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In-Reply-To: <1804801.tdWV9SEqCh@come-prox15amd>
Date: Mon, 10 Jan 2022 18:48:55 +0100
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To: jordan.ledoux@gmail.com
Cc: =?UTF-8?Q?C=C3=B4me_Chilliet?= <come@chilliet.eu>, internals@lists.php.net
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Subject: Re: [PHP-DEV] [VOTE] User Defined Operator Overloads
From: guilliam.xavier@gmail.com (Guilliam Xavier)

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Hi Jordan,

Many thanks for all your replies. But did you miss C=C3=B4me's mail (maybe
because you weren't direct recipient)? Anyway, here it is again:

On Tue, Jan 4, 2022 at 10:02 AM C=C3=B4me Chilliet <come@chilliet.eu> wrote=
:

> Hello,
>
> From the RFC:
>
> > If the left operand produces a TypeError due to the parameter types
> listed in the implementation, the operation is not retried with the right
> operand and the error is instead returned immediately. This is to help
> developers encounter errors in their program logic as early as possible.
>
> This feels wrong if I understand correctly.
>
> Let=E2=80=99s say I create a class A and I want to add support for "2 / n=
ew A()",
> which by default does not work.
>
> I can do
> class A
> {
>   operator /(int $other, OperandPosition $operandPos): mixed
>  {
>     return "example";
>  }
> }
>
> Now someone wants to build on my work, and add a class B that supports
> "new A() / new B()".
>
> class B
> {
>   operator /(A $other, OperandPosition $operandPos): mixed
>  {
>     return "example";
>  }
> }
>
> This will not work because it will first try A->{'/'}(B) that throws a
> TypeError? So it means what I was able to do for floats, cannot be done f=
or
> my new classes afterwards? This is inconsistent I think. It also means it
> is not possible to extend any existing class with operators interacting
> with a new class, meaning you can only use operators among classes aware =
of
> each other, most likely from the same package/library.
>
> Also, this was stated already I think but I did not see an answer, from
> RFC example:
> > class Matrix {
> >     public function __construct(readonly public array $value) {}
> >
> >     public operator *(Matrix $other, OperandPosition $operandPos): Numb=
er
> >     {
> >         if ($operandPos =3D=3D OperandPosition::LeftSide) {
> >             // Count of my columns needs to match
> >             // count of $other rows
> >         } else {
> >             // Count of my rows needs to match
> >             // count of $other columns
> >         }
> >     }
> > }
>
> The second branch of the if is dead code, as $matrix1 * $matrix2 will
> always call $matrix1->{'*'}($matrix2, LeftSide) and never the other way
> around.
> This means that $operandPos is useless in all cases where operators are
> only typed againts the same type, and points to this design solution bein=
g
> wrong.
>
> There is =C2=ABWhy not interfaces?=C2=BB in the FAQ, does that mean that =
operators
> cannot be added in interfaces? This is not stated clearly in the RFC.
>
> Also, it is not clear if operator overload will affect comparison
> operations used in core functions such as in_array, sort and so on.
> Does implementing operator =3D=3D allows using in_array to find an object=
 in
> an array?
> Which of these internal functions use =3D=3D and which use =3D=3D=3D, whi=
ch is not
> overloadable?
> Does implementing operator <=3D> allows sorting of arrays containing my
> objects?
>
> C=C3=B4me
>
> --
> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: https://www.php.net/unsub.php
>
>
I too would be interested in your answers to those.

Best regards,

--=20
Guilliam Xavier

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