hlist.scala

trait PolyFunc[Out] {
  def apply[In]: In => Out
}

sealed trait HList {
}


//the end of an HList
sealed class HNil extends HList {
	//the operator to prepend to an HNil
	def ::[T](v : T) = HCons(v, this)
	override def toString = "HNil"
}

//the current HList. has an operator to prepend an element to it
final case class HCons[H, T <: HList](head : H, tail : T) extends HList {
	//the operator to prepend v to this HCons
	def ::[T](v : T) = HCons(v, this)
	
	override def toString = "%s :: %s".format(head.toString, tail.toString)
}

// aliases for building HList types and for pattern matching
object HList {
	//the type to go between HList elements
  type ::[H, T <: HList] = HCons[H, T]
	
	//the operator to concatenate a value onto an HList
  val :: = HCons

	//the value to represent the end of an HList
	val HNil = new HNil
}

import HList._

//x and y are equivalent
val x = HCons("a", HCons("b", HCons(1, HNil)))
val y = "a" :: "b" :: 1 :: HNil

println("x = %s".format(x))
println("y = %s".format(y))