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Groups > comp.lang.java.programmer > #35768
| From | Michael Jung <miju@golem.phantasia.org> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: double == double |
| Date | 2016-10-15 17:44 +0200 |
| Organization | albasani.net |
| Message-ID | <87zim5sjli.fsf@golem.phantasia.org> (permalink) |
| References | (2 earlier) <8737k0qd38.fsf@golem.phantasia.org> <87zim5es30.fsf@golem.phantasia.org> <ntta21$osp$1@dont-email.me> <nttemi$mt3$1@gioia.aioe.org> <nttfev$bgj$1@dont-email.me> |
Eric Sosman <esosman@comcast-dot-net.invalid> writes:
> On 10/15/2016 10:32 AM, Arne Vajhøj wrote:
>> On 10/15/2016 9:13 AM, Eric Sosman wrote:
>>> The scare quotes around "argument" seem appropriate. I attempted
>>> to explain the basis of the simplistic "Don't use ==" advice, hoping
>>> that an informed understanding would trump blind obedience to some
>>> mysterious rule. (Perhaps I was overly optimistic.)
Those weren't scare quotes. Your explanation I also assume sufficient. I
was trying to find a rule-of-thumb that was "better" than the simple
"never use" clause but not too clumsy. It wasn't an argument at
all. Neither as argument nor as rule does this (unquoted) elaboration
apply to +0 and -0. I don't think Stefan fell for the usefulness of ==
with doubles but more possibly for the usefulness of +0 and -0. Anyway,
there's a scare quote up there now. :-)
[...]
> Allow me to pose a related question: Do you ever use > with
> floating-point values? And do you ever use >= similarly? Now:
> How do you choose between > and >=, and why?
> I contend that someone who blindly obeys "Never use ==" will
> have no (rational) way to decide whether to use > as opposed to >=,
> since the only difference between them is the equality comparison
> he's pledged to avoid.
">" = !"<=" and "<" = !">=". It turns out to be a matter of taste or
clarity in a situation, which to use. Equality doesn't really come into
it. I think, going for a rule-of-thumb on "==" is aiming too short. The
better rule-of-thumb is "to shy away from 0 with doubles and
calculations".
> That is, I contend there's no substitute for understanding.
> My own understanding is imperfect -- the field called Numerical
> Analysis is large, intricate, and subtle -- but nonetheless I feel
> that dicta like "Never" are, er, "Always" out of place. (Almost.)
Of course. An example for using "==" on zero with doubles _and
calculations_ (foiling my own "dicta") is
double a = 1;
int b = 1;
while (!(a == 0)) {
b++;
a = a/2;
}
System.out.println("b=" + b);
With a large enough numeric hammer you can possibly forge a useful
example out of it.
Michael
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Re: double == double Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-10-12 09:39 -0400
Re: double == double Michael Jung <miju@golem.phantasia.org> - 2016-10-13 21:10 +0200
Re: double == double Michael Jung <miju@golem.phantasia.org> - 2016-10-15 14:04 +0200
Re: double == double Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-10-15 09:13 -0400
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-15 10:32 -0400
Re: double == double Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-10-15 10:46 -0400
Re: double == double Michael Jung <miju@golem.phantasia.org> - 2016-10-15 17:44 +0200
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-15 17:36 +0100
Re: double == double Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-10-15 14:15 -0400
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-15 19:41 +0100
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-15 20:39 -0400
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-15 10:41 -0400
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-15 23:09 +0100
Re: double == double Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-10-15 18:28 -0400
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-16 03:13 +0100
Re: double == double Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-10-16 08:37 -0400
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-16 14:06 +0100
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-15 20:30 -0400
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-16 03:16 +0100
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-16 03:18 +0100
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-16 09:45 -0400
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-16 14:51 +0100
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-16 11:24 -0400
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-16 16:43 +0100
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-16 12:54 -0400
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-16 18:37 +0100
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-16 14:14 -0400
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-16 22:19 +0100
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-16 22:49 -0400
Re: double == double a.laforgia@gmail.com - 2016-10-17 01:53 -0700
Re: double == double Patrick Roemer <sangamon@netcologne.de> - 2016-10-17 19:04 +0200
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-17 20:17 +0100
Re: double == double Patrick Roemer <sangamon@netcologne.de> - 2016-10-17 23:11 +0200
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-17 22:46 +0100
Re: double == double Patrick Roemer <sangamon@netcologne.de> - 2016-10-18 18:55 +0200
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-18 18:52 +0100
Re: double == double Patrick Roemer <sangamon@netcologne.de> - 2016-10-20 15:03 +0200
True O-O [Was: double == double] Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-10-17 18:06 -0400
Re: True O-O Patrick Roemer <sangamon@netcologne.de> - 2016-10-18 18:32 +0200
Re: True O-O [Was: double == double] Arne Vajhøj <arne@vajhoej.dk> - 2016-10-19 22:09 -0400
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-19 21:58 -0400
Re: double == double Patrick Roemer <sangamon@netcologne.de> - 2016-10-17 18:58 +0200
Re: double == double 4ndre4 <626401fd-4bc7-4f8f-b641-563ae0f72920@626401fd-4bc7-4f8f-b641-563ae0f72920.invalid> - 2016-10-17 20:32 +0100
Re: double == double Patrick Roemer <sangamon@netcologne.de> - 2016-10-17 23:21 +0200
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-19 21:38 -0400
Re: double == double Arne Vajhøj <arne@vajhoej.dk> - 2016-10-19 21:47 -0400
Re: double == double Patrick Roemer <sangamon@netcologne.de> - 2016-10-20 15:01 +0200
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