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Date: Fri, 13 May 2022 09:26:37 -0500
To: "php internals" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] The future of objects and operators
From: larry@garfieldtech.com ("Larry Garfield")

On Fri, May 13, 2022, at 9:05 AM, Rowan Tommins wrote:
> On 6 May 2022 23:16:37 BST, Jordan LeDoux <jordan.ledoux@gmail.com> wrote:
>>I'm not sure at this point how voters think objects and operators should
>>work together into the future. I'd like to see if anyone is willing to have
>>high-level discussion about the ideas, instead of picking at the
>>implementation or details of a particular RFC.
>
>
> Hi Jordan,
>
> I like Larry's "4 levels", but I've been thinking that there's some 
> existing functionality in PHP which takes a different direction: rather 
> than overloading *operators*, the language lets you overload 
> *behaviour*. We have magic methods like __get and __call, and 
> interfaces like Iterator, Countable, and ArrayAccess. Some hook into a 
> particular function, or even operator, but they're generally described 
> in terms of what they do, not what they look like, if you see what I 
> mean.
>
> From that point of view, overloading comparison and equality 
> *behaviour* makes sense - it could affect not just the == and <=> 
> operators, but things like in_array() and sort(). I think this 
> distinction is more pronounced in PHP than some languages, because the 
> standard library isn't "self-hosted": a sort() call doesn't literally 
> compile to a call to $a <=> $b
>
> It's less obvious how that applies to mathematical operators - should 
> implementing "addition" allow an object to be used with array_sum() 
> perhaps? And what about deriving one operation from another, e.g. 
> $foo*3 running $foo+$foo+$foo, or $foo**3 running $foo*$foo*$foo?
>
> I don't really have a conclusion here, I just wanted to throw it out 
> there as a different mental model to consider.

Interesting point.  I think that's the most compelling argument I've heard for using `public function __lessThan` rather than `operator <`.  I'm not sure if it's enough to change my own preference on that front, but it's an interesting point.  Working with `in_array()` and `sort()` is a necessary feature for comparison overloading, IMO.  I'm unsure about something like `array_sum()`, but could be convinced.

Hum.

--Larry Garfield