implicit conversion from one type to another one

View Bound

// implicit conversion from one type to another one

// 1 way
object ViewBound {

  trait Show {
    def show: String
  }

  object Show {
    implicit class ShowDouble(x: Double) extends Show {
      def show: String = f"$x%.2f"
    }
    implicit class ShowSymbol(x: Symbol) extends Show {
      def show: String = ":" + x.name
    }
  }

  object Main {
    def pokaz_1[T](v: T)(implicit f: T => Show) = print(v.show)
    def pokaz_2[T <% Show](v: T) = print(v.show)
  }
}

// 2 way
object ContextBound {

  trait Show[T] {
    def show(x: T): String
  }

  object Show {
    implicit object ShowDouble extends Show[Double] {
      def show(x: Double): String = f"$x%.2f"
    }
    implicit object ShowSymbol extends Show[Symbol] {
      def show(x: Symbol): String = ":" + x.name
    }
  }
  
  def toShow[T](f: T => String): Show[T] = new Show[T] {
    override def show(t: T): String = f(t)
  }

  def apply[T](implicit showT: Show[T]): Show[T] = showT

  implicit val LongShow = toShow[Long](_.toString)
  implicit val DoubleShow = toShow[Double](_.toString)

  object Main extends Any {
    def pokaz_1[T](v: T)(implicit f: Show[T]) {

    }
  }

}