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In-Reply-To: <e52c06b30910141344t183f1b92t1fe863c109751829@mail.gmail.com>
Date: Thu, 15 Oct 2009 16:42:24 +0200
Cc: Lukas Kahwe Smith <mls@pooteeweet.org>,
 Stanislav Malyshev <stas@zend.com>,
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To: Tom Boutell <tom@punkave.com>
Subject: Re: [PHP-DEV] Request for Comments: Horizontal Reuse for PHP
From: php@stefan-marr.de (Stefan Marr)

Hi:

On 14 Oct 2009, at 22:44, Tom Boutell wrote:

> I'm very concerned about the practical consequences of introducing
> traits without state.
Well, we have not found a sufficient design until now, which would fit  
nicely into PHP from dynamic and simplicity perspective.

> A. They could do this using static hashes in global variables or a
> separate class. The result is a garbage collection failure as these
> references to $this will never go away. Designed-in GC failures are
> unacceptable post PHP 5.3.
Doing this would be less than advisable.


> B. PHP allows you to define properties at runtime. That is, you can  
> write:
>
> $this->title = 'my title';
>
> Without declaring var $title; at the class level.
>
> But PHP 6 seems to be moving toward more strictness, not less, and
> this style encourages the use of undeclared variables with the
> resulting potential for missed bugs.
Thats the currently preferred approach from my perspective.
The only thing you are going to lose here is a notion of separation of  
state from different traits, compared to a language supported approach.

However, if you prefer to be more strict, it is still perfectly  
possible to circumvent this problem by using getters and setters.


> Also, the 'instead' keyword is baffling - it could mean replace A with
> B or replace B with A depending on how you place your mental comma - I
> much prefer the assignment syntax alternative, or 'insteadof' which is
> unambiguous.
Yes, that was discussed before, but unfortunately did not make it into  
the list of alternative syntaxes, will try to keep track of it.

Best regards
Stefan



>
> On Wed, Oct 14, 2009 at 4:07 PM, Lukas Kahwe Smith  
> <mls@pooteeweet.org> wrote:
>>
>> On 14.10.2009, at 22:03, Stanislav Malyshev wrote:
>>
>>> Hi!
>>>
>>>>> So lets warm this up again.
>>>>> HEAD is for development .. so lets get this into HEAD so that it  
>>>>> will be
>>>>> part of the next bigger PHP release for sure!
>>>>
>>>> Well, the code is sitting here
>>>> http://github.com/gron/php-src/tree/PHP_6-traits
>>>> and waits to be merged. :)
>>>
>>> I thought before merging code it would be useful to have some  
>>> discussion
>>> on if the code is actually doing what we want. If it's based on
>>> http://wiki.php.net/rfc/horizontalreuse then for example I can see  
>>> some
>>> potential issues for bytecode caching related to renaming and  
>>> changing
>>> visibility.
>>> Also, it is not clear that we want grafts there at all, some  
>>> aspects of
>>> them seem to get too hairy, esp. $this issue or statics.
>>>
>>
>> i think Stefan is fully aware of that probably there will be a  
>> discussion
>> first ..
>> but i think we all agree that this feature is very high on the list  
>> of what
>> people want and therefore i wanted to get this discussion going, so  
>> that
>> after its concluded traits can be commited to HEAD.
>>
>> regards,
>> Lukas Kahwe Smith
>> mls@pooteeweet.org
>>
>>
>>
>>
>> --
>> PHP Internals - PHP Runtime Development Mailing List
>> To unsubscribe, visit: http://www.php.net/unsub.php
>>
>>
>
>
>
> -- 
> Tom Boutell
> P'unk Avenue
> 215 755 1330
> punkave.com
> window.punkave.com
>
> -- 
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>

-- 
Stefan Marr
Software Languages Lab
Former Programming Technology Lab
Vrije Universiteit Brussel
Pleinlaan 2 / B-1050 Brussels / Belgium
http://prog.vub.ac.be/~smarr
Phone: +32 2 629 3956
Fax:   +32 2 629 3525