(Almost) everything is expression

David Herman dherman at mozilla.com
Fri Nov 11 09:13:54 PST 2011


On Nov 11, 2011, at 8:19 AM, Mark S. Miller wrote:

> On Fri, Nov 11, 2011 at 7:40 AM, gaz Heyes <gazheyes at gmail.com> wrote:
> On 11 November 2011 15:33, Mark S. Miller <erights at google.com> wrote:
> let a = ({
> 
>  print('doing stuff');
>  100;
> });
> 
> How do you know the difference between a blank block statement and a object literal? Surely it becomes an expression once an assignment occurs anyway. 
> 
> Doh! Sorry, I completely mis-thought that. Nevermind.

Your idea of mandatory parens is still valid (if, IMO, a bit unsatisfyingly verbose) for most statement forms. It's only the block-statement-expression that doesn't work. Hence my do-expressions:

    http://wiki.ecmascript.org/doku.php?id=strawman:do_expressions

or Brendan's subtly-disambiguated-block-statement-expressions:

    http://wiki.ecmascript.org/doku.php?id=strawman:block_vs_object_literal

If Brendan's idea can be made to work, and it's not too confusing, I'm pretty sure I'd prefer it over do-expressions. You could simply write:

    let a = {
        print('doing stuff');
        100
    };

How gorgeous is that?

But I suspect as we work on evolving the syntax of object literals, it'll get harder to keep them disambiguated. For example, is this:

    let a = {
        foo(x)
        {
            alert(x)
        }
    }

...equivalent to this?

    let a = {
        foo: function(x)
        {
            alert(x);
        }
    };

...or this?

    let a = {
        foo(x);
        {
            alert(x);
        }
    };

So I just don't know if it's feasible.

Dave

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