TableExample.scala

package shapeless.examples

import shapeless._
import nat._
import ops.hlist._
import test._

object TableExample extends App {

  final case class Row[L <: HList](cells: L)

  final case class Table[L <: HList](rows: L) {
    def row[RR](rowNumber: Nat)(implicit atR: At.Aux[L, rowNumber.N, RR]): RR =
      atR(rows)
  }

  val test = Table(
    Row(1 :: 2 :: 3 :: HNil) ::
    Row(4 :: 5 :: 6 :: HNil) ::
    Row(7 :: 8 :: 9 :: HNil) ::
    HNil)

  type Int3Row = Row[Int :: Int :: Int :: HNil]

  val r0 = test.row(0) // Row(1 :: 2 :: 3 :: HNil) 
  typed[Int3Row](r0)
  assert(Row(1 :: 2 :: 3 :: HNil) == r0)
  
  val r1 = test.row(1) // Row(4 :: 5 :: 6 :: HNil) 
  typed[Int3Row](r1)
  assert(Row(4 :: 5 :: 6 :: HNil) == r1)
  
  val r2 = test.row(2) // Row(7 :: 8 :: 9 :: HNil)
  typed[Int3Row](r2)
  assert(Row(7 :: 8 :: 9 :: HNil) == r2)
}