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From: Eli Zaretskii <eliz@gnu.org>
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Subject: Re: hypotenuse (was: Re: Adding a generic mathematical library)
Date: Sun, 21 Jul 2024 18:00:37 +0300
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In-Reply-To: <86wmleby8w.fsf@gnu.org> (message from Eli Zaretskii on Sun, 21
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> Date: Sun, 21 Jul 2024 17:44:47 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: emacs-devel@gnu.org
> 
> > (defun hypotenuse (c1 c2)
> >   (sqrt (+ (* c1 c1) (* c2 c2))) )
> 
> This is not the best way of computing hypot: squaring a number could
> overflow or underflow, and you get bad result.  Try
> 
>     (hypotenuse 1.e-600 1.e-600)
> or
>     (hypotenuse 1.e600 1.e600)
> 
> and you will see it.

Sorry, that should have been 1.e-300 and 1.e300 instead.