yield syntax (diverging from: How would shallow generators compose with lambda?)

[Brendan Eich]

On May 17, 2009, at 12:43 PM, Mark S. Miller wrote:

> On Sun, May 17, 2009 at 11:00 AM, Brendan Eich <brendan at mozilla.com>  
> wrote:
>> Analogous to direct vs. indirect eval in ES5 (15.1.2.1.1), there is  
>> no
>> purely syntactic specification for what Neil proposes. A runtime  
>> check is
>> required. So I don't see why you are focusing only on syntax here.
>
> I don't follow. What runtime check? For the eval operator, the runtime
> check is whether the value of the eval variable is the original global
> eval function. It makes no sense to have a corresponding global yield
> function value.

If we reserve yield then you're right. One of the appealing (at least  
to me) aspects of Neil's suggestion was that it would avoid opt-in  
versioning required by reserving yield (which is used in extant web  
content, or was when we tried reserving it without opt-in versioning  
-- the particular use was as a formal parameter name, used as a flag  
not a function).

/be