Question

我使用的是Scala 2.11和Scala IDE。我有以下问题：我有2个文件，其中一个实现了Weight Biased Leftist Heap和一个驱动程序，它是一个对象，主要方法。

WBLHeap.scala

package heaps

abstract class WBLHeap[+A] {
  /**
   * O(1)
   * @return weight of the heap
   */
  def weight() : Int

  /**
   * 
   */
  def isWeightedLeftist(): Boolean
  /**
   * For any WBLT with n elements, the length of its right spine
   * is <= floor(log2(n+1))
   */

  def rightSpine() : List[A]
  /**
   * O(log(n))
   * @return A WBLHeap with the heap this and the heap h
   */

  def merge[B >: A](h: WBLHeap[B]) : WBLHeap[B]


  case object EmptyHeap extends WBLHeap[Nothing] {
    def weight(): Int = 0
    def isWeightedLeftist(): Boolean = true
    def rightSpine() : List[Nothing] = List()
    def merge[B >: Nothing](h: WBLHeap[B]) : WBLHeap[B] = h
  }

  case class Node[A](elem: A, weightNode: Int, left: WBLHeap[A], right: WBLHeap[A]) extends WBLHeap[A] {
    def weight(): Int = weightNode

    def isWeightedLeftist(): Boolean = 
      left.weight >= right.weight && left.isWeightedLeftist() && 
      right.isWeightedLeftist()

    def rightSpine() : List[A] = elem :: right.rightSpine()

    def merge[B >: A](h: WBLHeap[B]) : WBLHeap[B] = h match {
        case EmptyHeap => this
        case Node(e, w, l: WBLHeap[B], r: WBLHeap[B]) if this.weightNode <= w => buildNode(elem, left, r.merge(h) )
        case Node(e: B, w, l: WBLHeap[B], r: WBLHeap[B]) if this.weightNode > w => buildNode(e, l, this.merge(r))
        //There is a warning here but I don't know why. 
        //abstract type pattern A is unchecked since it is eliminated by erasure
      }

    private def buildNode[B >: A](x: B, h1: WBLHeap[B], h2: WBLHeap[B]): WBLHeap[B] = {
      val w1 = h1.weight()
      val w2 = h2.weight()
      val newWeight = w1 + w2 + 1
      if(w1 >= w2)
        return new Node[B](x, newWeight, h1, h2)
      else
        return new Node[B](x, newWeight, h2, h1)
    }

  }
}

Driver.scala

package heaps

object Driver {
  def main(args:Array[String]) = {

    val h = new Node[Char]('b', 2, 
        new Node[Char]('c', 1, EmptyHeap(), EmptyHeap()),
        EmptyHeap())


  }
}

在行中：＆＃34; val h =新节点[Char]（＆＃39; b＆＃39;，2，＆＃34;，我有一个错误：找不到：输入Node。它也会发生每次我使用对象EmptyHeap。

有人知道我做错了吗？

谢谢！

Answer 1

将Node定义移出abstract class WBLHeap，将abstract class WBLHeap更改为object，或将extends WBLHeap[...]添加到Driver，然后{ {1}}可以访问。

找不到：键入主方法scala

1 个答案: