Hi Francois, On Mon, Feb 16, 2015 at 8:08 AM, François Laupretre <franc...@php.net> wrote: > > > De : yohg...@gmail.com [mailto:yohg...@gmail.com] De la part de Yasuo Ohgaki > > > > D resolves that if parameter is contract or not at compile time and checks it if method > > is overriding parent's method. If method is overridden, D just ignores contract. > > That's true for pre-conditions, but that's not the way D handles post-conditions. > > >>> The same rule for class applies to interfaces. > >> > >> ?? I don't understand. > > > >Interface may have contracts just like class. > > OK, but when do you check interface conditions ? And how do you deal with interface (multiple) inheritance ?
Simply check all contracts on method calls. If property check (invariant) could be issue, class designer should use document for proper property management rather than contracts. Or we may drop invariant support for interface. > > >>> We cannot ignore parent class invariants. If developer violate parent > >>> property restrictions, > >>> it's violation of parent class type and this must be forbidden. It's > >>> checked by invariant contract. > >> > >> I agree. > > > > We have(had) weak type system. Choosing right type system for PHP would be very hard. > > I didn't intended to bring this topic... Could we introduce simple "Design by Contract" > > concept? Or are we going to discuss right type system for PHP? > > Sure, but are you realizing that you're discarding your own statement, not mine ? Type safety consideration was not intended at first. So I don't have problem with disregarding type safety. We may introduce type safety/system when we have template, strict types and/or overloading, for example. > I never told about the PHP type system because I don't understand what types have to do here. So, yes, I don't care about the PHP type system and that's not the subject. We are discussing about PHP conditions and when they are evaluated, that's all. > > And, sorry about that, but could you stop sending html messages ? It makes replies much harder. It seems gmail does not have the option, but I can only remove text formatting manually. Does this mail seems OK to you? Anyway, how about not to consider type safety too much now? and concentrate to introduce simple DbC? We may have option for strict type in the future for whatever type system we introduce at that time. Regards, -- Yasuo Ohgaki yohg...@ohgaki.net
