[MLton] Bug? print statement makes program terminate / run-forever

[Wesley W. Terpstra]

Depending on if the 'print' statement is present, the program either
loops forever or terminates rapidly.

val x = 5.0
fun sqrtx y =
   let
      val y' = ((x / y + y) / 2.0)
      val () = print (Real.toString y ^ " ...\n")
   in
      if Real.== (y', y) then y else sqrtx y'
   end

val () = print (Real.toString (sqrtx 2.0) ^ "\n")