Re: Eiffel and Java

[donh@syd.csa.com.au (Don Harrison)]

Vincent WEBER writes:

:Sather's contravariant mecanism seem very interesting too, has stronger and 
:safer theorical bases... 

Why does Sather use contravariance (apart from the safety issue). You would 
expect more specific actions to require more specific parameters.

: Sather also allow sepation between code inclusion and 
:subtyping. Is it cleaner, or just more complicated that the universal 
:inheritance mecanism ? any comment ?)

What is the purpose of separating interface and implementation inheritance? 
When would you need to inherit an implementation without needing it's interface 
as well (and vice versa)?

[...]

:  By the way, one more thing : I just had a look at ADA 95 and it's "OO" model. 
:Even if I admit it is powerful, I think it's very heavy. (The ADA 9X group had 
:to keep all the Ada 93 stuff...:)). However, one thing interested me : Ada 
:fanatics claim that the dot notation break the symetry of natural operation, 
:and that Ada's model of dynamic bindings in all the parameters of a procedure 
:is better (that is, writing for instance Add(VectorA, VectorB) instead of 
:VectorA.Plus(VectorB). I don't know what to think about this controversy. Any 
:idea ?

Don't mistake Ada's symmetrical syntax for multiple dispatching (binding
driven by more than one parameter). Ada is still single dispatched so for
dispatching operations, the symmetry is syntactic rather than semantic.  


Don.
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Don Harrison             donh@syd.csa.com.au