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Programming-Idioms

  • C
  • Lua

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.

table.sort(items, function(a,b)
	if a.p < b.p then return true end
end)
#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
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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