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Date: Tue, 28 Jan 2020 18:59:50 -0500
To: internals@lists.php.net
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Subject: Re: [PHP-DEV] Operator overloading for userspace objects
From: php@mjec.net ("Michael Cordover")

On Tue, Jan 28, 2020, at 18:47, Ben Ramsey wrote:
> If you take mutation off the table, then things become easier, IMO. We 
> only need two magic methods:
> 
> * __toInteger(): int
> * __toFloat(): float
> 
> Then, in any mathematical context, PHP could call the appropriate 
> method and use the number returned in the calculation.

I don't think this is enough to make operator overloading useful, even without mutation.

For example, the result of TimeInterval(1, 'ms') + TimeInterval(3, 'days') requires more information that we'd get out of __toInteger or __toFloat, but could still be a useful operation to perform, and ought to return a new TimeInterval (not an int). There are many of these tagged-number types where overloading would be helpful.

- mjec