[Numpy-discussion] Integers to integer powers

[Alan Isaac]

On 5/19/2016 11:30 PM, Nathaniel Smith wrote:
> the last bad
> option IMHO would be that we make int ** (negative int) an error in
> all cases, and the error message can suggest that instead of writing
>
>     np.array(2) ** -2
>
> they should instead write
>
>     np.array(2) ** -2.0
>
> (And similarly for np.int64(2) ** -2 versus np.int64(2) ** -2.0.)



Fwiw, Haskell has three exponentiation operators
because of such ambiguities.  I don't use C, but
I think the contrasting decision there was to
always return a double, which has a clear attraction
since for any fixed-width integral type, most of the
possible input pairs overflow the type.

My core inclination would be to use (what I understand to be)
the C convention that integer exponentiation always produces
a double, but to support dtype-specific exponentiation with
a function.  But this is just a user's perspective.

Cheers,
Alan Isaac