> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
> Behalf Of Jon Zeppieri
> Sent: 3. april 2008 10:10
> To: Lars Hansen
> Cc: [email protected]
> Subject: Re: Strict mode recap
>
> On Wed, Apr 2, 2008 at 11:15 PM, Lars Hansen
> <[EMAIL PROTECTED]> wrote:
> > >
> > > Is this already in AS3? If so, is it often used?
> >
> > The syntax comes from E4X, which is incorporated into AS3 and
> > Spidermonkey. Try this in Firefox:
> >
> > <script type="text/javascript;e4x=1">
> > var x = <ns:p xmlns:ns="http://www.opera.com/";><ns:q>Hi
> > there</ns:q></ns:p>
> > var ns = new Namespace("http://www.opera.com/";);
> > var em = "q"
> > document.writeln(x.ns::[em]);
> > </script>
>
> I'm aware of E4X. I meant: is it possible to refer to
> lexical bindings in this manner in AS3?
Yes. AS3 has an annoying restriction on where
user-defined namespaces may be used, but the
following example captures it without using E4X:
package X {
namespace myns;
class C {
myns var v = 37;
}
var x = myns;
var y = "v";
print((new C).x::[y]);
}
This does print '37' if compiled with ASC and run through
the Tamarin VM.
> I guess I don't see what use case is satisfied by this
> feature that isn't already met by the existence of Map.
>
> After all, the effect of this feature is to turn lexical
> environments into (quasi) first class maps, with the peculiar
> restriction that new name/value pairs cannot be added, though
> existing ones can be mutated. If a user actually needs that
> functionality, it wouldn't be difficult to subclass Map to get it.
>
> And, yes, I know it's already possible to do this with
> lexically scoped eval. But why do you want to add another
> way to do it?
Let me turn it around.
The syntax ns::v is in the language, for constant identifier v.
If E4X is implemented in an implementation (as it will be in
ActionScript and presumably in Firefox, at least), so is
ns::[expr]. How would a restriction to require ns to be a
compile-time constant (in either form) and not a run-time
value, or a restriction to disallow the latter form in ES4
but not in E4X, benefit ES4?
--lars
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