On Tue, 2004-03-16 at 10:25, Dan Sugalski wrote:
> Unless I missed something, child classes inherit parent class roles,
> so if I have Foo with a role of X, and Bar inherits from Foo, Bar
> does the X role. Looks like inheritance to me...
That's normal inheritance and that's fine.
Consider instead a class that does a role but does not inherit anything.
Roles should not affect method dispatch. Inheritance should.
Compilation
-----------
- Roles - apply methods from a role
- mark that the applying class does the role
- Inheritance - mark that the inheriting class inherits
Method dispatch
---------------
- Roles - do not look at any applied roles for methods
not present in the invocant's class
- Inheritance - look in the parent classes for methods not present
in the invocant's class
Type checking
-------------
- Roles - look at the applied roles for a match
- Inheritance - look at the parent classes for a match
That all leads me to believe there are two separate questions:
1) What is the type of this object (what kind of behavior can I expect
from it)?
2) Where does it get its methods?
I think mixing those two in one mechanism would be a mistake.
-- c
