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Date: Tue, 10 Feb 2015 08:49:26 +0000
Message-ID: <CAL=_i_kZGFFFUy8prehtyJP_ruTZZ0nGfHrM1Sj+bsE-Y++=pg@mail.gmail.com>
To: Dmitry Stogov <dmitry@zend.com>
Cc: Yasuo Ohgaki <yohgaki@ohgaki.net>, Patrick Schaaf <php@bof.de>, internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=047d7b677884d8aa09050eb7f6f1
Subject: Re: [PHP-DEV] Design by Contract
From: pthreads@pthreads.org (Joe Watkins)

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Content-Type: text/plain; charset=UTF-8

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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