Re: Ada Interfaces and the Liskov Substitution Principle

[Markus E Leypold <development-2006-8ecbb5cc8aREMOVETHIS@ANDTHATm-e-leypold.de>]

> I bet that as soon as someone popularizes a mathematical model
> that does away with variance issues for example, then people will
> stop fighting over contravariance versus covariance.
> Until then, only this or that kind of variance is allowed to exist,
> for either mathematical or problem domain reasons, because the
> other solution cannot but create an unmaintainable mess...
>
> If I had the money, I'd put up a challange that triggers some
> programming oriented model research (as opposed to research that
> will move the focus of modelling to formal properties of models
> only.)


Somehow you seem to think, we can just do away with the models, if we
just approach it right. That ignores (a) historical experience -- see
structured programming which has become so commonplace that we don't
percieve it as exceptional any more, and (b) that there is no
alternative[tm]: As you can't do quantum mechnics without a certain
amount of a certain sort of mathematics you cannot state a contract or
specify a design without some sort of logical and basically
mathematical model behind. Without you don't even have a language to
complain to your compiler writer about bugs.

Progress, well, progresses. We get used to it, but it usually doesn't
go away. The hope to get rid of "the variance issue" (which actually
is just a point in how contracts can be stated precisely) after we
discovered it, is just misguided.

Regards -- Markus