let rec qArraySort (array : 'a []) : 'a [] when 'a : comparison =
   if array.Length > 1 then
      let pivot = array.[0]
      let small = Array.filter ((>) pivot) array
      let big = Array.filter ((<) pivot) array
      let mid = Array.filter ((=) pivot) array
      let id x = x
      Array.collect id [|qArraySort small; mid; qArraySort big|]
   else array