Re: Design by Contract

Hi Patrick, On Thu, Feb 5, 2015 at 9:13 PM, Patrick Schaaf <php@bof.de> wrote: > On Thursday 05 February 2015 15:14:04 Dmitry Stogov wrote: > > > > function foo() > > requre(<input-assert-expression>) > > ensure(<output-assert-expression>) > > { > > ... > > } > > > > It would require only one new reserved word "ensure". > > Regarding syntax.... This could be another place where the irrationally- > dreaded declare would make sense: > > function foo() { > declare(pre) { > if (whatever...) return false; > // arbitrary PHP code > } > declare(post=$resultvar) { > if ($resultvar == XXX) return true; > return false; > } > } > > This way, no new reserved words are needed at all, and the programmer can > give > a name to the "variable that holds the result" locally to avoid clashes > with > anything else in the function. > > I'm a bit undecided whether returning true/false there to give the verdict, > would be the best way. Maybe better would be another use for declare, > without > a block, to declare that the pre/postcondition failed - giving a nice > place to > put a suitable message, too. And again without introducing any extra > keywords: > > function foo() { > declare(post=$resultvar) { > if ($resultvar == XXX) declare(fail="My $resultvar looks fishy"); > } > } > The idea of "declare(post=$resultvar)" seems interesting, even though post=$resulvar looks wired. $resultvar is L value, but it's located as R value. There may be better syntax. Regards, -- Yasuo Ohgaki yohgaki@ohgaki.net