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Date: Wed, 26 Feb 2020 16:22:51 +0100
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To: Rowan Tommins <rowan.collins@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Support rewinding of generators
From: nikita.ppv@gmail.com (Nikita Popov)

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On Wed, Feb 26, 2020 at 4:03 PM Rowan Tommins <rowan.collins@gmail.com>
wrote:

> Hi Nikita,
>
> On 26 February 2020 11:47:14 GMT+00:00, Nikita Popov
> <nikita.ppv@gmail.com> wrote:
> >There is a relatively simple (at least conceptually) way to make
> generators
> >rewindable: Remember the original arguments of the function, and basically
> >"re-invoke" it on rewind().
>
> This is an interesting idea.
>
> There is a gotcha though, neatly demonstrated by your example:
>
> >function map(callable $function, iterable $iterable): \Iterator {
> >    foreach ($iterable as $key => $value) {
> >        yield $key => $function($value);
> >    }
> >}
>
> If the $iterable passed in is anything other than an array,
> re-invoking the function won't actually rewind it.


Point of order: foreach() always rewinds the array / Iterator it gets. The
code does work correctly under the proposed scheme.

Nikita

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