Scala:我可以轻推一个组合器解析器在本地贪婪吗？

Question

假设我在组合器解析器中表达了一种含糊不清的语言.有没有办法让某些表达在当地贪婪？这是我的意思的一个例子.

import scala.util.parsing.combinator._

object Example extends JavaTokenParsers {
  def obj: Parser[Any] = (shortchain | longchain) ~ anyrep

  def longchain: Parser[Any] = zero~zero~one~one
  def shortchain: Parser[Any] = zero~zero

  def anyrep: Parser[Any] = rep(any)
  def any: Parser[Any] = zero | one
  def zero: Parser[Any] = "0"
  def one: Parser[Any] = "1"
  def main(args: Array[String]) {
    println(parseAll(obj, args(0) ))
  }
}

编译后,我可以运行如下:

$ scala Example 001111
[1.7] parsed: ((0~0)~List(1, 1, 1, 1))

我想以某种方式指示第一部分obj是本地贪婪和匹配longchain.如果我改变顺序,它会匹配longchain,但这不是因为贪婪.

def obj: Parser[Any] = (longchain | shortchain) ~ anyrep

Answer 1

用途|||:

object Example extends JavaTokenParsers {
  def obj: Parser[Any] = (shortchain ||| longchain) ~ anyrep

  def longchain: Parser[Any] = zero~zero~one~one
  def shortchain: Parser[Any] = zero~zero

  def anyrep: Parser[Any] = rep(any)
  def any: Parser[Any] = zero | one
  def zero: Parser[Any] = "0"
  def one: Parser[Any] = "1"
  def main(args: Array[String]) {
    println(parseAll(obj, args(0) ))
  }
}

scala> Example.main(Array("001111"))
[1.7] parsed: ((((0~0)~1)~1)~List(1, 1))