matrix implementation, was: patch for $addrow needed?



> > I see your point, but the line between data structures and
> > mathematical objects is pretty blurry, so I don't think it's
> > practical to try to distinguish the two. A uniform policy would
> > be easy to explain -- I am inclined to support a policy of
> > never sharing data (or at least never appearing to share
> > data).
>
> This is equivalent, I think, to making matrices immutable   (that is, once
> they are constructed you cannot alter the entries).

I agree that many people would be unhappy about immutable matrices,
but I don't see how no data sharing implies it.
No data sharing means only that A[i,j] : FOO can change only A.
I don't see that this implies that no matrix can be changed.

best,
Robert Dodier