On Jun 13, 2016 10:54 AM, "Marten van Kerkwijk" <m.h.vankerkw...@gmail.com> wrote: > > Hi All, > > I think we're getting a little off the rails, perhaps because two questions are being conflated: > > 1. What in principle is the best return type for int ** int (which Josef I think most properly rephrased as whether `**` should be thought of as a float operator, like `/` in python3 and `sqrt` etc.); > > 2. Whether one is willing to possibly break code by implementing this. > > My sense is that most discussion is about (1), where a majority may well agree the answer is float, instead of about (2), where it ends up boiling down to a judgment call of "eternal small pain" or "possible short-time big pain but consistency from now on". > > Perhaps I can introduce an alternative (likely shot down immediately...). For this, note that for division at least, numpy follows python closely, so that one has the following in python2: > ``` > In [2]: np.arange(10) / 2 > Out[2]: array([0, 0, 1, 1, 2, 2, 3, 3, 4, 4]) > > In [3]: from __future__ import division > > In [4]: np.arange(10) / 2 > Out[4]: array([ 0. , 0.5, 1. , 1.5, 2. , 2.5, 3. , 3.5, 4. , 4.5]) > ``` > Since negative exponents are really just 1 over the positive one, could we use the same logic for **? I.e., let what type is returned by int1 ** int2 be the same as that returned by int1 / int2?
There isn't any reasonable way for numpy's ** operator to check whether the caller has future division enabled, so I think this proposal boils down to, int ** int returning int in py2 and float on py3? It has a certain Solomonic appeal, in that I think it would make everyone equally unhappy :-). But probably now is not the time to be introducing new py2/py3 incompatibilities... > If we then also ensure that for integer output type, int1 ** -int2 returns 1 // (int1 ** int2), we have well-defined rules all around, so there would be no need for raising zero-division error. Not sure what to make of this part -- converting int ** -int into 1 // (int ** int) will return zero in almost all cases, is the unfortunate behavior that kicked off this whole discussion. AFAICT everyone agrees that we don't want *that*. And I don't think this gets around the need to decide how to handle 0 ** -1, whether by raising ZeroDivisionError or what. -n
_______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org https://mail.scipy.org/mailman/listinfo/numpy-discussion
