🚀 go-pugleaf

In reply to article: <407ol9$m03@metro.ucc.su.OZ.AU> 
    from maxtal@Physics.usyd.edu.au (John Max Skaller):

Are you saying that ALL OO designs should treat the equivalent of virtual
base classes as abstract, or just those designs that are going to be
realised in C++ ??

IMHO there is no reason why a pure OO design should restrict the equivalent
of virtual base classes to be abstract.  If the design is then to be 
implemented in a language (e.g. C++) whose support for such class hierarchy 
designs is limited, then further design is required to work round these 
restrictions imposed by the language.

I am not saying that the language is faulty in this instance, just very
restrictive.

The existance of such language restrictions and hence the need for 
additional design is painful but not insurmountable, although it will 
increase development costs!  As such language designers ideally should
review such restrictions to see if the reasons why they were originally
introduced are still valid, with a view to removing such restrictions 
whenever possible.

So when you say "Just do it the right way", I assume you mean use an 
appropriate work around when implementing in C++.  To say that such a
mechanism "is mandatory for a quality OO library class" is too generalistic 
and incorrect.  C++ is not the only OO language available, and some other
languages may support multiple inheritance in a more coherent manner.

This is clearly an area where the General C++ Design Rule "Don't try to
force people" [D&E of C++ Section 4.2] was compromised to achieve 
other requirements.

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Bryan Drew,                              Email: bdrew@hi-q.demon.co.uk
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