Play with adding size of col and row as type parameters to a matrix

SizedMatrix.scala

import shapeless.ops.hlist.Length
import shapeless.{::, HList, HNil, LUBConstraint, Nat, Poly1, Succ}
import shapeless.Nat._

abstract class Matrix[Col <: Nat, Row <: Nat, A] {
  type RowLst <: HList
  type ConLst <: HList
  val data: ConLst
}

object Matrix {
  type Aux[C <: Nat, R <: Nat, A, H <: HList, T <: HList] = Matrix[C, R, A] {
    type RowLst = H
    type ConLst = H :: T
  }

  def apply
  [HH, HT <: HList, T <: HList, C <: Nat, R <: Nat]
  (d: (HH :: HT) :: T)
  (implicit
   lcRow: LUBConstraint[HT, HH], // Everything in the "tail of the head" must match the "head of the head"
   lcCol: LUBConstraint[T, HH :: HT], // Everything in the tail must match the head (HH :: HT)
   lcol: Length.Aux[HH :: HT, C], // The length of the columns is the length of the first row aka Head (HH :: HT)
   lrow: Length.Aux[(HH::HT)::T, R] // The length of the rows is the length of the whole list (Head :: T) or ((HH :: HT) :: T)
  ): Matrix[C, R, HH]
  = new Matrix[C, R, HH] {
    type RowLst = HH :: HT
    type ConLst = (HH :: HT) :: T
    val data: ConLst = d
  }
}

object Main extends App {
  val row1 = HList(1, 2, 3)
  val row2 = HList(4, 5, 6)

  val matrix: Matrix[_3, _2, Int] = Matrix(row1 :: row2 :: HNil)
}