Simple Scala higher kinded type example plus type class resolution, pure scala, no Cats

HK1.scala

// Higher kinded type example

object HK1 extends App{

  // Container C must take a type parameter
  trait Maker[C[_]] {
    def apply(i: Int): C[Int]
  }

  implicit object MakerList extends Maker[List] {
    def apply(i: Int): List[Int] = List(i)
  }

  println(MakerList(10))

  type EitherString[T] = Either[String, T]

  implicit object MakerEitherString extends Maker[EitherString] {
    def apply(i: Int): Either[String, Int] = Right(i)
  }

  // If you use kind projector plugin
  // addCompilerPlugin("org.typelevel" %% "kind-projector" % "0.11.0" cross CrossVersion.full)

//  object MakerEitherString extends Maker[Either[String, *]] {
//    def apply(i: Int): Either[String, Int] = Right(i)
//  }

  println(MakerEitherString(11))

  type Id[T] = T

  implicit object MakerId extends Maker[Id] {
    def apply(i: Int): Id[Int] = i
  }

  println(MakerId(12))

  // The magic of type classes and implicit resolution

  object Maker {
    def apply[C[_]](i:Int)(implicit c: Maker[C])= c(i)
  }

  println(Maker[List](20))
  println(Maker[EitherString](21))
  println(Maker[Id](22))

}

hk1_output.txt

List(10)
Right(11)
12
List(20)
Right(21)
22

HK2.scala

// Higher kinded type example, this time more polymorphic, not just Ints

object HK2 extends App{

  // Container C must take a type parameter
  trait Maker[C[_], T] {
    def apply(i: T): C[T]
  }

  implicit object MakerList extends Maker[List, Int] {
    def apply(i: Int): List[Int] = List(i)
  }

  println(MakerList(10))

  type EitherString[T] = Either[String, T]

  implicit object MakerEitherString extends Maker[EitherString, Int] {
    def apply(i: Int): Either[String, Int] = Right(i)
  }

  println(MakerEitherString(11))

  type Id[T] = T

  implicit object MakerId extends Maker[Id, Int] {
    def apply(i: Int): Id[Int] = i
  }

  println(MakerId(12))

  // The magic of type classes and implicit resolution

  object Maker {
    def apply[C[_],T](i:T)(implicit c: Maker[C, T])= c(i)
  }

  println(Maker[List, Int](20))
  println(Maker[EitherString, Int](21))
  println(Maker[Id, Int](22))

  implicit object MakerListString extends Maker[List, String] {
    def apply(i: String): List[String] = List(i)
  }

  println(Maker[List, String]("hello"))
  
   implicit object MakerFutureString extends Maker[Future, String] {
    def apply(i: String): Future[String] = Future.successful(i)
  }

  val fut=Maker[Future,String]("hello future")

  import scala.concurrent.duration._

  val string=Await.result(fut, 3.seconds)

  println(string)

}

hk2_output.txt

List(10)
Right(11)
12
List(20)
Right(21)
22
List(hello)
hello future