A Date With Tim Peters...

[Rob W. W. Hooft]

>>>>> "TP" == Tim Peters <tim_one at email.msn.com> writes:

>>>>> [Tres Seaver]
 >> Heh, I recall fondly one machine where +0 and -0 were different,
 >> so why not?
 >> 
 >> (A Cyber mainframe, ones-complement, if the faded label on the
 >> card deck box isn't fooling me :)

 TP>>> import math 
 TP>>> zero = 0.0 
 TP>>> math.atan2(zero, zero)
 TP> 0.0
 TP>>> zero = -zero 
 TP>>> math.atan2(zero, zero)
 TP> -3.14159265359

 TP> That is, IEEE-754 mandates signed zeroes too, in part so that an
 TP> underflow "remembers which direction it came from".

Python 1.5.2b1 (#4, Jan 14 1999, 12:05:48)  [GCC egcs-2.90.21 971202 (egc on irix5
Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
>>> import math
>>> zero=0.0
>>> math.atan2(zero,zero)
Traceback (innermost last):
  File "<stdin>", line 1, in ?
ValueError: math domain error
>>> 
no11[101]nonius% uname -a
IRIX no11 5.3 02091401 IP22 mips

So it is not portable.....

IIRC, on a VAX Using -0.0 would result in an "operand reserved to digital"
fault.

Regards,

-- 
=====   rob at hooft.net          http://www.xs4all.nl/~hooft/rob/  =====
=====   R&D, Nonius BV, Delft  http://www.nonius.nl/             =====
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