Re: Ada OO Mechanism

[Hyman Rosen <hymie@prolifics.com>]

Samuel Mize <smize@imagin.net> writes:
>   -- This dispatches on both parameters, so they have to match
>   -- at run-time
>   procedure Operation_4 (A: A_Type; B: B_Type);

(Do you mean B: A_Type ?)

Thanks, this is the kind of example I meant! This is something that
C++ can't do by itself. When you say "match at runtime" do you mean
that their dynamic types must be the same? Does the code raise an
exception if they happen not to match?

If I were to code this in C++, I could do the following:

	void Operation_4(A_Type &A, A_Type &B)
	{
		if (typeid(A) != typeid(B))
			throw "Mismatched types!";
		A.Operation_4(B);
	}

The method Operation_4 of all subclasses of A_Type would have to be
written to take a paremeter of type A_Type, so it's not nearly as
nice as Ada, where I assume that this does not have to be the case.

> Did you intend that paragraph to sound contentious?  To my ear,
> at least, it has rather a "you're all liars, I'm naming names"
> sound to it -- I hope that isn't what you meant.

I wanted it to sound somewhat contentious. The named people each
claimed in a posting that there were object-oriented techniques
that were harder, or less elegant, in C++ than in Ada. I asked
for examples with the thought that perhaps the posters didn't know
C++ as well as they knew Ada, and were therefore perhaps mistaken.
There were responses, but no code, so I got a little testy.