[VOTE] array_part()

On Tue, 29 May 2012 02:28:05 +0200, Stas Malyshev smalyshev@sugarcrm.com
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.

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.

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] ]);

Gustavo Lopes