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Date: Mon, 26 Aug 2024 11:40:49 +0100
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Subject: Re: [PHP-DEV] [RFC] Default expression
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From: bilge@scriptfusion.com (Bilge)

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On 26/08/2024 08:28, Rowan Tommins [IMSoP] wrote:
> As far as I can see, nobody has actually justified reading values out in this way, only said it's a side-effect of the current implementation.
It's pretty useful for testing.
> Aside: one of those examples brings up an interesting question: is the value pulled out by "default" calculated only once, or each time it's mentioned? In other words, would this create 3 pointers to the same object, or 3 different objects?
>
> foo(array|Something $x=new Something);
> foo([default, default, default]);

Thanks for this interesting question. Here is the output from your 
(slightly modified) script:

class Something {}
function foo(array|Something $x=new Something) {return $x;}
var_dump($x = foo([default, default, default]));
var_dump($x[0] === $x[1]);

array(3) {
   [0]=>
   object(Something)#1 (0) {
   }
   [1]=>
   object(Something)#2 (0) {
   }
   [2]=>
   object(Something)#3 (0) {
   }
}
bool(false)

As you can observe from the object hashes, each object is unique. That 
is, we fetch the default value each time the keyword appears, which in 
the case of objects, creates a new instance each time. I will update the 
RFC with this information.

Cheers,
Bilge

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    <div class="moz-cite-prefix">On 26/08/2024 08:28, Rowan Tommins
      [IMSoP] wrote:<br>
    </div>
    <blockquote type="cite"
      cite="mid:88BCC47D-C8FF-44DB-8816-17CB899CD887@rwec.co.uk"><span
      style="white-space: pre-wrap">
</span>
      <pre class="moz-quote-pre" wrap="">As far as I can see, nobody has actually justified reading values out in this way, only said it's a side-effect of the current implementation.</pre>
    </blockquote>
    It's pretty useful for testing.<span style="white-space: pre-wrap">
</span><span style="white-space: pre-wrap">
</span><span style="white-space: pre-wrap">
</span><span style="white-space: pre-wrap">
</span>
    <blockquote type="cite"
      cite="mid:88BCC47D-C8FF-44DB-8816-17CB899CD887@rwec.co.uk">
      <pre class="moz-quote-pre" wrap="">Aside: one of those examples brings up an interesting question: is the value pulled out by "default" calculated only once, or each time it's mentioned? In other words, would this create 3 pointers to the same object, or 3 different objects? 

foo(array|Something $x=new Something);
foo([default, default, default]);
</pre>
    </blockquote>
    <p>Thanks for this interesting question. Here is the output from
      your (slightly modified) script:</p>
    <p>class Something {}<br>
      function foo(array|Something $x=new Something) {return $x;}<br>
      var_dump($x = foo([default, default, default]));<br>
      var_dump($x[0] === $x[1]);<br>
    </p>
    <p>array(3) {<br>
        [0]=&gt;<br>
        object(Something)#1 (0) {<br>
        }<br>
        [1]=&gt;<br>
        object(Something)#2 (0) {<br>
        }<br>
        [2]=&gt;<br>
        object(Something)#3 (0) {<br>
        }<br>
      }<br>
      bool(false)<br>
    </p>
    <p>As you can observe from the object hashes, each object is unique.
      That is, we fetch the default value each time the keyword appears,
      which in the case of objects, creates a new instance each time. I
      will update the RFC with this information.</p>
    <p>Cheers,<br>
      Bilge<br>
    </p>
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