10 绘制螺旋示例

1.Element类和伴生对象

import Element.elem

abstract class Element {
  def contents: Array[String]

  def height: Int = contents.length

  def width: Int = if (height == 0) 0 else contents(0).length

  def above(that: Element): Element = {
    val this1 = this widen that.width
    val that1 = 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
    val contents = new Array[String](this.contents.length)
    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"

}

object Element{

  class ArrayElement(val contents: Array[String]) extends Element

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

    override val width: Int = s.length

    override val height: Int = 1
  }

  class UniformElement(ch: Char,override val width: Int, override val height: Int) extends Element {

    private val line: String = ch.toString * width

    override val 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)

}

2.Spiral对象

import Element.elem

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)
    }
  }

  def main(args: Array[String]): Unit = {
    val nSides = 11
    println(spiral(nSides, 0))
  }
  
}

3.打印示例

+----------
|          
| +------+ 
| |      | 
| | +--+ | 
| | |  | | 
| | ++ | | 
| |    | | 
| +----+ | 
|        | 
+--------+