[Numpy-discussion] Ticket #794 and can o' worms.
Charles R Harris
charlesr.harris@gmail....
Sun Jul 20 17:42:42 CDT 2008
Hi All,
I "fixed" ticket #754, but it leads to a ton of problems. The original
discussion is here<http://thread.gmane.org/gmane.comp.python.numeric.general/21526/focus=21537>.
The problems that arise come from conversion to different types.
In [26]: a
Out[26]: array([ Inf, -Inf, NaN, 0., 3., -3.])
In [27]: sign(a).astype(int)
Out[27]:
array([ 1, -1, -2147483648, 0, 1,
-1])
In [28]: sign(a).astype(bool)
Out[28]: array([ True, True, True, False, True, True], dtype=bool)
In [29]: sign(a)
Out[29]: array([ 1., -1., NaN, 0., 1., -1.])
In [30]: bool(NaN)
Out[30]: True
So there are problems with at minimum the following.
1) The way NaN is converted to bool. I think it should be False.
2) The way NaN is converted to int types. I think it should be 0.
These problems show up in failing tests. I'm reverting the fix for now, but
I wonder what we should do about these things.
Chuck
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