Pimp My Library + Monoid List Operation

MonoidPML.scala

trait Monoid[A]{
  def mappend(a1: A, a2: A): A
  def mzero: A
}

object Monoid {
  implicit val IntMonoid: Monoid[Int] = new Monoid[Int] {
    def mappend(a: Int, b: Int): Int = a + b
    def mzero: Int = 0
  }

  implicit val StringMonoid: Monoid[String] = new Monoid[String] {
    def mappend(a: String, b: String): String = a + b
    def mzero: String = ""
  }
}

trait MonoidList[A] {
  val F: Monoid[A]
  val value: List[A]
  def sum[A]() = value.foldLeft(F.mzero)(F.mappend)
}


object MonoidList{
  implicit def toMonoidList[A: Monoid](xs: List[A]): MonoidList[A] = new MonoidList[A] {
    val value = xs
    val F = implicitly[Monoid[A]]
  }
}

object Example {
  def main(args: Array[String]): Unit = {
    val intList: MonoidList[Int] = List(1,2,3)
    println(intList.sum())
    
    val stringList: MonoidList[String] = List("a","b","c")
    println(stringList.sum())
  }
}