[Numpy-discussion] Integers to negative integer powers, time for a decision.

[josef.pktd at gmail.com]

On Fri, Oct 7, 2016 at 9:12 PM, Charles R Harris
<charlesr.harris at gmail.com> wrote:
> Hi All,
>
> The time for NumPy 1.12.0 approaches and I like to have a final decision on
> the treatment of integers to negative integer powers with the `**` operator.
> The two alternatives looked to be
>
> Raise an error for arrays and numpy scalars, including 1 and -1 to negative
> powers.
>
> Pluses
>
> Backward compatible
> Allows common powers to be integer, e.g., arange(3)**2
> Consistent with inplace operators
> Fixes current wrong behavior.
> Preserves type
>
>
> Minuses
>
> Integer overflow
> Computational inconvenience
> Inconsistent with Python integers
>
>
> Always return a float
>
> Pluses
>
> Computational convenience
>
>
> Minuses
>
> Loss of type
> Possible backward incompatibilities
> Not applicable to inplace operators
>
>
>
> Thoughts?

2: +1
I'm still in favor of number 2: less buggy code and less mental
gymnastics (watch out for that int, or which int do I need)

(upcasting is not applicable for any inplace operators, AFAIU  <int> *=0.5 ?
zz = np.arange(5)
zz**(-1)
zz *= 0.5

tried in
>>> np.__version__
'1.9.2rc1'
>>> np.__version__
'1.10.4'
backwards compatibility ?
)


Josef


>
> Chuck
>
>
>
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