Programming-Idioms

History of Idiom 28 > diff from v30 to v31

Edit summary for version 31 :
Restored version 29
↷

Version 30

2016-02-18, 16:57:58

Version 31

2016-02-18, 17:21:46

Idiom #28 Sort by a property

Sort elements of array-like collection items in ascending order of x.p, where p is a field of type Item of the objects in items.

Idiom #28 Sort by a property

Sort elements of array-like collection items in ascending order of x.p, where p is a field of type Item of the objects in items.

Code
class Item
{
    public $p;

    public function __construct($p)
    {
        $this->p = $p;
    }
}

function cmp($a, $b)
{
    if ($a->p == $b->p) {
        return 0;
    }

    return ($a->p < $b->p) ? -1 : 1;
}

$items[] = new Item(5.0);
$items[] = new Item(3.0);
$items[] = new Item(-1.0);
$items[] = new Item(2.5);

usort($items, "cmp"); // sort itemsay of Items using `cmp` function

foreach ($items as $x) {
    echo "{$x->p}\n";
}
Comments bubble
Classic use of usort with a custom function for sorting objects by property.
Doc URL
http://php.net/manual/en/function.usort.php
Demo URL
http://codepad.org/OsWlhVpV
Imports
with Ada.Containers.Vectors;
use Ada.Containers;
Code
declare
   function Compare_Function (Left, Right : Item) return Boolean is (Left.P < Right.P);
   
   package Item_Vector_Sorting is new Item_Vectors.Generic_Sorting (Compare_Function);

   use Item_Vector_Sorting;
begin
   Sort (Items);
end;