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To: "'Dmitry Stogov'" <dmitry@zend.com>,
	"'Yasuo Ohgaki'" <yohgaki@ohgaki.net>,
	"'PHP Internals'" <internals@lists.php.net>
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Date: Thu, 5 Feb 2015 12:47:40 +0100
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Subject: AW: [PHP-DEV] Design by Contract
From: php@tutteli.ch ("Robert Stoll")

Hi Dimitry

> -----Urspr=C3=BCngliche Nachricht-----
> Von: Dmitry Stogov [mailto:dmitry@zend.com]
> Gesendet: Donnerstag, 5. Februar 2015 12:14
> An: Yasuo Ohgaki; PHP Internals
> Betreff: [PHP-DEV] Design by Contract
>=20
> Hi Yasuo,
>=20
> Following our conversation, I tried to imagine how DbC should look =
like in PHP from user perspective. Finally, I was
> influenced by the semantic proposed in D, and syntax proposed for =
Java. So, these are my initial
> thoughts:
>=20
> For php it may look like the following:
>=20
> function foo()
>     requre(<input-assert-expression>)
>     ensure(<output-assert-expression>)
> {
>   ...
> }
>=20
> It would require only one new reserved word "ensure".
>=20
> The assert expressions may be checked or not depending on ini =
directive.
> It should be also possible to prevent code generation for assertions =
(zero cost asserts). It was already implemented for
> https://wiki.php.net/rfc/expectations
>=20
> For inherited methods, only the self <input-assert-expression> should =
be checked, and all parent <output-asser-
> expression>. This is borrowed from D but not necessary to be repeated =
exactly.
>=20
> I think we shouldn't introduce "invariant" constraints for classes =
now. May be later.
>=20
> Implementation is going to generate code for input constraint after =
all RECV opcodes and before code for function body,
> and code for output constraint before RETURN opcode (may be reusing =
implementation of "finally").
>=20
> See:
> http://dlang.org/contracts.html
> http://jan.newmarch.name/java/contracts/paper-long.html
>=20
> Thanks. Dmitry.

I am not sure if this new syntactic sugar really improves readability. =
What is the difference between the above and having something like?

function foo($x, $y){
  if(validateFoo($x, $y)){}
 =20
  //do something
  $result =3D 'some value';

  if(postValidateFoo($result){
    return $ result;
  }
}

Actually putting everything in one function seems even worse from a =
single responsibility point of view. But I suppose I am missing =
something essential here.

Cheers,
Robert