[Numpy-discussion] Proposal to make power return float, and other such things.
Nathaniel Smith
njs at pobox.com
Tue Feb 18 07:00:49 EST 2014
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.
On 18 Feb 2014 06:57, "Robert Kern" <robert.kern at gmail.com> wrote:
> On Tue, Feb 18, 2014 at 11:44 AM, Sturla Molden <sturla.molden at gmail.com>
> wrote:
> > Robert Kern <robert.kern at gmail.com> wrote:
> >
> >> We're talking about numpy.power(), not just ndarray.__pow__(). The
> >> equivalence of the two is indeed an implementation detail, but I do
> >> think that it is useful to maintain the equivalence. If we didn't, it
> >> would be the only exception, to my knowledge.
> >
> > But in this case it makes sence.
>
> Every proposed special case we come up with "makes sense" in some way.
> That doesn't mean that they are special enough to break the rules. In
> my opinion, this is not special enough to break the rules. In your
> opinion, it is.
>
> > math.pow(2,2) and 2**2 does not do the same. That is how Python behaves.
>
> Yes, because the functions in the math module are explicitly thin
> wrappers around floating-point C library functions and don't have any
> particular relationship to the special methods on int objects. numpy
> does have largely 1:1 relationship between its ndarray operator
> special methods and the ufuncs that implement them. I believe this is
> a useful relationship for learning the API and predicting what a given
> expression is going to do.
>
> --
> Robert Kern
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