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To: Andrea Faulds <ajf@ajf.me>, internals@lists.php.net
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Date: Sun, 29 Mar 2020 12:52:11 +0200
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Subject: Re: [PHP-DEV] [VOTE] Userspace operator overloading
From: cmbecker69@gmx.de ("Christoph M. Becker")

On 28.03.2020 at 22:21, Andrea Faulds wrote:

> Christoph M. Becker wrote:
>> (frankly, I would not have not supported __concat() at all).=C2=A0 Also=
,
>> overloaded operators should be programmed defensively, i.e. they should
>> not accept arbitrary arguments (how could that even work?), but only
>> those they can handle.=C2=A0 If implementations adhere to these "rules"=
, I
>> don't see real issues.
>
> Consider a type implementing some kind of list. Perhaps someone would
> want to overload the + operator to mean adding an item to the list. If
> the list accepts any type of value as a valid item, then you have an
> example of an unconditional overload.

I had already considered this, and wrote immediately above the quote:

> If, for example, the + operator is overloaded to add something to a
> collection, the normal expectation that + is commutative is already
> violated.  Operator overloading should definitely not be used for
> "anything", but only for those rare cases which resemble math
> operations

Thanks,
Christoph