Re: DbC for PHP?

2014-01-29 Yasuo Ohgaki <yohgaki@ohgaki.net> > Hi Sebastian, > > On Tue, Jan 28, 2014 at 5:36 PM, Sebastian Krebs <krebs.seb@gmail.com>wrote: > >> I'm wandering if we could have DbC (Design by Contract) for PHP 6. >>> http://en.wikipedia.org/wiki/Design_by_contract >>> >>> There is user land implementation already. >>> >>> >>> https://gitorious.org/higher-order-php/php-contracts/source/5b0a53b9732f0e4dbe79345212c84c74526def3b >>> : >>> >>> It could be done with dbc mode INI switch as follows. >>> >>> When dbc=on, automatically includes >>> >>> include __dbc_ . __SCRIPT_NAME__; >>> >>> when a script is loaded. No error if there is not the script. >>> When function/method is called >>> >>> __dbc_pre_. __FUNCTION__() is called before calling function(). >>> __dbc_post_.___FUNCTION__() is called after function() call. >>> >>> No error if there is not the function. >>> >> >> Couldn't you achieve the same with assert()? >> > > Assert can be used for DbC and there are such implementations. > > Precondition is easy with assert(), but post condition is rather difficult > since > we need assert() before every 'return'. > Well .. Yeah. But that is difficult? > This could damage production code > (code executed on production environment) and contract readability. It > increases > chances of omitting post condition check by mistake. > This is possible with every implementation... > > Similar mistake may happen with this. > We may better to have option to warn non existent pre/post check. > > > Like Alexander explained, pure OO code can use DbC. It may be enough > for people who are interested in DbC. > > This is just an idea. It's simple, powerful and easy to adopt. Since there > is no DbC code in production code, it's fast while assert() need > compilation > overhead. It does not matter much with opcache, though. > No, at least not measurable. You can disable it. In that case it behaves like an empty function body. > > With this approach, user has to look up contract in other file. This is > disadvantage over other methods. > > I wander how many of us are interested in such feature. > > Regards, > > -- > Yasuo Ohgaki > yohgaki@ohgaki.net > > -- github.com/KingCrunch