print CodeTree of Assignment4 (FPPiS)

TreeUtil.scala

  def mkString(tree: CodeTree): String = {
    def __mkString(tree: CodeTree, depth: Int): String =
      List.fill(depth)('\t').mkString + "(" + chars(tree).mkString + ") " + weight(tree) + "\n" +
        (tree match {
          case Fork(left, right, chars, weight) =>
            __mkString(left, depth + 1) + __mkString(right, depth + 1)
          case Leaf(chars, weight) =>
            ""
        })
    __mkString(tree, 0)
  }

this is not SOLUTION about assignment of FPPiS. this is just utility function to helping solve an assignment.