Functions to time other functions.

1_timer.sml

local
  (* sum of a list of ints
     sum : int list -> int *)
  fun sum l = foldl op+ 0 l

  (* avarage of a list of ints
     avg : int list -> real *)
  fun avg l = real(sum(l)) / real(length(l))
in
  (* calculate the amount of time it takes to run a function once
     returns the time in milliseconds
     time : (unit -> a') -> int *)
  fun time f =
    let
      val timer = Timer.startRealTimer()
      val _ = f()
      val time = Timer.checkRealTimer timer
    in Time.toMilliseconds time
    end

  (* calculate the avarage amount of time it takes to run a function
     100 times
     returns the avarage time in milliseconds
     avgTime : (unit -> a') -> real *)
  fun avgTime f =
    let
      fun helper (0, acc) = avg acc
        | helper (n, acc) = helper (n-1, time(f) :: acc)
    in helper (100, [])
    end
end

2_example_use.sml

use "./timer.sml";

fun fib 0 = 0
  | fib 1 = 1
  | fib n = fib(n-1) + fib(n-2)

val fibAvg = avgTime (fn () => fib 20)