[Numpy-discussion] Integers to integer powers

[Warren Weckesser]

On Fri, May 20, 2016 at 4:22 PM, Alan Isaac <alan.isaac at gmail.com> wrote:

> 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.



C doesn't have an exponentiation operator.  The C math library has pow,
powf and powl, which (like any C functions) are explicitly typed.

Warren


  But this is just a user's perspective.
>
> Cheers,
> Alan Isaac
>
>
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