So this should be added as a failing test in FloatTest?

Dave

On Fri, Jan 27, 2017 at 08:42:15AM +0100, Das.Linux at gmx.de wrote:
> Hi
> 
> On 27.01.2017, at 08:37, Tobias Pape <Das.Linux at 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 at 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 at programmer.net>, glass at lists.gemtalksystems.com
> >> Reply-To: Martin McClure <martin.mcclure at gemtalksystems.com>
> >> Delivered-To: glass at 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 at lists.gemtalksystems.com
> >> http://lists.gemtalksystems.com/mailman/listinfo/glass
> > 
> > 
> 
>