scalamuUnfoldExamples.sc

val zeroTo: GenericCoalgebra[Int, Option, Int] = n => {
  require { n >= 0 }
  if   (n == 0) (0, None)
  else          (n, Some(n - 1))
}

val treeFromInt: GenericCoalgebra[Int, List, Int] = n => {
  require { n >= 0 }
  if (n == 0) (0, List.empty)
  else        (n, List(n - 1, n - 1))
}

def treeFromInt2(n: Int): (Int, () => Stream[Int]) = {
  require { n >= 0 }
  if (n == 0) (0, () => Stream.empty)
  else        (n, () => Stream(n - 1, n - 1))
}

// Tree.unfoldTree(3)(treeFromInt)