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Thread-Topic: [PHP-DEV] ARRAY_UNIQUE_IDENTICAL option
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Date: Mon, 7 Nov 2022 22:45:34 +0000
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Subject: Re: [PHP-DEV] ARRAY_UNIQUE_IDENTICAL option
From: tysonandre775@hotmail.com (tyson andre)

Hi Levi Morrison,=0A=
=0A=
> A bit off topic, but not entirely:=0A=
>=0A=
> In my opinion, adding another flag isn't the _real_ fix. Any function=0A=
> which does comparisons should take a callable for users to provide any=0A=
> comparison they wish. An iteratively better API would be:=0A=
>=0A=
> =A0=A0=A0 function array_unique<T>(list<T> $array, callable(T $a, T $b): =
int $comparator);=0A=
>=0A=
> Of course, there are other things like instead of using int for `0`,=0A=
> `-1`, `1`, we could have used an enum but we don't have one today. I=0A=
> just mean the core idea of taking callable is better than mucking=0A=
> around with flags while also allowing for custom comparison. Note that=0A=
> it doesn't necessarily prevent optimizations either. For instance, if=0A=
> they had passed `php_compare` or some function which represents `$a=0A=
> <=3D> $b`, we could identify that just as we identify a specific flag=0A=
> and take an optimized pass.=0A=
=0A=
1. Calling php functions from C is fairly slow. Sorting compared to hash ma=
ps is also slow=0A=
=0A=
If we did want a specialized implementation for user-provided=0A=
equality criteria, `?callable(T $a): U $iteratee =3D null` would seems more=
 practical to me=0A=
(Calling a function `n` times rather than `n log n` times would be faster,=
=0A=
and this would work even for cases such as=0A=
`[$obj->nonObjectField1, $obj->field2->toNormalizedRepresentation()]` inste=
ad of using a comparator in most cases=0A=
=0A=
(by putting both arrays into the internal hash map)=0A=
=0A=
(same approach as https://lodash.com/docs/#uniqBy)=0A=
=0A=
2. `<=3D>` isn't a stable order for int/string/float (etc) in various ways,=
=0A=
   so some comparators would have issues and return duplicates.=0A=
=0A=
   It's possible to implement stable comparisons, but I don't really expect=
 enthusiasm for that=0A=
   https://github.com/TysonAndre/pecl-teds/#stable-comparison=0A=
3. I expect a majority of cases could use the `ARRAY_UNIQUE_IDENTICAL` dire=
ctly.=0A=
   (or use that on array_map()ped values to find the keys of the original a=
rray to use)=0A=
   So requiring the use of $comparator would result in longer code and more=
 possible sources of bugs=0A=
   (e.g. a comparator returning `$a - $b` might overflow/underflow int if u=
sers don't realize `<=3D>` should be used)=0A=
=0A=
Thanks,=0A=
Tyson=0A=