[Numpy-discussion] A crazy masked-array thought

[Charles R Harris]

On Wed, Apr 25, 2012 at 9:58 AM, Richard Hattersley
<rhattersley at gmail.com>wrote:

> The masked array discussions have brought up all sorts of interesting
> topics - too many to usefully list here - but there's one aspect I haven't
> spotted yet. Perhaps that's because it's flat out wrong, or crazy, or just
> too awkward to be helpful. But ...
>
> Shouldn't masked arrays (MA) be a superclass of the plain-old-array (POA)?
>
> In the library I'm working on, the introduction of MAs (via numpy.ma)
> required us to sweep through the library and make a fair few changes.
> That's not the sort of thing one would normally expect from the
> introduction of a subclass.
>
> Putting aside the ABI issue, would it help downstream API compatibility if
> the POA was a subclass of the MA? Code that's expecting/casting-to a POA
> might continue to work and, where appropriate, could be upgraded in their
> own time to accept MAs.
>
>
That's a version of the idea that all arrays have masks, just some of them
have "missing" masks. That construction was mentioned in the thread but I
can see how one might have missed it. I think it is the right way to do
things. However, current libraries and such will still need to do some work
in order to not do the wrong thing when a "real" mask was present. For
instance, check and raise an error if they can't deal with it.

Chuck
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