[Numpy-discussion] Should bool_ subclass int?
Travis Oliphant
oliphant.travis@ieee....
Sat Jul 7 11:16:00 CDT 2007
>
>
> On 7/6/07, *Travis Oliphant* <oliphant.travis@ieee.org
> <mailto:oliphant.travis@ieee.org>> wrote:
>
> Timothy Hochberg wrote:
> >
> > I'm working on getting some old code working with numpy and I
> noticed
> > that bool_ is not a subclass of int. Given that python's bool
> > subclasses into and that the other scalar types are subclasses of
> > their respective counterparts it seems at first glance that
> > numpy.bool_ should subclass python's bool, which in turn subclasses
> > int. Or am I missing something here?
> The reason it is not, is because it is not binary compatible with
> Python's integer. The numpy bool_ is always only 8-bits while the
> Python integer is 32-bits or 64-bits.
>
> This could be changed I suspect, but then it would break the
> relationship between scalars and their array counterparts
>
>
> Do you have and idea off the top of your head head how painful this
> would be from an implementation standpoint. And is there a theoretical
> reason that it is important that the scalar and array implementations
> match? I would think that, conceptually, they are all 1-bit integers,
> and it seems that the 8-bit, versus 32- or 64-bits is just an
> implementation detail.
It would probably take about 2-3 hours to make the change and about 3
more hours to fix the problems that were not anticipated. Basically,
we would have to special-case the bool like we do the unicode scalar
(which also doesn't necessarily match the array-based representation but
instead follows the Python implementation).
I guess I don't really see a problem in switching just the numpy.bool_
scalar to be a sub-class of the Python bool type and adjusting the code
to make the switch when creating a scalar.
-Travis
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