[Numpy-discussion] dtype subarray comparison
Pauli Virtanen
pav at iki.fi
Thu Oct 21 14:18:14 EDT 2010
Thu, 21 Oct 2010 11:03:52 -0600, Charles R Harris wrote:
[clip]
> I think the important thing to settle here is just how dtype comparisons
> are supposed to work. The current implementation might well be intended
> and if so we need to know why it is so. I'd like Travis to weigh in
> here.
To me it seems that sub-arrays were not considered in the initial
implementation for `==`.
I do not see reasons why one would want to have
a = dtype([('a', 'i1', (3, 3))])
b = dtype([('a', 'i1', 9)])
a == b
In any case the current implementation is inconsistent, since currently
hash(a) != hash(b)
However, I can see why one would want to have CanCastSafely to be true
between these types.
***
The other issue of allowing broadcasting in sub-arrays --- it does not
seem very useful to me. Unlike arrays, the dimensions of sub-arrays
cannot be manipulated easily, and so many use-cases of broadcasting just
disappear.
Pauli
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