Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:49720
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.214.42 as permitted sender)
DomainKey-Status: bad
DomainKey-Signature: a=rsa-sha1; c=nofws;
        d=gmail.com; s=gamma;
        h=message-id:date:from:user-agent:mime-version:to:subject:references
         :in-reply-to:content-type:content-transfer-encoding;
        b=dVsMZFdm+0Ie+pB6clqGyi+KM1aQA/JD4BHQV8FW28Ta/zyGHMhcL8txYfFcFlRSY7
         7R/KwnZtnPRJ4x7VCnJMQX7PYcEdcIPOFJohjUUzlXheMATRj8ABITbDT9vrsVCn+0eN
         mDfWyFHW2WKzSPUm+ww3u7CO32owLpGYbcjP0=
Message-ID: <4C926083.605@gmail.com>
Date: Thu, 16 Sep 2010 21:22:59 +0300
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.6; en-US; rv:1.9.2.9) Gecko/20100825 Thunderbird/3.1.3
MIME-Version: 1.0
To: internals@lists.php.net
References: <39505F13-655A-43AF-941E-77750B7F7201@gmail.com>	<4C8FC695.2060800@sugarcrm.com>	<AANLkTimOaicMidzH8oYWcieaCyx2bLefPGkXGQDZPQ6Y@mail.gmail.com>	<4C8FD72B.1070108@sugarcrm.com>	<AANLkTimEMdn6Z64O0Jt9KYEdHfDRa0iLt5eh1D16i_st@mail.gmail.com>	<4C906333.4030204@sugarcrm.com>	<7.0.1.0.2.20100915085504.17eab4d8@zend.com>	<12617cf66ae07d7a2fd79a293ed69b85@beberlei.de>	<4C9095D5.1050206@toolpark.com>	<AANLkTik0H9RWyE0vxtGTjnpvVKHGRtkcF2Rte1HkZWqF@mail.gmail.com>	<000001cb5511$467949f0$d36bddd0$@com>	<AANLkTimaXnTa=DXKjgc+fC-WeQ1zmb8fm-YM_Y4xf3cw@mail.gmail.com>	<AANLkTikxp334TDT1WHu0xf-DmpNAK0X+iZ+eA755M0kf@mail.gmail.com>	<AANLkTimUUQWr5HnWLM1aYuZnrCzqoQXM-GTmpBOs51Ni@mail.gmail.com>	<64b4e95cac44ee297a12601d26a5453c@localhost>	<AANLkTin52bJB34XoL09q18VRxg7o4iYHrQC_UBxwCCbQ@mail.gmail.com>	<AANLkTikg0v-53WN0Bs2wZYsjx+uf=nVQXqOVFzSB9mXQ@mail.gmail.com> <AANLkTimD0DgoxWzHLUFirJAXERYE689v6nipLRNX22nz@mail.gmail.c om> <4C9258C1.9080207@sugarcrm.com>
In-Reply-To: <4C9258C1.9080207@sugarcrm.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Subject: Lambdas assigned to constants. Was PHP Annotations RFC + Patch
From: ionut.g.stan@gmail.com ("Ionut G. Stan")

On 16/Sep/10 8:49 PM, Stas Malyshev wrote:
> No, we can't have python decorators because unlike Python PHP functions
> and classes aren't first-class objects. In Python, this:
>
> @dec2
> @dec1
> def func(arg1, arg2, ...):
> pass
>
> means this:
>
> def func(arg1, arg2, ...):
> pass
> func = dec2(dec1(func))
>
> However, you can't write equivalent code in PHP.

I had the same idea regarding decorators, and I saw the same problem 
that you see, functions are not first-class citizens in PHP. I was 
wondering, though, whether the possibility to assign expressions to 
constants couldn't change that. Let me explain a little what I'm 
thinking exactly.

Currently, PHP supports lambda expressions and they're pretty much as 
first-class citizens as possible. PHP, also supports variable functions 
in an attempt to make global functions look like they'd be first-class 
citizens.

So, the following snippet isn't yet working, but AFAIK it will work in 
the next PHP release:


function foo() {
     echo "foo was called";
}

function bar() {
     return 'foo';
}

bar()(); // prints "foo was called";


Now, assume I define this constant:

define('foo', 'foo');

Now I can write:


function bar() {
     return foo;
}

And the "foo" function will look more like a first-class citizens.
But, how about being able to write:

const foo = function () use ($globalVar) {

};

which would be the desugaring of:

function foo () {
     global $globalVar;
}

Now foo would be an instance of Closure, and would allow us to pass it 
around free.


Does that make any sense to any of you? Is it at least possible with the 
current Zend Engine implementation? What problems would it pose?


Getting back to decorators...

Having the above syntax, we would be able to write:

const func = dec2(dec1(function () {

}));

which can be further sugared to some decorator specific syntax.


I guess the gist of my whole email is that it would be nice to get rid 
of the dollar sign in identifiers that designate lambda expressions. 
That would somehow level things up.

-- 
Ionuț G. Stan  |  http://igstan.ro