Scoped binding of a method to an object

John Lenz concavelenz at gmail.com
Mon Oct 14 09:59:54 PDT 2013


Does this performance hit still exist in light of Symbol? It seems you
could build  lexical extensions on top of it without introducing a
performance penalty.
On Oct 13, 2013 10:49 AM, "Brendan Eich" <brendan at mozilla.com> wrote:

> Erik Arvidsson <mailto:erik.arvidsson at gmail.**com<erik.arvidsson at gmail.com>
>> >
>> October 13, 2013 10:32 AM
>> We did proposes this back in 2011
>>
>> http://wiki.ecmascript.org/**doku.php?id=strawman:scoped_**
>> object_extensions<http://wiki.ecmascript.org/doku.php?id=strawman:scoped_object_extensions>
>>
>> I wasn't at this actual F2F meeting so I don't know many details.
>> Brendan might remember what the blocking issue was?
>>
>
> I wrote why in my reply, cited below:
>
>  Your subject recalls a defunct proposal to add lexically-scoped but
>> heap-based -- therefore object property-lookup performance hindering --
>> extension properties. This proposal died precise because of the performance
>> problem.
>>
>
> Every property access sprouts a third parameter beyond object and property
> name, namely a lexical scope token of some kind. All property maps in
> objects shared in the heap also sprout such a scope token along with
> property name.
>
> (This is quite reminiscent of ES4 namespaces, which we agreed to reject
> from any future ECMA-262 in order to forge Harmony in 2008. See
> https://mail.mozilla.org/**pipermail/es-discuss/2008-**August/006837.html<https://mail.mozilla.org/pipermail/es-discuss/2008-August/006837.html>
> .)
>
> Implementors objected, including V8 folks (if I recall correctly, Andreas
> Rossberg). This was at the May 2011 TC39 meeting hosted at the University
> of California at Santa Cruz.
>
> /be
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