On Sun, 2017-06-25 at 18:59 +0200, Julian Taylor wrote: > On 25.06.2017 18:45, Stefan van der Walt wrote: > > Hi Chuck > > > > On Sun, Jun 25, 2017, at 09:32, Charles R Harris wrote: > > > The boolean binary '-' operator was deprecated back in NumPy 1.9 > > > and > > > changed to an error in 1.13. This caused a number of failures in > > > downstream projects. The choices now are to continue the > > > deprecation > > > for another couple of releases, or simply give up on the change. > > > For > > > booleans, `a - b` was implemented as `a xor b`, which leads to > > > the > > > somewhat unexpected identity `a - b == b - a`, but it is a handy > > > operator that allows simplification of some functions, > > > `numpy.diff` > > > among therm. At this point I'm inclined to give up on the > > > deprecation > > > and retain the old behavior. It is a bit impure but perhaps we > > > can > > > consider it a feature rather than a bug. > > > > What was the original motivation behind the deprecation? `xor` > > seems > > like exactly what one would expect when subtracting boolean arrays. > > > > But, in principle, I'm not against the deprecation (we've had to > > fix a > > few problems that arose in skimage, but nothing big). > > > > Stéfan > > > > > > I am against this deprecation for apparently cosmetic reasons. > Is there any practical drawback in that it makes subtraction > commutative > for booleans? > > numpy should not be imposing change of style when the existing sub > par > historical style does not cause actual bugs. > > While I don't like it I can accept a deprecation warning that will > never > be acted upon.
Dunno, that is also weird, then a UserWarning might even be better ;), but more visible.... For the unary minus, there are good reasons. For subtract, I don't remember really, but I don't think there was any huge argument for it. Probably it was mostly that many feel that: `False - True == -1` as is the case in python while we have: `np.False_ - np.True_ == np.True_`. And going to a deprecation would open up that possibility (though maybe you could go there directly). Not that I am convinced of that option. So, I don't mind much either way, but unless there is a concrete plan with quite a bit of support we should maybe just go with the conservative option. - Sebastian > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@python.org > https://mail.python.org/mailman/listinfo/numpy-discussion
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