Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:81000
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: error (pb1.pair.com: domain garfieldtech.com from 66.111.4.27 cause and error)
Message-ID: <54C1807E.2050004@garfieldtech.com>
Date: Thu, 22 Jan 2015 16:58:06 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0
MIME-Version: 1.0
To: internals@lists.php.net
References: <CANUQDCgq5hPEk=dMg8enSLrxAdmLqHRJoKXB0rkhNff+KbaUag@mail.gmail.com> <CALrkBjY-aFOOLPbyrsRqaeqLV9EDZw0gTq7RE5fAM4Q=WrU0fQ@mail.gmail.com> <54BE7749.2010603@gmail.com>
In-Reply-To: <54BE7749.2010603@gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [PHP-DEV] in Operator
From: larry@garfieldtech.com (Larry Garfield)

On 01/20/2015 09:42 AM, Rowan Collins wrote:
> Mike Willbanks wrote on 20/01/2015 03:30:
>> I am very familiar with the in operator. However,  the implementation
>> would be incomplete without handling loops via the in operator. Many
>> people when seeing an in operator also think of JavaScript.  In that 
>> case
>> the in operator iterates over properties.  As such in PHP we should 
>> be able
>> to iterate over associative arrays should the syntax be added.
>> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in 
>>
>
> I don't really see how this is related to the in operator, other than 
> that some languages reuse the same keyword for both purposes.
>
> My immediate association when I saw this proposal was not "ah, like 
> the loop syntax in JavaScript", but "ah, like the IN() operator in SQL".
>
> Given the ability to write foreach ( $foo as $key => $value ), I'm not 
> sure adding a variant syntax of for ( $key in $foo ) has that much 
> value for PHP.
>
> Regards,

I like the idea of a boolean IN.  If nothing else it would simplify the 
common cases for strpos and in_array() and friends.  I agree that 
leaving out for/foreach is a good idea as that's a different thing that 
would just so happen to use the same new reserved word. That's fine; 
"use" became reserved for namespaces and then was reused for traits 
without incident.

However, we should also ask what happens with objects.  I've seen a lot 
of people trying to push toward collection objects rather than plain 
arrays for a variety of reasons, and of course we run smack into the 
"PHP has all of these cool array-manipulation functions that are almost 
great for functional programming but don't work on iterators, ah crap" 
problem.

So what would the following do:

$o = new stdclass;
$o->a = 'b';
$o->c = 'd';

print 'a' in $o;

print 'b' in $o;

Or more to the point:

$a = new ArrayObject(['a', 'b', 'c']);
print 'c' in $a;

There are likely lots of implementation details around making it work, 
but it would be lovely if at least some collection objects could support 
IN.  Perhaps an Innable interface? :-)  (Which then an iterator could 
also implement if it made logical sense for it to do so, which is not 
always the case.)

--Larry Garfield