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Date: Wed, 8 Jun 2011 12:17:38 +0200
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To: =?UTF-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>
Cc: Stas Malyshev <smalyshev@sugarcrm.com>, "Matthew Weier O'Phinney" <weierophinney@php.net>, 
	internals@lists.php.net
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Subject: Re: [PHP-DEV] Callable type
From: hannes.magnusson@gmail.com (Hannes Magnusson)

2011/6/8 Johannes Schl=C3=BCter <johannes@schlueters.de>:
> On Wed, 2011-06-08 at 10:38 +0200, Hannes Magnusson wrote:
>> 2011/6/8 Johannes Schl=C3=BCter <johannes@schlueters.de>:
>> > On Tue, 2011-06-07 at 12:12 -0700, Stas Malyshev wrote:
>> >> Hi!
>> >>
>> >> > https://wiki.php.net/rfc/callable
>> >>
>> >> It is good there's an RFC. However it seems to lack code examples. I
>> >> understand it may be obvious to the proposers how it looks like, but
>> >> it'd be nice to have the actual example there as it is done nearly
>> >> everywhere else.
>> >
>> > The RFC is missing information about what happens in codebases which
>> > already have a "callable" type declared. Will that be prevented or wil=
l
>> > they hit a runtime error? ("callable expected, callable type found")
>>
>> You mean an interface/class with that name?
>> The error would be 'expected instanceof callable, string/array/closure r=
ecieved.
>>
>> gettype("strpos") will still return a string, not callable.
>>
>> A callable wouldn't be fully featured type.
>
> Which means that
> =C2=A0 class callable { }

No. 'callable' is a parser token.



>> > What about default values? Will
>> > =C2=A0 =C2=A0function foo(callback $cb =3D 'strpos') { }
>> > be valid?
>>
>> No default values, other then NULL allowed.
>> Otherwise we would need to support array("classname", "methodname")
>> too, and then people would want default array values for array
>> typehinting etc etc etc.
>
> Ok. I assume NULL as default value would be allowed, though. This would
> be consistent for the language and allow such things:
>
> function foo(callback $cb =3D NULL) {
> =C2=A0 =C2=A0if (!$cb) {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0$cb =3D function() { /* .. default implementat=
ion */
> =C2=A0 =C2=A0}
> =C2=A0 =C2=A0....
> }

Etienne pointed out that default values for arrays can actually contain val=
ues..
I actually had no idea.

I suppose we then need to support default values for an array callable.

But yes, a callable can have the default value of null, following the
rules of class hinting.


-Hannes