Sum.scala

object Sum extends Application with MKML  {

  val a = Var("0")
  val b = Var("0")

  def start() = {
    div(
      input(`value` =:= a),
      span(" + "),
      input(`value` =:= b),
      span(" = "),
      span(
        Bind {
          try {
            val sum = a().toInt + b().toInt
            sum.toString
          }
          catch {
            case _: NumberFormatException => "Enter a number"
          }
        }
      )
    )
  }
}