Robert Withers wrote:
> 
> > Another point.  Jesse Welton already pointed out that objects are not copied
> > by closures.  If two closures refer to same object through their variables,
> > changes made using one closure will be visible through another.  it is
> > important that not only objects are not copied, the bindings are not copied
> > as well.  Two closures created within the same environment see the same
> > bindings, so changes done to a variable of that environment from one closure
> > are visible from another.  For example:
> > 
> >   | cell |
> >   ^Array
> >     with: [:arg | cell := arg]
> >     with: [cell]
> 
> -- ??? Really??   This surprises me.  I thought that a closure would
> have it's own binding seperate from any other binding.  This is
> different that two bindings holding the same reference and changing the
> internal state of that reference.  Aren't you saying that two bindings
> pointing to the same reference and one changes the reference, then the
> other binding will also have  a changed reference?

Yes, this is exactly right.  This is necessary to allow (among other
things) assignments to propagate upwards.  Consider:

    | sum |
    sum := 0.
    1 to: self length do: [ :i | sum := sum + self at: i ].
    ^sum

In order from something like this to work, "sum" must name the same
reference both within and without the block.

-Jesse