[Numpy-discussion] np.diff on boolean arrays now raises

[Charles R Harris]

On Thu, Jun 15, 2017 at 6:16 AM, Charles R Harris <charlesr.harris at gmail.com
> wrote:

>
>
> On Thu, Jun 15, 2017 at 4:35 AM, Ralf Gommers <ralf.gommers at gmail.com>
> wrote:
>
>>
>>
>> On Thu, Jun 15, 2017 at 7:08 PM, Jaime Fernández del Río <
>> jaime.frio at gmail.com> wrote:
>>
>>> There is an ongoing discussion on github:
>>>
>>> https://github.com/numpy/numpy/issues/9251
>>>
>>> In 1.13 np.diff has started raising on boolean arrays, since
>>> subtraction of  boolean arrays is now deprecated.
>>>
>>> A decision has to be made whether:
>>>
>>>    - raising an error is the correct thing to do, and only the
>>>    docstring needs updating, or
>>>    - backwards compatibility is more important and diff should still
>>>    work on boolean arrays.
>>>
>>>
>> The issue is bigger than np.diff. For example, there's a problem with the
>> scipy.ndimage morphology functions (https://github.com/scipy/scip
>> y/issues/7493) that looks pretty serious. All ndimage.binary_* functions
>> (7 of them) for example return boolean arrays, and chaining those is now
>> broken. Unfortunately it seems that that wasn't covered by the ndimage test
>> suite.
>>
>> Possibly reverting the breaking change in 1.13.1 is the best way to fix
>> this.
>>
>
> There were two related deprecations of boolean operators: subtraction and
> negative. I haven't heard any complaints about the second, which I think is
> less controversial, but I think reversion is the way to go for subtraction,
> at least for 1.13.1. The main virtue of the deprecations is clarity, xor is
> more informative when applied to boolean values than `-`, although the
> latter is certainly correct in F_2.
>
>
See reversion at https://github.com/numpy/numpy/pull/9255.

Chuck
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