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Subject: Re: [PHP-DEV] Feature request and RFC
From: rowan.collins@gmail.com (Rowan Collins)

On 08/03/2015 15:45, Grégory Planchat wrote:
> class BarSortable implements Sorter
> {
>     public function sort(Sortable $collection)
>     {
>         $previousKey = null;
>         $previousElement = null;
>
>         foreach ($collection as $key => $element) {
>             if ($previousKey === null) {
>                 $previousKey = $key;
>                 $previousElement = $element;
>                 continue;
>             }
>             if ($previousElement < element) {
>                 $collection->swap($previousKey, $key);
>             }
>
>             $previousKey = $key;
>             $previousElement = $element;
>         }
>     }
> }

Unfortunately, this won't actually sort the array - it only makes one 
check of each value, so [4, 1, 2, 3, 5] would come out as [4, 2, 3, 1, 
5], when it should be [5, 4, 3, 2, 1] (your < sign means you're sorting 
largest value first). It's *almost* like a bubble sort, though (you keep 
swapping things until you know that there's no more swaps to be made), 
which is the simplest but also least efficient way of sorting a list.

I think insertion sort, which is simple and efficient for small lists, 
could be done with iteration plus a single callback of 
"insertElementAt". For larger lists, though, you're going to want a 
quicksort, and I can't quite picture what callbacks that would need to 
run on the collection as it went; it ultimately requires some way of 
partitioning the list into multiple pieces.

Regards,

-- 
Rowan Collins
[IMSoP]