regression/ref-flatten.sml

   1 datatype t =
   2    A of int ref * int
   3  | B
   4
   5 val n = 100
   6
   7 val a = Array.tabulate (n, fn i =>
   8                         case i mod 3 of
   9                            0 => B
  10                          | 1 => A (ref 13, 14)
  11                          | 2 => A (ref 15, 16))
  12
  13 val a' =
  14    Array.tabulate (n, fn i =>
  15                    case Array.sub (a, i) of
  16                       B => B
  17                     | A (r, n) => A (r, n + 1))
  18
  19 val _ = Array.app (fn A (r, n) => r := 17 + n + !r  | B => ()) a
  20
  21 val _ =
  22    case Array.sub (a', 1) of
  23       A (r, _) => print (concat [Int.toString (!r), "\n"])
  24     | B => ()