gistfile1.scala

import shapeless._
import shapeless.PolyDefns.~>
import shapeless.HList._

object Test {

  object size extends (Id ~> Const[Int]#λ) {
    def apply[T](t : T) = 1
  }
  implicit def sizeString = size.λ[String](s => s.length)
  implicit def sizeTuple[T, U](implicit st : size.λ[T], su : size.λ[U]) =
    size.λ[(T, U)](t => 1+size(t._1)+size(t._2))
  
  def main(args: Array[String]) {

    val alist = 1 :: ("a", 2) :: "aa" :: HNil

    println(alist map size toList)

  }

}