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Date: Wed, 27 Jun 2018 16:55:48 +0200
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To: rudolf.theunissen@gmail.com
Cc: Wes <netmo.php@gmail.com>, PHP Internals List <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] User-defined object comparison
From: michal@brzuchalski.com (=?UTF-8?Q?Micha=C5=82_Brzuchalski?=)

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=C5=9Br., 27 cze 2018 o 03:29 Rudolf Theunissen <rudolf.theunissen@gmail.co=
m>
napisa=C5=82(a):

> > I would like to see this in an extension first, i think it's perfectly
> doable and people can test it before merging to core
>
>
It was possible in Sara's extension[1], so maybe now also? Take a look.



> Actually not sure this can be done as an extension because it changes
> zend_operators and introduces a new handler to make it all work.
>
> > Would be nice if compareTo and equals were used only if left operand an=
d
> right operand used the same comparator function.
> In other words, $a =3D=3D $b must not work if $a->__equals and $b->__equa=
ls are
> two different functions
>
> So effectively it means we only call __equals if both sides are instances
> of the same class?
>
> > If $left operand and $right operand both have the magic methods, it wil=
l
> call $left->__magic($right), otherwise, if only the right one has the
> handler? What if the right one has compareTo and the left has only equal?
> you probably should add a table that explains which method is called
> depending in the availability of the two magic methods in the operands.
>
> Good idea. :) In brief, as it's implemented right now, the LHS takes
> precedence and the RHS will be called if it's the only one that implement=
s
> the operation. I'll write some more tests for these cases and build that
> table for the RFC.
>
> > I'd introduce a debug mode that forces php to call both
> $left->__equals($right) and $right->__equals($left) so that symmetry is
> guaranteed by design.
>
> If we want to guarantee symmetry by design, we have to either compare bot=
h
> sides or only compare if instances of the same class, or document that
> comparison should be implemented such that a > b =3D=3D b < a, etc. I'm n=
ot
> convinced that a double comparison outweighs the responsibility on the us=
er
> to be sensible.
>
> On Tue, 26 Jun 2018 at 21:04, Wes <netmo.php@gmail.com> wrote:
>
> > some ideas and concerns:
> >
> > - I would like to see this in an extension first, i think it's perfectl=
y
> > doable and people can test it before merging to core
> >
> > - would be nice if compareTo and equals were used only if left operand
> and
> > right operand used the same comparator function.
> > In other words, $a =3D=3D $b must not work if $a->__equals and $b->__eq=
uals
> > are two different functions
> >
> > - otherwise RFC should specify the precedence. if $left operand and
> $right
> > operand both have the magic methods, it will call $left->__magic($right=
),
> > otherwise, if only the right one has the handler?
> >   what if the right one has compareTo and the left has only equal? you
> > probably should add a table that explains which method is called
> depending
> > in the availability of the two magic methods in the operands.
> >
> > - I'd introduce a debug mode that forces php to call both
> > $left->__equals($right) and $right->__equals($left) so that symmetry is
> > guaranteed by design. You could do that when "assertions" are active.
> >
> > gl
> >
>

[1] https://github.com/php/pecl-php-operator/blob/master/operator.c
--=20
regards / pozdrawiam,
--
Micha=C5=82 Brzuchalski
about.me/brzuchal
brzuchalski.com

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