Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:120465
Content-Type: text/plain;
	charset=us-ascii
Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.600.7\))
In-Reply-To: <CAB-BujY2f3tM5CwRVAuVj962iC_9K=1X1A0at2QVdORxQDqx3A@mail.gmail.com>
Date: Tue, 30 May 2023 18:27:12 +0200
Cc: internals@lists.php.net
Content-Transfer-Encoding: quoted-printable
Message-ID: <B35AAF0F-B899-4771-AAFD-1109BE7A9B7D@gmail.com>
References: <289E585B-EF8B-4B17-89BE-BE8295FD9FE1@gmail.com>
 <CAB-BujYyz4vFAmi+OKi0rjqViE02eUjDpkkYyAMRCf10t8mNXA@mail.gmail.com>
 <4CA1668E-A342-452E-A994-5839C377CB27@gmail.com>
 <CAB-BujY2f3tM5CwRVAuVj962iC_9K=1X1A0at2QVdORxQDqx3A@mail.gmail.com>
To: Andreas Hennings <andreas@dqxtech.net>
Subject: Re: [PHP-DEV] [RFC] [Discussion] Add new function `array_group`
From: buritomath@gmail.com (Boro Sitnikovski)

Hi,

Thank you for your thoughts.

> I would say the more common desired behavior is the one in your first
> example. And even for that we don't have a native function.

This Google search might give more insight into the number of =
discussions about a grouping functionality: =
https://www.google.com/search?q=3Dphp+group+elements+site:stackoverflow.co=
m

> Your behavior can be implemented in userland like so:
> https://3v4l.org/epvHm

Correct, but then again, we can also implement =
`array_map`/`array_filter`/etc. in userland :)

> I think you need to make a case as to why the behavior you describe
> justifies a native function.

Similar to my previous answer, but also in general - ease of access and =
also performance.

> E.g. if you find a lot of public php code that does this kind of =
grouping.
>=20
> I personally suspect it is not that common.
>=20
> Cheers
> Andreas
>=20
>=20
> On Tue, 30 May 2023 at 17:08, Boro Sitnikovski <buritomath@gmail.com> =
wrote:
>>=20
>> Hey,
>>=20
>> Thanks for the suggestion.
>>=20
>> For the previous case in the code, I added these in a Gist to not =
clutter here too much:
>>=20
>> 1. The first example corresponds to =
https://gist.github.com/bor0/b5f449bfe85440d96abd933b9f03b310#file-test_ma=
nual_group-php
>> 2. The second example corresponds to =
https://gist.github.com/bor0/b5f449bfe85440d96abd933b9f03b310#file-test_ar=
ray_group-php
>> 3. Another example, addressing the problem of increasing subsequences =
is very simple with `array_group`: =
https://gist.github.com/bor0/b5f449bfe85440d96abd933b9f03b310#file-test_ar=
ray_incr_subseqs-php
>>=20
>> Best,
>>=20
>> Boro
>>=20
>>> On 30.5.2023, at 16:57, Andreas Hennings <andreas@dqxtech.net> =
wrote:
>>>=20
>>> Hello Boro,
>>> I think you should include the "expected result" in your code =
examples.
>>> Maybe this is in your patch file, but I don't think we want to look =
at
>>> that for discussion.
>>>=20
>>> Cheers
>>> Andreas
>>>=20
>>> On Tue, 30 May 2023 at 13:35, Boro Sitnikovski =
<buritomath@gmail.com> wrote:
>>>>=20
>>>> Hello all,
>>>>=20
>>>> As per the How To Create an RFC instructions, I am sending this =
e-mail in order to get your feedback on my proposal.
>>>>=20
>>>> I propose introducing a function to PHP core named `array_group`. =
This function takes an array and a function and returns an array that =
contains arrays - groups of consecutive elements. This is very similar =
to Haskell's `groupBy` function.
>>>>=20
>>>> For some background as to why - usually, when people want to do =
grouping in PHP, they use hash maps, so something like:
>>>>=20
>>>> ```
>>>> <?php
>>>> $array =3D [
>>>> [ 'id' =3D> 1, 'value' =3D> 'foo' ],
>>>> [ 'id' =3D> 1, 'value' =3D> 'bar' ],
>>>> [ 'id' =3D> 2, 'value' =3D> 'baz' ],
>>>> ];
>>>>=20
>>>> $groups =3D [];
>>>> foreach ( $array as $element ) {
>>>>   $groups[ $element['id'] ][] =3D $element;
>>>> }
>>>>=20
>>>> var_dump( $groups );
>>>> ```
>>>>=20
>>>> This can now be achieved as follows (not preserving keys):
>>>>=20
>>>> ```
>>>> <?php
>>>> $array =3D [
>>>> [ 'id' =3D> 1, 'value' =3D> 'foo' ],
>>>> [ 'id' =3D> 1, 'value' =3D> 'bar' ],
>>>> [ 'id' =3D> 2, 'value' =3D> 'baz' ],
>>>> ];
>>>>=20
>>>> $groups =3D array_group( $array, function( $a, $b ) {
>>>> return $a['id'] =3D=3D $b['id'];
>>>> } );
>>>> ```
>>>>=20
>>>> The disadvantage of the first approach is that we are only limited =
to using equality check, and we cannot group by, say, `<` or other =
functions.
>>>> Similarly, the advantage of the first approach is that the keys are =
preserved, and elements needn't be consecutive.
>>>>=20
>>>> In any case, I think a utility function such as `array_group` will =
be widely useful.
>>>>=20
>>>> Please find attached a patch with a proposed implementation. =
Curious about your feedback.
>>>>=20
>>>> Best,
>>>>=20
>>>> Boro Sitnikovski
>>>>=20
>>=20