[Numpy-discussion] abs for max negative integers - desired behavior?

David Cournapeau cournape@gmail....
Wed Oct 12 02:46:16 CDT 2011


On Tue, Oct 11, 2011 at 8:16 PM, Charles R Harris
<charlesr.harris@gmail.com> wrote:
>
>
> On Tue, Oct 11, 2011 at 12:23 PM, Matthew Brett <matthew.brett@gmail.com>
> wrote:
>>
>> Hi,
>>
>> I recently ran into this:
>>
>> In [68]: arr = np.array(-128, np.int8)
>>
>> In [69]: arr
>> Out[69]: array(-128, dtype=int8)
>>
>> In [70]: np.abs(arr)
>> Out[70]: -128
>>
>
> This has come up for discussion before, but no consensus was ever reached.
> One solution is for abs to return an unsigned type, but then combining that
> with signed type of the same number of bits will cause both to be cast to
> higher precision. IIRC, matlab was said to return +127 as abs(-128), which,
> if true, is quite curious.

In C, abs(INT_MIN) is undefined, so both 127 and -128 work :)

David


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