scala type class example

Example: scala type class

Encode the Expression Problem in Scala 2.x 
(from: https://scalac.io/blog/typeclasses-in-scala/):

trait Show[A] {
  def show(a: A): String
}

object Show {
  def apply[A](implicit sh: Show[A]): Show[A] = sh

  //needed only if we want to support notation: show(...)
  def show[A: Show](a: A) = Show[A].show(a)

  implicit class ShowOps[A: Show](a: A) {
    def show = Show[A].show(a)
  }

  //type class instances
  implicit val intCanShow: Show[Int] =
    int => s"int $int"

  implicit val stringCanShow: Show[String] =
    str => s"string $str"
}