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Groups > comp.lang.forth > #53463
| From | anton@mips.complang.tuwien.ac.at (Anton Ertl) |
|---|---|
| Newsgroups | comp.lang.forth |
| Subject | Re: f.) for Gorth |
| Date | 2016-12-21 07:29 +0000 |
| Organization | Institut fuer Computersprachen, Technische Universitaet Wien |
| Message-ID | <2016Dec21.082902@mips.complang.tuwien.ac.at> (permalink) |
| References | (6 earlier) <o39d4p$tu$1@dont-email.me> <HKSdnUNw5_MWbsXFnZ2dnUU7-Q-dnZ2d@supernews.com> <c710b65d-1694-4d4e-b105-79ee9acb7918@googlegroups.com> <2016Dec20.133512@mips.complang.tuwien.ac.at> <o3cp09$muc$1@dont-email.me> |
Charles Montgomery <cgm@physics.utoledo.edu> writes:
>Anton Ertl wrote:
>> ...
>> My guess is that the motivation for providing approximate FP equality
>> instead of F= is that F= often returns FALSE when the corresponding
>> operations on real numbers would have returned true, and sometimes
>> even vice versa (the classical issue "a!=b, but a-b=0" for FP numbers
>> without denormals is an example of the latter); this problem is
>> compounded by differences between different FP variants (as were still
>> rampant when Forth-94 was developed).
...
>F0= is already in the Standard floating word set.
It is, to my surprise.
>If exact equality is wanted, it is easy to get: F- FABS F0=
Works in IEEE FP and the FABS is unnecessary. But without denormals,
it produces true for some pairs of numbers where F= produces false.
>(Note that this tests whether the internal representation of the difference
>is the same as the internal representation of 0e , which might in
>unusual situations be different from a bitwise comparison of the two
>internal representations. If this could matter, I'd say you are treading on
>such thin ice that you should probably find a safer path to your
>destination.)
F= is not a bitwise comparison, either:
0e -0e f= . -1 ok
(0e has a different bit representation than -0e, but they compare
equal).
0e 0e f/ fdup f= . 0 ok
Here we compare a NaN with itself, and that returns false despite
having the same bit representation.
>If what I intend is to test approximate equality, I would never use F~.
>First I would need to recall which form of the third argument provides
>what I want and then make sure it is entered correctly. Two opportunities
>for a bug. A human reading the code (probably me) has the same problems.
>It is easy, quick, and clear to spell out just what is wanted.
Please demonstrate. I wonder how you avoid the "enter correctly" bug
opportunity. And spelling out the equivalent of F~REL is not
particularly easy, quick, and clear. It's not as bad for F~ABS, but
you still involve a number of words, making it harder to read and
opening an opportunity for bugs.
>Apart from its desirability or value, I consider F~ to be badly designed.
>If there are two values on the fp stack to compare, it is a bad idea to
>put a third value on top of them which will have to moved out of the way
>with some sort of floating stack dancing. Ugh.
That aspect of F~ is well designed. It's better to require stack
juggling in the implementation of a word than in the use of a word.
If you had F~ ( r3 r1 r2 -- f ) instead, a typical use of F~ would
look like
... 1e-6 frot frot f~
instead of (for the standard F~ ( r1 r2 r3 -- f )):
... 1e-6 f~
- anton
--
M. Anton Ertl http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
New standard: http://www.forth200x.org/forth200x.html
EuroForth 2016: http://www.euroforth.org/ef16/
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f.) for Gorth josv@planet.nl - 2016-12-06 03:40 -0800
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-06 15:48 +0100
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-06 17:59 +0000
Re: f.) for Gorth josv@planet.nl - 2016-12-06 13:17 -0800
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-07 11:11 +0000
Re: f.) for Gorth Julian Fondren <julian.fondren@gmail.com> - 2016-12-07 06:11 -0800
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-07 17:50 +0000
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-07 15:23 +0100
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-08 16:18 +0000
Re: f.) for Gorth josv@planet.nl - 2016-12-07 06:46 -0800
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-07 17:41 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-06 10:34 -0800
Re: f.) for Gorth josv@planet.nl - 2016-12-09 12:11 -0800
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-23 13:23 +1100
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-15 15:42 -0800
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-07 13:06 +1100
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-06 18:32 -0800
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-07 12:41 +0100
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-07 19:49 -0800
Re: f.) for Gorth Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2016-12-08 08:12 +0000
Re: f.) for Gorth Rod Pemberton <NeedNotReplyHere@xrsevnneqk.cem> - 2016-12-08 18:53 -0500
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2016-12-09 00:01 +0000
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-09 12:17 +0100
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-09 13:01 +0000
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-09 11:19 +1100
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-08 22:23 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-09 07:11 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-20 22:40 -0800
Re: f.) for Gorth Julian Fondren <julian.fondren@gmail.com> - 2016-12-20 23:59 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-21 21:17 -0800
Re: f.) for Gorth The Beez <the.beez.speaks@gmail.com> - 2016-12-13 08:51 -0800
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-09 12:47 +0000
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-10 11:54 +1100
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-09 17:28 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-09 18:20 -0800
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-10 14:26 +0000
Re: f.) for Gorth The Beez <the.beez.speaks@gmail.com> - 2016-12-13 09:14 -0800
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-13 19:24 +0100
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-14 07:29 -0600
Re: f.) for Gorth Hans Bezemer <the.beez.speaks@gmail.com> - 2016-12-14 18:29 +0100
Re: f.) for Gorth Julian Fondren <julian.fondren@gmail.com> - 2016-12-14 10:13 -0800
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-15 03:45 -0600
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-15 10:42 +0000
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-15 05:11 -0600
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-15 12:36 +0000
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-15 07:33 -0600
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-15 14:31 +0000
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-15 14:34 -0600
Re: f.) for Gorth Paul Rubin <no.email@nospam.invalid> - 2016-12-15 16:20 -0800
Re: f.) for Gorth Julian Fondren <julian.fondren@gmail.com> - 2016-12-15 16:46 -0800
Re: f.) for Gorth Julian Fondren <julian.fondren@gmail.com> - 2016-12-17 09:23 -0800
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-19 02:56 -0600
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-16 08:10 +0000
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-16 10:00 -0600
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-18 10:32 +0000
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-19 03:22 -0600
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-16 14:14 +0100
Re: f.) for Gorth Bernd Paysan <bernd@net2o.de> - 2016-12-19 19:41 +0000
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-20 03:02 -0600
Re: f.) for Gorth mhx@iae.nl - 2016-12-20 01:27 -0800
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-20 12:35 +0000
Re: f.) for Gorth Charles Montgomery <cgm@physics.utoledo.edu> - 2016-12-20 21:23 -0500
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-21 07:29 +0000
Re: f.) for Gorth Charles Montgomery <cgm@physics.utoledo.edu> - 2016-12-21 22:24 -0500
Re: f.) for Gorth "David N. Williams" <williams@umich.edu> - 2016-12-22 08:10 -0500
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-22 17:39 +0000
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-15 12:53 +0100
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-15 05:59 -0600
Re: f.) for Gorth "Robert L." <No_spamming@noWhere_7073.org> - 2017-01-03 16:15 +0000
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-14 17:06 +0000
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-18 10:58 +1100
Re: f.) for Gorth Paul Rubin <no.email@nospam.invalid> - 2016-12-17 17:26 -0800
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-19 13:16 +1100
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-18 19:19 -0800
Re: f.) for Gorth john <anon@example.com> - 2016-12-19 11:03 +0000
Re: f.) for Gorth Mark Wills <markwills1970@gmail.com> - 2016-12-20 01:46 -0800
Re: f.) for Gorth john <anon@example.com> - 2016-12-20 12:14 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-20 17:34 -0800
Re: f.) for Gorth Paul Rubin <no.email@nospam.invalid> - 2016-12-18 19:25 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-18 19:45 -0800
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-22 11:32 +1100
Re: f.) for Gorth Bernd Paysan <bernd@net2o.de> - 2017-01-03 19:33 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2017-01-03 22:13 -0800
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2017-01-04 23:03 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2017-01-06 22:52 -0800
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2017-01-07 22:45 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2017-01-07 17:23 -0800
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2017-01-08 09:13 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2017-01-08 17:10 -0800
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2017-01-09 10:22 +0000
Re: f.) for Gorth stephen@mpeforth.com - 2017-01-08 07:00 -0800
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-20 14:09 +0200
Re: f.) for Gorth Matthias Trute <matthias.trute@gmail.com> - 2017-01-11 01:14 -0800
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-07 12:26 +0100
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-08 10:21 +1100
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-20 15:45 +0100
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2016-12-20 15:33 +0000
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-22 11:37 +1100
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-22 14:19 +0100
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-23 12:11 +1100
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-22 17:49 -0800
Re: f.) for Gorth "HAA" <someone@microsoft.com> - 2016-12-23 20:41 +1100
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-05-20 14:21 +0200
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-15 22:31 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-16 18:26 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-18 16:41 -0800
Re: f.) for Gorth stephen@mpeforth.com - 2016-12-20 02:20 -0800
Re: f.) for Gorth anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2016-12-20 13:04 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-20 17:27 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-17 10:36 -0800
Re: f.) for Gorth Julian Fondren <julian.fondren@gmail.com> - 2016-12-17 11:51 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-18 19:35 -0800
Re: f.) for Gorth albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2016-12-19 14:17 +0100
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-19 10:10 -0800
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2016-12-19 20:33 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-19 18:11 -0800
Re: f.) for Gorth Julian Fondren <julian.fondren@gmail.com> - 2016-12-19 19:03 -0800
Re: f.) for Gorth Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2016-12-20 08:10 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-20 18:05 -0800
Re: f.) for Gorth - what is a number? Jan Coombs <jenfhaomndgfwutc@murmic.plus.com> - 2016-12-21 09:04 +0000
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2016-12-20 15:26 +0000
Re: f.) for Gorth Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-20 11:30 -0600
Language stds (was Re: f.) for Gorth) Alex <alex@rivadpm.com> - 2016-12-20 19:49 +0000
Re: Language stds (was Re: f.) for Gorth) john <anon@example.com> - 2016-12-20 20:06 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-20 17:52 -0800
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2016-12-21 13:47 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-21 20:46 -0800
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2016-12-22 14:33 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-22 07:06 -0800
Re: f.) for Gorth Julian Fondren <julian.fondren@gmail.com> - 2016-12-22 07:21 -0800
Re: f.) for Gorth Gerry Jackson <gerry@jackson9000.fsnet.co.uk> - 2016-12-23 07:41 +0000
Re: f.) for Gorth Alex <alex@rivadpm.com> - 2016-12-23 08:33 +0000
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-23 18:22 -0800
Re: f.) for Gorth Julian Fondren <julian.fondren@gmail.com> - 2016-12-23 20:28 -0800
Re: f.) for Gorth hughaguilar96@gmail.com - 2016-12-26 18:30 -0800
Language stds (Re: f.) for Gorth) "HAA" <someone@microsoft.com> - 2016-12-24 12:12 +1100
Re: Language stds (Re: f.) for Gorth) Andrew Haley <andrew29@littlepinkcloud.invalid> - 2016-12-24 03:28 -0600
Re: Language stds (Re: f.) for Gorth) "Elizabeth D. Rather" <erather@forth.com> - 2016-12-24 10:02 -0600
Re: Language stds (Re: f.) for Gorth) hughaguilar96@gmail.com - 2016-12-24 16:13 -0800
Re: Language stds (Re: f.) for Gorth) Alex <alex@rivadpm.com> - 2016-12-24 18:13 +0000
Re: Language stds (Re: f.) for Gorth) "HAA" <someone@microsoft.com> - 2016-12-28 09:24 +1100
Re: Language stds (Re: f.) for Gorth) "Elizabeth D. Rather" <erather@forth.com> - 2016-12-27 17:10 -0600
Re: Language stds (Re: f.) for Gorth) hughaguilar96@gmail.com - 2016-12-27 22:58 -0800
Re: Language stds (Re: f.) for Gorth) "HAA" <someone@microsoft.com> - 2016-12-29 10:12 +1100
Re: Language stds (Re: f.) for Gorth) "Elizabeth D. Rather" <erather@forth.com> - 2016-12-29 17:03 -0800
Re: Language stds (Re: f.) for Gorth) hughaguilar96@gmail.com - 2016-12-29 19:35 -0800
Re: Language stds (Re: f.) for Gorth) Howerd <howerdo@yahoo.co.uk> - 2016-12-30 05:27 -0800
Re: Language stds (Re: f.) for Gorth) hughaguilar96@gmail.com - 2016-12-30 19:11 -0800
Re: Language stds (Re: f.) for Gorth) hughaguilar96@gmail.com - 2016-12-31 06:42 -0800
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