[Numpy-discussion] Boolean binary '-' operator

Charles R Harris charlesr.harris at gmail.com
Sun Jun 25 12:32:26 EDT 2017

Hi All,

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.

The unary `-` operator for booleans, now an error, was also deprecated in
1.9 and changed to an error in 1.13. There have been no complaints about
that (yet), and it seems like a reasonable thing to do, so I am inclined to
leave that error in place.

What do others think the correct way forward is?

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