regression/unary.sml

   1 datatype num = Z | S of num
   2
   3 val rec plus =
   4    fn (n, Z) => n
   5     | (n, S m) => S (plus (n,m))
   6
   7 val zero = Z
   8 val one = S Z
   9 val two = plus (one,one)
  10
  11 val rec times =
  12    fn (_, Z) => Z
  13     | (n, S m) => plus (n, times (n,m))
  14
  15 val square = fn n => times (n,n)
  16
  17 val four = square two
  18
  19 val sixteen = square four
  20
  21 val two56 = square sixteen
  22
  23 val rec fib =
  24    fn Z => Z
  25     | S Z => S Z
  26     | S (S n) => plus (fib (S n), fib n)
  27
  28 val x = fib (S Z)
  29