IgnoreAllMyComments.scala

object IgnoreAllMyComments extends App {

  def ignoreComments(in: Iterator[Char])(out: Char => Unit): Unit = 
    ((0, None) /:[(Int, Option[Char])] in) { case ((n, last), current) => 
      last match {
        case None => (n, Some(current))
        case Some(ch) => ""+ch+current match {
          case "/*" => (n+1, None)
          case "*/" if n>0 => (n-1, None)
          case _ => 
            if (n==0) out(ch)
            (n, Some(current))
        }
      }
    } match {
      case (0, Some(ch)) => out(ch)
      case _ => 
    }
    

  val writer = new java.io.PrintWriter("e.small.out")
  try {
    writer.println("Case #1:")
    ignoreComments(io.Source.fromFile("E-small-practice.in").iter)(writer.print)
  } finally {
    writer.flush(); writer.close()
  }

}