"Peter Suk" <peter.kwangjun.suk / mac.com> wrote in message

> > The fact that Ruby instance variables appear on demand, and so
> > references to
> > instance-vars cannot be directly mapped to integer offsets from a known
> > class definition, will likely mean some performance trade-off.
>
> Already covered this.

Replacing every existing object of a class with a new static layout has a
very different performance profile from updating the dynamic layout of a
single object. Silently creating a singleton class might result in subtle
changes in Ruby semantics. Going all-dynamic layout takes a big performance
hit.

Sounds like a performance trade-off area to me.