Eliot Miranda wrote:
> Arguably not.  (BTW VW has had it from 98).  The crucial difference is that
> in VW an extension can be in more than one package.  In Squeak a selector 
> can only be in a single Monticello extension category.  That leads to 
> the awful bug that when an MC package patches a base selector to extend 
> it to fix a bug it ends up in the package and its membership of the 
> package it was in previously being lost.  I understand that with method 
> history this situation can be detected but if you e.g. condense changes 
> then that history is lost, and the base package selector becomes only an 
> extension  Ouch.

That's a bug in condenseChanges, not a conceptual problem. BTW, I really 
fail to see how it would make any difference whatsoever if extension 
methods are in multiple packages or not. In either case you are 
*completely* screwed if you have multiple packages trying to extend the 
same method. Seriously, has there ever been a situation where that 
actually works? (my personal preference is actually that MC should blow 
up straight into your face if you try to change a method that's in an 
extension category already, but that's just me - I generally avoid 
extensions like the plague)

> The VW "solution" is OK as far as it goes; a package is a set of class, 
> selector pairs (more than this, but this is the essence).  An MC package 
> is defined by class and method categories.  VW's parcels are 
> intensional, MC packages are extensional. 

I don't understand the distinction you are making between intensional 
and extensional. Care to elaborate?

MC internally actually uses a set of class and selector pairs as well, 
it just derives them via PackageInfo from categories. And it most 
certainly can have methods in multiple packages. For example, if you add 
a method in category '*Foo-Bar-Baz' it will be part of the packages 
'Foo-Bar-Baz', 'Foo-Bar' and 'Foo' (if those exist).

The only thing that prevents you from having other combinations of 
multiple package memberships is that there is no UI that allows you to 
specify which combinations of packages a method should be part of. The 
category hack is great because it works with existing tools, but 
existing tools don't allow for methods in multiple categories. If you 
fix that you get your multiple package membership in Monticello for 
free. Alternatively provide a UI to specify which other packages the 
method should be part of, and you're there, too.

Cheers,
   - Andreas