[Numpy-discussion] Deprecate boolean math operators?

[josef.pktd at gmail.com]

On Fri, Dec 6, 2013 at 12:23 PM, Alexander Belopolsky <ndarray at mac.com> wrote:
> On Fri, Dec 6, 2013 at 11:13 AM, Alan G Isaac <alan.isaac at gmail.com> wrote:
>
>> On 12/5/2013 11:14 PM, Alexander Belopolsky wrote:
>> > did you find minus to be as useful?
>>
>>
>> It is also a correct usage.
>>
>
> Can you provide a reference?
>
>
>>
>> I think a good approach to this is to first realize that
>> there were good reasons for the current behavior.
>>
>
> Maybe there were, in which case the current behavior should be documented
> somewhere.
>
> What is the rationale for this:
>
>>>> -array(True) + array(True)
> True
>
> ?
>
> I am not aware of any algebraic system where unary minus denotes anything
> other than additive inverse.

I would be perfectly happy if numpy would cast (negative) overflow to
the smallest value, instead of wrapping around.
The same is true for integers.

>>> np.array(0, np.int8) - np.array(-128, np.int8)
-128
>>> - np.array(-128, np.int8)
-128

Josef
<It's consistent. But does it make sense?>
>
> Having bools form a semiring under + and * is a fine (yet somewhat unusual)
> choice, but once you've made that choice you loose subtraction because True
> + x = True no longer has a unique solution.
>
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