Hi Jeroen,
On 2016-10-10, Jeroen Demeyer <jdeme...@cage.ugent.be> wrote:
> Try this:
>
> sage: from sage.misc.inherit_comparison import
> InheritComparisonClasscallMetaclass
> sage: class A(Element, UniqueRepresentation):
> ....: __metaclass__ = InheritComparisonClasscallMetaclass
In other words, we have custom made metaclasses that combine various
"basic" metaclasses. Such as
DynamicInheritComparisonClasscallMetaclass
found in sage.structure.dynamic_class: It combines DynamicMetaclass,
InheritComparisonMetaclass and ClasscallMetaclass, and if I see that
correctly it fails to include NestedClassMetaclass (which is a
sub-metaclass of ClasscallMetaclass for a mere technical reason).
Several years ago, I played with the idea to have certain atomic
metaclasses for Sage, each of which implementing just a single feature.
And to be able to automatically combine them, the atomic metaclasses are
instances of a common meta-metaclass: The meta-metaclass would take the
atomic metaclasses appearing in the bases of a class definition "Foo",
and would automatically/dynamically create a composed metaclass, that
combines all the features of the given atomic metaclasses and would
serve as the metaclass of the resulting class "Foo".
In other words, there would be no need to hard-code
DynamicInheritComparisonClasscallMetaclass in SageMath: The
meta-metaclass would dynamically create it from DynamicMetaclass,
InheritComarisonMetaclass, and ClasscallMetaclass.
I had a proof of concept, at a time when SageMath used less metaclasses
than it does now. Do you think it would find support from the SageMath
community to revive my project to sanitise metaclass usage? The more
SageMath is relying on metaclasses, the more I feel it makes sense to
structure it by means of a meta-metaclass.
Best regards,
Simon
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