Re: Design by Contract

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 >