qsort

using System;

def qsort(a : list[IComparable]){
  | [] => []
  | _ => def g = n => a.Filter(x => x.CompareTo(a.Head) == n);
         qsort(g(-1)) + g(0) + qsort(g(1))
}

def r = Random(DateTime.Now.Millisecond);
Console.Write(qsort($[r.Next()|_ in [0..9]]))

def qsort(a){
  if(!a) return []
  def g = a.groupBy{ it <=> a[0] }
  qsort(g[-1]) + g[0] + qsort(g[1])
}

print qsort((0..9).collect{ Math.random() })

def qsort a
  return [] if a.nil? or a.empty?
  g = a.group_by{|x| x <=> a[0] }
  qsort(g[-1]) + g[0] + qsort(g[1])
end

p qsort (0..9).map{ rand }

+

list#Partition を発見。こっちのがいいな。

using System;

def qsort(a : list[IComparable]){
  | h :: t => def (l, r) = t.Partition(x => x.CompareTo(h) < 0);
              qsort(l) + [h] + qsort(r)
  | _ => []
}