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Re: A value for "nothing"

From: Mark H Weaver
Subject: Re: A value for "nothing"
Date: Mon, 27 Aug 2018 16:46:05 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)

I wrote:
> If he would like people to be able to write code that uses his library
> and works on multiple Scheme implementations, then it will certainly be
> an impediment to use a Racket-specific value for Nil on Racket, and a
> Guile-specific value for Nil on Guile.  It would be much better to use a
> portable Scheme data structure uniformly.

One might object, and point out that since the library will presumably
include procedures to construct and test for nil, it shouldn't matter if
they are represented by different objects under the hood.

The problem is, if #nil is used, it's quite likely that some code built
on top of this library and developed using Guile will end up relying on
the fact that #nil is considered false, and that (null? #nil) returns
true.  That would lead to possibly subtle breakage when the same code is
then used on another implementation.


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