|
![](/i/fill.gif) |
Warp wrote:
> Darren New <dne### [at] san rr com> wrote:
>> Warp wrote:
>>> Darren New <dne### [at] san rr com> wrote:
>>>> That's certainly part of it, but you don't need to support multiple
>>>> inheritance in the same way C++ does it. Eiffel has multiple inheritance,
>>>> garbage collection, and O(1) virtual dispatch. (That last would probably be
>>>> quite difficult if you didn't compile everything at the same time, of course.)
>>> As I have mentioned before, you can cast an object pointer to an
>>> incompatible type assuming that:
>
>> Right. I'm not sure what that had to do with what I was saying.
>
> Nothing. Not everything has to be a direct answer to what has been written.
> It's chatter.
OK. Just checking. :-)
>> I believe the mechanism relies on knowing at compile time what every class
>> in the system will be.
>
> You mean it doesn't support precompiled libraries? (Why does that seem to
> be so common with "higher-level" languages?)
It does, but I think you need more than just the object code in there. Kind
of like the way C# is "precompiled" I guess. I'm not sure of the actual
implementation details.
And it's not like C++ supports precompiled templates, either. :-)
>
>>> I wonder if Eiffel supports this as well.
>
>> Eiffel lets you cast up and down the heirarchy. All methods are semantically
>> virtual (even if the compiler optimizes them to direct jumps), so the fact
>> that you're casting up and down doesn't make it "invalid". You can't cast a
>> reference to an object to a type that isn't in that object's parent class
>> heirarchy.
>
> Does that mean "no"?
I wasn't 100% sure what the "this" was.
> Note that in the case I was talking about you are not casting only up or
> only down in the hierarchy. You are actually casting down and then up in one
> go (in a multiple inheritance situation), without seeing any of the
> intermediate classes directly.
Oh. Honestly, I'm not so up on Eiffel I could answer that without looking it
up. But I would suspect not. I mean, if you have Gamma inherit from Alpha
and Beta, and you have a variable declared as Beta and you want to assign it
to a variable of type Alpha, while you could get Gamma to do that, I don't
think you could compile that without first casting the Beta to a Gamma or
something. I really don't know, honestly.
--
Darren New, San Diego CA, USA (PST)
Yes, we're traveling together,
but to different destinations.
Post a reply to this message
|
![](/i/fill.gif) |