Re: [RFC] [Discussion] Add new function `array_group`

Thank you, this clarifies and it confirms my initial assumption of what you are proposing. So you want to slice an array by comparing adjacent values. My personal feedback: I think the need for the grouping behavior you describe is not common enough that it needs its own native function. 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. Your behavior can be implemented in userland like so: https://3v4l.org/epvHm $arr1 = array(1,2,2,3,1,2,0,4,5,2); $groups = []; $group = []; $prev = NULL; foreach ($arr1 as $value) { if ($group && $prev > $value) { $groups[] = $group; $group = []; } $group[] = $value; $prev = $value; } if ($group) { $groups[] = $group; } print_r($groups); If needed, the comparison function can be separated out and passed as a parameter. So the array_group() function with a comparison callback parameter can be implemented in userland. I think you need to make a case as to why the behavior you describe justifies a native function. E.g. if you find a lot of public php code that does this kind of grouping. I personally suspect it is not that common. Cheers Andreas On Tue, 30 May 2023 at 17:08, Boro Sitnikovski <buritomath@gmail.com> wrote: > > Hey, > > Thanks for the suggestion. > > For the previous case in the code, I added these in a Gist to not clutter here too much: > > 1. The first example corresponds to > https://gist.github.com/bor0/b5f449bfe85440d96abd933b9f03b310#file-test_manual_group-php > 2. The second example corresponds to > https://gist.github.com/bor0/b5f449bfe85440d96abd933b9f03b310#file-test_array_group-php��Ə@X|�ȵ� > ��!^ > 3. Another example, addressing the problem of increasing subsequences is very simple with > array_group: > https://gist.github.com/bor0/b5f449bfe85440d96abd933b9f03b310#file-test_array_incr_subseqs-php > > Best, > > Boro > > > On 30.5.2023, at 16:57, Andreas Hennings <andreas@dqxtech.net> wrote: > > > > 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. > > > > Cheers > > Andreas > > > > On Tue, 30 May 2023 at 13:35, Boro Sitnikovski <buritomath@gmail.com> wrote: > >> > >> Hello all, > >> > >> As per the How To Create an RFC instructions, I am sending this e-mail in order to get > >> your feedback on my proposal. > >> > >> 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. > >> > >> For some background as to why - usually, when people want to do grouping in PHP, they > >> use hash maps, so something like: > >> > >> ``` > >> <?php > >> $array = [ > >> [ 'id' => 1, 'value' => 'foo' ], > >> [ 'id' => 1, 'value' => 'bar' ], > >> [ 'id' => 2, 'value' => 'baz' ], > >> ]; > >> > >> $groups = []; > >> foreach ( $array as $element ) { > >> $groups[ $element['id'] ][] = $element; > >> } > >> > >> var_dump( $groups ); > >> ``` > >> > >> This can now be achieved as follows (not preserving keys): > >> > >> ``` > >> <?php > >> $array = [ > >> [ 'id' => 1, 'value' => 'foo' ], > >> [ 'id' => 1, 'value' => 'bar' ], > >> [ 'id' => 2, 'value' => 'baz' ], > >> ]; > >> > >> $groups = array_group( $array, function( $a, $b ) { > >> return $a['id'] == $b['id']; > >> } ); > >> ``` > >> > >> 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. > >> > >> In any case, I think a utility function such as > >> array_group will be widely useful. > >> > >> Please find attached a patch with a proposed implementation. Curious about your > >> feedback. > >> > >> Best, > >> > >> Boro Sitnikovski > >> >