MAINT, ENH: Refactor numpy ** operators for numpy scalar integer powers #8221
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This change is the upshot of a long discussion on the numpy mailing list where is was decided that numpy scalar integers should raise a ValueError when raised to a negative integer power. This behavior differs from the Python case where the result is of float type, but because numpy arrays cannot contain value dependent types and the desire was to be consistent with numpy scalar arrays, we diverge from Python in this regard. Previously numpy arrays would return zero in this case, but because that is not a correct value they now also raise a ValueError.
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Don't merge yet, I'm going to refactor this. |
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Replaced by #8231, a more minimal patch. So closing this. |
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☔ The latest upstream changes (presumably #8240) made this pull request unmergeable. Please resolve the merge conflicts. |
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The previous behavior depended on whether numpy scalar integers or numpy integer arrays were involved.
For arrays
For scalars
All of these cases now raise a
ValueErrorexcept for those integer combinations whose common type is float, for instance uint64 and int8. It was felt that a simple rule was the best way to go rather than have special exceptions for the integer units. If you need negative powers, use an inexact type.Note that the
np.powerufunc is used for everything. At this point I think it is more important to settle the behavior than optimize for speed. There are now some bits of code I left in that are currently unused.