Hi Mark!
On Tue, Feb 18, 2014 at 11:36:13PM -0500, Mark Shimozono wrote:
> Can I think of a sage category as an abstract
> superclass that lives outside the usual class hierarchy,
> but imposes structure on the instance, even to the point of
> promising certain kinds of methods and so on,
> which must possess certain properties?
Yes, one definitely should think about categories, or more precisely
about their associated C.parent_class/C.element_class/..., as abstract
classes. That's really what they are at the end: the only deviation is
that the inheritance is set dynamically rather than statically.
And then, as every abstract class, they impose a contract on their
concrete subclasses, typically like specifying the existence,
signature, and semantic of certain methods.
> To be useful a category needs to have some "enforcement power".
Yes! That's what "abstract_methods" and "_test_methods" are here for,
even though this is not as rigid as what you can have with statically
checked languages like java (e.g. the compiler barks if you don't
override an abstract method having a given signature with a concrete
method with the same signature).
Cheers,
Nicolas
--
Nicolas M. Thiéry "Isil" <nthi...@users.sf.net>
http://Nicolas.Thiery.name/
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