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Programming-Idioms

  • C#
  • C

Idiom #28 Sort by a property

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

#include <stdlib.h>
int compareProp (const void *a, const void *b)
{
    return (*(const Item**)a)->p - (*(const Item**)b)->p;
}

qsort(items, N, sizeof(Item*), compareProp);

items is an array of Item* with length N
using System.Linq;
items.OrderBy(x => x.p)

The LINQ-to-objects extension method OrderBy is available for all IEnumerable<T>
using System.Collections.Generic;
System.Array.Sort(items, Comparer<Item>.Create((a, b) => a.p - b.p));

Sorts the array items in-place.
with Ada.Containers.Vectors;
use Ada.Containers;
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;

New implementation...
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