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Date: Tue, 10 Feb 2015 15:53:34 +0400
Message-ID: <CA+9eiLuU9FcxC5k0aK1svKeu2Ary6fGDK2cDmM7hWqRj25hiyw@mail.gmail.com>
To: Joe Watkins <pthreads@pthreads.org>
Cc: Yasuo Ohgaki <yohgaki@ohgaki.net>, Patrick Schaaf <php@bof.de>, internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=20cf307d00765da046050eba8932
Subject: Re: [PHP-DEV] Design by Contract
From: dmitry@zend.com (Dmitry Stogov)

--20cf307d00765da046050eba8932
Content-Type: text/plain; charset=UTF-8

Hi Joe,

You are welcome to edit https://wiki.php.net/rfc/dbc2
It looks like we have similar views, so just make it better in a way you
think.

Thanks. Dmitry.

On Tue, Feb 10, 2015 at 11:49 AM, Joe Watkins <pthreads@pthreads.org> wrote:

> I'm happy to clean up the RFC after Dmitry's changes are merged.
>
> Happy to author some of the content if Yasuo is busy or wants help ?
>
> Cheers
> Joe
>
>
> On Tue, Feb 10, 2015 at 8:29 AM, Dmitry Stogov <dmitry@zend.com> wrote:
>
>> A bit updated version of RFC is attached.
>> As I removed more than added, I decided not to put it on wiki before
>> internal agreement.
>> Actually, I would also remove most part of introduction as well, to make
>> RFC more compact and clean.
>>
>> I cnahged $> into $ret, because $> just won't work. Some better solution
>> is welcome.
>>
>> The RFC misses contract inheritance rules. They must be defined
>> separately for preconditions, postconditions and invariants.
>> Yasuo, could you please check, how it's implemented in D and add missing
>> section.
>>
>> We will need English correction after all.
>>
>> Thanks. Dmitry.
>>
>> On Tue, Feb 10, 2015 at 11:19 AM, Dmitry Stogov <dmitry@zend.com> wrote:
>>
>>> completely agree. contracts must be permanent.
>>>
>>> Thanks. Dmitry.
>>>
>>> On Tue, Feb 10, 2015 at 10:40 AM, Joe Watkins <pthreads@pthreads.org>
>>> wrote:
>>>
>>>> Example code never works, I can just say that's a bad abstraction,
>>>> vertebrate and invertebrate are distinct and abstraction should reflect
>>>> that.
>>>>
>>>> Why should we provide a way to change contracts is the question ?
>>>>
>>>> It doesn't seem to make sense to do that, a derived class should be
>>>> able to define additional contracts, but not change the contracts of it's
>>>> parent.
>>>>
>>>> Cheers
>>>> Joe
>>>>
>>>> On Tue, Feb 10, 2015 at 7:36 AM, Yasuo Ohgaki <yohgaki@ohgaki.net>
>>>> wrote:
>>>>
>>>>> Hi Joe,
>>>>>
>>>>> On Tue, Feb 10, 2015 at 4:31 PM, Joe Watkins <pthreads@pthreads.org>
>>>>> wrote:
>>>>>
>>>>>> Actually I'm not sure it's at all sane to try to override contracts,
>>>>>> I'd actually avoid that completely, so no need to name contracts and no
>>>>>> need for magic __invariant.
>>>>>
>>>>>
>>>>> For example,
>>>>>
>>>>> class Animal {
>>>>>    protected $legs;
>>>>>    require($legs >= 0);
>>>>> }
>>>>>
>>>>> class Snake extends Animal {
>>>>>   // Snake is fine, no leg
>>>>> }
>>>>>
>>>>> class Human extends Animal {
>>>>>   // 2 legs. $this->leg === 2
>>>>> }
>>>>>
>>>>> Overriding makes sense for many cases.
>>>>>
>>>>> Regards,
>>>>>
>>>>> --
>>>>> Yasuo Ohgaki
>>>>> yohgaki@ohgaki.net
>>>>>
>>>>
>>>>
>>>
>>
>

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