gistfile1.scala

object Nafg {

  object Tuples {

    trait HT[A] {
      type H
      type T
      def hd(a: A): H
      def tl(a: A): T
    }

    implicit def t2[A, B] = new HT[(A, B)] {
      type H = A
      type T = B
      def hd(t: (A, B)) = t._1
      def tl(t: (A, B)) = t._2
    }

    implicit def t3[A, B, C] = new HT[(A, B, C)] {
      type H = A
      type T = (B, C)
      def hd(t: (A, B, C)) = t._1
      def tl(t: (A, B, C)) = (t._2, t._3)
    }

    implicit def t4[A, B, C, D] = new HT[(A, B, C, D)] {
      type H = A
      type T = (B, C, D)
      def hd(t: (A, B, C, D)) = t._1
      def tl(t: (A, B, C, D)) = (t._2, t._3, t._4)
    }

    def hd[A](a: A)(implicit ht: HT[A]) = ht.hd(a)
    def tl[A](a: A)(implicit ht: HT[A]) = ht.tl(a)

    implicit class Id[A](a:A) {
      def head(implicit ht: HT[A]) = hd(a)
      def tail(implicit ht: HT[A]) = tl(a)
    }
    
    val tup = (1, "2", false)
    val a: Int = tup.head
    val bc: (String, Boolean) = tup.tail

  }

}