Hi all,
it seems, we also suffer from this bug:
{ 0 sign. 0.0 sign. -0 sign. -0.0 sign. } "=> #(0 0 0 -1)"
Begin forwarded message:
From: Martin McClure via Glass glass@lists.gemtalksystems.com Subject: Re: [Glass] Negative infinity and positive infinity have the same sign Date: 26. Januar 2017 21:10:32 MEZ To: monty monty2@programmer.net, glass@lists.gemtalksystems.com Reply-To: Martin McClure martin.mcclure@gemtalksystems.com Delivered-To: glass@mail.commonhouse.net
On 01/25/2017 12:45 PM, monty via Glass wrote:
On 3.3.0, "-0.0 sign = 0.0 sign". On Pharo, "-1 sign = -1", "-0.0 sign = -1", "0.0 sign = 0", and "1 sign = 1". IEEE Standard 754 mandates that negative zero have the same sign bit as a negative number. _______________________________________________
Hi Monty,
The ANSI Smalltalk standard says that #sign should answer 0 if "the receiver equals zero". This agrees with ISO/IEC 10967 Portable Numerics standard, which says the same thing. The IEEE 754 spec does not specify a "sign" operation. The closest equivalent I see is the "isSignMinus" operation. We don't currently have that message in GemStone, but we might add it. In GemStone, you can distinguish positive and negative zero by sending #_sign.
Pharo's implementation seems very odd. It looks like it's been that way a long time (John Maloney in 1998?) but the comment contradicts itself. It says "Answer 1 if the receiver is greater than 0, -1 if less than 0, else 0. Handle IEEE-754 negative-zero by reporting a sign of -1"
But negative zero *is* equal to 0, so it claims to be answering both 0 and -1 for -0.0. Leaving that aside, it's disturbingly asymmetric to answer 0 for 0.0 but -1 for -0.0.
Regards,
-Martin _______________________________________________ Glass mailing list Glass@lists.gemtalksystems.com http://lists.gemtalksystems.com/mailman/listinfo/glass
Hi
On 27.01.2017, at 08:37, Tobias Pape Das.Linux@gmx.de wrote:
Hi all,
it seems, we also suffer from this bug:
{ 0 sign. 0.0 sign. -0 sign. -0.0 sign. } "=> #(0 0 0 -1)"
PS: why bug? IEEE-754 says that 0.0 and -0.0 are equal and equal numbers have same sign, but for us
(0.0 = -0.0) ==> (0.0 sign = -0.0 sign)
is false, while it should be true.
Begin forwarded message:
From: Martin McClure via Glass glass@lists.gemtalksystems.com Subject: Re: [Glass] Negative infinity and positive infinity have the same sign Date: 26. Januar 2017 21:10:32 MEZ To: monty monty2@programmer.net, glass@lists.gemtalksystems.com Reply-To: Martin McClure martin.mcclure@gemtalksystems.com Delivered-To: glass@mail.commonhouse.net
On 01/25/2017 12:45 PM, monty via Glass wrote:
On 3.3.0, "-0.0 sign = 0.0 sign". On Pharo, "-1 sign = -1", "-0.0 sign = -1", "0.0 sign = 0", and "1 sign = 1". IEEE Standard 754 mandates that negative zero have the same sign bit as a negative number. _______________________________________________
Hi Monty,
The ANSI Smalltalk standard says that #sign should answer 0 if "the receiver equals zero". This agrees with ISO/IEC 10967 Portable Numerics standard, which says the same thing. The IEEE 754 spec does not specify a "sign" operation. The closest equivalent I see is the "isSignMinus" operation. We don't currently have that message in GemStone, but we might add it. In GemStone, you can distinguish positive and negative zero by sending #_sign.
Pharo's implementation seems very odd. It looks like it's been that way a long time (John Maloney in 1998?) but the comment contradicts itself. It says "Answer 1 if the receiver is greater than 0, -1 if less than 0, else 0. Handle IEEE-754 negative-zero by reporting a sign of -1"
But negative zero *is* equal to 0, so it claims to be answering both 0 and -1 for -0.0. Leaving that aside, it's disturbingly asymmetric to answer 0 for 0.0 but -1 for -0.0.
Regards,
-Martin _______________________________________________ Glass mailing list Glass@lists.gemtalksystems.com http://lists.gemtalksystems.com/mailman/listinfo/glass
Mind the title, it's positive zero, not infinity :)
2017-01-27 8:42 GMT+01:00 Das.Linux@gmx.de:
Hi
On 27.01.2017, at 08:37, Tobias Pape Das.Linux@gmx.de wrote:
Hi all,
it seems, we also suffer from this bug:
{ 0 sign. 0.0 sign. -0 sign. -0.0 sign. } "=> #(0 0 0 -1)"
PS: why bug?
It's a bug because it is against ANSI smalltalk, and because it creates small incompatibilities with gemstone unecessarily. I have a patch ready for squeak.
IEEE-754 says that 0.0 and -0.0 are equal and equal numbers have same sign,
but for us
(0.0 = -0.0) ==> (0.0 sign = -0.0 sign)is false, while it should be true.
More exactly, the logic is rather: the sign of zero is zero. Float negativeZero value cannot be distinguished from zero, so it is zero, and sign should be zero.
But we can still have another message like signBit immune to this logic.
Begin forwarded message:
From: Martin McClure via Glass glass@lists.gemtalksystems.com Subject: Re: [Glass] Negative infinity and positive infinity have the
same sign
Date: 26. Januar 2017 21:10:32 MEZ To: monty monty2@programmer.net, glass@lists.gemtalksystems.com Reply-To: Martin McClure martin.mcclure@gemtalksystems.com Delivered-To: glass@mail.commonhouse.net
On 01/25/2017 12:45 PM, monty via Glass wrote:
On 3.3.0, "-0.0 sign = 0.0 sign". On Pharo, "-1 sign = -1", "-0.0 sign
= -1", "0.0 sign = 0", and "1 sign = 1". IEEE Standard 754 mandates that negative zero have the same sign bit as a negative number.
Hi Monty,
The ANSI Smalltalk standard says that #sign should answer 0 if "the receiver equals zero". This agrees with ISO/IEC 10967 Portable Numerics standard, which says the same thing. The IEEE 754 spec does not specify a "sign" operation. The closest equivalent I see is the "isSignMinus" operation. We don't currently have that message in GemStone, but we might add it. In GemStone, you can distinguish positive and negative zero by sending #_sign.
Pharo's implementation seems very odd. It looks like it's been that way a long time (John Maloney in 1998?) but the comment contradicts itself. It says "Answer 1 if the receiver is greater than 0, -1 if less than 0, else 0. Handle IEEE-754 negative-zero by reporting a sign of -1"
But negative zero *is* equal to 0, so it claims to be answering both 0 and -1 for -0.0. Leaving that aside, it's disturbingly asymmetric to answer 0 for 0.0 but -1 for -0.0.
Regards,
-Martin _______________________________________________ Glass mailing list Glass@lists.gemtalksystems.com http://lists.gemtalksystems.com/mailman/listinfo/glass
So this should be added as a failing test in FloatTest?
Dave
On Fri, Jan 27, 2017 at 08:42:15AM +0100, Das.Linux@gmx.de wrote:
Hi
On 27.01.2017, at 08:37, Tobias Pape Das.Linux@gmx.de wrote:
Hi all,
it seems, we also suffer from this bug:
{ 0 sign. 0.0 sign. -0 sign. -0.0 sign. } "=> #(0 0 0 -1)"
PS: why bug? IEEE-754 says that 0.0 and -0.0 are equal and equal numbers have same sign, but for us
(0.0 = -0.0) ==> (0.0 sign = -0.0 sign)
is false, while it should be true.
Begin forwarded message:
From: Martin McClure via Glass glass@lists.gemtalksystems.com Subject: Re: [Glass] Negative infinity and positive infinity have the same sign Date: 26. Januar 2017 21:10:32 MEZ To: monty monty2@programmer.net, glass@lists.gemtalksystems.com Reply-To: Martin McClure martin.mcclure@gemtalksystems.com Delivered-To: glass@mail.commonhouse.net
On 01/25/2017 12:45 PM, monty via Glass wrote:
On 3.3.0, "-0.0 sign = 0.0 sign". On Pharo, "-1 sign = -1", "-0.0 sign = -1", "0.0 sign = 0", and "1 sign = 1". IEEE Standard 754 mandates that negative zero have the same sign bit as a negative number. _______________________________________________
Hi Monty,
The ANSI Smalltalk standard says that #sign should answer 0 if "the receiver equals zero". This agrees with ISO/IEC 10967 Portable Numerics standard, which says the same thing. The IEEE 754 spec does not specify a "sign" operation. The closest equivalent I see is the "isSignMinus" operation. We don't currently have that message in GemStone, but we might add it. In GemStone, you can distinguish positive and negative zero by sending #_sign.
Pharo's implementation seems very odd. It looks like it's been that way a long time (John Maloney in 1998?) but the comment contradicts itself. It says "Answer 1 if the receiver is greater than 0, -1 if less than 0, else 0. Handle IEEE-754 negative-zero by reporting a sign of -1"
But negative zero *is* equal to 0, so it claims to be answering both 0 and -1 for -0.0. Leaving that aside, it's disturbingly asymmetric to answer 0 for 0.0 but -1 for -0.0.
Regards,
-Martin _______________________________________________ Glass mailing list Glass@lists.gemtalksystems.com http://lists.gemtalksystems.com/mailman/listinfo/glass
Be sure to fix Float printing of negative zero. I guess this is the only reason it was implemented this way.
- Bert -
On Fri, Jan 27, 2017 at 2:11 PM, David T. Lewis lewis@mail.msen.com wrote:
So this should be added as a failing test in FloatTest?
Dave
On Fri, Jan 27, 2017 at 08:42:15AM +0100, Das.Linux@gmx.de wrote:
Hi
On 27.01.2017, at 08:37, Tobias Pape Das.Linux@gmx.de wrote:
Hi all,
it seems, we also suffer from this bug:
{ 0 sign. 0.0 sign. -0 sign. -0.0 sign. } "=> #(0 0 0 -1)"
PS: why bug? IEEE-754 says that 0.0 and -0.0 are equal and equal numbers have same
sign,
but for us
(0.0 = -0.0) ==> (0.0 sign = -0.0 sign)is false, while it should be true.
Begin forwarded message:
From: Martin McClure via Glass glass@lists.gemtalksystems.com Subject: Re: [Glass] Negative infinity and positive infinity have the
same sign
Date: 26. Januar 2017 21:10:32 MEZ To: monty monty2@programmer.net, glass@lists.gemtalksystems.com Reply-To: Martin McClure martin.mcclure@gemtalksystems.com Delivered-To: glass@mail.commonhouse.net
On 01/25/2017 12:45 PM, monty via Glass wrote:
On 3.3.0, "-0.0 sign = 0.0 sign". On Pharo, "-1 sign = -1", "-0.0
sign = -1", "0.0 sign = 0", and "1 sign = 1". IEEE Standard 754 mandates that negative zero have the same sign bit as a negative number.
Hi Monty,
The ANSI Smalltalk standard says that #sign should answer 0 if "the receiver equals zero". This agrees with ISO/IEC 10967 Portable
Numerics
standard, which says the same thing. The IEEE 754 spec does not
specify
a "sign" operation. The closest equivalent I see is the "isSignMinus" operation. We don't currently have that message in GemStone, but we might add it. In GemStone, you can distinguish positive and negative zero by sending #_sign.
Pharo's implementation seems very odd. It looks like it's been that
way
a long time (John Maloney in 1998?) but the comment contradicts
itself.
It says "Answer 1 if the receiver is greater than 0, -1 if less than 0, else
Handle IEEE-754 negative-zero by reporting a sign of -1"
But negative zero *is* equal to 0, so it claims to be answering both 0 and -1 for -0.0. Leaving that aside, it's disturbingly asymmetric to answer 0 for 0.0 but -1 for -0.0.
Regards,
-Martin _______________________________________________ Glass mailing list Glass@lists.gemtalksystems.com http://lists.gemtalksystems.com/mailman/listinfo/glass
squeak-dev@lists.squeakfoundation.org
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Bert Freudenberg -
Das.Linux＠gmx.de -
David T. Lewis -
Nicolas Cellier -
Tobias Pape