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Date: Wed, 26 Feb 2020 16:51:56 +0000
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To: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Support rewinding of generators
From: rowan.collins@gmail.com (Rowan Tommins)

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On Wed, 26 Feb 2020 at 15:23, Nikita Popov <nikita.ppv@gmail.com> wrote:

> Point of order: foreach() always rewinds the array / Iterator it gets. The
> code does work correctly under the proposed scheme.
>


Ah, I'd missed that, sorry; that makes the entire first half of my e-mail
irrelevant. :)


The proposed behaviour is actually closer to current behaviour than I
thought, because the initial code before the first yield actually runs when
you first rewind the iterator:

function foo() {
    echo 'Begin';
    yield 42;
}
$f = foo(); // Doesn't echo yet
$f->rewind(); // Now echoes 'Begin'

$f2 = foo();
foreach ( $f2 as $x ) {
    // echoes 'Begin' before first loop
    echo $x;
}


Just to check, would the proposed behaviour still special-case a generator
which hasn't been progressed?

$f = foo();
$f->rewind(); // echoes 'Begin'
$f->rewind(); // this would still do nothing?
$f->next();
$f->rewind(); // this currently throws an error, and would echo 'Begin'
again?



Regards,
-- 
Rowan Tommins
[IMSoP]

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