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Date: Tue, 3 Mar 2015 12:55:27 +0100
Message-ID: <CANUQDCgbwwULdxq3wCKLAqOz61yFMf1RZbhBPastgm4z=qFaQQ@mail.gmail.com>
To: Rowan Collins <rowan.collins@gmail.com>
Cc: Daniel Lowrey <rdlowrey@php.net>, "internals@lists.php.net" <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=089e01493f60ba06390510610289
Subject: Re: [PHP-DEV] [RFC Discuss] Generator Delegation
From: me@kelunik.com (Niklas Keller)

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2015-03-03 12:34 GMT+01:00 Rowan Collins <rowan.collins@gmail.com>:
>
> Niklas Keller wrote on 03/03/2015 10:55:
>>
>>  Gr, top-posting...
>
>
> Sorry, was on mobile. ;-)
>
>> However, since the existence of the word "yield" is the only thing that
>> marks a coroutine now, how about using a variant of that for the final
>> value, e.g. "yield final $foo"?
>
>
> What's the final value? The last "yield"ed value or a return?
>
>
> "yield final" would mark the final result of the coroutine, as opposed to
the intermediate values passed out with a normal "yield".
>
>
> Just to give you some real world example:
> If you're using "return", it would look like that:
>
> public function getSession ($sessionId) {
>     $result = yield $this->redis->get("session.{$sessionId}")); // We're
waiting here until redis responded.
>     return json_decode($result);
> }
>
>
> My suggestion is simply to change the keyword:
>
> public function getSession ($sessionId) {
>     $result = yield $this->redis->get("session.{$sessionId}")); // We're
waiting here until redis responded.
>     yield final json_decode($result);
> }
>
>
> The reasoning being that when you run getSession(42), it *doesn't* return
the result of json_decode(), it returns a pointer to the coroutine's state,
which you can resume later.
>
> Actually, I don't think that example makes sense, because JSON gets sent
out at the first yield, and then sent back in, so the caller would look
something like this:
>
> $foo = getSession(42);
> $json_data = $foo->current();
> $foo->send($json_data);
> $decoded = $foo->getReturn();
>
> But never mind, I think we both get the idea.
>
> I understand the desire for a "final result", but I don't like reusing
the word "return", because it's never "returned" as the result of running
the function, it's just made available through some specific method/syntax.
>
> Regards,
> --
> Rowan Collins
> [IMSoP]

$foo = getSession(42);
> $json_data = $foo->current();
> $foo->send($json_data);
> $decoded = $foo->getReturn();


Yes, it doesn't make sense if you call it directly, actually, this an
example from my chat that uses the amp-framework (
https://github.com/amphp/amp), so this isn't called directly.

To me, it isn't obvious that "yield final ..." makes the generator end, but
anyone would know if there's a "return".

Regards, Niklas

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