import scala.concurrent._

import scala.concurrent.duration._

import ExecutionContext.Implicits.global

import scala.language.postfixOps 

lazy val f = Future {

  assert(der('a', ZERO | ONE) == (ZERO | ZERO))

  assert(der('a', (CHAR('a') | ONE) ~ CHAR('a')) == ALT((ONE | ZERO) ~ CHAR('a'), ONE))

  assert(der('a', STAR(CHAR('a'))) == (ONE ~ STAR(CHAR('a'))))

  assert(der('b', STAR(CHAR('a'))) == (ZERO ~ STAR(CHAR('a'))))

}

Await.result(f, 120 second)