About squeak image compatibility (3.6/7/8)

Adrian Lienhard adi at netstyle.ch
Mon Jan 9 11:08:30 UTC 2006

On Jan 9, 2006, at 07:20 , Andreas Raab wrote:

> Cees De Groot wrote:
>> Could you substantiate that claim? I think that Traits introduces
>> extremely little compatibility issues...
> Well, I think that depends a *lot* on your perspective of the  
> system. It would be more accurate to restate the above to say that  
> there should be very little compatibility issues, UNLESS:
> * you actually start using 3.9, in which case you'll have issues  
> with porting back stuff to older Squeak versions (this will be a  
> serious issue for packages that are and should be used in older  
> versions of Squeak - will these older versions of Monticello be  
> able to deal with class definition that have been created in 3.9? etc)

yes, you can load packages built with a MC 3.9 version in an older MC  
version if the package does not include traits.

> * you assume a stable interface in classes and meta classes (this  
> got seriously broken in 3.7, then again in 3.8, and now again in  
> 3.9 - it is amazing how little continuity there has been in such a  
> critical part of the system)

For traits, we tried to maintain the existing class/metaclass  
interface as much as possible. Do you have a concrete problematic  
example where this is not the case?

> * you use meta tools that rely on the previously available semantic  
> entities (which excludes traits)
> * you use meta tools that rely on previously stable representations  
> (class definitions in particular)

> Now, I'm not saying that everyone will be affected by (or even care  
> about) the above but if you are in either situation it is pretty  
> safe to assume you'll be severely screwed one way or another. Case  
> in point: Without appropriate fixes Monticello and file contents  
> browser are invariably broken (and so is the VW parcel that allows  
> people to load Squeak code).

Do you have examples?


> And of course, another major difference in perspective is whether  
> you are on the breaking or the broken side of things. People don't  
> like their stuff to get broken by other people so any claim that  
> this is "extremely little" is not likely to get you many friends -  
> in particular if the breakage (as so often) is undocumented and  
> you'll probably find out the hard way. And I think you'd be well  
> advised to keep that in mind.
> Cheers,
>   - Andreas

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