Re: Eiffel and Java + Ada dispatching

[jezequel@piccolo.is.s.u-tokyo.ac.jp (Jean-Marc Jezequel)]

In article <JSA.96Oct30213354@alexandria>, jsa@alexandria (Jon S Anthony) writes:
>In article <557ce3$ojh@tjnews.is.s.u-tokyo.ac.jp> jezequel@piccolo.is.s.u-tokyo.ac.jp (Jean-Marc Jezequel) writes:
>
>> 2) but this is combined with the static overloading inherited from
>> Ada83; which is merely syntactic sugar for routine having
>> (statically) different signatures.
>
>Criminey!  This is wrong too.  It is not "merely syntactic sugar", as it
>is part and parcel of why Ada does not need any system validity checks!

I do not claim to be any expert in Ada95: actually I practiced Ada83 only.
So I might be wrong. In that case I would admit it without problem.
But you cannot simply say: you are wrong and stay at this level of generality.
What has "static overloading" to do with "system validity checks" ?
If it is not syntactic sugar, please tell us what it is. Or if you're lazy,
give a pointer to a relevant section of the reference manual, or to another easily
accessible litterature.

>> In this respect, it is exactly like C++ or Java, but for the
>> symetric syntax.
>
>This isn't correct either.  There are some other semantic aspects
>floating around that make it different from C++/Java in this area.

I didn't say (god forbid!) that Ada95 was anywhere the same as C++/Java!
I was limiting the scope of my comment to the ability
of having both *overloading* and *single dispatch*. 
Do you find it funny to cut one's statements at strategic points to distort
their meaning, or what? Sorry, but I still believe in good faith discussions.
And this has not to degenerate in a language war: Ada and Eiffel deserve better than that.

My only point in this post was that mixing *overloading* (a static mechanism AFAIK)
with *single dispatch* dynamic binding, using the same syntax for the call, was
making things a bit confusing for the user of the language. Since this is a
subjective point, I have no problem with you not agreeing with me. But I expect
real arguments on your side to be able to explain it myself to others.

The rest of your post is thus a bit off-topic:

>> The only thing you really need to make use of OO polymorphism is
>> dynamic binding.  While having at the same time static overloading
>> can make some code fragment more "natural" to write, the apparent
>> proximity of this feature with dynamic binding yield so much
>> confusion on the non-expert eyes that you do not wonder why I prefer
>> to teach Eiffel rather than C++, Java or even Ada95.
>
>I guess you like system validity problems.

System validity is not a problem in Eiffel from the theoritical point of view (at least
when only close systems are considered). Anyway, what is *your* problem with
system validity checks? Have you written real, usefull Eiffel code that bite you lately?
I'd be curious to know...

But I do not claim Eiffel is perfect (can you claim Ada95 is?).
And yes, system validity is one of the weak points.

---
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