Need encouraging...

[James Dennett]

Steven Schveighoffer wrote:
> "Arlen Albert Keshabyan" wrote
>> Steven Schveighoffer Wrote:
>>
>>> Do the listener types have any implementation?  If not, you can code them 
>>> as
>>> interfaces, and you don't need multiple inheritance.  The JUCE project 
>>> may
>>> have used multiple inheritance to emulate interfaces because interfaces 
>>> are
>>> not available with C++.
>>>
>>>
>> That's not true! C++ has interfaces! Even more, abstract C++ classes can 
>> be used as interfaces, as abstract classes itself and as interfaces with 
>> partially implemented factions and data.
> 
> No, C++ does not have interfaces. 

No, C++ does have interfaces.

> It has abstract classes. 

Which subsume the notion of interfaces; an interface is a
special case of a C++ abstract class, needing no additional
or special language support.

> Interfaces are 
> not allowed to have implementations. 

Or, to put it another way, a pure abstract base class is
also known as an "interface".  An abstract base class with
implementation details is not a pure abstract base class,
i.e., not an interface.

> C++ can *mimic* interfaces with 
> abstract classes that have no implementation, but the concept of an 
> interface is not a language feature. 

It's not mere mimicry, it's an realization of the abstract
notion of an OO "interface".

> What I meant by my comment is that 
> perhaps JUCE used abstract classes/multiple inheritance to mimic interfaces 
> because interfaces are not supported, but I see from your comment below that 
> they have some implementation.

You might have met less resistance if you'd just said that JUCE
might use MI only for interfaces, and while D doesn't support MI
in general, it has specific facilities for this special case
(which provides some of the good features of MI, while avoiding
many of the complexities).

-- James