ChooseSort.scala

trait Eq[A] {
  val eq: String
}
trait Ord[A] {
  val ord: String
}

implicit val eqInt: Eq[Int]
 = new Eq[Int] { val eq = "eqInt"}
implicit val ordInt: Ord[Int]
 = new Ord[Int] { val ord = "ordInt" }

implicit val eqString: Eq[String]
 = new Eq[String] { val eq = "eqString" }

trait Sortable[A] {
  def sortMe(l: List[A]): String
}

trait LowPrio {
  implicit def sortEq[A](implicit ev: Eq[A]): Sortable[A]
    = new Sortable[A] {
      def sortMe(l: List[A]) = "sorted using " + ev.eq
    }
}

object HighPrio extends LowPrio {
  implicit def sortOrd[A](implicit ev: Ord[A]): Sortable[A]
    = new Sortable[A] {
      def sortMe(l: List[A]) = "sorted using " + ev.ord
    }
}

import HighPrio._

def sort[A](l: List[A])(implicit ev: Sortable[A]): String
 = ev.sortMe(l)

println(sort(List(1,2,3)))
// sorted using ordInt
println(sort(List("a","b","c")))
// sorted using eqString