Re: [Etoile-dev] ANN: New Objective-C Runtime

Hey Quentin,


On 11 Nov 2007, at 00:42, Quentin Mathé wrote:

> As we already discussed it, I really like the whole design except the
> fact protocols are only available at class level.

I tried to clarify this a bit in the blog posting.  What I call  
'classes' in the current runtime are closer to mixins in Animorphic  
Smalltalk; they can be viewed as mixins, categories, classes or  
concrete protocols, depending on what you are doing with them.  A  
class is essentially just a mixin applied to the null class.  You  
might like to take a look a this paper to see where my inspiration  
comes from:

http://www.strongtalk.org/downloads/mixins-paper.ps

I don't really want to move protocols down to the object layer because  
that would bloat the metaobject model - protocols are just syntactic  
sugar for method collections at the moment, just as classes are just  
sugar for factory objects.

> I may submit a patch later to implement them at object level. Class
> would override protocol handling to handle the case where you pass a
> protocol which is a class and not an object. In this former case, the
> handling would be extended to deal with instance and class methods at
> the same time rather than only instance methods.

I'd be interested in seeing this.

I am not completely convinced by the Io question.  I could easily add  
another parameter to the message lookup function at the moment,  
however any compiler producing code from Objective-C wouldn't know  
what to do with this (not that that's a significant problem - I've  
added other things to the runtime that are not used by Objective-C,  
but I'm not sure what the default should be.  NULL?  The sender's  
version of self?)  I think I'd have to take a look at a lookup  
function for Io before I made a final decision.  In your -isReadable  
example, it seems like -isReadable:(id)sender would give the same kind  
of behaviour.  In principle, I really like the idea of getting a  
sender implicitly added, but in practice I think we don't gain much  
from having it as anything other than a parameter in the method  
itself.  Methods that make use of this third argument will have to  
have different signatures to all Objective-C methods (we can't  
redefine IMP without breaking a lot of code).

David
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