Suggestion: Walter Bright, why not to implement multiple inheritance in D?

[Larry Evans]

On 12/02/2006 10:11 PM, Burton Radons wrote:
> Larry Evans wrote:
> 
>> On 12/02/2006 09:27 AM, Burton Radons wrote:
[snip]
> And allow the diamond because Winged can't override anything from 
> Animal. This is bad because Animal might have stuff Winged has an 
> opinion on, but more discrete selections of inheritance (which are a 
> good idea anyway) allows us to defeat the diamond when we need to:
> 
>     Reproduction
>     Movement
>     Animal : Reproduction, Movement
>     Mammal : abstract Animal, Reproduction
>     Winged : abstract Animal, Movement
>     Bat : Mammal, Winged
> 
> In this case Mammal and Winged are exclusive, so the tree works properly.
> 
> I'd analyse your example more but I'm unfamiliar with Boost. Can you 
> factor the problem so that it can be expressed in terms of animals? :-)

Well, I'm kinda agreeing with Walter.  AFAICT, the example in
boost which used inherit was used to create a tuple, and since
there's now a better way (as Walter pointed-out), I'm reluctant
to try.  However, if I did, there would be a problem with the
abstract Animal (or virtual Animal in c++ case).  I don't
see a way that can be done with c++ metaprogramming since
all the args to boost::mpl::inherit have to be types, and, AFAICT,
there's no type, virtual X, for any type X, in c++.