regression/ref-flatten.5.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 datatype t =
  14    A' of int ref * int
  15  | B'
  16
  17 val a' =
  18    Array.tabulate (n, fn i =>
  19                    case Array.sub (a, i) of
  20                       B => B'
  21                     | A (r, n) => A' (r, n + 1))
  22
  23 val _ = Array.app (fn A (r, n) => r := 17 + n + !r  | B => ()) a
  24
  25 val _ =
  26    case Array.sub (a', 1) of
  27       A' (r, n) => print (concat [Int.toString (!r + n), "\n"])
  28     | B' => ()