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 <46B14427-44B2-4665-BC14-6018AC34B0CF@sakiot.com> <efe19f77-058f-48c4-aa33-fcc9223836ac@bastelstu.be>
In-Reply-To: <efe19f77-058f-48c4-aa33-fcc9223836ac@bastelstu.be>
Date: Fri, 5 Apr 2024 13:04:40 -0700
Message-ID: <CAMrTa2EXd7Z6p2Uzy0kJnhnQ62GdRZPERq+Z05RS=2JF6G6iyg@mail.gmail.com>
Subject: Re: [PHP-DEV] [RFC] [Discussion] Support object type in BCMath
To: =?UTF-8?Q?Tim_D=C3=BCsterhus?= <tim@bastelstu.be>
Cc: Saki Takamachi <saki@sakiot.com>, Lynn <kjarli@gmail.com>, 
	Aleksander Machniak <alec@alec.pl>, php internals <internals@lists.php.net>
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From: jordan.ledoux@gmail.com (Jordan LeDoux)

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On Fri, Apr 5, 2024 at 1:00=E2=80=AFPM Tim D=C3=BCsterhus <tim@bastelstu.be=
> wrote:

> Hi
>
> On 4/5/24 21:42, Saki Takamachi wrote:
> > The only solution I can think of at the moment is to impose the
> constraint that
> > when computing operator overloading, if the operands are both objects,
> they must
> > be of the exact same class.
>
> Even that would allow for confusing behavior:
>
>      class MyNumber extends Number {
>          private $importantMetadata;
>
>          public function doSomething() {
>              $this->importantMetadata =3D random_int(1, 100);
>          }
>      }
>
>      $a =3D new MyNumber(5);
>      $a->doSomething();
>      $b =3D new MyNumber(10);
>      $b->doSomething();
>
>      $what =3D $a + $b;
>
> What should be the value of $what->importantMetadata be? The property is
> private, so as a user adding two of MyNumber would not even be able to
> manually fix it up with the correct value, thus requiring the addition
> of a "fixup" method that fixes the internal state of the object,
> possibly even lacking the necessary information to properly fix up the
> state, because it does not know which operations lead to the state.
>
> Best regards
> Tim D=C3=BCsterhus
>

That is an absurd example. Why would anyone use inheritance for that class
design? If what you are arguing is "if you look at use cases where
composition is clearly the correct choice then inheritance causes
problems", then I'm not sure what the point of the discussion is.

Jordan

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Fri, Apr 5, 2024 at 1:00=E2=80=AFP=
M Tim D=C3=BCsterhus &lt;<a href=3D"mailto:tim@bastelstu.be">tim@bastelstu.=
be</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margi=
n:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex=
">Hi<br>
<br>
On 4/5/24 21:42, Saki Takamachi wrote:<br>
&gt; The only solution I can think of at the moment is to impose the constr=
aint that<br>
&gt; when computing operator overloading, if the operands are both objects,=
 they must<br>
&gt; be of the exact same class.<br>
<br>
Even that would allow for confusing behavior:<br>
<br>
=C2=A0 =C2=A0 =C2=A0class MyNumber extends Number {<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0private $importantMetadata;<br>
<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0public function doSomething() {<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0$this-&gt;importantMetadata=
 =3D random_int(1, 100);<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0}<br>
=C2=A0 =C2=A0 =C2=A0}<br>
<br>
=C2=A0 =C2=A0 =C2=A0$a =3D new MyNumber(5);<br>
=C2=A0 =C2=A0 =C2=A0$a-&gt;doSomething();<br>
=C2=A0 =C2=A0 =C2=A0$b =3D new MyNumber(10);<br>
=C2=A0 =C2=A0 =C2=A0$b-&gt;doSomething();<br>
<br>
=C2=A0 =C2=A0 =C2=A0$what =3D $a + $b;<br>
<br>
What should be the value of $what-&gt;importantMetadata be? The property is=
 <br>
private, so as a user adding two of MyNumber would not even be able to <br>
manually fix it up with the correct value, thus requiring the addition <br>
of a &quot;fixup&quot; method that fixes the internal state of the object, =
<br>
possibly even lacking the necessary information to properly fix up the <br>
state, because it does not know which operations lead to the state.<br>
<br>
Best regards<br>
Tim D=C3=BCsterhus<br></blockquote><div><br></div><div>That is an absurd ex=
ample. Why would anyone use inheritance for that class design? If what you =
are arguing is &quot;if you look at use cases where composition is clearly =
the correct choice then inheritance causes problems&quot;, then I&#39;m not=
 sure what the point of the discussion is.</div><div><br></div><div>Jordan =
<br></div></div></div>

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