D vs C++ classes?

[IGotD-]

On Tuesday, 22 June 2021 at 02:13:33 UTC, zjh wrote:
>
> multiple inheritance is very good.I dont know why they are 
> objective.
> 10+ years ago,they refuse to listen others' suggestion.
> I dont know if they still refuse now.

It's because the diamond problem. The diamond problem is purely 
an academic problem and it very seldom happens in the real world 
and if it does you probably did something wrong in your design. 
Happen to me once in 30 years because I messed up. Multiple 
inheritance is often flat, which means that one class inherits 
from several others at the same level. Instead of disallow 
multiple inheritance you can disallow the diamond pattern.

D went another way with composition with template mixins. Nothing 
particular wrong with this model but I think the D documentation 
isn't clear about its intended use. Also the overlap with alias 
this makes it more confusing.