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[PHP-DEV] [VOTE] array_part()

Posted by Gustavo Lopes 
Gustavo Lopes
[PHP-DEV] [VOTE] array_part()
May 28, 2012 03:40PM
I've opened the array_part() vote:

https://wiki.php.net/rfc/array_part#vote

The vote asks whether the branch at
https://github.com/cataphract/php-src/tree/array_part should be merged.
This implementation has been tested and has 100% code coverage on the
reachable code.

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Gustavo Lopes

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Stas Malyshev
Re: [PHP-DEV] [VOTE] array_part()
May 29, 2012 02:30AM
Hi!

> I've opened the array_part() vote:
>
> https://wiki.php.net/rfc/array_part#vote
>
> The vote asks whether the branch at
> https://github.com/cataphract/php-src/tree/array_part should be merged.
> This implementation has been tested and has 100% code coverage on the
> reachable code.

This looks very complicated. It might be that some use cases require
this level of complexity, but I can't remember a case where I would need
it. That alone does not disqualify the proposal, but I personally very
much like having something like array_column() rather than whole array
slicing engine with it's own declarative language inside. The engine
might be fine, but I imagine many users would want just something like
array_column() - so at least it'd be nice to have both.
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Stanislav Malyshev, Software Architect
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(408)454-6900 ext. 227

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Gustavo Lopes
Re: [PHP-DEV] [VOTE] array_part()
May 29, 2012 10:10AM
On Tue, 29 May 2012 02:28:05 +0200, Stas Malyshev <[email protected]>
wrote:

> This looks very complicated. It might be that some use cases require
> this level of complexity, but I can't remember a case where I would need
> it. That alone does not disqualify the proposal, but I personally very
> much like having something like array_column() rather than whole array
> slicing engine with it's own declarative language inside. The engine
> might be fine, but I imagine many users would want just something like
> array_column() - so at least it'd be nice to have both.

1)
Independently for whether we want array_column this function does things
that no other function built-in currently does and some that no userland
function can even do:

* Extract slices without side effects (array_slice() has side effects).
* Extract slices based on keys on time proportional to the size of the
slice and not to the size of the array.
* Pick an arbitrary number of elements from an array in any permutation
and traversing the array, in worst case -- if we request an element in the
middle --, only once.

2)
A lot of people seem to think this is too complicated. I think that
objection comes from several places:

* People focusing on the most complex usages of the function. The test
cases have to cover complex usages in order to exercise the implementation
correctly, but that doesn't mean the majority of use cases will be that
complex.
* The syntax for contiguous slices is verbose (e.g. ['start'=>1, 'end'=>3]
instead of [1:3] or [1..3] like in other languages).
* Specifying we want all the elements in a level could be simpler (e.g.
using null instead of ['start'=>0] or ['start'=>null]). See above.
* The description of the function aims to be precise and is therefore
verbose. This was probably a strategic miscalculation on my part.

Let me exemplify how this function may make things simpler. Right now,
let's suppose you want to drop the first element on each level. Let's say
you have this array:

$arr =
[
['col1', 'col2', 'col3'],
['line1', 0, 1 ],
['line2', 1, 0 ],
]

To drop the headers, you'd now have to do:

array_slice(array_map(function($a) { return array_slice($a,1); }, $arr),
1);

With array_part, you can do:

array_part($arr, [ ['start'=>1], ['start'=>1] ]);

or in this case:

array_part($arr, [ [1, 2], [1, 2] ]);
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Gustavo Lopes

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