Bugs item #1118729, was opened at 2005-02-09 01:26
Message generated for change (Comment added) made by quiver
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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: Martin v. Löwis (loewis)
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.
----------------------------------------------------------------------
>Comment By: George Yoshida (quiver)
Date: 2005-09-16 14:02
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Can anyone else review this patch before the new 2.4 gets
released?
The patch is ready to be commited.
----------------------------------------------------------------------
Comment By: George Yoshida (quiver)
Date: 2005-05-15 21:22
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The fix seems reasonable to me and it passed the test
suites.
Please apply it.
----------------------------------------------------------------------
Comment By: Martin v. Löwis (loewis)
Date: 2005-05-15 16:57
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What do you think about the patch attached?
----------------------------------------------------------------------
Comment By: George Yoshida (quiver)
Date: 2005-03-20 02:11
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Martin, what's your take on this?
The representation of '-(1+0j)' has changed since Revision 2.71
(complexobject.c) and you applied the patch.
# original patch
making Python LC_NUMERIC agnostic
http://www.python.org/sf/774665
----------------------------------------------------------------------
Comment By: George Yoshida (quiver)
Date: 2005-02-10 09:02
Message:
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Hi, Björn.
Sorry, not to be clear about what my complaint is. I'm not
talking about if -(0j) should be 0j or -0j. It's been that way
for a long time, so changing it would break old codes.
My point is the signature of imaginary part. As you can see,
it's represented as '+-'. Before the commit of patch #774665,
it was represented as '-1-0j'. But after that, '-1+-0j'.
If you test it with Python <= 2.3, you'll get (-1-0j) and I think
this is how -(1+0j) should be represented on machines where -
(0j) is represented as -0j.
----------------------------------------------------------------------
Comment By: Björn Lindqvist (sonderblade)
Date: 2005-02-10 03:54
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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https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1118729&group_id=5470
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Message generated for change (Comment added) made by quiver
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1118729&group_id=5470
Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: Python Interpreter Core
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: George Yoshida (quiver)
Assigned to: Martin v. Löwis (loewis)
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.
----------------------------------------------------------------------
>Comment By: George Yoshida (quiver)
Date: 2005-09-16 14:02
Message:
Logged In: YES
user_id=671362
Can anyone else review this patch before the new 2.4 gets
released?
The patch is ready to be commited.
----------------------------------------------------------------------
Comment By: George Yoshida (quiver)
Date: 2005-05-15 21:22
Message:
Logged In: YES
user_id=671362
The fix seems reasonable to me and it passed the test
suites.
Please apply it.
----------------------------------------------------------------------
Comment By: Martin v. Löwis (loewis)
Date: 2005-05-15 16:57
Message:
Logged In: YES
user_id=21627
What do you think about the patch attached?
----------------------------------------------------------------------
Comment By: George Yoshida (quiver)
Date: 2005-03-20 02:11
Message:
Logged In: YES
user_id=671362
Martin, what's your take on this?
The representation of '-(1+0j)' has changed since Revision 2.71
(complexobject.c) and you applied the patch.
# original patch
making Python LC_NUMERIC agnostic
http://www.python.org/sf/774665
----------------------------------------------------------------------
Comment By: George Yoshida (quiver)
Date: 2005-02-10 09:02
Message:
Logged In: YES
user_id=671362
Hi, Björn.
Sorry, not to be clear about what my complaint is. I'm not
talking about if -(0j) should be 0j or -0j. It's been that way
for a long time, so changing it would break old codes.
My point is the signature of imaginary part. As you can see,
it's represented as '+-'. Before the commit of patch #774665,
it was represented as '-1-0j'. But after that, '-1+-0j'.
If you test it with Python <= 2.3, you'll get (-1-0j) and I think
this is how -(1+0j) should be represented on machines where -
(0j) is represented as -0j.
----------------------------------------------------------------------
Comment By: Björn Lindqvist (sonderblade)
Date: 2005-02-10 03:54
Message:
Logged In: YES
user_id=51702
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.
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1118729&group_id=5470
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Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/list-python-bugs%40lists.gossamer-threads.com