From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Float conversion
Date: Fri, 30 Jul 2010 10:43:20 +0200
Date: 2010-07-30T10:43:20+02:00 [thread overview]
Message-ID: <1naf3ekl5k916$.f7ugc92galdz$.dlg@40tude.net> (raw)
In-Reply-To: 1d617940-d138-4b8c-a321-ed23b47431b8@x21g2000yqa.googlegroups.com
On Thu, 29 Jul 2010 18:30:06 -0700 (PDT), Phil Clayton wrote:
> On Jul 29, 8:15�pm, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
> wrote:
>> You should never use equality or inequality for floating-point types.
>
> Inequalities (<, <=, >, >=) are ok - I think you meant don't use 'not
> equals' (which is still an equality operator).
Yes I did, thanks for correction.
> However, just because equality between floating point numbers is a
> dubious concept and should be avoided, it does not mean e.g. "<" and
> "<=" are simply interchangeable. Far from it.
They are almost same. According to the extension principle:
I1<=I2
T (true) if forall x in I1, forall y in I2 x<=y
F (false) if forall x in I1, forall y in I2 not x<=y
_|_ (undefined) otherwise
I1<I2
T if forall x in I1, forall y in I2 x<y
F if forall x in I1, forall y in I2 not x<y
_|_ otherwise
The difference comes from _|_ being rendered T for "<=" and F for "<" when
I1 and I2 are equal as sets. It would be ill-advised to exploit this
difference without care.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2010-07-30 8:43 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-29 12:23 Float conversion Henrique
2010-07-29 12:44 ` Jacob Sparre Andersen
2010-07-29 12:46 ` Dmitry A. Kazakov
2010-07-29 15:08 ` Georg Bauhaus
2010-07-29 15:10 ` Georg Bauhaus
2010-07-29 15:35 ` Dmitry A. Kazakov
2010-07-29 18:21 ` Henrique
2010-07-29 19:08 ` Jeffrey R. Carter
2010-07-29 19:15 ` Dmitry A. Kazakov
2010-07-30 1:30 ` Phil Clayton
2010-07-30 8:43 ` Dmitry A. Kazakov [this message]
2010-07-30 13:14 ` Phil Clayton
2010-07-30 14:34 ` Dmitry A. Kazakov
2010-07-31 15:12 ` Stephen Leake
2010-08-03 1:07 ` Phil Clayton
2010-08-03 3:31 ` Shark8
2010-08-03 10:38 ` Georg Bauhaus
2010-08-04 7:27 ` Stephen Leake
2010-08-04 16:15 ` Georg Bauhaus
2010-08-04 16:32 ` Phil Clayton
2010-08-04 7:26 ` Stephen Leake
2010-08-04 12:52 ` Robert A Duff
2010-08-04 14:32 ` Dmitry A. Kazakov
2010-08-04 19:36 ` Simon Wright
2010-08-04 19:46 ` Dmitry A. Kazakov
2010-08-04 20:29 ` Georg Bauhaus
2010-08-05 12:05 ` Stephen Leake
2010-08-07 5:54 ` Shark8
2010-08-07 8:56 ` Georg Bauhaus
2010-08-07 13:49 ` Shark8
2010-08-05 10:20 ` Phil Clayton
2010-07-30 13:16 ` Henrique
2010-07-29 15:37 ` Warren
2010-07-29 14:56 ` Georg Bauhaus
2010-07-29 17:56 ` Jeffrey R. Carter
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