Hi Erik
On 2018-05-28, Erik Bray <erik.m.b...@gmail.com> wrote:
> I think Sage could use a better way to keep
> track of and/or enforce immutability of classes (that is, instances of
> classes). For example, have some base class which can be used as a
> mix-in (or an ABC) that designates something as immutable, and
> disallow assigning any attributes to its dict that aren't also
> immutable (including of course support for all the common built-in
> types).
I don't think this could possibly work. But actually that's not a Sage
problem but a Python problem: Perhaps somewhere in the Python ecosystem
such a mix-in class exists?
However, I find your notion of immutability ("do not allow assigning
attributes and make all existing attributes immutable") far too narrow.
IIRC, immutable means that once the object is created, its equivalence
class with respect to the "==" operator will be preserved no matter what
of its (no-underscore?) methods are called.
Thus, I believe it must be allowed to assign to an attribute of object X,
as long as the behaviour of X==Y remains unchanged for all objects Y
(and of course hash(X) doesn't change either).
Best regards,
Simon
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