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[RFC][List/Assoc\unique]

php.internals

Ilija Tovilo

3 years ago

Hi everyone

After the discussion on adding a new ARRAY_UNIQUE_IDENTICAL flag has
revealed that most would prefer a new function I've decided to create
an RFC for this.

https://wiki.php.net/rfc/list_assoc_unique

This RFC proposes adding two new functions, List\unique() and
Assoc\unique() as alternatives using strict equality (===) semantics,
the former discarding and the latter preserving keys.

Let me know what you think.

Regards,
Ilija

Side note: I *really* hope the discussion will be about more than just
the namespaces.

Tim Düsterhus

3 years ago

Hi

On 12/1/22 19:22, Ilija Tovilo wrote:

> https://wiki.php.net/rfc/list_assoc_unique
>
> This RFC proposes adding two new functions, List\unique() and
> Assoc\unique() as alternatives using strict equality (===) semantics,
> the former discarding and the latter preserving keys.

I believe this would be better solved as part of the more generic
"expanded iterable helper functions" proposal (which I really hope makes
it into a proper RFC that is accepted):

https://externals.io/message/118896

Deduplication is reasonably well-defined for arbitrary iterators (even
infinite iterators) and I don't think iterators (esp. Generators) should
remain second-class citizens to arrays going forward.

> Side note: I *really* hope the discussion will be about more than just
> the namespaces.
>

In addition to the reasons above: Yes, adding two new single-function
namespaces IMO is not a good thing, because it only adds to the
inconsistency. Adding new namespaces should be part of a "bigger picture".

Best regards
Tim Düsterhus

=?utf-8?B?5rGf5rmW5aSn6Jm+5LuB?=

3 years ago

Hi Ilija,

Thanks for the RFC. In general, I like the idea but there are certain things not clear to me.

1. What will happen if we pass a list to ` Assoc\unique`?
```
Assoc\unique([1, 2, 3, 1]);
```

2. What will happen if the array (no matter list or assoc) contains pure value and reference which are strict equal? As the RFC says "references are preserved."
```
$a = 1;
$arr1 = [$a, &$a];
$arr2 = [&$a, $a];
List\unique($arr1);
List\unique($arr2);
```

3. Currently the RFC (proposal section, function signature) claims the parameter are bool type, which is obvious wrong. But this is just a minor mistake, what I really want to ask here is do we support array only or any array like input?

> Side note: I *really* hope the discussion will be about more than just the namespaces.

Adding two new namespaces with single function doesn't look good to me, especially I cannot think of anything that we may add to these two namespace in the future.

Regards,
CHU Zhaowei