Idiom #246 Count distinct elements

Set c to the number of distinct elements in the list items.

Perl

use List::Util qw(uniq);

my $c = scalar(uniq @items);

using System.Linq;

int c = items.Distinct().Count();

Demo
Doc

var c = items.toSet().length;

Demo
Doc

c = items |> Enum.uniq |> length

func count[T comparable](items []T) int {
	distinct := make(map[T]bool)
	for _, v := range items {
		distinct[v] = true
	}
	return len(distinct)
}

Demo

distinct := make(map[T]bool)
for _, v := range items {
	distinct[v] = true
}
c := len(distinct)

Demo
Doc

import Data.List

c = count . nub $ items

const c = new Set(items).size;

long c = items.stream().distinct().count();

Demo
Doc

val c = items.distinct().size

Demo
Doc

$c = count(array_unique($items));

Demo
Doc

uses classes;

function CountUniqueItems(Items: TStrings): Integer;
var
  List: TStringList;
begin
  List := TStringList.Create;
  List.Duplicates := dupIgnore;
  List.Sorted := True;
  List.AddStrings(Items);
  Result := List.Count;
  List.Free;
end;

begin
 ...
 c := CountUniqueItems(items);
 ...
end.