[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [objc-improvements] Warnings when compiling GNUStep
From: |
Ziemowit Laski |
Subject: |
Re: [objc-improvements] Warnings when compiling GNUStep |
Date: |
Wed, 3 Sep 2003 16:46:49 -0700 |
On Wednesday, Sep 3, 2003, at 13:37 US/Pacific, Dirk Theisen wrote:
Hello, Ziemowit!
Let me first say, I'm glad someone is cleaning up the compiler.
It seems that you also have the relevant background knowledge to do it
the "right" way.
You are touching a spot I long wish ObjC had it:
Covariant return types. Those are absolutely valid and I think you
know that. If not, I can dig up the relevant (oldish) papers. This
would give ObjC a little bit more expressive power in some cases and
another advantage over Java.
Covariant return types (unlike covariant arguments :-) ) are valid in
an OO-theoretic sense, but I'm not sure how well they it in with
_existing_ Objective-C usage.
For example, how should the compiler deal with invariant, unrelated or
contra-variant return types?
What I want is to declare:
@interface ImmutableClass: NSObject
- (NSArray*) allElements;
@end
@interface MutableClass: ImmutableClass
- (NSMutableArray*) allElements;
@end
You can declare that today, without prejudice (or warnings). The
problem arises if you're sending an 'allElements' message to 'id',
which takes us back to the ongoing discussion on discuss-gnustep. :-)
(BTW, I have contacted "the proper authorities" on setting up an
Apple-hosted ObjC mailing list; please stay tuned.)
--Zem
--------------------------------------------------------------
Ziemowit Laski 1 Infinite Loop, MS 301-2K
Mac OS X Compiler Group Cupertino, CA USA 95014-2083
Apple Computer, Inc. +1.408.974.6229 Fax .5477
- [objc-improvements] Warnings when compiling GNUStep, Ziemowit Laski, 2003/09/02
- Re: [objc-improvements] Warnings when compiling GNUStep,
Ziemowit Laski <=
- Re: [objc-improvements] Warnings when compiling GNUStep, Alexander Malmberg, 2003/09/03
- Re: [objc-improvements] Warnings when compiling GNUStep, Ziemowit Laski, 2003/09/03
- Re: [objc-improvements] Warnings when compiling GNUStep, Riccardo Mottola, 2003/09/04
- Re: [objc-improvements] Warnings when compiling GNUStep, Alexander Malmberg, 2003/09/04
- Re: [objc-improvements] Warnings when compiling GNUStep, Ziemowit Laski, 2003/09/04
- Re: [objc-improvements] Warnings when compiling GNUStep, Alexander Malmberg, 2003/09/04
- Re: [objc-improvements] Warnings when compiling GNUStep, Ziemowit Laski, 2003/09/04
- Re: [objc-improvements] Warnings when compiling GNUStep, Nicola Pero, 2003/09/05