parboiled2非法规则合成

Question

我正在写一个cron解析器，但是编译器抱怨非法的规则组合，

我的解析器怎么了？

import org.parboiled2._

sealed trait Part
case class Fixed(points: Seq[Int]) extends Part
case class Range(start: Int, end: Int) extends Part
case class Every(start: Int, interval: Int) extends Part
case object Full extends Part
case object Ignore extends Part

class CronParser(val input: ParserInput) extends Parser {

  def number = rule { capture(digits) ~> (_.toInt) }

  def digits = rule { oneOrMore(CharPredicate.Digit) }

  def fixed = rule { oneOrMore(number).separatedBy(",") ~> Fixed }

  def range = rule { digits ~ '-' ~ digits ~> Range }

  def every= rule { digits ~ '/' ~ digits ~> Every }

  def full= rule { '*' ~ push(Full) }

  def ignore = rule { '?' ~ push(Ignore) }

  def part = rule { fixed | range | every | full | ignore }

  def expr = rule { part ~ part ~ part ~ part ~ part}
}

Answer 1

您使用的是digits，我认为您想要使用number。以下内容应该可以很好地工作：

class CronParser(val input: ParserInput) extends Parser {
  def number = rule { capture(digits) ~> (_.toInt) }
  def digits = rule { oneOrMore(CharPredicate.Digit) }
  def fixed = rule { oneOrMore(number).separatedBy(",") ~> Fixed }
  def range = rule { number ~ '-' ~ number ~> Range }
  def every = rule { number ~ '/' ~ number ~> Every }
  def full = rule { '*' ~ push(Full) }
  def ignore = rule { '?' ~ push(Ignore) }
  def part = rule { fixed | range | every | full | ignore }
  def expr = rule { part ~ part ~ part ~ part ~ part }
}

问题是digits不推送值，这意味着range等是希望从堆栈中弹出值的规则，而这些规则不能与~组合。