Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:82334
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain zend.com designates 209.85.220.171 as permitted sender)
MIME-Version: 1.0
In-Reply-To: <CAGa2bXY6OO2svdcguHLEYxQ_XUHjssBjgwJ_Had+JPjFzbZ80g@mail.gmail.com>
References: <CA+9eiLuNjTa8JzBgnZE5iuv5BZ4Kw4Ehk1ivxPUetNSmZ43JMw@mail.gmail.com>
	<54D7ED22.3080001@gmail.com>
	<CA+9eiLvn7BzfG5N+5Oca8pVO1OTzN9=jWof6NrVDfxvvu-XqPA@mail.gmail.com>
	<CAL=_i_m78Zo5euReKsvFfrLknFq7KEzoNnrrBefC987u+=+yHQ@mail.gmail.com>
	<CA+9eiLuUFiKwOR-BqQEmkQirpAMxgb0GE70Zz7h4WDsd1Me8FQ@mail.gmail.com>
	<CAGa2bXYDvdvRLiOpDk8EnvE00JE4x47SXB9fET4uO2Er_F6s_w@mail.gmail.com>
	<CAL=_i_=mGc_0u0YDCQ7Jiqn_ggyJmQSd_mk_snf7ArDpDXO53A@mail.gmail.com>
	<CA+9eiLur0DVGBNkzFkiTj3POL5B9H0D8=5wE-wuwN2O-FQZNyg@mail.gmail.com>
	<CAL=_i_m=XDKtc2iCSjoquaHkmX862gyMweKS5Xw4AS--oLj19w@mail.gmail.com>
	<CA+9eiLsX=mOOgXmNBKD1L6WKx2=Vy81mThaKa1XCjjAw6R=2vA@mail.gmail.com>
	<CAGa2bXYYp0WQmnTnbsHXzc8XGG0PxOVHu7XvwiMCSJiUWoKeCg@mail.gmail.com>
	<CA+9eiLtj79MevMVg1cBSzGvfcdH=jszWym1Bf50zRsQ+94jp5w@mail.gmail.com>
	<CAGa2bXY6OO2svdcguHLEYxQ_XUHjssBjgwJ_Had+JPjFzbZ80g@mail.gmail.com>
Date: Tue, 10 Feb 2015 10:49:33 +0400
Message-ID: <CA+9eiLshS+v06fCdMTchUdehpczsyYB6_bRMGm1-U6r8iMaG6g@mail.gmail.com>
To: Yasuo Ohgaki <yohgaki@ohgaki.net>
Cc: PHP Internals <internals@lists.php.net>, Stanislav Malyshev <smalyshev@gmail.com>, 
	Joe Watkins <pthreads@pthreads.org>
Content-Type: multipart/alternative; boundary=089e0115fd0214085c050eb64ae7
Subject: Re: [PHP-DEV] Design by Contract
From: dmitry@zend.com (Dmitry Stogov)

--089e0115fd0214085c050eb64ae7
Content-Type: text/plain; charset=UTF-8

Hi,

can I make some minor correction?

Thanks. Dmitry.



On Tue, Feb 10, 2015 at 9:25 AM, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote:

> Hi Dmitry,
>
> On Tue, Feb 10, 2015 at 1:43 PM, Dmitry Stogov <dmitry@zend.com> wrote:
>
>> On Feb 9, 2015 11:20 PM, "Yasuo Ohgaki" <yohgaki@ohgaki.net> wrote:
>> >
>> > Hi Dmitry and Joe,
>> >
>> > On Mon, Feb 9, 2015 at 8:27 PM, Dmitry Stogov <dmitry@zend.com> wrote:
>> >>
>> >> yes. this may work.
>> >> probably better to put it after extends and implements.
>> >>
>> >>
>> >> Dmitry.
>> >>
>> >> On Mon, Feb 9, 2015 at 2:19 PM, Joe Watkins <pthreads@pthreads.org>
>> wrote:
>> >>>
>> >>> Could this be described as a requirement of the class ?
>> >>>
>> >>> class Mine
>> >>>     require(invariant-expr)
>> >>>     extends Something
>> >>>     implements Someface {
>> >>>
>> >>>     public function method($param) : return
>> >>>         require(input-expr),
>> >>>         return(output-expr) {
>> >>>
>> >>>     }
>> >>> }
>> >>>
>> >>> To avoid invariant keyword maybe.
>> >
>> >
>> > This would work.
>> > If users have adopted DbC in some way, 'invariant' may be used already.
>> >
>> > I see two issues.
>> >
>> > Interface works, but most classes are class without interfaces. Then
>> users have to repeat
>> > require()/return() many times to check class state or have to use
>> interface for DbC.
>> >
>>
>> In D classes may have "invariant" constraints. We may use "require"
>> keyword for it. The constraints ineritance rules and order of calls to
>> constrains must be the same s in D.
>>
>> class Foo {
>>     private $sum = 0;
>>     require($this->sum >= 0); // invariant constraint will be called
>> before and after every method
>>     function add($n) {
>>          $this->sum += $n;
>>     }
>> }
>>
>
> OK. I'll update the RFC.
>
>
>> > Since compiler does not know a method() is for DbC invariant, it will
>> be compiled and exists
>> > in production execution.
>> >
>> > Use of interface:
>> >   - no additional keyword (pros)
>> >   - requires interface for DbC, most classes does not require interface
>> (cons)
>> >   - if interface is not used, user has to repeat invariant conditions
>> over and over (cons)
>> >   - requires to define method that should not exist in production (cons)
>>
>> I didn't understand you idea.
>>
>
> Joe's idea was to use Interface for invariant condition grouping.
> If we use your idea, issue is solved.
>
> class Foo {
>>     private $sum = 0;
>>     require($this->sum >= 0); // invariant constraint will be called
>> before and after every method
>>     function add($n) {
>>          $this->sum += $n;
>>     }
>> }
>>
> Ok.
>
>> >
>> > New keyword:
>> >   - does not require interface for efficient definition (pros).
>> >   - new keyword (cons)
>> >
>> > It seems we are better to choose proper keyword for 'invariant'.
>> 'invariant' is not common, so 'invariant'
>> > may be good enough choice. Does anyone use 'invariant' as
>> function/method/class/constant names?
>> > If there is better name, suggestion is appreciated.
>> >
>> > On place closure call like javascript is not supported in PHP, but
>> function works with assert.
>> >
>> > <?php
>> > function foo() { return FALSE; }
>> > assert(foo());
>> > ?>
>> > PHP Warning:  assert(): Assertion failed in - on line 3
>> >
>> > This wouldn't be changed for require()/return()/invariant()?
>> >
>> > We need a switch to change development/production. I'll use
>> "dbc=On/Off" for now.
>> > If you have any better idea, please let me know. (dbc will be
>> INI_SYSTEM)
>>
>> Check the "expectations" RFC. I think, it's going to be 3 state switch,
>> zero-cost disable, run-time disable, run-time enable. So, it may be
>> INI_ALL, but it won't be possible to switch from/to zero-cost at run-time.
>>
>
> Ok.
>
>> >
>> > For CLI, there will be no command line switch for dbc. It executes
>> script production mode by
>> > default. If user needs development mode
>> >
>> > php -d dbc=1 script.php
>> >
>> > should be used.
>> >
>> >
>> > And finally, are we going to allow custom assertion error message? e.g.
>> >
>> > require($a > 0, 'Parameter $a must be positive number');
>>
>> I think, it may be useful.
>>
> Ok. I'll use it.
>
>> >
>> > Since this contract is definition like "implements"/"extends", we may
>> not allow
>> > custom error message. I'll write the RFC not to allow custom error
>> messages unless
>> > you dislike it.
>> >
>> > I think we have enough consensus/information to start writing the RFC.
>> > If I have any concern, I'll ask here.
>>
>> Ok, go forward :)
>>
> Updated wiki page.
> https://wiki.php.net/rfc/dbc2
>
> If you would like to change something, please let me know.
> I don't think finished draft at all and I don't mind going back and forth.
>
> Regards,
>
> --
> Yasuo Ohgaki
> yohgaki@ohgaki.net
>

--089e0115fd0214085c050eb64ae7--