前面我们基本完成了布局元素的函数库，现在我们就可以写个程序来使用这个函数库，下面显示螺旋线的程序如下：
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]) {
val nSides=args(0).toInt
println(spiral(nSides,0))
}
}因为Sprial为一单例对象，并包含main方法，因此它为一Scala应用程序，可以在命令行使用scala Sprial xx来运行这个应用。
root@mail:~/scala# scala Spiral 5 +---- | | ++ | | +--+ root@mail:~/scala# scala Spiral 23 +---------------------- | | +------------------+ | | | | | +--------------+ | | | | | | | | | +----------+ | | | | | | | | | | | | | +------+ | | | | | | | | | | | | | | | | | +--+ | | | | | | | | | | | | | | | | | | | | ++ | | | | | | | | | | | | | | | | | | | +----+ | | | | | | | | | | | | | | | +--------+ | | | | | | | | | | | +------------+ | | | | | | | +----------------+ | | | +--------------------+
这个例子的完整代码如下：
object Element {
private class ArrayElement(val contents: Array[String])
extends Element
private class LineElement(s:String) extends Element {
val contents=Array(s)
override def width = s.length
override def height = 1
}
private class UniformElement (ch :Char,
override val width:Int,
override val height:Int
) extends Element{
private val line=ch.toString * width
def contents = 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)
}
import Element.elem
abstract class Element {
def contents: Array[String]
def height: Int = contents.length
def width: Int = 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
Element.elem(
for(
(line1,line2) <- this1.contents zip that1.contents
) yield line1+line2
)
}
def widen(w: Int): Element =
if (w <= width) this
else {
val left = Element.elem(' ', (w - width) / 2, height)
var right = Element.elem(' ', w - width - left.width, height)
left beside this beside right
}
def heighten(h: Int): Element =
if (h <= height) this
else {
val top = Element.elem(' ', width, (h - height) / 2)
var bot = Element.elem(' ', width, h - height - top.height)
top above this above bot
}
override def toString = contents mkString "\n"
}
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]) {
val nSides=args(0).toInt
println(spiral(nSides,0))
}
}到目前为止，你看到了Scala里与面向对象编程有关的更多的概念。其中，你遇到了抽象类，继承和派生，类层次，参数化字段，及方法重载。你应当已经建立了在Scala里构造不太小的类层次的感觉。
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