Point.scala

object Point extends App {
 
  trait Semigroup[T]  {
    def append(p1: T, p2: T): T
  }
 
  case class Point2D(x: Int, y: Int)
  case class Point3D(x: Int, y: Int, z: Int)

  object Point2D {
    implicit def toPoint3D(p:Point2D):Point3D = Point3D(p.x,p.y,0)
  }


  implicit object Point2DAdder extends Semigroup[Point2D] {
    def append(p1: Point2D, p2: Point2D): Point2D = Point2D(p1.x + p2.x, p1.y + p2.y)
  }
 
  implicit object Point3DAdder extends Semigroup[Point3D] {
    def append(p1: Point3D, p2: Point3D): Point3D = Point3D(p1.x + p2.x, p1.y + p2.y, p1.z + p2.z)
  }


  case class addWrapper[T:Semigroup](w:T) {
    def add(t:T):T = implicitly[Semigroup[T]].append(w, t)
  }

  implicit def toAddWrapper[T:Semigroup](t:T) = addWrapper(t)
 
  
  val point1 = Point2D(1, 2)
  val point2 = Point3D(1, 2, 3)
 
  println(point2.add(point1)) 
}

mais println(point1.add(point2)) ne marchera pas non ?