Lazy ML

-- Quicksort implementation in Lazy ML
-- This demonstrates lazy evaluation and pattern matching

fun quicksort [] = []
  | quicksort (x::xs) =
      let val smaller = filter (fn y => y < x) xs
          val larger = filter (fn y => y >= x) xs
      in
          quicksort smaller @ [x] @ quicksort larger
      end;

-- Filter function
fun filter p [] = []
  | filter p (x::xs) =
      if p x then x :: filter p xs
      else filter p xs;

-- Example usage
val sorted = quicksort [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5];