signature MLTON_ITIMER =
   sig
      datatype t =
         Prof
       | Real
       | Virtual
      val set: t * {interval: Time.time, value: Time.time} -> unit
      val signal: t -> Posix.Signal.signal
   end
- 
set (t, {interval, value})sets the interval timer (using
setitimer) specified bytto the givenintervalandvalue. - 
signal treturns the signal corresponding to
t.