"Tanaka Akira" wrote
....
> > I'd also like to know if other OO languages (SmallTalk, Eiffel, Sather,
> > etc.) allow class modifications.
>
> Various (but mainly research) languages have it:
> CLOS, AspectJ, MultiJava, Cecil, MixJuice etc.
>
> The author of a paper of MultiJava calls the modifiable class `open
> class'.

This is a  rather interesting collection of languages

3 out 5 have multi-method support of some kind (I never
heard of MixJuice so maybe it is really 4 out 5).

This  runs squarely against a prominent argument of the
 ``anti multi-method camp''   that Ruby's  ``open classes''
(a very descriptive term btw.)  somehow reduce the need
of method overloading.

Apparently the exact opposite seems to be true:
Method overloading (preferable in the incarnation of
full blown multi-methods)  and ''class openness' seem
to form a very strong synergy ...


/Christoph