Tom Van Cutsem <mailto:[email protected]>
September 11, 2013 3:30 AM
On Sep 10, 2013, at 10:48 AM, Till Schneidereit wrote:
> Wasn't a major point in favor of having an [[Invoke]] trap that
it wouldn't require returning a function from the trap at all?
We'd lose this quality with both of these proposals.
No, the major motivation was to provide a way to deal with
different styles of |this| mapping that are needed for different
styles of proxies. However, the ability to implement a method
code without producing a function is a desirable secondary benefit
That's not how I would characterize it.
Till's argument is the argument we had identified in favor of an
invoke() trap almost from day 1 of the Proxy proposal. It was offset
by the desire to keep the invoke = get+call invariant and to avoid
non-extractable callable properties. Much later, we figured invoke()
was needed to allow proxy handlers to cheaply rebind |this| when
intercepting method calls. This tipped the balance in favor of adding
invoke(). But the idea of avoiding the creation of a temporary
function object is to me at least as important.
Cheers,
Tom
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Allen Wirfs-Brock <mailto:[email protected]>
September 10, 2013 11:39 AM
No, the major motivation was to provide a way to deal with different
styles of |this| mapping that are needed for different styles of
proxies. However, the ability to implement a method code without
producing a function is a desirable secondary benefit
Allen
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Till Schneidereit <mailto:[email protected]>
September 10, 2013 10:48 AM
On Tue, Sep 10, 2013 at 11:11 AM, Allen Wirfs-Brock
<[email protected] <mailto:[email protected]>> wrote:
> Having to create a new bound function on every method call seems
too expensive.
Only for proxy method calls, and it's easily optimized away in the
default case (i.e. there is no .getMethod handler method).
(As an aside, exchanges like the above have gotten so frequent they
are beginning to feel a bit pro forma. I don't mean to sweep all
performance concerns into one pile here.)
> But what about:
>
> 6. Let method = O.[[Get]](P).
> 7. ReturnIfAbrupt(method).
> 8. If IsCallable(method) is false, throw a TypeError.
> 9. Return O.[[InvokeFunction]](method,O, args).
>
> Using [[InvokeFunction]] the Proxy still mediates the [[Call]]
to method but it is assume the [[Get]] step has already been
performed and has produced method.
This is appealing. There are a few things [[GetMethod]] can do that
this can't: [[InvokeFunction]] can't be used to make a proxy that
mimics the behavior of __noSuchMethod__, for example. I don't think it
can mimic ActionScript 3 Proxy.callMethod either.
If [[InvokeFunction]] is deemed powerful enough, I'm all for it.
Wasn't a major point in favor of having an [[Invoke]] trap that it
wouldn't require returning a function from the trap at all? We'd lose
this quality with both of these proposals.
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Jason Orendorff <mailto:[email protected]>
September 10, 2013 10:45 AM
On Tue, Sep 10, 2013 at 11:11 AM, Allen Wirfs-Brock
<[email protected]> wrote:
Having to create a new bound function on every method call seems too expensive.
Only for proxy method calls, and it's easily optimized away in the
default case (i.e. there is no .getMethod handler method).
(As an aside, exchanges like the above have gotten so frequent they
are beginning to feel a bit pro forma. I don't mean to sweep all
performance concerns into one pile here.)
But what about:
6. Let method = O.[[Get]](P).
7. ReturnIfAbrupt(method).
8. If IsCallable(method) is false, throw a TypeError.
9. Return O.[[InvokeFunction]](method,O, args).
Using [[InvokeFunction]] the Proxy still mediates the [[Call]] to method but it
is assume the [[Get]] step has already been performed and has produced method.
This is appealing. There are a few things [[GetMethod]] can do that
this can't: [[InvokeFunction]] can't be used to make a proxy that
mimics the behavior of __noSuchMethod__, for example. I don't think it
can mimic ActionScript 3 Proxy.callMethod either.
If [[InvokeFunction]] is deemed powerful enough, I'm all for it.
-j
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Allen Wirfs-Brock <mailto:[email protected]>
September 10, 2013 9:11 AM
Having to create a new bound function on every method call seems too
expensive. But what about:
6. Let method = O.[[Get]](P).
7. ReturnIfAbrupt(method).
8. If IsCallable(method) is false, throw a TypeError.
9. Return O.[[InvokeFunction]](method,O, args).
Using [[InvokeFunction]] the Proxy still mediates the [[Call]] to
method but it is assume the [[Get]] step has already been performed
and has produced method.
Allen
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