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dengsibao dengsibao

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scala 2.10.2版本的一些变化 scala > val list = List[Int] ( ) 而 val arr = new Array[Int] ( ) //这里List不能new 实例化，因为List定义为abstract scala > import scala.collection.mutable.ListBuffer scala > val buf = new ListBuffer[Int] ( ) //可见列表缓存不是abstact class scala > buf += 1 res1 : buf.type = ListBuffer(1) scala > buf += 2 res2 : buf.type = ListBuffer(1, 2) scala > 3 +: buf res3 : scala.collection.mutable.ListBuffer[Int] = ListBuffer(3, 1, 2) scala > buf.toList res4 : Lsit[Int] = List(1, 2) 这个 +: 前缀操作符，返回的是新列表，与programming in scala 2nd Edition 写的不同数组缓存（ArrrayBuffer）也是一样的变化 scala > import scala.collection.immutable.Queue scala > val empty = new Queue[Int] ( ) <console> : error ...............这里Queue不能new 实例化 scala> val empty = Queue[int]( ) res5: scala.collection.immutable.Queue[Int] = Queeu ( )

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) ··················

各位学长学姐，学弟学妹。跪求外语学院刘小兵老师电话！！！！！各位学长学姐，学弟学妹。跪求外语学院刘小兵老师电话！！！！！

江财蛟桥园南校区，“东门”本校学生开了个炒粉店。希望大家大光顾光顾！

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