Multiple Inhertiance?

[via Digitalmars-d]

On Thursday, 6 November 2014 at 15:25:11 UTC, Patrick Jeeves 
wrote:
> I don't really see how multiple alias this is better or worse
> than multiple inheritance.

It is worse because:

1. When you design a class hierarchy with multiple inheritance 
you don't reuse something made for another purpose, you design it 
as a whole for a particular purpose and you can use virtual base 
class and virtual function to resolve problems.

2. "multiple alias this" messes with the type system in bad ways. 
Classical multiple inheritance does not (due to the resolution 
mechanisms).

But there is no good reason to include either because you should 
model not from the object, but from how you care going to use the 
object. Therefore you can usually decide one view as more 
important for a particular application.

> IMHO MI is too useful a feature to be left out of any language,
> even if most languages butcher it to the point that it's used as
> an is-both relationship.

If you want good MI then you need to build the language around it 
from the start, but you can always do without.

Yes, that means you have to select one perspective and break down 
the model in a different way, but it isn't that hard to do. And 
you can resolve conflicts by adding virtual functions in the base 
class if you want that kind of model.

For a game it would be better to break up the representation for 
the game object into more than a single aggregate. Using MI and a 
single object is going to hurt performance.