def OPT(r: Rexp) = ALT(r, ONE)+
−
+
−
def NTIMES(r: Rexp, n: Int) : Rexp = n match {+
−
  case 0 => ONE+
−
  case 1 => r+
−
  case n => SEQ(r, NTIMES(r, n - 1))+
−
}+
−
+
−