Re: [GD-General] Eiffel

[Thatcher U. <tu...@tu...>]

On Dec 22, 2001 at 04:30 -0800, Jesse Jones wrote:
> 
> Unfortunately MI has a bad reputation in C++. Even people who should 
> know better like Scot Myers rag on it. But essentially all of the 
> problems with MI in C++ are because of virtual base classes. So how 
> do you avoid virtual base classes? By avoiding diamond shaped 
> inheritance hierarchies.
> 
> One way to do this is by using mixin classes. You have your main-line 
> classes like Widget or Monster or whatever and then you have mixin 
> classes like ReferenceCountedMixin or ObserverMixin or whatever. 
> Mixins only descend from other mixins so you never wind up with the 
> diamond of death.

I've been pondering this.  I've always depended on virtual inheritance
for effective mixins.  For example, how do you implement smart
pointers to mixins of ref-counted classes, without virtual
inheritance?  It would be great if I'm wrong, since virtual
inheritance is a PITA in some ways (in other ways, I think it's the
only usable form of C++ MI, but lets leave that aside for now).

-- 
Thatcher Ulrich <tu...@tu...>
http://tulrich.com