scala程序运行错误，以下是源代码！大家帮忙看看

文件Element.scala 代码：
package work
import Element.elem
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 = this widen that.width
val that1 = that widen this.width
assert(this1.width == that1.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)
var right = elem(' ',w - width - left.width, height)
left beside this beside right
} ensuring(w <= _.width)
def heighten(h: Int): Element =
if(h <= height) this
else {
val top = elem(' ',width, (h - height) / 2)
var bot = elem(' ',width, h - height - top.height)
top above this above bot
}
override def toString = contents mkString "\n"
}
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(height.toString,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)
}
文件stairway.scala 代码：
package work
import work.Element._
sealed abstract class Expr
case class Var(name:String) extends Expr
case class Number(num:Double) extends Expr
case class UnOp(operator:String, arg:Expr) extends Expr
case class BinOp(operator:String, left:Expr, right:Expr) extends Expr
import work._
class ExprFormatter {
private val opGroups = Array(
Set("|", "||"),
Set("&", "&&"),
Set("^"),
Set("==", "!="),
Set("<", "<=", ">", ">="),
Set("+", "-"),
Set("*", "%")
)
private val precedence = {
val assocs =
for {
i <- 0 until opGroups.length
op <- opGroups(i)
} yield op -> i
Map( ) ++ assocs
}
private val unaryPrecedence = opGroups.length
private val fractionPrecedence = -1
private def format(e:Expr, enclPrec:Int): Element =
e match {
case Var(name) =>
elem(name)
case Number(num) =>
def stripDot(s:String) =
if (s endsWith ".0") s.substring(0, s.length - 2)
else s
elem(stripDot(num.toString))
case UnOp(op,arg) => elem(op) beside format(arg, unaryPrecedence)
case BinOp("/", left, right) =>
val top = format(left, fractionPrecedence)
val bot = format(right, fractionPrecedence)
val line = elem('-', top.width max bot.width, 1)
val frac = top above line above bot
if (enclPrec != fractionPrecedence) frac
else elem(" ") beside frac beside elem (" ")
case BinOp(op, left, right) =>
val opPrec = precedence(op)
val l = format(left, opPrec)
val r = format(right, opPrec + 1)
val oper = l beside elem(" " + op + " ") beside r
if (enclPrec <= opPrec) oper
else elem("(") beside oper beside elem(")")
}
def format(e:Expr):Element = format(e, 0)
}
文件Express.scala 代码：
package work
object Express {
def main(args:Array[String]){
val f = new ExprFormatter
val e1 = BinOp("*", BinOp("/", Number(1), Number(2)),
BinOp("+", Var("x"), Number(1)))
val e2 = BinOp("+", BinOp("/", Var("x"), Number(2)),
BinOp("/", Number(1.5), Var("x")))
val e3 = BinOp("/", e1, e2)
def show(e:Expr) = println(f.format(e) + "\n\n")
for( e <- Array(e1, e2, e3)) show(e)
}
}
在eclipse 中运行，出现异常：
Exception in thread "main" java.lang.StackOverflowError
at java.lang.reflect.Array.newArray(Native Method)
at java.lang.reflect.Array.newInstance(Unknown Source)
at scala.reflect.ClassTag$class.newArray(ClassTag.scala:62)
at scala.reflect.ClassTag$$anon$1.newArray(ClassTag.scala:144)
at scala.collection.mutable.ArrayBuilder$ofRef.mkArray(ArrayBuilder.scala:64)
at scala.collection.mutable.ArrayBuilder$ofRef.resize(ArrayBuilder.scala:70)
at scala.collection.mutable.ArrayBuilder$ofRef.ensureSize(ArrayBuilder.scala:82)
at scala.collection.mutable.ArrayBuilder$ofRef.$plus$eq(ArrayBuilder.scala:87)
at scala.collection.mutable.ArrayBuilder$ofRef.$plus$eq(ArrayBuilder.scala:57)
at scala.collection.TraversableLike$WithFilter$$anonfun$map$2.apply(TraversableLike.scala:722)
at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:108)
at scala.collection.TraversableLike$WithFilter.map(TraversableLike.scala:721)
at work.Element.beside(Element.scala:22)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
at work.Element.above(Element.scala:11)
at work.Element.heighten(Element.scala:39)
at work.Element.beside(Element.scala:18)
at work.Element.widen(Element.scala:31)
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