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Date: Tue, 5 Jan 2016 00:26:30 +0100
CC: Sara Golemon <pollita@php.net>,
 PHP internals <internals@lists.php.net>
References: <CAESVnVqoikwzKAnB13x-6pjoJnw3jCzAh1BdZpX=yE0ffpQfcg@mail.gmail.com> <1451936344.323.14.camel@kuechenschabe>
To: =?utf-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>
Subject: Re: [PHP-DEV] RFC Operator Overloading in Userspace
From: bobwei9@hotmail.com (Bob Weinand)

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> Am 4.1.2016 um 20:39 schrieb Johannes Schl=C3=BCter =
<johannes@schlueters.de>:
>=20
> On Sat, 2016-01-02 at 18:14 -0800, Sara Golemon wrote:
>> https://wiki.php.net/rfc/operator-overloading
>=20
> Back in the days when I created the first implementation of operator
> overloading in the engine[1] I didn't see it fit for the language.
> Meanwhile we have more type hints and stuff making it a bit less =
magic.
> I still don't think this approach is really good. for instance we =
loose
> associativity; taking the Complex example:
>=20
>   <?php
>   $a =3D new Complex(1, 2);
>   $b =3D 3;
>   echo $a + $b; // works
>   echo $b + $a; // will error out
>   ?>
>=20
> Of course this can easily be fixed by looking at the order, at least =
in
> this simple case. In a more complex example where a function might
> return an integer, double or complex number this becomes more
> complicated.
>=20
> For this to work we'd need non-member functions to do this and we need
> function overloading ...
>=20
> I believe  we'll only get a half-baked solution and I prefer the =
current
> state over half-baked.
>=20
> johannes
>=20
> [1] http://news.php.net/php.internals/14558

Then that must be very long ago, as, looking at code even as old as 5.6, =
http://lxr.php.net/xref/PHP_5_6/Zend/zend_operators.h#959 =
<http://lxr.php.net/xref/PHP_5_6/Zend/zend_operators.h#959> clearly =
checks both operand for object with custom do_operation.

The only issue is when you try to compare two objects with each custom =
operation handlers, like, e.g. an instance of Complex and Fractional. To =
have that working, we couldn=E2=80=99t just use real fractionals, but =
would need a special ComplexFractional, as Fractional may not be aware =
of Complex.

This really is the limit of this abstraction=E2=80=A6 But I guess, it =
won=E2=80=99t be too much of an issue in real world.

Bob=

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