Re: Simple example on interfaces

["Randy Brukardt" <randy@rrsoftware.com>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> wrote in message 
news:ruprf8$1h6q$1@gioia.aioe.org...
...
>> universal_integer is anonymous and doesn't have any operations (except 
>> automatic conversion).
>
> Yes. In a never ending discussion with Randy I insist that this stuff 
> should be made explicit, available for any types.

As I've often said, for a new language that would certainly be a good idea. 
For Ada, reproducing all of the quirks of Ada would lead to an inpentrable 
mess. And not reproducing them would break a lot of code (and more 
importantly, no one could tell if their code would be broken and in extreme 
cases, wouldn't even know as the code would silently change meaning).

As far as full multiple inheritance being too expensive to implement, I tend 
to think that is true for interfaces as well. :-) As always, the question is 
whether one wants fast code or just something that works. Full multiple 
inheritance certainly can be implemented by converting all selectors to 
Getter/Setter pairs and dispatching on every use. But that's pretty 
expensive for accessing an integer component. Of course, most of the time it 
won't matter (Janus/Ada does something like this for shared generics, and I 
have yet to have someone complain about performance of generic code). But 
there will be cases where it does matter, and this is a distributed 
overhead -- it applies to all types whether or not you use it (because 
someone could extend this type in some future unit not even written yet).

                                        Randy.