From: Marcin Borkowski <mbork@mbork.pl>
To: Emanuel Berg <moasenwood@zoho.eu>
Cc: help-gnu-emacs@gnu.org, Ingemar Holmgren <dag.h@hotmail.se>
Subject: Re: Calculator: no exponent, full number ?
Date: Fri, 07 Jun 2019 21:36:11 +0200 [thread overview]
Message-ID: <878sud9oij.fsf@mbork.pl> (raw)
In-Reply-To: <86wohyodxs.fsf@zoho.eu>
On 2019-06-06, at 18:50, Emanuel Berg via help-gnu-emacs <help-gnu-emacs@gnu.org> wrote:
> Marcin Borkowski wrote:
>
>>> (defun hypotenuse (c1 c2)
>>> (sqrt (+ (* c1 c1) (* c2 c2))) )
>>
>> Just for the fun, let me mention that this is
>> not a very good algorithm for computing the
>> Pythagorean sum - it may happen that both the
>> operands and the result lie within the bounds
>> for the given type but this calculation blows
>> up because of large squares overflowing.
>
> Well, first let it be known that Marcin is
> a professional mathematician, famous for his
Professional - maybe, famous - luckily not.
> remarkable calculations. That said, the above
> comment is on the computer side of things,
> right? In the math world, what would happen is
> just a very large triangle, again - right?
Of course. There is no overflow in maths;-).
>> Also, it is slow because of the need to
>> compute square roots. Interestingly, there
>> exists a clever algorithm that does not have
>> these problems.
>
> Why don't you post it in Elisp to prove my
> point one can use Elisp for math, even advanced
> math! <3
Not enough time... Maybe in the future...
>> It is used (among others) in Donald Knuth's
>> METAFONT. The algorithm is described in the
>> paper (using Emanuel's favorite format;-)):
>
> That's true, I frekking *love* Biblatex! [2]
>
>> @ARTICLE{5390405,
>> author={C. {Moler} and D. {Morrison}},
>> journal={IBM Journal of Research and Development},
>> title={Replacing Square Roots by Pythagorean Sums},
>> year={1983},
>> volume={27},
>> number={6},
>> pages={577-581},
>> keywords={},
>> doi={10.1147/rd.276.0577},
>> ISSN={0018-8646},
>> month={Nov},
>> }
>
> Only I keep mine much neater :)
"Mine" was autogenerated by some service on the web.
Best,
--
Marcin Borkowski
http://mbork.pl
next prev parent reply other threads:[~2019-06-07 19:36 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-04 19:43 Calculator: no exponent, full number ? jonetsu
2019-06-04 22:42 ` Emanuel Berg via help-gnu-emacs
2019-06-05 11:15 ` Emanuel Berg via help-gnu-emacs
2019-06-05 4:11 ` Marcin Borkowski
2019-06-05 4:26 ` Emanuel Berg via help-gnu-emacs
2019-06-05 13:53 ` jonetsu
2019-06-05 23:47 ` Emanuel Berg via help-gnu-emacs
2019-06-06 14:50 ` Nick Dokos
2019-06-26 4:09 ` Xavier Maillard
2019-06-06 15:47 ` Marcin Borkowski
2019-06-06 16:50 ` Emanuel Berg via help-gnu-emacs
2019-06-06 17:04 ` tomas
2019-06-06 17:11 ` Emanuel Berg via help-gnu-emacs
2019-06-06 17:25 ` tomas
2019-06-07 19:36 ` Marcin Borkowski [this message]
2019-06-14 12:20 ` Van L
2019-06-14 13:26 ` Robert Pluim
2019-06-14 19:57 ` Stefan Monnier
2019-06-15 9:29 ` Van L
2019-06-14 19:43 ` Emanuel Berg via help-gnu-emacs
2019-06-15 9:23 ` Van L
-- strict thread matches above, loose matches on Subject: below --
2019-06-06 17:28 Joe Trivers via help-gnu-emacs
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