On Jul 10, 2008, at 1:58 PM, Allen Wirfs-Brock wrote:
Maybe, I’m missing something subtle, but 21 is clearly the right
answer and is what I believe is specified by the version of section
10 that I sent out yesterday regardless of the scoping of block
nested functions. Of course, that’s just spec-ware…
21 is the right answer, I agree. But it requires reifying what could
otherwise be lexical bindings the compiler tracks and then throws
away, just so the compiler invoked by eval can see the bindings
again. It's true that catch variables also need this kind of
infrastructure, and named function expressions. So you could argue
"in for a penny, ...". But block-scoped const in ES3.1, without let
or function, is kind of half-a-pound, if you get my meaning. All the
implementation cost, half the utility.
/be
From: [EMAIL PROTECTED] [mailto:es4-discuss-
[EMAIL PROTECTED] On Behalf Of Brendan Eich
Sent: Thursday, July 10, 2008 1:45 PM
To: Mark S. Miller
Cc: [EMAIL PROTECTED]; [email protected]; Herman Venter
Subject: Re: Update on ES3.1 block scoped function declarations
On Jul 10, 2008, at 1:28 PM, Mark S. Miller wrote:
On Thu, Jul 10, 2008 at 11:05 AM, Brendan Eich
<[EMAIL PROTECTED]> wrote:
So what would this program print in ES3.1?
const C = 42;
function f(x, y) {
const C = 33;
if (x) {
const C = 21;
return eval(y);
}
return C;
}
print(f(true, "C"));
21
What does it print in ES4-opt-in?
Call it ES4, please. There's no point in playing games about opt-
in, since we know we can't "break the web". ES3 added new syntax,
so did ES2. No one bugged out about "opt-in".
21 is the right answer, although reflecting lexical blocks into
something eval can see is a big pain (we did this in Firefox 2).
It's a lot of work just for block-scoped const. Sorry if I missed
the discussion, but was restricting const to top level considered?
/be
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