Re: The ES6 iteration protocol

[Brendan Eich]

Axel Rauschmayer wrote:

There are two different aspects:

1. If you get an iterable, it sometimes matters whether iteration 
restarts when you ask the iterable for an iterator.


Rather, if you have an object o and o[Symbol.iterator]() === o then you 
have an iterator.


2. Self-iterability is how iterators turn themselves into iterables so 
that constructs that work with iterables can be used. It also enables 
generators to play two roles: generator methods can implement 
`[Symbol.iterator]` and generator functions can implement 
iterable-returning functions.


I'm not clear on what 2 means. Generator functions definitely return 
generator-iterators when called. A generator function gf does not have a 
gf[Symbol.iterator] property, though.


In this particular case, I’m interested in #1. I probably have to come 
up with a better term for it.


Yes, "singleton" is the wrong word. Perhaps you want "iterator"? :-P

/be
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Re: The ES6 iteration protocol

[Axel Rauschmayer]

There are two different aspects:

1. If you get an iterable, it sometimes matters whether iteration restarts when 
you ask the iterable for an iterator.
2. Self-iterability is how iterators turn themselves into iterables so that 
constructs that work with iterables can be used. It also enables generators to 
play two roles: generator methods can implement `[Symbol.iterator]` and 
generator functions can implement iterable-returning functions.

In this particular case, I’m interested in #1. I probably have to come up with 
a better term for it.



> On 06 Apr 2015, at 23:30, Dmitry Soshnikov  wrote:
> 
> Exactly, that's what I tried to explain. Since in one case it considers just 
> an iterable (an array), and in other case -- an iterator (which is by 
> "coincidence" is also an iterable). But an array's iterator is an iterable as 
> well, and also always returns itself for iterator protocol.
> 
> Yeah, the "self-iterable" makes much more sense in this case.
> 
> Dmitry
> 
> On Monday, April 6, 2015, Allen Wirfs-Brock  > wrote:
> 
> > On Apr 6, 2015, at 2:23 PM, Dmitry Soshnikov  > > wrote:
> >
> > I guess all built-in iterators return themselves for `Symbol.iterator` 
> > protocol. So they are all "singletons". I described in detail where 
> > confusion/substitution of concepts happens in that analysis in the recent 
> > two comments.
> >
> 
> I don’t think “singleton” is the correct term for the concept that Axel is 
> trying to describe.  A “singleton” is normally an kind of object for which 
> there is only a single instances.  There may be many instances of, for 
> example %ArrayIterator%, so it isn’t correct to call %ArrayIterator% a 
> singleton
> 
> What Axel is describing might be characterized as “self iterable”, it returns 
> itself when recieving a Symbol.iterator request.
> 
> Allen
> 
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Dr. Axel Rauschmayer
a...@rauschma.de
rauschma.de



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Re: The ES6 iteration protocol

[Dmitry Soshnikov]

Exactly, that's what I tried to explain. Since in one case it considers
just an iterable (an array), and in other case -- an iterator (which is by
"coincidence" is also an iterable). But an array's iterator is an iterable
as well, and also always returns itself for iterator protocol.

Yeah, the "self-iterable" makes much more sense in this case.

Dmitry

On Monday, April 6, 2015, Allen Wirfs-Brock  wrote:

>
> > On Apr 6, 2015, at 2:23 PM, Dmitry Soshnikov  > wrote:
> >
> > I guess all built-in iterators return themselves for `Symbol.iterator`
> protocol. So they are all "singletons". I described in detail where
> confusion/substitution of concepts happens in that analysis in the recent
> two comments.
> >
>
> I don’t think “singleton” is the correct term for the concept that Axel is
> trying to describe.  A “singleton” is normally an kind of object for which
> there is only a single instances.  There may be many instances of, for
> example %ArrayIterator%, so it isn’t correct to call %ArrayIterator% a
> singleton
>
> What Axel is describing might be characterized as “self iterable”, it
> returns itself when recieving a Symbol.iterator request.
>
> Allen
>
>
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Re: The ES6 iteration protocol

[Allen Wirfs-Brock]

> On Apr 6, 2015, at 2:23 PM, Dmitry Soshnikov  
> wrote:
> 
> I guess all built-in iterators return themselves for `Symbol.iterator` 
> protocol. So they are all "singletons". I described in detail where 
> confusion/substitution of concepts happens in that analysis in the recent two 
> comments.
> 

I don’t think “singleton” is the correct term for the concept that Axel is 
trying to describe.  A “singleton” is normally an kind of object for which 
there is only a single instances.  There may be many instances of, for example 
%ArrayIterator%, so it isn’t correct to call %ArrayIterator% a singleton

What Axel is describing might be characterized as “self iterable”, it returns 
itself when recieving a Symbol.iterator request.

Allen

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Re: The ES6 iteration protocol

[Dmitry Soshnikov]

I guess all built-in iterators return themselves for `Symbol.iterator`
protocol. So they are all "singletons". I described in detail where
confusion/substitution of concepts happens in that analysis in the recent
two comments.

Dmitry

On Mon, Apr 6, 2015 at 1:07 PM, joe  wrote:

> Regardless of what the spec says, you cannot avoid singleton iterators in
> real-world code.  In my opinion, the spec should refrain from specifying
> when object creation happens within the iteration protocol, wait for the
> relevant code and contract patterns to develop and then include something
> in ES7.
>
> On Sun, Mar 29, 2015 at 12:08 AM, Dmitry Soshnikov <
> dmitry.soshni...@gmail.com> wrote:
>
>> Good write up, although "fresh vs singleton" topic doesn't make sense,
>> and doesn't reflect the spec. I responded on the gist.
>>
>> Dmitry
>>
>> On Sat, Mar 28, 2015 at 4:41 AM, Axel Rauschmayer 
>> wrote:
>>
>>> FWIW: I have written down my understanding of the ES6 iteration protocol
>>> (shaped by discussions I had on this mailing list).
>>>
>>> https://gist.github.com/rauschma/73e5f86a595b7709f39e
>>>
>>> --
>>> Dr. Axel Rauschmayer
>>> a...@rauschma.de
>>> rauschma.de
>>>
>>>
>>>
>>>
>>> ___
>>> es-discuss mailing list
>>> es-discuss@mozilla.org
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>>>
>>>
>>
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>
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Re: The ES6 iteration protocol

[joe]

Regardless of what the spec says, you cannot avoid singleton iterators in
real-world code.  In my opinion, the spec should refrain from specifying
when object creation happens within the iteration protocol, wait for the
relevant code and contract patterns to develop and then include something
in ES7.

On Sun, Mar 29, 2015 at 12:08 AM, Dmitry Soshnikov <
dmitry.soshni...@gmail.com> wrote:

> Good write up, although "fresh vs singleton" topic doesn't make sense, and
> doesn't reflect the spec. I responded on the gist.
>
> Dmitry
>
> On Sat, Mar 28, 2015 at 4:41 AM, Axel Rauschmayer 
> wrote:
>
>> FWIW: I have written down my understanding of the ES6 iteration protocol
>> (shaped by discussions I had on this mailing list).
>>
>> https://gist.github.com/rauschma/73e5f86a595b7709f39e
>>
>> --
>> Dr. Axel Rauschmayer
>> a...@rauschma.de
>> rauschma.de
>>
>>
>>
>>
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>>
>
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Re: The ES6 iteration protocol

[Dmitry Soshnikov]

Good write up, although "fresh vs singleton" topic doesn't make sense, and
doesn't reflect the spec. I responded on the gist.

Dmitry

On Sat, Mar 28, 2015 at 4:41 AM, Axel Rauschmayer  wrote:

> FWIW: I have written down my understanding of the ES6 iteration protocol
> (shaped by discussions I had on this mailing list).
>
> https://gist.github.com/rauschma/73e5f86a595b7709f39e
>
> --
> Dr. Axel Rauschmayer
> a...@rauschma.de
> rauschma.de
>
>
>
>
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>
>
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The ES6 iteration protocol

[Axel Rauschmayer]

FWIW: I have written down my understanding of the ES6 iteration protocol 
(shaped by discussions I had on this mailing list).

https://gist.github.com/rauschma/73e5f86a595b7709f39e

-- 
Dr. Axel Rauschmayer
a...@rauschma.de
rauschma.de



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