dependency injection by passing parameterised functions

dependencyInjection.scala

trait Pen 
type Drawing = Unit

trait Side
case object Right extends Side
case object Left extends Side

object Drawing {
  //pens everywhere, distracting us from the main drawing logic
  
  def drawHead(pen: Pen): Drawing = ???
  def drawFoot(pen: Pen, side: Side): Drawing = ???
  def drawHand(pen: Pen, side: Side): Drawing = ???

  def drawHuman(pen: Pen): List[Drawing] = {
    val head: Drawing = drawHead(pen)
    val rightHand: Drawing = drawHand(pen, Right)
    val leftHand: Drawing = drawHand(pen, Left)
    val rightFoot: Drawing = drawFoot(pen, Right)
    val leftFoot: Drawing = drawFoot(pen, Left)

    List(head, rightHand, leftHand, rightFoot, leftFoot)
  }
}

object DrawingSemiFP {

  val drawHeadInstructions: Pen => Unit = ???
  def drawFootInstructions(side: Side): Pen => Drawing = ???
  def drawHandInstructions(side: Side): Pen => Drawing = ???

  val drawHumanInstructionsTheOldWay: Pen => List[Drawing] = {
    pen =>
      val head: Drawing = drawHeadInstructions(pen)
      val rightHand: Drawing = drawHandInstructions(Right)(pen)
      val leftHand: Drawing = drawHandInstructions(Left)(pen)
      val rightFoot: Drawing = drawFootInstructions(Right)(pen)
      val leftFoot: Drawing = drawFootInstructions(Left)(pen)

      List(head, rightHand, leftHand, rightFoot, leftFoot)
  }

  val drawHumanInstructions: Pen => List[Drawing] = {
    pen =>
      val head: Pen => Drawing = drawHeadInstructions
      val rightHand: Pen => Drawing = drawHandInstructions(Right)
      val leftHand: Pen => Drawing = drawHandInstructions(Left)
      val rightFoot: Pen => Drawing = drawFootInstructions(Right)
      val leftFoot: Pen => Drawing = drawFootInstructions(Left)

      List(head, rightHand, leftHand, rightFoot, leftFoot).map(_(pen))
  }
}

object DrawingFP {

  val drawHeadInstructions: Pen => Drawing = ???
  val drawFootInstructions: Side => Pen => Drawing = ???
  val drawHandInstructions: Side => Pen => Drawing = ???

  val drawHumanInstructions: Pen => List[Drawing] = {
    pen =>
      val head: Pen => Drawing = drawHeadInstructions
      val rightHand: Pen => Drawing = drawHandInstructions(Right)
      val leftHand: Pen => Drawing = drawHandInstructions(Left)
      val rightFoot: Pen => Drawing = drawFootInstructions(Right)
      val leftFoot: Pen => Drawing = drawFootInstructions(Left)

      List(head, rightHand, leftHand, rightFoot, leftFoot).map(_(pen))
  }
}