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Message-ID: <e666c3890808031503v5a966b75y4d81c750b43b64b7@mail.gmail.com>
Date: Mon, 4 Aug 2008 00:03:01 +0200
Sender: ekneuss@gmail.com
To: "PHP Internals List" <internals@lists.php.net>, 
	"Marcus Boerger" <helly@php.net>
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References: <e666c3890808021036p58de549as422bec8471b7a992@mail.gmail.com>
Subject: Re: __invoke concerns
From: colder@php.net ("Etienne Kneuss")

Hello,

On Sat, Aug 2, 2008 at 7:36 PM, Etienne Kneuss <colder@php.net> wrote:
> Hi,
>
> this is probably not the best time to raise concerns about __invoke
> (closures) now that alpha1 is already realeased, but I believe it's
> worth it.
>
> 1) I don't believe that having it thrown as another of those magic
> method is a good idea. Rather, I'd like to have it represented by an
> interface: Invokable. That way, type hints/checks can be done in user
> land in a sane matter:
>
> function foo(Invokable $obj) {
>    $obj();
> }
>
> if ($foo instanceof Invokable) $foo();
>
> etc..
>
> 2) Do we really want __invoke's argument to be mapped to caller
> arguments. Providing an array of arguments, ala __call(Static) sounds
> more consistent.
> class A { public function __invoke($arg) {var_dump($arg); }} $a = new
> A; $a(1,2); // int(1), currently. IMHO it should be array(1,2)
>
>
> 3) Do we really want to allow both static and non-static versions of __invoke ?
> class A { public static function __invoke($args) { .. }} $a = new A;
> $a(); being a static call to __invoke doesn't make much sense to me.
>
>
> I hope these issues can be discussed and maybe addressed before a
> final 5.3 release. I'm willing to do patches for all three concerns if
> I sense a positive feeling towards this.
>
> Regards,
>
> --
> Etienne Kneuss
> http://www.colder.ch
>
> Men never do evil so completely and cheerfully as
> when they do it from a religious conviction.
> -- Pascal
>

After looking deeper into it, I noticed that this interface brings a
lot of problems:

1) With the interface, the prototype is fixed.
Which means that the following are no longer possible:

Class A {
public function &__invoke(&$a, $b, $c) { return $a; }
}
$a = new A; $e =& $a($b,$c, $d);

2) __invoke($args) seems more consistent, and would give a consistent
prototype, but
2.1) references are no longer possible (1)
2.2) __invoke of actual closures/lambdas needs to map parameters for
$a = function($b,$c){}; to work properly. I don't believe $cl =
function($args){..} is something we want

So, with those counter-concerns in mind, this Invokable interface is
no longer implementable, IMO.

However, I'd still like to make closures more flexible and
internals-friendly by implementing zend_get_closure as a handler.
The only (tiny) issue here is that we export a bit more
closure-material in the engine, and it's no longer so much
self-contained in zend_closures.

Patches:
http://patches.colder.ch/Zend/zend_get_closure_handler_53.patch?markup
http://patches.colder.ch/Zend/zend_get_closure_handler_HEAD.patch?markup

ps: this patches also expose the __invoke method for reflection. (Or
is there an actual reason behind not exposing it? )
-- 
Etienne Kneuss
http://www.colder.ch

Men never do evil so completely and cheerfully as
when they do it from a religious conviction.
-- Pascal