[Numpy-discussion] Integers to integer powers, let's make a decision

[josef.pktd at gmail.com]

On Mon, Jun 13, 2016 at 10:05 AM, Alan Isaac <alan.isaac at gmail.com> wrote:

> On 6/13/2016 4:47 AM, Antoine Pitrou wrote:
>
>> Currently, the choice is simple: if you want an int output,
>> have an int input; if you want a float output, have a float output.
>>
>
>
> That is a misunderstanding, which may be influencing the discussion.
> Examples of complications:
>
> >>> type(np.int8(2)**2)
> <type 'numpy.int32'>
> >>> type(np.uint64(2)**np.int8(2))
> <type 'numpy.float64'>
>
> I don't think anyone has proposed first principles
> from which the desirable behavior could be deduced.
> I do think reference to the reasoning used by other
> languages in making this decision could be helpful.


I think the main principle is whether an operator is a "float" operator.

for example, I don't think anyone would expect sqrt(int) to return int,
even if it would have exact results in a countable infinite number of cases
(theoretically)

another case is division which moved from return-int to return-float
definition in the py2 - py3 move.

My argument is that `**` is like integer division and sqrt where the domain
where integer return are the correct numbers is too small to avoid
headaches by users.

Josef


>
>
> Alan Isaac
> (on Windows)
>
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