super呼び出し順序

Scala
  • インスタンス自体の呼び出しの次は、右端から順番に線形に処理される。ただし、同じtraitが2回以上登場する場合はその中でも一番左端のものが採用される。
object Main extends App {
  val first = new FirstClass()
  first.run()
}

class SecondClass { def run() { println("SecondClass") } }
trait ThirdTrait  extends SecondClass { override def run() { println("ThirdTrait"); super.run() } }
trait SecondTrait extends SecondClass { override def run() { println("SecondTrait"); super.run() } }
trait FirstTrait  extends SecondTrait { override def run() { println("FirstTrait"); super.run() } }
class FirstClass  extends SecondClass with ThirdTrait with FirstTrait { override def run() { println("FirstClass"); super.run() } }


FirstClass
FirstTrait
SecondTrait
ThirdTrait
SecondClass
class FirstClass  extends SecondClass with ThirdTrait with SecondTrait with FirstTrait { override def run() { println("FirstClass"); super.run() } }

FirstClass
FirstTrait
SecondTrait
ThirdTrait
SecondClass
class FirstClass  extends SecondClass with SecondTrait with ThirdTrait  with FirstTrait { override def run() { println("FirstClass"); super.run() } }

FirstClass
FirstTrait
ThirdTrait
SecondTrait
SecondClass

sample code spiral

Scala 
import Element.elem

object Main extends App {
  val nSides = 100
  println(Spiral.spiral(nSides, 0))
}

object Spiral {
  val space = elem(" ")
  val corner = elem("+")

  def spiral(nEdges: Int, direction: Int): Element = {
    if (nEdges == 1)
      elem("+")
    else {
      val sp = spiral(nEdges - 1, (direction + 3) % 4)

      def verticalBar = elem('|', 1, sp.height)

      def horizontalBar = elem('-', sp.width, 1)

      if (direction == 0)
        (corner beside horizontalBar) above (sp beside space)
      else if (direction == 1)
        (sp above space) beside (corner above verticalBar)
      else if (direction == 2)
        (space beside sp) above (horizontalBar beside corner)
      else
        (verticalBar above corner) beside (space above sp)
    }
  }
}


object Element {

  private class ArrayElement(override val contents: Array[String]) extends Element {
  }

  private class LineElement(s: String) extends Element {
    override val contents: Array[String] = Array(s)

    override def width: Int = s.length

    override def height: Int = 1
  }

  private class UniformElement(ch: Char,
                               override val width: Int,
                               override val height: Int
                              ) extends Element {
    private val line = ch.toString * width

    override def contents: Array[String] = Array.fill(height)(line)
  }

  def elem(contents: Array[String]): Element =
    new ArrayElement(contents)

  def elem(chr: Char, width: Int, height: Int): Element =
    new UniformElement(chr, width, height)

  def elem(line: String): Element =
    new LineElement(line)
}

abstract class Element {
  def contents: Array[String]

  def width: Int = contents(0).length

  def height: Int = contents.length

  def above(that: Element): Element = {
    val this1: Element = this widen that.width
    val that1: Element = that widen this.width
    elem(this1.contents ++ that1.contents)
  }

  def beside(that: Element): Element = {
    val this1 = this heighten that.height
    val that1 = that heighten this.height
    elem(
      for (
        (line1, line2) <- this1.contents zip that1.contents
      ) yield line1 + line2
    )
  }

  def widen(w: Int): Element =
    if (w <= width) this
    else {
      val left = elem(' ', (w - width) / 2, height)
      val right = elem(' ', w - width - left.width, height)
      left beside this beside right
    }

  def heighten(h: Int): Element =
    if (h <= height) this
    else {
      val top = elem(' ', width, (h - height) / 2)
      val bot = elem(' ', width, h - height - top.height)
      top above this above bot
    }

  override def toString: String = contents mkString "\n"
}