rotten news relay - comp.lang.scheme - Re: Why is it allowed to deduce from undefined?

Subject: Re: Why is it allowed to deduce from undefined?
From: Tristan Wibberley
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Date: Sat, 2 Mar 2024 12:17 UTC
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From: tristan.wibberley+netnews2@alumni.manchester.ac.uk (Tristan Wibberley)
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Subject: Re: Why is it allowed to deduce from undefined?
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On 10/11/2023 08:21, ceving wrote:
> The following looks like a contradiction to me:
>
> (if (if #f #f) #t #f) ;; => #t
> (equal? (if #f #f) #t) ;; => #f
>
> Why does Scheme allowed this? And why is it anything other than division by zero?

In Guile:
*There seems to be a common object available with the name
"*unspecified*" which 'if' uses for an unspecified branch.

* It's 'equal?' to itself as well as 'eq?' and 'eqv?' - I didn't try
others.

* It's distinct from both end-of-list and #f.

I would expect division by zero only should 'if' be defined at least in
part by division.

--
Tristan

Subject	Author
Re: Why is it allowed to deduce from undefined?	Tristan Wibberley

Be different: conform.

comp / comp.lang.scheme / Re: Why is it allowed to deduce from undefined?