f) and various other expressions return,
> and which prints as "#<unspecified>".
> 
> However, the fact that some existing code out there might depend on the
> existence of this distinguished object, and that certain expressions in
> Guile return it, is historical baggage which carries non-zero costs as
> we move to native code generation.
> 
> I would also argue that it carries a terrible conceptual cost, in that
> it leads to confusion between the concept of a truly unspecified return
> value (as in R5RS) and this distinguished value in Guile that is called
> "the unspecified value", a non-sensical notion.
> 
> I would also avoid Guile's #nil.  That is a very special value, for one
> purpose relating to Elisp compatibility, and ideally it should not be
> used for anything else.

I must admit that I'm... pretty confused about this very prescriptive
tone.

Sorry.

Cheers
- -- tomás
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