object Mengen extends Application {
      val A = Set(2, 1, 3, 1); val B = Set(3, 1, 4); val C = List(3, 1, 4, 1)
      
      println(A)         // => Set(2, 1, 3)
      println(A + 5)     // => Set(2, 1, 3, 5)
      println(A - 1)     // => Set(2, 3)
      println(A & B)     // => Set(1, 3)
      println(A | B)     // => Set(2, 1, 3, 4)
      println(A ++ C)    // => Set(2, 1, 3, 4)
      println(A &~ B)    // => Set(2, 1, 3, 4)
      println(A -- C)    // => Set(2)
      
      val staedte = Set("London", "Oslo", "Paris", "Amsterdam", "Berlin")
      val besucht = List("Berlin", "Oslo")
      val text    = (staedte -- besucht).toString replace("Set(", "") replace(")","")
      println("Ich muss noch " + text + " besuchen")
   }