Quick-Select & Quick-Sort in F#

quick-select.fs

// tail-recursive quick-select

let select vs k =
  let rec selectImpl vs k result = 
    match vs with
    | [] -> result
    | head :: tail ->
      let (less, more) = tail |> List.partition ((>=) head)
      match List.length less with
      | x when x < k -> selectImpl more (k - x) (less @ result)
      | x when x > k -> selectImpl less k result
      | _ -> (less @ result)
  in selectImpl vs k []

// tail-recursive quick sort in CPS
let sort vs = 
  let rec sortImpl vs result cont = 
    match vs with
    | [] -> cont result
    | head :: [] -> cont (head :: result)
    | head :: rest ->
      let (less, more) = rest |> List.partition ((>=) head)
      sortImpl more result (fun sortedMore -> 
      sortImpl less (head :: sortedMore) cont)
  in sortImpl vs [] id