Re: proposal for new assignment operators

[Hyman Rosen <hyrosen@mail.com>]

Dmitry A. Kazakov wrote:
> What happens [with assignments] if you derive from Matrix?

Generally speaking, assignment should only be meaningful
between things of the same type. Polymorphic hierarchies
should most likely disallow assignment altogether. If the
Matrix subclasses are used for things like optimizing
storage (eg., diagonal matrices), then assignment remains
meaningful, and the semantics is just to assign each
matrix element from the source to the target.

Remembering previous posts, I suppose I should add the
caveat that this refers to derivation as normally used,
not derivation as you would like to have it. In C++, we
would most likely implement storage variations using
templates, not inheritance.

> What happens if you aggregate Matrix in some other type?

When you write assignment for that type, you decide how
to assign the aggregated pieces. In C++, you get a default
assignment operator if you don't declare your own, and that
does memberwise assignment, so the Matrix component would
be assigned using its own assignment operator.