# 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.

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;
#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);
(sort-by :p items)
#include <algorithm>
struct {
bool operator()(const Item &lhs, const Item &rhs) const { return lhs.p < rhs.p; }
} custom_sort;

std::sort(begin(items), end(items), custom_sort);
#include <algorithm>
std::sort(begin(items), end(items), [](const auto& a, const auto& b) { return a.p < b.p; });
using System.Collections.Generic;
System.Array.Sort(items, Comparer<Item>.Create((a, b) => a.p - b.p));
using System.Linq;
items.OrderBy(x => x.p)
import std.algorithm.sorting;
sort!("a.p < b.p")(items);
items.sort((a, b) => Comparable.compare(a.p, b.p));
items.sort((a, b) => (a.p).compareTo(b.p));
Enum.sort_by(items, &(&1.p))

sort_by_birth(ListOfMaps) ->
lists:sort(
fun(A, B) ->
maps:get(birth, A, undefined) =< maps:get(birth, B, undefined)
end, ListOfMaps).

sort_by_birth(ListOfRecords) -> lists:keysort(#item.birth, ListOfRecords).
import "golang.org/x/exp/slices"
less := func(a, b Item) bool {
return a.p < b.p
}
slices.SortFunc(items, less)
import "sort"
type ItemPSorter []Item
func (s ItemPSorter) Len() int{ return len(s) }
func (s ItemPSorter) Less(i,j int) bool{ return s[i].p<s[j].p }
func (s ItemPSorter) Swap(i,j int) { s[i],s[j] = s[j],s[i] }

func sortItems(items []Item){
sorter := ItemPSorter(items)
sort.Sort(sorter)
}
import "sort"
less := func(i, j int) bool {
return items[i].p < items[j].p
}
sort.Slice(items, less)
items.sort { x -> x.p }
items.sort { x, y -> x.p <=> y.p }
sortBy (comparing p) items
import qualified Data.List as List
List.sortOn p items
items.sort(function(a,b) {
return compareFieldP(a.p, b.p);
});
import java.util.Arrays;
import java.util.Comparator;
Arrays.sort(items, new Comparator<Item>(){
public int compare(Item a, Item b){
return a.p - b.p;
}
});
import java.util.Comparator;
items.stream().sorted(Comparator.comparing(x -> x.p))
import java.util.Collections;
import java.util.Comparator;
Collections.sort(items, new Comparator<Item>(){
@Override
public int compare(Item a, Item b){
return a.p - b.p;
}
});
items.sortedBy { it.p }
(sort #'< items :key #'p)
table.sort(items, function(a,b)
if a.p < b.p then return true end
end)
@import Foundation;
[items sortedArrayUsingDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:@"p" ascending:YES]]]
function cmp(\$a, \$b)
{
if (\$a->p == \$b->p) {
return 0;
}

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

usort(\$items, 'cmp');
uses fgl;
type

TItem = class p: Integer; end;
TItems = specialize TFPGObjectList<TItem>;

var items: TItems;

function compare(const a, b: TItem): Integer;
begin
Result := a.p - b.p;
end;

begin
items := TItems.Create;
items.Sort(@compare);
end.
@items = sort { \$a->{p} cmp \$b->{p} } @items;
items = sorted(items, key=lambda x: x.p)
from operator import attrgetter
items = sorted(items, key=attrgetter('p'))
items.sort_by(&:p)
items.sort_by(|a,b| a.p.cmp(&b.p));
items.sort_by_key(|x| x.p);
items.sortBy(_.x)
case class S(x: Int)
val items = List(S(3), S(4), S(2))
items.sortBy( item: S => item.x )
(define-struct item (p x y) #:transparent)
(define items (list (item 1 2 3) (item 0 0 0) (item 5 2 1)))
(sort items < #:key item-p)
items sorted: [:x :y | x p <= y p].
Imports System.Linq
items.OrderBy(Function(x) x.p)
Imports System.Collections.Generic
System.Array.Sort(items, Comparer(Of Item).Create(Function(a, b) a.p - b.p))

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