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Re: Lisp reader syntax and bootstrap


From: Ulrich Mueller
Subject: Re: Lisp reader syntax and bootstrap
Date: Fri, 14 Jul 2023 07:05:18 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/28.3 (gnu/linux)

>>>>> On Fri, 14 Jul 2023, Paul Eggert wrote:

> @@ -283,6 +279,12 @@ Float Basics
>  conversely, @code{(equal 0.0 -0.0)} returns @code{nil} whereas
>  @code{(= 0.0 -0.0)} returns @code{t}.
>  
> +  Infinities and NaNs are not available on legacy systems that lack
> +IEEE floating-point arithmetic.  On a circa 1980 VAX, for example, the
> +Lisp reader approximates an infinity with the nearest finite value,

"Nearest" sounds a little strange here. HUGE_VAL has still an infinite
distance from infinity.

Maybe some wording like "approximates positive and negative infinities
with the largest and smallest representable finite numbers" would be
more accurate?

> +and a NaN with some other non-numeric Lisp object that provokes an
> +error if used numerically.



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