[Numpy-discussion] __iadd__(ndarray<int>, ndarray<float>)
Stéfan van der Walt
stefan@sun.ac...
Mon Mar 24 19:26:09 CDT 2008
Hi Andreas
On Mon, Mar 24, 2008 at 7:28 PM, Andreas Klöckner
<lists@informa.tiker.net> wrote:
> I just got tripped up by this behavior in Numpy 1.0.4:
>
> >>> u = numpy.array([1,3])
> >>> v = numpy.array([0.2,0.1])
> >>> u+=v
> >>> u
> array([1, 3])
> >>>
>
> I think this is highly undesirable and should be fixed, or at least warned
> about. Opinions?
I know the result is surprising, but it follows logically. You have
created two integers in memory, and now you add 0.2 and 0.1 to both --
not enough to flip them over to the next value. The equivalent in C
is roughly:
#include <stdio.h>
int
main()
{
int i;
int x[2] = {1,3};
x[0] += 0.2;
x[1] += 0.1;
printf("[%d %d]\n", x[0], x[1]);
}
Which results in the same answer.
Regards
Stéfan
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