TaglessFinal.scala

object Main {

  trait Language {
    type F[X]

    def num(i: Int): F[Int]
    def add(l: F[Int], r: F[Int]): F[Int]
  }

  def expression(adder: Language) = {
    import adder._

    add(num(1), num(2))
  }

  val idLanguage = new Language {

    type F[X] = X

    def add(l: Int, r: Int): Int = l + r

    def num(i: Int): Int = i
  }


  def main(args: Array[String]): Unit = {
    println(expression(idLanguage))
  }
}