[Numpy-discussion] Bitwise operations and unsigned types

Charles R Harris charlesr.harris@gmail....
Fri Apr 6 00:45:34 CDT 2012


On Thu, Apr 5, 2012 at 11:39 PM, Charles R Harris <charlesr.harris@gmail.com
> wrote:

>
>
> On Thu, Apr 5, 2012 at 11:16 PM, Travis Oliphant <travis@continuum.io>wrote:
>
>> Which version of NumPy are you using.  This could be an artefact of the
>> new casting rules.
>>
>> This used to work.   So, yes, this is definitely a bug.
>>
>>
> It's because the '3' is treated as signed, so the uint64 needs to be cast
> to something of higher precision, of which there is none. You can either
> use uint64(3) or just stick to int64. I don't know if this used to work or
> not, mixing signed and unsigned has always led to higher precision in
> arithmetic operations, even (mistakenly in my opinion) promoting uint64(5)
> + 3 to lower precision float64.
>
>
In particular, in this case it is because two scalars are used. It works
fine for arrays

In [11]: ones(3, uint64) & 3
Out[11]: array([1, 1, 1], dtype=uint64)

Chuck
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