[Numpy-discussion] Proposal to make power return float, and other such things.
josef.pktd at gmail.com
josef.pktd at gmail.com
Tue Feb 18 09:37:29 EST 2014
On Tue, Feb 18, 2014 at 8:53 AM, Robert Kern <robert.kern at gmail.com> wrote:
> On Tue, Feb 18, 2014 at 1:46 PM, Nathaniel Smith <njs at pobox.com> wrote:
>> On 18 Feb 2014 07:07, "Robert Kern" <robert.kern at gmail.com> wrote:
>>>
>>> On Tue, Feb 18, 2014 at 12:00 PM, Nathaniel Smith <njs at pobox.com> wrote:
>>> > Perhaps integer power should raise an error on negative powers? That way
>>> > people will at least be directed to use arr ** -1.0 instead of silently
>>> > getting nonsense from arr ** -1.
>>>
>>> Controllable by np.seterr(invalid=...)? I could get behind that.
>>
>> I'm not sure the np.seterr part would work or be a good idea, given that we
>> have no way to return or propagate NaN... I vote for just an unconditional
>> error.
>
> <shrug> We issue configurable warning/error/ignore behavior for
> integer 0/0 through this mechanism too without any NaNs. However,
> that's `divide` and not `invalid`. Your point is taken that `invalid`
> usually implies that a `NaN` is generated, though I don't think this
> is ever stated anywhere. I just suggested `invalid` as that is usually
> what we use for function domain violations.
I thought 0/0 = 0 has been removed a few versions ago. Does numpy
still have silent casting of nan to 0 in ints.
I thought invalid and divide error/warnings are for floating point
when we want to signal that the outcome is nan or inf, not that we are
casting and return a result that is just wrong.
Josef
>
> --
> Robert Kern
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