On Sat, 16 Apr 2022 at 11:00, Steven D'Aprano <steve@pearwood.info> wrote:
and therefore would become the only thing that offers "full MI", displacing other languages. It's a meaningless concept, unless there is some form of absolute completeness that can be attained
Well duh Chris, sometimes I wonder if you read my posts before jumping in to disagree with me, that is *exactly* what I am arguing.
You placed a LOT of caveats on it. I don't count that as "absolute completeness". It is the most complete that YOU, right now, think could ever be possible.
If you exclude models of MI which are logically incoherent and inconsistent, (such as Python's prior to version 2.3), then Python's model of MI is objectively as complete as you can get.
If you assume that what we know in 2022 is the most we will ever know, then yes, you would be correct. Do you really think that nobody will ever learn anything new about ways of doing MI? I don't know whether you're mistaken or utterly arrogant.
My view: If a class inherits two parents, in any meaning of the word "inherits" that follows the normal expectation that a subclass IS an instance of its parent class(es), then it's MI.
Inheritance and "is-a" relationships are independent.
In some languages (but not Python), mixins provide inheritance but not an "is-a" relationship. In Python, virtual subclassing provides "is-a" without inheritance.
Virtual subclassing is still subclassing, just implemented differently. Reassigning to __class__ is still subclassing, just spelled differently. What is "inheritance" if it isn't that is-a relationship? How do you distinguish inheritance from delegation? Is inheritance only a thing if it happens on the line of code that says "class X"? (Not the case in Pike.) Is inheritance only a thing if it happens as the class is first created? (Is the case with mixins.) What's your point? ChrisA