scala self-type:类型参数错误的成员

Question

这是这个问题的后续内容.

为什么这段代码无法编译,我该如何解决？

trait Vec[V] { self:V =>
  def -(v:V):V
  def dot(v:V):Double

  def norm:Double = math.sqrt(this dot this)
  def dist(v:V):Double = (this - v).norm
}

错误是:

Vec.scala:6: error: value norm is not a member of type parameter V
  def dist(v:V):V = (this - v).norm
                               ^

Answer 1

通过改变 - 的定义

def -(v:V):Vec[V]