fun fib'(0,a,b) = a
  | fib'(n,a,b) = fib'(n-1,a+b,a)
fun fib n = fib'(n,0,1)

structure Main =
   struct
      fun doit() =
         if 701408733 <> fib 44
            then raise Fail "bug"
         else ()

      val doit =
        fn n =>
        let
          fun loop n =
            if n = 0
              then ()
              else (doit();
                    loop(n-1))
        in loop (n * 1000000)
        end
   end