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Date: Tue, 21 Dec 2021 14:20:29 -0800
Message-ID: <CAMrTa2F8GZRp3W7zOZqkfcWMeei6m=HNaZtHiUVPWxfhPz_fMA@mail.gmail.com>
To: Andreas Hennings <andreas@dqxtech.net>
Cc: Dan Ackroyd <Danack@basereality.com>, Stanislav Malyshev <smalyshev@gmail.com>, 
	PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="000000000000657b0f05d3af6a7b"
Subject: Re: [PHP-DEV] [RFC] User Defined Operator Overloads (v0.6)
From: jordan.ledoux@gmail.com (Jordan LeDoux)

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On Tue, Dec 21, 2021 at 5:47 AM Andreas Hennings <andreas@dqxtech.net>
wrote:

> I see the "Implied Operators" section.
> I assume this means that a new instance will be created, and stored on
> the same variable, _if_ the original operator is written in an
> immutable way (which it should be)?
>
> E.g.
>
> $money = new Money(5);
> $orig = $money;
> $m2 = $money + new Money(2);
> assert($money === $orig);  // Checking object identity.
> assert($m2 !== $orig);
> $money += new Money(1);  // Equivalent to $money = $money + new Money(1);
> assert($money !== $orig);
> assert($orig->amount() === 5);
>
> I think we need a strong recommendation to implement operators as
> immutable.
>

 Yes. The documentation for operator overloads should be much larger than
this RFC, and if this passes my focus for the rest of 8.2 will be on two
things:

- Working on a few smaller follow up RFCs (sorting/ordering enum,
polymorphic handler resolution)
- Working to help on the documentation of this feature

All of the examples in the documentation should be for immutable
implementations, and there should be an explicit recommendation for
immutable implementations as well. With operators, mutable versions are
created with the operators under the "Implied" section instead of by
creating an immutable implementation of the operator itself.

Jordan

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