> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Jon Zeppieri > Sent: 2. april 2008 20:51 > To: Lars Hansen > Cc: [email protected] > Subject: Re: Strict mode recap > > On 4/2/08, Lars Hansen <[EMAIL PROTECTED]> wrote: > > > > > > I meant something like: > > > > > > var foo::[bar] = baz; > > > > > > My objection to expr::[expr] in earlier messages was based on > > > the assumption that these computed names could be used on the > > > left-hand side of an assignment expression -- which, I'm > pretty > > sure, is syntactically valid. > > > > > > But that by itself can't introduce bindings (except global ones). > > I didn't know that, but I'm happy to hear it. I figured, > from the syntactic form alone, that: > > var foo::[bar] = ... > > ... would introduce a function-local binding (if the name > wasn't already bound) -- since that's what var normally does.
That form is not allowed, to my knowledge. If the grammar allows it then this could be (a) a bug or (b) missing semantic constraints. > > If you want to introduce a new binding then you have to do eg > > > > ns var x = E > > > > to introduce ns::x, and ns has to reference a namespace > definition, > > so it's not variable. Nor is the x, obviously. > > Good. But then why allow: > > var expr::[expr] = ... > > ... at all? It's not. > (I'm specifically referring to the fact that 'var' > appears before the name.) I understand that. > This has the syntactic form of a > definition, but it can't actually be one, according to what > you've written. It could only be an assignment. (Okay, I > guess it could introduce a property on the global object, but > that's already a special case and doesn't require definition syntax.) It should be illegal. > > But in that case: > > > > var v1 = ns > > var v2 = "x" > > v1::[v2] = 20 > > > > updates ns::x, AFAIK. Nothing you can't do with lexically scoped > > eval. > > That, by itself, isn't exactly an selling point; no one likes > lexically scoped eval. I would say that "almost no one likes lexically scoped eval, almost all of the time". :) And the main reasons to dislike it are that it can introduce bindings and that it is invisible (if implemented like in Firefox, which is not required by ES3). > I find computed names less objectionable now that I know > local bindings can't be introduced by them. (I thought that > shadowing could occur, which wouldn't be detectable until > runtime. Of course, that is true of 'with' -- but, again, > hardly a selling point.) Can't say I'd be sorry if they were > removed from the language, though. > > 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> --lars _______________________________________________ Es4-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es4-discuss
