[ python-Bugs-1118729 ] Error in representation of complex numbers(again)

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Bugs item #1118729, was opened at 2005-02-08 17:26
Message generated for change (Comment added) made by sonderblade
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Category: Python Interpreter Core
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: George Yoshida (quiver)
Assigned to: Nobody/Anonymous (nobody)
Summary: Error in representation of complex numbers(again)

Initial Comment:
>>> -(1+0j)
(-1+-0j)

I encountered this while I was calculating conjugate of 
complex numbers(e.g. z.conjugate()).

Related bug
* http://www.python.org/sf/1013908

One thing to note is that -(0j) can return 0j or -0j 
dependeing on OSes.

Confirmed on SuSE 9.1 & cygwin.

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Comment By: Björn Lindqvist (sonderblade)
Date: 2005-02-09 19:54

Message:
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What you are seeing is negative zero (-0.0). It is distinct 
from positive zero (0.0) but 0.0 == -0.0 is always true. On 
some machines you can also see it by typing:

>>> -0.0
-0.0

On other machines you will see "0.0" instead. You can also try 
printf("%f\n", -0.0); and you will notice the same thing. So 
I'm not sure it is a bug per se. However, it can be worked 
around by adding "if (v->cval.imag == 0.) v->cval.imag = 
0.0;" to complexobject.c, assuming ofcourse it is OK to 
change negative zeros to positive ones.

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