On Oct 13, 2011, at 3:55 PM, John J Barton wrote:
>
> Suppose for a moment we allowed objects on the RHS:
> var o3 = p <| o2;
> Would we imagine that o2 was mutated in any way? I don't think so. Maybe
> there are binary ops that mutate operands, but they don't come to mind. So
> the entire business about mutation of [[ProtoLink]] is not related to my
> interest in allowing object expressions on the RHS of protoLinkSet operator.
Note that my original thoughts that lead to <| included the possibility that
the RHS could be an arbitrary expression. In order to avoid [[Prototype]]
mutation that meant that the RHS would have to be shallow cloned to produce a
new object whose [[Prototype]] was the LHS value. The semantics of cloning is
not as trivial as somebody seems to assume and the primary use case I was
trying to address ("subclass" Arrays , Functions, and other objects with
special implementation level behaviors) didn't require it. So it punted and
specified that the RHS must be a literal. This left open the possibility that
at some future date we might want to reconsider that restriction.
I still haven't found a really compelling use case for a non-literal <| RHS and
a good definition for object cloning is still a nut to crack. But both
plausibly might occur.
Allen
_______________________________________________
es-discuss mailing list
es-discuss@mozilla.org
https://mail.mozilla.org/listinfo/es-discuss
