การกำหนดอินสแตนซ์

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

object Main {
  implicit val intShow: Show[Int] = (a: Int) => s"Int=$a"

  def display[A](a: A)(implicit s: Show[A]): String = s.show(a)

  def main(args: Array[String]): Unit = {
    println(display(123))
  }
}

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

object Main {
  implicit val intShow: Show[Int] = (a: Int) => s"<$a>"

  def main(args: Array[String]): Unit = {
    val s = implicitly[Show[Int]]
    println(s.show(8))
  }
}

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

case class Point(x: Int, y: Int)

object Main {
  implicit val pointShow: Show[Point] = (p: Point) => s"(${p.x}, ${p.y})"

  def display[A](a: A)(implicit s: Show[A]): String = s.show(a)

  def main(args: Array[String]): Unit = {
    println(display(Point(3, 4)))
  }
}

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

object Main {
  implicit val intShow: Show[Int] = (a: Int) => a.toString

  implicit def listShow[A](implicit s: Show[A]): Show[List[A]] =
    (xs: List[A]) => xs.map(s.show).mkString("[", ", ", "]")

  def display[A](a: A)(implicit s: Show[A]): String = s.show(a)

  def main(args: Array[String]): Unit = {
    println(display(List(1, 2, 3)))
  }
}

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

object Show {
  implicit val intShow: Show[Int] = (a: Int) => s"i:$a"
  implicit val strShow: Show[String] = (a: String) => s"s:$a"
}

object Main {
  def display[A](a: A)(implicit s: Show[A]): String = s.show(a)

  def main(args: Array[String]): Unit = {
    println(display(5))
    println(display("hi"))
  }
}

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

object Main {
  implicit val intShow: Show[Int] = (a: Int) => s"n=$a"

  def display[A: Show](a: A): String = implicitly[Show[A]].show(a)

  def main(args: Array[String]): Unit = {
    println(display(77))
  }
}

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

object Show {
  def apply[A](implicit s: Show[A]): Show[A] = s
  implicit val intShow: Show[Int] = (a: Int) => s"=$a"
}

object Main {
  def main(args: Array[String]): Unit = {
    println(Show[Int].show(10))
  }
}

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

object Show {
  def apply[A](implicit s: Show[A]): Show[A] = s
  implicit val intShow: Show[Int] = _.toString
  implicit def listShow[A](implicit s: Show[A]): Show[List[A]] =
    (xs: List[A]) => xs.map(s.show).mkString(", ")
}

object Main {
  def main(args: Array[String]): Unit = {
    println(Show[List[Int]].show(List(4, 5, 6)))
  }
}