def two_args_base (a: String, b: String) = "(" + a + "-" + b + ")"
def two_args (xs: String*) = n_ary(two_args_base)(xs.head, xs.tail)

def n_ary(f: (String, String) => String): ((String, String*) => String) = {

    def apply(ar: String, ar2: String*): String = {
      if (ar2 == Nil) ar
      else f(ar, apply(ar2.head, ar2.tail:_*))
    }
    return apply
  }