On Fri, Nov 9, 2018 at 6:46 PM Nathaniel Smith <njs@pobox.com> wrote:

But matrix isn't the only problem with asanyarray. np.ma also violates
Liskov. No doubt there are other problematic ndarray subclasses out
there too...

Please forgive my ignorance (I don't really use mask arrays), but how specifically do masked arrays violate Liskov? In most cases shouldn't they work the same as base numpy arrays, except with operations keeping track of masks?

I'm sure there are some cases where masked arrays have different semantics than NumPy arrays, but are any of these intentional?

I would guess that the worst current violation is that there is a risk of losing mask information in some operations, but implementing __array_function__ would presumably make it possible to fix most of these.