上下文与Infix运算符绑定

Question

For the given abstract class Edge2D I am taking a generic type T with context bound to some interface Point2DInterface.

abstract class Edge2D[T : Point2DInterface] {

  val p1: T
  val p2: T

  def length(): Double = {
    implicitly[Point2DInterface[T]].Sub(p1, p2)
  }
}

trait Point2DInterface[T] {
  def Sub(first: T, second: T): Double
}

With the following implementation, when T=DoublePoint2D

object Implicits {

  implicit object DoublePoint2DInterface extends Point2DInterface[DoublePoint2D] {
    def Sub(first: DoublePoint2D, second: DoublePoint2D): Double = {
      first - second
    }
  }
}

How can I create an infix operator for T? so I could write

  def length(): Double = {
    p1 - p2
  }

Regardless to the previous question, I wonder, is there a way to combine the implementations of the implicit objects? For example, combining DoublePoint2DInterface and IntPoint2DInterface.

object Implicits {

  implicit object DoublePoint2DInterface extends Point2DInterface[DoublePoint2D] {
    def Sub(first: DoublePoint2D, second: DoublePoint2D): Double = {
      first - second
    }
  }

implicit object IntPoint2DInterface extends Point2DInterface[IntPoint2D] {
    def Sub(first: IntPoint2D, second: IntPoint2D): Double = {
      first - second
    }
    }

Answer 1

How can I create an infix operator for T?

implicit class Point2DInterfaceOps[T](x: T)(implicit evidence: Point2DInterfaceOps[T]) {
  def -(y: T) = evidence.Sub(x, y)
  ...
}

Regardless to the previous question, I wonder, is there a way to combine the implementations of the implicit objects?

Make it generic, ie replace IntPoint2D and DoublePoint2D with Point2D[T: Numeric] and the two implicit objects with implicit def numericPoint2D[T: Numeric]: Point2DInterface[Point2D[T]]