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Re: Making 'eq' == 'eql' in bignum branch

From: Helmut Eller
Subject: Re: Making 'eq' == 'eql' in bignum branch
Date: Wed, 29 Aug 2018 07:40:56 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)

On Wed, Aug 29 2018, Herring, Davis wrote:

> Of course +/-inf are numbers.  They're not real numbers, but neither
> are complex numbers, split-complex numbers, dual numbers, p-adic
> numbers, quaternions, octonions, sedenions, hyperreal numbers, or
> (please no) surreal numbers.  With all due respect to your
> mathematician friend, she has no exclusive claim over the definition
> (such as it is) of "number" (and I'm a bit surprised if she hadn't
> heard of at least one of the extended real lines I linked).

Also, it seems quite common to define max/min so that +/-inf are the
neutral elements <https://en.wikipedia.org/wiki/Identity_element>.

In Lisp, many associative operations return the neutral element if
called with zero arguments, e.g. (*) => 1.  So I think it's quite nice
that (max) returns -infinity.

In Scheme, the syntax +inf.0 and -inf.0 is used for infinities.  Emacs
Lisp could use the same as +inf.0 is just an ordinary symbol.  At least
Schemers could remember that.

One could also write (/ 1 0.0) for +infinity; the easiest to remember


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