From: Eli Zaretskii <eliz@gnu.org>
To: Emanuel Berg <incal@dataswamp.org>
Cc: emacs-devel@gnu.org
Subject: Re: hypotenuse (was: Re: Adding a generic mathematical library)
Date: Sun, 21 Jul 2024 17:44:47 +0300 [thread overview]
Message-ID: <86wmleby8w.fsf@gnu.org> (raw)
In-Reply-To: <87plr6u8al.fsf_-_@dataswamp.org> (message from Emanuel Berg on Sun, 21 Jul 2024 16:30:26 +0200)
> From: Emanuel Berg <incal@dataswamp.org>
> Date: Sun, 21 Jul 2024 16:30:26 +0200
>
> Richard Stallman wrote:
>
> > Onsider, for instance, `hypotenuse'. The benefit of having
> > that functoin would not quite be zero, but it would be
> > small. Is it enough to justify the additional function name,
> > and the complexity of documenting it?
>
> RMS has really performed excellently in this discussion and my
> favorite part of his critique must be this.
>
> What a sharp eye, to immediately identify the problem of
> a proposed solution!
>
> Indeed: Is it enough to justify the "complexity of documenting
> it"?
>
> That is an excellent question, and I leave it free for all
> to contemplate. Can we justify the complexity?
You are mocking questions which happen to be serious and non-trivial
to answer.
> Or does the below two lines of Elisp belong to the dustbin
> of computing?
>
> (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.
Like I said: a high-quality math library needs to use solid algorithms
that produce valid results whenever the problem has a solution.
Stable and accurate algorithms for hypot are known, and the libm
implementation usually follows it (and if it doesn't, we can roll our
own).
next prev parent reply other threads:[~2024-07-21 14:44 UTC|newest]
Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-12 16:47 Add elisa to GNU ELPA Sergey Kostyaev
2024-07-16 12:54 ` Philip Kaludercic
2024-07-16 13:57 ` Sergey Kostyaev
2024-07-16 16:04 ` Philip Kaludercic
2024-07-16 16:35 ` Sergey Kostyaev
2024-07-17 13:21 ` Andrew Hyatt
2024-07-16 16:41 ` Sergey Kostyaev
2024-07-16 17:02 ` Philip Kaludercic
2024-07-16 17:47 ` Adding a generic mathematical library Philip Kaludercic
2024-07-16 22:06 ` Emanuel Berg
2024-07-17 2:54 ` Christopher Dimech
2024-07-17 5:58 ` Emanuel Berg
2024-07-19 16:16 ` Richard Stallman
2024-07-19 17:38 ` Christopher Dimech
2024-07-21 5:20 ` Emanuel Berg
2024-07-20 12:45 ` Max Nikulin
2024-07-20 13:53 ` Christopher Dimech
2024-07-21 5:19 ` Emanuel Berg
2024-07-21 6:15 ` Emanuel Berg
2024-07-21 7:40 ` Emanuel Berg
2024-07-21 8:45 ` Emanuel Berg
2024-07-21 8:29 ` Emanuel Berg
2024-07-21 7:27 ` Christopher Dimech
2024-07-21 8:03 ` Emanuel Berg
2024-07-21 9:14 ` Christopher Dimech
2024-07-21 9:48 ` Emanuel Berg
2024-07-21 11:20 ` Emanuel Berg
2024-07-21 11:53 ` Christopher Dimech
2024-07-21 12:10 ` Emanuel Berg
2024-07-21 12:27 ` Emanuel Berg
2024-07-21 12:46 ` Emanuel Berg
2024-07-21 13:03 ` Christopher Dimech
2024-07-21 13:17 ` Emanuel Berg
2024-07-21 14:33 ` Eli Zaretskii
2024-07-21 14:41 ` Christopher Dimech
2024-07-21 14:49 ` Eli Zaretskii
2024-07-21 14:58 ` Christopher Dimech
2024-07-21 15:02 ` Eli Zaretskii
2024-07-21 15:18 ` Christopher Dimech
2024-07-21 13:18 ` Christopher Dimech
2024-07-21 13:26 ` Emanuel Berg
2024-07-21 14:35 ` Christopher Dimech
2024-07-21 19:28 ` Emanuel Berg
2024-07-21 19:33 ` Emanuel Berg
2024-07-21 19:51 ` Emanuel Berg
2024-07-21 20:01 ` Emanuel Berg
2024-07-21 20:17 ` Emanuel Berg
2024-07-21 12:41 ` Christopher Dimech
2024-07-21 13:13 ` Emanuel Berg
2024-07-21 13:41 ` Emanuel Berg
2024-07-21 12:20 ` Emanuel Berg
2024-07-21 12:04 ` Emanuel Berg
2024-07-21 14:30 ` hypotenuse (was: Re: Adding a generic mathematical library) Emanuel Berg
2024-07-21 14:44 ` Eli Zaretskii [this message]
2024-07-21 15:00 ` Eli Zaretskii
2024-07-21 15:12 ` Christopher Dimech
2024-07-21 15:42 ` Eli Zaretskii
2024-07-21 16:13 ` Christopher Dimech
2024-07-21 15:54 ` hypotenuse Max Nikulin
2024-07-21 16:12 ` hypotenuse Eli Zaretskii
2024-07-21 16:17 ` hypotenuse Christopher Dimech
2024-07-21 19:01 ` hypotenuse (was: Re: Adding a generic mathematical library) Emanuel Berg
2024-07-21 19:13 ` Emanuel Berg
2024-07-21 17:38 ` tomas
2024-07-17 7:09 ` Adding a generic mathematical library Michael Heerdegen via Emacs development discussions.
2024-07-17 7:54 ` Philip Kaludercic
2024-07-17 7:56 ` Michael Heerdegen via Emacs development discussions.
2024-07-18 6:07 ` Emanuel Berg
2024-07-18 6:45 ` Christopher Dimech
2024-07-18 7:12 ` Emanuel Berg
2024-07-18 7:49 ` Christopher Dimech
2024-07-21 4:56 ` Emanuel Berg
2024-07-18 7:29 ` Eli Zaretskii
2024-07-18 7:57 ` Emanuel Berg
2024-07-18 9:03 ` Eli Zaretskii
2024-07-21 4:52 ` Emanuel Berg
2024-07-18 8:15 ` Emanuel Berg
2024-07-18 9:04 ` Eli Zaretskii
2024-07-18 9:13 ` Christopher Dimech
2024-07-21 4:59 ` Emanuel Berg
2024-07-19 13:22 ` Emanuel Berg
2024-07-19 16:12 ` Christopher Dimech
2024-07-19 16:15 ` Stefan Kangas
2024-07-19 16:29 ` Christopher Dimech
2024-07-19 16:16 ` Richard Stallman
2024-07-19 18:00 ` Christopher Dimech
2024-07-17 21:26 ` Add elisa to GNU ELPA Sergey Kostyaev
2024-07-17 22:12 ` Philip Kaludercic
2024-07-18 3:45 ` Sergey Kostyaev
2024-07-18 11:06 ` Sergey Kostyaev
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