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Date: Mon, 10 Apr 2017 11:04:09 +0900
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To: Rasmus Schultz <rasmus@mindplay.dk>
Cc: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a113e535e7a16a2054cc6667c
Subject: Re: [PHP-DEV] scalar type-casting
From: yohgaki@ohgaki.net (Yasuo Ohgaki)

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Hi Rasmus,

Although DbC is not what you need, but DbC could solve your issue
more efficiently. i.e. Faster execution, not shorter code.

https://wiki.php.net/rfc/dbc2

With DbC, caller has responsibility to pass correct parameters.

On Sun, Apr 9, 2017 at 6:30 PM, Rasmus Schultz <rasmus@mindplay.dk> wrote:

>
> $one = "1";
> $one_int = (int) $one;
> add_one($one_int);
>


add_one(&$value)
  require (is_int($value))
{
   $value += 1;
}

// Caller has responsibility to pass correct parameters.
$one = filter_validate($_GET['var'], FILTER_VALIDATE_INT);
add_one($one);




> class Foo { public function __toString() { return "foo"; } }
> function append_to(string &$str) { $str .= "_bar"; }
> $foo = new Foo();
> append_to($foo);
> var_dump($foo); // string(7) "foo_bar"



class Foo { public function __toString() { return "foo"; } }

function append_to(&$str)
  require (is_string($str))
{
  $str .= "_bar";
}

$foo = new Foo();

// Caller has responsibility to pass correct parameters, but it's not
append_to($foo); // Error at DbC precondition check in append_foo()
var_dump($foo); // Cannot reach here in dev mode



I really like parameter type check.
Problem is type check makes execution slower.
Another problem is type check is not enough for many codes.

With DbC support, we can specify any expressions. Therefore, we can
check much more complex requirements for functions/methods at
development time.



e.g.
function save_age($user_age)
  require (is_int($user_age))
  require ($user_age >= 0)
  require ($user_age < 150)
{
   save_to_somewehre($user_age);
}
//Note: All input parameters must be validated to be correct value for the
app. e.g. use filter_validate()/etc


What you really need might be DbC.

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net

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