On Jun 22, 2011, at 4:02 PM, Axel Rauschmayer wrote:
>> From: Brendan Eich <bren...@mozilla.com>
>> Date: June 23, 2011 0:21:17 GMT+02:00
>>
>>> Is there no per-call cost whatsoever to adding static super?
>>
>> No, it's static -- an internal property of the function object set once on
>> creation and (in my view) never changed thereafter unless unobservably
>> (Allen's point about optimizing Object.defineMethod when "handing off" an
>> otherwise-useless function expression).
>
>
> How does a function get access to its properties? Doesn’t the ability to
> access "thisFunction" incur any costs? I would expect static super to work as
> follows:
>
> var Sub = Super <| {
> foo: function me(x) {
> me.super.foo.call(this, x);
> }
> }
>
> Does the named function expression cost nothing here?
This is entirely beside the point.
Dynamic |super| as Sean proposes requires *every call site* to pass the |here|
parameter or something derived from it, no way around that.
Paying for 'super' if you use it, buying by the yard, is not a problem.
Making *every function call* in the language slow, increasing register
pressure, etc. -- absent aggressive inference to identify callees and
specialize call sites to them (inlining VMs do this but it can backfire, so
there will be a default case that can't do this) -- is a big problem.
/be
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