Type classes in scala

typeClasses.scala

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

object Show {
  
  // def apply[A](implicit sh: Show[A]): Show[A] = sh
  def apply[A: Show]: Show[A] = implicitly[Show[A]]
  
  object ops {
    //def show[A](a: A)(implicit sh: Show[A]) = sh.show(a)
    //def show[A: Show](a: A) = implicitly[Show[A]].show(a)
    def show[A: Show](a: A) = Show[A].show(a)
  
    /*
    implicit class ShowOps[A: Show](a: A) {
      def show = Show[A].show(a)
    }*/
    implicit class ShowOps[A](val a: A) extends AnyVal {
      def show(implicit sh: Show[A]) = sh.show(a)
    }
    
  }
  
  /*
  implicit val intCanShow: Show[Int] = new Show[Int] {
    override def show(a: Int): String = s"int $a"
  }
  
  implicit val stringCanShow: Show[String] = new Show[String] {
    override def show(a: String): String = s"string $a"
  }
  */
  
  implicit val intCanShow: Show[Int] = a => s"int $a"
  
  implicit val stringCanShow: Show[String] = a => s"string $a"

}

import Show._
import Show.ops._

println(intCanShow.show(20))
println(show(20))

println(20.show)
println("30".show)

case class Event(val msg: String)
implicit def eventCanShow: Show[Event] = event => s"event ${event.msg}"

println(Event("occured").show)
println(show(Event("occured")))