pws.scala

import scala.language.higherKinds

object cats {
  trait Show[A] {
    def apply(x: A): String
  }

  object Show {
    implicit def stringShow: Show[String] = new Show[String] {
      def apply(x: String): String = x
    }
  }
}

trait Printer[A] {
  def print(x: A): String
}

object Printer {
  implicit def fallbackP[A]: Printer[A] =
    new Printer[A] {
      def print(x: A): String = x.toString
    }
}

object CatsPrinter {
  implicit def catP[A](implicit s: cats.Show[A]): Printer[A] =
    new Printer[A] {
      def print(x: A): String = s(x)
    }
}

object DemoFallback {
  def r[A](x: A)(implicit p: Printer[A]): String = p.print(x)

  r("foo")
}

object DemoCats {
  import CatsPrinter._

  def r[A](x: A)(implicit p: Printer[A]): String = p.print(x)

  r("foo")
}