Re: Ada OO Mechanism

[Hyman Rosen <hymie@prolifics.com>]

Mark A Biggar <mark.a.biggar@lmco.com> writes:
> 1) It's not really part of the class as it has to be defined as 
> an external "friend" function.

Friend functions and classes constitute parts of an interface.
Some people would like to criticize C++ both for "requiring that
everything be inside a class" and then again for using friends
"which are not part of the class". They merely, or willfully,
misunderstand the C++ model.

> 2) It therefore CANNOT be made virtual so you can't dispatch on it.

So you mean in Ada, I can write a dot(a,b) which will dispatch on
either a or b? I wasn't aware that this was the case. I actually
think that this is in fact *not* the case, in which case I have no
trouble writing a dispatching version in C++ either - just have
dot(a,b) call a.dot(b). In both Ada and C++, the apparent external
symmetry will then hide the internal asymmetry.

> 3) This also greatly complicates its use in generic (template) algorithms.
> None of those problems exist in Ada.

Once again, I will ask for an example demonstrating this, where
something is more complicated to use in C++ generics than in Ada.
This will make you the fourth person I have asked for this type
of example, the others being Richard D. Riehle, Samuel Mize, and
Robert Dewar. None of the others have chosen to post such an
example.