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From: Eric Sosman <esosman@comcast-dot-net.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: Fwd: Re: double == double
Date: Thu, 20 Oct 2016 15:37:33 -0400
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On 10/20/2016 2:59 PM, Michael Jung wrote:
> Eric Sosman <esosman@comcast-dot-net.invalid> writes:
>> On 10/19/2016 1:39 PM, Michael Jung wrote:
>>> Eric Sosman <esosman@comcast-dot-net.invalid> writes:
>>>> On 10/19/2016 9:03 AM, Mike Amling wrote:
> [...]
>
> max has the weird distinction between +0, -0, min doesn't, now that's
> weird.

     Hmmm?  Math.min promises to treat -0 as "less than" +0, and says
that min(+0.0, -0.0) will be -0.0.

>>     (A final point: All this argument over the sign of nothing leaves
>> me, I confess, a bit perplexed.  However, those with more numerical
>> sophistication find the distinction between +0 and -0 to be of great
>> practical importance.  William Kahan is particularly vehement on the
>> topic; look for his presentation titled "Branch Cuts for Complex
>> Elementary Functions or Much Ado About Nothing's Sign Bit," and
>> bring more mathematical prowess to your reading than I can. :)
>
> max is not a complex elementary function. sin would be, but I doubt sin
> makes the distinction of +0 and -0 (in fact, it looks like this is OS
> dependent).

     I've already admitted my inability to follow all of Prof. Kahan's
argument, but I think he considers the distinction between -0 and +0
to be essential when one tries to *implement* certain functions.  He's
almost virulent about Fortran's approach to complex quantities, and was
horrified to learn that the Javafolk were thinking about adopting it.
(It seems they dropped the matter; I don't know whether Kahan's
opposition influenced their decision.)

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM