Steven D'Aprano <st...@pearwood.info> writes: > - If all classes are part of a single hierarchy, it must logically end at > one (or more, if you support multiple inheritance, which Python does) > bases classes. (Unless there are loops, which are generally prohibited in > all OOP systems I know of). The simplest way to do this is with a single > base class.
The original Lisp Machine "Flavors" system (one of the ancestors of the Common Lisp Object System) allowed inheritance to be an arbitrary directed graph -- possibly with cycles. I don't believe that this was done for any deep principled reason, but rather it was just permitted because the algorithm for computing method resolution order didn't actually care whether there were inheritance cycles -- it still terminated and returned an ordered list of component classes. I do not remember seeing any code that made use of this ability, so don't ask me if it was good for anything, but it was definitely there... -- Alan Bawden -- https://mail.python.org/mailman/listinfo/python-list
