[RFC] Spaceship operator RFC

Hi!

There is the following example in the RFC:

// only values are compared
$a = (object) ["a" => "b"];
$b = (object) ["b" => "b"];
echo $a <=> $b; // 0

But the actual result is currently 1, not 0.

Ahh, I see. I think it's the mistake in the RFC. These objects are not
equal, so <=> can not return 0. These objects are compared as hashtables
(see zend_hash_compare), since $a has key "a" and $b does not,
comparison returns 1. Since objects by default are not well-ordered,
comparison does not follow the rules of order, i.e. it may happen that
both $a > $b and $b > $a. That's how compare_function works and always
worked, and <=> is just a call to that function.

When there is no "right" value, why not raising E_NOTICE at least. It

I'm not a big fan of throwing too many notices. They are usually not
very helpful an din this case it would be not easy to distinguish
between intentional and unintentional use.

appears to me that returning 1 (as "undefined") without further notice
is too misleading, as it suggests that $a is greater than $b, but that
is not true: ($a > $b === false).

$a > $b being false is an artifact of how ">" works in the engine - $a >
$b is essentially ($b < $a). Since in this case both $a > $b and $b >
$a, the result of ($b < $a) is false. That's what you get when you
compare non-well-ordered things...

--
Stas Malyshev
smalyshev@gmail.com