hlist-operations.scala

val l = 1 :: "hello" :: true :: HNil
// l: shapeless.::[Int,shapeless.::[String,shapeless.::[Boolean,shapeless.HNil]]] = 1 :: hello :: true :: HNil

l.head
// res7: Int = 1

l.tail
// res8: shapeless.::[String,shapeless.::[Boolean,shapeless.HNil]] = hello :: true :: HNil

l(1)
// res9: String = hello

l(2)
// res10: Boolean = true

l.length // Return's a type representation of a natural number
// res11: shapeless.Succ[shapeless.Succ[shapeless.Succ[shapeless._0]]] = Succ()

l.length.toInt // Type class ToInt[l.length] is implicitly computed at compile time.
// res12: Int = 3

l.drop(3)
// res13: shapeless.HNil = HNil

l.drop(4)
// <console>:17: error: Implicit not found: shapeless.Ops.Drop[shapeless.::[Int,shapeless.::[String,shapeless.::[Boolean,shapeless.HNil]]],
// shapeless.Succ[shapeless.Succ[shapeless.Succ[shapeless.Succ[shapeless._0]]]]].
// You requested to drop an element at the position shapeless.Succ[shapeless.Succ[shapeless.Succ[shapeless.Succ[shapeless._0]]]],
// but the HList shapeless.::[Int,shapeless.::[String,shapeless.::[Boolean,shapeless.HNil]]] is too short.
//        l.drop(4)
//              ^

l.copy(head = true)
// res14: shapeless.::[Boolean,shapeless.::[String,shapeless.::[Double,shapeless.HNil]]] = true :: a :: 3.14 :: HNil

l.runtimeList
// res15: List[Any] = List(1, a, 3.14)