good point, but I think we can do nothing about that. Anyway, it should be reflected in RFC.
Dmitry. On Tue, Feb 10, 2015 at 9:59 AM, Joe Watkins <[email protected]> wrote: > I'm not sure we can always enforce invariant contracts ... > > Evaluating invariant expressions on entry and exit is not enough, since a > property can be changed without the use of a method. > > Can or should, we do anything about that ? > > This should also be covered in the RFC, I think. > > Cheers > Joe > > On Tue, Feb 10, 2015 at 6:49 AM, Dmitry Stogov <[email protected]> wrote: > >> Hi, >> >> can I make some minor correction? >> >> Thanks. Dmitry. >> >> >> >> On Tue, Feb 10, 2015 at 9:25 AM, Yasuo Ohgaki <[email protected]> wrote: >> >>> Hi Dmitry, >>> >>> On Tue, Feb 10, 2015 at 1:43 PM, Dmitry Stogov <[email protected]> wrote: >>> >>>> On Feb 9, 2015 11:20 PM, "Yasuo Ohgaki" <[email protected]> wrote: >>>> > >>>> > Hi Dmitry and Joe, >>>> > >>>> > On Mon, Feb 9, 2015 at 8:27 PM, Dmitry Stogov <[email protected]> >>>> 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 <[email protected]> >>>> 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 >>> [email protected] >>> >> >> >
