Pet3ris

sealed trait Tensor[V] {
  val n, m: Int
  def apply(vs: List[V], vds: List[V => Double]): Double
}
 
case class TUnit[V](v: V) extends Tensor[V] {
  val n = 1
  val m = 0
  def apply(vs: List[V], vds: List[V => Double]): Double = vds head(v)
}