'function *' is not mandatory

Brendan Eich brendan at mozilla.com
Sat Aug 31 12:58:31 PDT 2013


Let's not go in circles -- the primary reason for function* is because 
yield is not reserved in JS and is used by web content as a plain 
identifier. It is a low-precedence unary prefix operator, so cannot be 
contextually reserved by a grammatical restriction as "module" can. It 
needs opt-in syntax.

Separately, some on TC39 want a flag on the function, in the head 
syntax, to alert readers to the generator. That's a secondary reason, 
independent and not as strong in my view.

There's nothing to "get" or "not get" about backward compatbility. It 
just "is". :-|

/be

> Yuichi Nishiwaki <mailto:yuichi.nishiwaki at gmail.com>
> August 31, 2013 12:55 PM
> I can't get the point, why you need to know if the function is a
> generator or not at a glance?
>
> 1. Forcing users to mark the function as a generator is only a
> duplication. It basically doesn't have any meaning other than
> double-checking, and fundamental risk for the unintentional creation
> is still not removed.
> 2. Even if you know the function is a generator in early, you still
> need to read the entire source code to get the information about what
> the generator yields and when it stops.
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>
> Oliver Hunt <mailto:oliver at apple.com>
> August 31, 2013 12:25 PM
> On Aug 31, 2013, at 12:15 PM, Yuichi Nishiwaki<yuichi.nishiwaki at gmail.com>  wrote:
>
>> Hi all, I just found a post that the current generator syntax
>> (function *) seems have decided in:
>>
>> https://mail.mozilla.org/pipermail/es-discuss/2011-July/015799.html
>>
>> According to the post, the biggest reason the star syntax is adopted
>> for now is that you cannot write empty generators with star-less
>> functions in a consistent simple way. But the situation has changed,
>> and in the current spec (rev 17) yield* is now capable of taking any
>> kind of iterator, so you can make empty generators just like
>>
>> ```js
>> function * () {
>>     yield * [];
>> }
>> ```
>>
>> This looks enough good and simple at least to me. And I wonder if even
>> now generators still need to be declared with 'star's. What are the
>> advantages of 'star'ed generators rather than 'star'-lesses? If not
>> exist, shouldn't it be removed (for the simplicity)?
>>
>
> The reason for the * is substantially (IIRC) to make it possible for an engine
> to help prevent developers from unintentionally creating a generator function,
> and to make it possible for someone attempting to use a function to identify immediately
> whether it is a generator or a regular function.
>
> --Oliver
>
>> Thank you.
>>
>> --
>> Yuichi Nishiwaki
>> _______________________________________________
>> es-discuss mailing list
>> es-discuss at mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>
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> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
> Yuichi Nishiwaki <mailto:yuichi.nishiwaki at gmail.com>
> August 31, 2013 12:15 PM
> Hi all, I just found a post that the current generator syntax
> (function *) seems have decided in:
>
> https://mail.mozilla.org/pipermail/es-discuss/2011-July/015799.html
>
> According to the post, the biggest reason the star syntax is adopted
> for now is that you cannot write empty generators with star-less
> functions in a consistent simple way. But the situation has changed,
> and in the current spec (rev 17) yield* is now capable of taking any
> kind of iterator, so you can make empty generators just like
>
> ```js
> function * () {
> yield * [];
> }
> ```
>
> This looks enough good and simple at least to me. And I wonder if even
> now generators still need to be declared with 'star's. What are the
> advantages of 'star'ed generators rather than 'star'-lesses? If not
> exist, shouldn't it be removed (for the simplicity)?
>
> Thank you.
>
> --
> Yuichi Nishiwaki
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>


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