[issue15544] math.isnan fails with some Decimal NaNs
Mark Dickinson
report at bugs.python.org
Sat Aug 4 19:45:29 CEST 2012
Mark Dickinson added the comment:
> Why not add a is_nan() method to float numbers instead?
That could work. The duplication of float.is_nan and math.isnan (not to mention the different spellings) would be a bit ugly, but perhaps worth it. It would make sense to add float.is_infinite and (possibly) float.is_finite methods at the same time.
Looks like we've got two separate issues here, that should probably be split into two separate bug reports. The first issue is that Decimal.__float__ is brain-dead when it comes to NaNs with payloads; I consider that a clear bug, and Steven's patch fixes it nicely for the Python version of decimal. The second has to do with finding a nice type-agnostic way of determing whether something is a NaN---anyone mind if I open a separate issue for this?
W.r.t. the first issue: Steven, thanks for the patch; looks fine to me at first glance.
Two questions: (1) What would you think about raising ValueError explicitly for the signaling NaN case rather than falling back to the ValueError coming from the string-to-float conversion. I think the intentions of the code would be a little clearer that way; and we get to choose a more informative error message that way, too. (2) Should we apply the fix to 2.7 and/or 3.2 as well?
I'll look at extending Steven's fix to the cdecimal code, unless Stefan really wants to do it (which would be fine with me :-).
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assignee: -> mark.dickinson
versions: +Python 2.7
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<http://bugs.python.org/issue15544>
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