structure SpaceDfa =
struct
  val dead = 0
  val start = 1
  val final = 2

  fun makeDead _ = 0

  fun makeStart i =
    let val chr = Char.chr i
    in if Char.isSpace chr then final else dead
    end

  val deadTable = Vector.tabulate (255, makeDead)
  val startTable = Vector.tabulate (255, makeStart)
  val finalTable = startTable

  val tables = #[deadTable, startTable, finalTable]

  fun isFinal state = state = final

  fun next (state, chr) =
    let
      val table = Vector.sub (tables, state)
      val idx = Char.ord chr
    in
      Vector.sub (table, idx)
    end
end