At Mon, 30 Dec 2002 09:29:22 -0500, Marc Feeley wrote:
> No "copy-on-write" is not a valid implementation.  The reason is that
> the "swapping" semantics requires the child thread to have an
> independent copy of the parent's thread.  So the child must get a
> snapshot of the parent's dynamic environment which will make the
> child's mutations invisible to the parent ***AND*** the parent's
> mutations invisible to the child.  The copy-on-write approach you
> suggest only makes the child's mutations invisible to the parent.

Depends on what you mean by "copy on write". I'd say that MzScheme uses
"copy on write", and I mean that a copy is made whenever the parent or
child changes a parameter value. (I think that's consistent with
Felix's suggestion.)

Matthew