Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:62090
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain ajf.me designates 64.22.89.133 as permitted sender)
Message-ID: <5022D22B.9050906@ajf.me>
Date: Wed, 08 Aug 2012 21:55:07 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:14.0) Gecko/20120714 Thunderbird/14.0
MIME-Version: 1.0
To: Stas Malyshev <smalyshev@sugarcrm.com>
CC: Nikita Popov <nikita.ppv@gmail.com>, 
 PHP internals <internals@lists.php.net>
References: <CAF+90c_47HtYHnMztUUb7Gd5_gKhpJYJN=G-KJFSmSt_=w2+Lw@mail.gmail.com> <50108D60.9090509@sugarcrm.com> <CAF+90c-w_1H8Raq90AzM3B7Fw67Ss-dCOi-8p_KxkGVj8-T9rA@mail.gmail.com> <CAF+90c936qah8bsBzdZh3Q_oPe2wvyp0AzZUwDa_Y+PoJ0wayg@mail.gmail.com> <5022CF62.7060705@sugarcrm.com>
In-Reply-To: <5022CF62.7060705@sugarcrm.com>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [PHP-DEV] Generators in PHP
From: ajf@ajf.me (Andrew Faulds)

On 08/08/12 21:43, Stas Malyshev wrote:
> Hi!
>
>
>> https://wiki.php.net/rfc/generators#yield_keyword
>> https://wiki.php.net/rfc/generators#sending_values
> I'm not sure $data = (yield $value) makes a lot of sense. Why we have
> two variables here? Why it is only operator in the language that
> requires parentheses around? All these complex parentheses rules seem
> unnecessarily complicated. I'd rather do it in a more simple way: yield
> in an expression means incoming yield. I.e.:
> $data = yield;
> foo(yield, 1, 2);
> list($a, $b) = yield;
>
> Same with:
> call(yield $value) - what is the meaning of $value here? Why not just
> call(yield)?
>
> I would also not support array((yield $key => $value)) - it seems to be
> really unclear how it works. I'd just have yield produce a value which
> was sent, and that's it, and you could use this value in the same way
> you'd use any other expression.
>
> Only question I have here is what happens if you use yield in the middle
> of function call expression, for example:
> call(foo(bar(), $foo, yield, 3), baz());
>
> We are kind of stopping the function in the middle of the function call
> and going to unrelated code here, and may never return back. Where the
> required cleanups, etc. should happen?
>
> Another question is, if my function is like this:
> function foo()
> {
> 	var_dump(yield);
> }
>
> And I do: foo()->current() - what happens? Do I get null there? What
> happens if after that I do send() on the same generator? In general,
> interaction between incoming and outgoing yields is not very clear,
> especially what happens when you combine them.
>
> Also, small point: yield is repeatably called "statement" in the doc,
> but in fact it can be both statement and expression with returning yield.
>
Hmm. This is just a quick thought:

Considering the yield syntax will vary about needing () round it, why 
not make it a "fake" function (language construct).

This way it's consistent: yield(), yield($v), yield($k => $v), $a = 
yield(), etc.

(yield $x) is just messy as an expression. We don't have (isset $x), we 
have isset($x).

-- 
Andrew Faulds
http://ajf.me/