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Groups > comp.lang.forth > #43639
| From | "David N. Williams" <williams@umich.edu> |
|---|---|
| Newsgroups | comp.lang.forth |
| Subject | Re: RfD: D>F and S>F first draft |
| Date | 2015-11-22 10:41 -0600 |
| Organization | University of Michigan |
| Message-ID | <n2sr3g$2ev$1@dont-email.me> (permalink) |
| References | <n2qss7$2mo$1@dont-email.me> |
I agree that this would be a good clarification of the standard, up to
the kind of wordsmithing that people are suggesting.
For reference, below is the text about D>F from the last available
online draft of the IEEE floating-point proposal from 2009, which was
vigorously discussed in this forum. It was not finished enough to be an
actual candidate for standardization, but was far enough along to serve
as a resource for IEEE floating point library implementers.
Note that this proposal was specifically about IEEE 754 floating point.
Hence the language:
1) "it shall be rounded according to the current rounding mode".
Charles' language
2) "nearest to n in the sense of 'round to nearest' as given in 12.3.2. "
corresponds to the first of the five IEEE 754-2008 rounding modes, which
is also the IEEE default:
roundTiesToEven
roundTowardPositive
roundTowardNegative
roundTowardZero
roundTiesToAway
The first four of these are typically implemented in desktop hardware.
I think the language 2) is consistent enough with IEEE, since the
concept of "current rounding mode" does not exist in the current Forth
standard. It would presumably mean that any future IEEE fp optional
standard word set would have to declare as an environmental dependency
that round to nearest is only the default among its rounding modes for
D>F. (It wouldn't be practical to use a different name.) That's an
argument for doing IEEE fp word sets as libraries instead of part of the
standard.
-- David
-----------------------------------------
PROPOSAL FOR AN OPTIONAL IEEE 754, BINARY
FLOATING-POINT WORD SET
version 0.5.4a
29-Aug-09
http://www.umich.edu/~williams/archive/temp/ieee-fp-0.5.4a.txt
----------
D>F ( d -- ) ( f: -- r )
The result r is the floating-point equivalent of d. If
conversion of d cannot be represented precisely in the
default fp format, it shall be rounded according to the
current rounding mode, and the inexact or overflow exception
shall be handled just as for arithmetic operations. See
IEEE 754-2008 5.4.1, "Arithmetic operations",
formatOf-convertFromInt(int).
[**RATIONALE
Default handling for overflow/inexact is given by IEEE 754-2008
7.4/7.6. The fp status flags are set, and overflow produces
+/-infinity, while inexact rounds. Default overflow handling
sets the inexact flag as well.
Note that d is always in range for any of the formats binary32,
binary64, binary80, and binary128, for 32- or 64-bit systems.
A programmer can assume that
( d) 2DUP D>F F>D D= ( flag)
results in a true flag *only* when |d| < 2^(p+1), where p is the
format precision, so that rounding does not occur. Rounding
does occur, for example, with 32-bit systems and binary64, when
|d| >= 2^54.
]
----------
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RfD: D>F and S>F first draft C G Montgomery <cgm@physics.utoledo.edu> - 2015-11-21 17:59 -0500
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-11-22 18:25 +1100
Re: D>F and S>F first draft krishna.myneni@ccreweb.org - 2015-11-22 06:20 -0800
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-11-23 10:58 +1100
Re: D>F and S>F first draft Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-23 02:57 +0100
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-11-24 13:16 +1100
Re: D>F and S>F first draft Paul Rubin <no.email@nospam.invalid> - 2015-11-23 18:49 -0800
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-11-25 11:51 +1100
Re: D>F and S>F first draft Paul Rubin <no.email@nospam.invalid> - 2015-11-24 17:26 -0800
Re: D>F and S>F first draft Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-25 02:43 +0100
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-11-26 12:16 +1100
Re: D>F and S>F first draft Paul Rubin <no.email@nospam.invalid> - 2015-11-25 17:47 -0800
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-11-26 15:47 +1100
Re: D>F and S>F first draft Paul Rubin <no.email@nospam.invalid> - 2015-11-25 23:07 -0800
Re: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-26 07:27 +0000
Re: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-26 09:19 +0000
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-11-28 04:26 +1100
Re: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-28 11:31 +0000
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-11-29 20:23 +1100
Re: D>F and S>F first draft Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-29 20:39 +0100
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-12-05 17:48 +1100
Re: D>F and S>F first draft Julian Fondren <julian.fondren@gmail.com> - 2015-12-04 23:58 -0800
Re: D>F and S>F first draft mhx@iae.nl - 2015-12-05 02:19 -0800
Re: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-12-05 11:25 +0000
Re: D>F and S>F first draft Albert van der Horst <albert@spenarnc.xs4all.nl> - 2015-12-05 13:11 +0000
Re: D>F and S>F first draft mhx@iae.nl - 2015-12-05 05:27 -0800
Re: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-12-05 15:33 +0000
Re: D>F and S>F first draft mhx@iae.nl - 2015-12-07 10:10 -0800
Re: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-12-09 16:58 +0000
Re: D>F and S>F first draft krishna.myneni@ccreweb.org - 2015-12-06 10:23 -0800
Re: D>F and S>F first draft Bernd Paysan <bernd.paysan@gmx.de> - 2015-12-06 21:37 +0100
Re: D>F and S>F first draft Bernd Paysan <bernd.paysan@gmx.de> - 2015-12-05 19:08 +0100
Re: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-30 08:33 +0000
Re: D>F and S>F first draft "Elizabeth D. Rather" <erather@forth.com> - 2015-11-25 21:43 -1000
Re: D>F and S>F first draft "HAA" <someone@microsoft.com> - 2015-11-28 19:28 +1100
Re: D>F and S>F first draft Albert van der Horst <albert@spenarnc.xs4all.nl> - 2015-11-26 11:37 +0000
Re: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-22 15:10 +0000
Re: D>F and S>F first draft Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-22 20:48 +0100
Re: D>F and S>F first draft "Elizabeth D. Rather" <erather@forth.com> - 2015-11-22 13:42 -1000
Re: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-23 11:50 +0000
Re: D>F and S>F first draft "Elizabeth D. Rather" <erather@forth.com> - 2015-11-23 12:46 -1000
Forth libraries Lars Brinkhoff <lars.spam@nocrew.org> - 2015-11-24 08:55 +0100
Re: RfD: D>F and S>F first draft krishna.myneni@ccreweb.org - 2015-11-22 06:33 -0800
Re: RfD: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-22 16:00 +0000
Re: RfD: D>F and S>F first draft krishna.myneni@ccreweb.org - 2015-11-22 08:53 -0800
Re: RfD: D>F and S>F first draft krishna.myneni@ccreweb.org - 2015-11-22 09:11 -0800
Re: RfD: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-22 18:24 +0000
Re: RfD: D>F and S>F first draft Paul Rubin <no.email@nospam.invalid> - 2015-11-22 09:07 -0800
Re: RfD: D>F and S>F first draft stephen@mpeforth.com (Stephen Pelc) - 2015-11-22 18:10 +0000
Re: RfD: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-22 18:26 +0000
Re: RfD: D>F and S>F first draft rickman <gnuarm@gmail.com> - 2015-11-22 13:58 -0500
Re: RfD: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-23 12:34 +0000
Re: RfD: D>F and S>F first draft Albert van der Horst <albert@spenarnc.xs4all.nl> - 2015-11-23 16:39 +0000
Re: RfD: D>F and S>F first draft Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-24 03:00 +0100
Re: RfD: D>F and S>F first draft Lars Brinkhoff <lars.spam@nocrew.org> - 2015-11-23 13:48 +0100
Re: RfD: D>F and S>F first draft mhx@iae.nl - 2015-11-23 05:19 -0800
Re: RfD: D>F and S>F first draft mhx@iae.nl - 2015-11-23 16:09 -0800
Re: RfD: D>F and S>F first draft Bernd Paysan <bernd.paysan@gmx.de> - 2015-11-22 20:42 +0100
Re: RfD: D>F and S>F first draft C G Montgomery <cgm@physics.utoledo.edu> - 2015-11-22 16:43 -0500
Re: RfD: D>F and S>F first draft krishna.myneni@ccreweb.org - 2015-11-22 18:40 -0800
Re: RfD: D>F and S>F first draft krishna.myneni@ccreweb.org - 2015-11-22 18:51 -0800
Re: RfD: D>F and S>F first draft C G Montgomery <cgm@physics.utoledo.edu> - 2015-11-25 15:47 -0500
Re: RfD: D>F and S>F first draft anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-11-22 14:29 +0000
Re: RfD: D>F and S>F first draft "David N. Williams" <williams@umich.edu> - 2015-11-22 10:41 -0600
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