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Date: Fri, 6 Feb 2015 00:00:39 +0900
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To: Patrick Schaaf <php@bof.de>
Cc: "internals@lists.php.net" <internals@lists.php.net>, Dmitry Stogov <dmitry@zend.com>
Content-Type: multipart/alternative; boundary=001a11c12d769ce4e2050e5893aa
Subject: Re: [PHP-DEV] Design by Contract
From: yohgaki@ohgaki.net (Yasuo Ohgaki)

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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

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