scala 2.11.8だとこうなる
scala> import collection.mutable._ import collection.mutable._ scala> val q = new PriorityQueue[Int]() q: scala.collection.mutable.PriorityQueue[Int] = PriorityQueue() scala> q += 1 += 2 += 3 res0: q.type = PriorityQueue(3, 1, 2) scala> val qq = q.reverse.reverse qq: scala.collection.mutable.PriorityQueue[Int] = PriorityQueue(3, 1, 2) scala> q.ord eq qq.ord res1: Boolean = false // これをtrueに