Run-length encoding of a list (direct solution). Implement the so-called run-length encoding data compression method directly. I.e. don't use other methods you've written (like P09's pack); do all the work directly. Example: scala> encodeDirect(List('a, 'a, 'a, 'a, 'b, 'c, 'c, 'a, 'a, 'd, 'e, 'e, 'e, 'e)) res0: List[(Int, Symbol)] = List((4,'a),…

runLengthEncoder.scala

def encodeDirect[A](input: List[A]): List(Int, A) = input match {
  case Nil => Nil
  case h :: t => collapse(collate(input))
}


def collate(input: List[A]): List[A] = input match {
  case Nil => Nil
  case h :: t => if(t.headOption.map(_==h).getThisOr(false)) h :: collate(t) else list(h) :: collate(t)
}

def collapse(input: List[List[A]]): List(Int, A) = input match{
  case Nil => Nil
  case h :: t => List(h.length, h.head) :: collapse(t)
}