Re: Eiffel and Java + Ada dispatching

[jsa@alexandria (Jon S Anthony)]

In article <55c9e4$59m@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

Right - I wrote another note stating a bit about this.  The full knock down
drag out is in a thread called "Real OO" posted to c.l.a,c.l.e,comp.object
back in fall '95.


> 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.

Yes, I am getting lazy on this stuff - the pointer is above.  In fact,
I really should just stop wasting time on this...


> >> 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*. 

So was I.  The "overloading" bit is different from J/C++ for a few
reasons which I pointed out in another note (and which depend in part
on the distinction between specific and class wide types, which are
analogous to Sather concrete and abstract classes).


> 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.

No - and I didn't do this.  The important bit is "In this respect" -
which refers to the business of overloading - not languages in
general.  And to say that "in this respect" it (Ada) is _exactly_ like
the other two (C++/J) is not correct.


> And this has not to degenerate in a language war: Ada and Eiffel
> deserve better than that.

Right.  Besides, that's been done to death and its boring.


> 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.

Sounds right.  As I point out in another note, this "confusing"
assesement stems in large part from not being familiar with the
distinction between specific and class-wide types.  It is worth noting
that in C++/J this distinction is not made and the confusion really
does have a more "objective" basis.


> But I do not claim Eiffel is perfect (can you claim Ada95 is?).

Are you kidding? :-) I have flamed Ada on a number of points.  What I
don't like is seeing someone make assertions which do not reflect
various facts.  I'm sure I've made these sort of assertions too as
people have "shown me the error of my ways".  I'm not going to go
around making assertions about Eiffel here without first making pretty
damn sure I understand the relevant bits in ETL and related
information.


/Jon
-- 
Jon Anthony
Organon Motives, Inc.
Belmont, MA 02178
617.484.3383
jsa@organon.com