> I read the CaesarJ tutorial until it said
>
>  if(comp instanceof Container)
>   {returnContainerNode((Container)comp);}
>  else{returnComponentNode(comp);}
>
> which is about "wrappers are selected depending on the dynamic type  
> of the wrappee".
>
> In this simple example there are just containers and components. I  
> fear that in more complex situations the actual number of "if (x  
> instanceof Y)" becomes unmanageable :(

It seems to me that this piece of code is automatically generated.  
Slide 44 shows how it works underneath i guess.
As a simple user, you just have to declare inner classes.

Cheers,
Alexandre


>
> On Sat, 03 Mar 2007 17:36:03 +0100, Alexandre Bergel wrote:
>
>>>> I don't think it would be conceptually hard to do something similar
>>>> in Smalltalk if you were to have class lookup work similarly to
>>>> method lookup but along namespace hierarchies.
>>
>> No, this is not difficult to achieve. This is even called "virtual  
>> classes", or "virtual type".
>> Want some example of existing systems? CaesarJ [1], Keris [2],  
>> gbeta [3],
>>
>> [1] http://caesarj.org/
>> [2] Author's web page: http://zenger.org/research.html
>> [3] http://www.daimi.au.dk/~eernst/gbeta/ and particularly http:// 
>> www.daimi.au.dk/~eernst/papers/fampol.ps
>> [4] Thesis of William Cook, http://www.cs.utexas.edu/~wcook/papers/ 
>> thesis/cook89.pdf , most interesting for our purpose is Section  
>> 3.5 page 27.
>>
>>> I'm working on that.
>>>
>>> Now... if I make a stable, usable, clean and largely
>>> backwards-compatible solution, will people integrate it into Squeak?
>>> It would be a very large, dare I say revolutionary change.
>>
>> Should be trivial to implement in Squeak. Some issue arise when  
>> implementing this in a static type language (http:// 
>> www.daimi.au.dk/~eernst/papers/tr-pb577.pdf), however this is not  
>> an issue for squeak.
>>
>> Where you might have some problems is to achieve a complete  
>> integration with the tools...
>>
>>
>>
>>>> The other thing that
>>>> would make extension safe is a copy on write semantic with class
>>>> wherein extensions to classes that are not local to your namespace
>>>> result in a new class with the same name in your namespace being
>>>> created that derives from the class in the parent namespace.  Thus,
>>>> your mods are kept local to your context.  It does make class  
>>>> binding
>>>> harder as class names have to be resolved dynamically in the  
>>>> methods
>>>> that reference them.
>>>
>>> That's harder.
>>
>> This is a hard problem. I spend 4 years on it (http:// 
>> www.iam.unibe.ch/~scg/Archive/Papers/ 
>> Berg05aclassboxesJournal.pdf , feel free to skip the greek stuff  
>> if you're not comfortable with).
>>
>> I am interested in having virtual classes in Squeak.
>>
>> Cheers,
>> Alexandre
>
>
>

-- 
_,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:
Alexandre Bergel  http://www.cs.tcd.ie/Alexandre.Bergel
^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;._,.;:~^~:;.