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Date: Tue, 9 Jun 2020 16:52:36 +0200
Message-ID: <CABdc3WrTZ4ONQENVOvMOTQn0V4X0cZS5OGSgS3Oi8Us9rf2kAg@mail.gmail.com>
To: Nikita Popov <nikita.ppv@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Re: Making all Traversables an Iterator or IteratorAggregate
From: michal.brzuchalski@gmail.com (=?UTF-8?Q?Micha=C5=82_Brzuchalski?=)

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wt., 9 cze 2020, 15:33 u=C5=BCytkownik Nikita Popov <nikita.ppv@gmail.com>
napisa=C5=82:

> On Tue, May 12, 2020 at 10:26 AM Nikita Popov <nikita.ppv@gmail.com>
> wrote:
>
> > On Wed, Mar 11, 2020 at 10:50 AM Nikita Popov <nikita.ppv@gmail.com>
> > wrote:
> >
> >> Hi internals,
> >>
> >> Userland classes that implement Traversable must do so either through
> >> Iterator or IteratorAggregate. The same requirement does not exist for
> >> internal classes: They can implement the internal get_iterator
> mechanism,
> >> without exposing either the Iterator or IteratorAggregate APIs. This
> makes
> >> them usable in get_iterator(), but incompatible with any Iterator base=
d
> >> APIs.
> >>
> >
> > This should have said: "This makes them usable in foreach(), but
> > incompatible with any Iterator based APIs."
> >
> > A lot of internal classes do this, because exposing the userland APIs i=
s
> >> simply a lot of work. I would like to add a general mechanism to make
> this
> >> simpler: https://github.com/php/php-src/pull/5216 adds a generic
> >> "InternalIterator" class, that essentially converts the internal
> >> get_iterator interface into a proper Iterator. Internal classes then
> only
> >> need to a) implement the IteratorAggregate interface and b) add a
> >> getIterator() method with an implementation looking like this:
> >>
> >> // WeakMap::getIterator(): Iterator
> >> ZEND_METHOD(WeakMap, getIterator)
> >> {
> >>     if (zend_parse_parameters_none() =3D=3D FAILURE) {
> >>         return;
> >>     }
> >>     zend_create_internal_iterator_zval(return_value, ZEND_THIS);
> >> }
> >>
> >> This allows internal classes to trivially implement IteratorAggregate,
> >> and as such allows us to enforce that all Traversables implement
> Iterator
> >> or IteratorAggregate.
> >>
> >
> > Does anyone have thoughts on this change? Mostly this is a feature for
> > extensions, but also user-visible in that a bunch of classes will switc=
h
> > from being Traversable to being IteratorAggregate.
> >
> > We may also want to convert some existing Iterators to
> IteratorAggregates.
> > For example SplFixedArray currently implements Iterator, which means th=
at
> > it's not possible to have nested loops over SplFixedArray. We could now
> > easily fix this by switching it to use IteratorAggregate, which will
> allow
> > multiple parallel iterators to work on the same array. Of course, there
> is
> > BC break potential in such a change.
> >
> > There's some bikeshed potential here regarding the class name. I picked
> > "InternalIterator" as an iterator for internal classes, but "internal
> > iteration" is also a technical term (the opposite of "external
> iteration"),
> > so maybe that name isn't ideal.
> >
>
> Unfortunately this bikeshed remains unpainted... The proposed names were:
>
>  1. InternalIterator
>  2. ZendIterator
>  3. IteratorForExtensionClassImplementations
>  4. EngineIterator
>
> I'm somewhat partial to the third option, with a less verbose name:
> IteratorForExtensions.
>

ExtensionsIterator??

BR,
Micha=C5=82

>

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