首页 / SCALA / scala编程第15章
scala编程第15章
内容导读
互联网集市收集整理的这篇技术教程文章主要介绍了scala编程第15章,小编现在分享给大家,供广大互联网技能从业者学习和参考。文章包含2108字,纯文字阅读大概需要4分钟。
内容图文
![scala编程第15章](/upload/InfoBanner/zyjiaocheng/1327/1a5415d52b334d7196355e99fd12946b.jpg)
package myscala15
import myscala.Element.elem
import myscala.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
class ExprFormatter {
//包含了递增优先级的组中的操作符
private val opGroups =
Array(
Set("|", "||"),
Set("&", "&&"),
Set("^"),
Set("==", "!="),
Set("<", "<=", ">", ">="),
Set("+", "-"),
Set("*", "%")
)
//操作符优先级映射
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)
}
object Express extends App {
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 (val e <- Array(e1, e2, e3)) show(e) 显示出错可做如下等价修改
Array(e1, e2, e3).foreach(e => show(e))
}
原文:http://www.cnblogs.com/gaopeng527/p/4079276.html
内容总结
以上是互联网集市为您收集整理的scala编程第15章全部内容,希望文章能够帮你解决scala编程第15章所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错,欢迎将互联网集市网站推荐给程序员好友。
内容备注
版权声明:本文内容由互联网用户自发贡献,该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容, 请发送邮件至 gblab@vip.qq.com 举报,一经查实,本站将立刻删除。
内容手机端
扫描二维码推送至手机访问。