On Thu, 31 Jul 2008 21:28:03 +0200, Igor Stasenko wrote:

...
> I think it should be sealed by behavior, by preventing any methods,
> which can modify an instance, to appear in class.

This is no con for the other proposals, but pro for the best that I've  
ever seen :)

Go Smalltalk, go ! :)

/Klaus

> So, the only real
> thing which can guarantee that given object remain unchanged during
> its lifetime is a class. An immutability bit is much worse thing
> comparing to this.
>
> And second, its against the spirit of smalltalk. Smalltalk is one of
> the languages, where it tries to implement all things through
> behavior, not through using different VM/language magic intrinsics.
> It is not a problem, what VM having or not having an immutablity bit,
> its a problem, that current kernel classes and/or collections designed
> without looking at possible use cases where user wants to prevent
> object from being changed during its lifetime.
> So, maybe we should think how to refactor these classes instead of
> including one more magic thing?
>