Given instances

[eed3si9n]

https://docs.scala-lang.org/scala3/reference/contextual/givens.html

given intOrd: Ord[Int] with
  def compare(x: Int, y: Int) =
    if x < y then -1 else if x > y then +1 else 0

given listOrd[T](using ord: Ord[T]): Ord[List[T]] with

  def compare(xs: List[T], ys: List[T]): Int = (xs, ys) match
    case (Nil, Nil) => 0
    case (Nil, _) => -1
    case (_, Nil) => +1
    case (x :: xs1, y :: ys1) =>
      val fst = ord.compare(x, y)
      if fst != 0 then fst else compare(xs1, ys1)