解析器组合器：如何终止关键字重复

发布于 2024-08-07 12:53:57 字数 660 浏览 10 评论 0原文

我试图弄清楚如何使用关键字终止单词的重复。一个例子：

class CAQueryLanguage extends JavaTokenParsers {
    def expression = ("START" ~ words ~ "END") ^^ { x =>
        println("expression: " + x);
        x
    }
    def words = rep(word) ^^ { x =>
        println("words: " + x)
        x
    }
    def word = """\w+""".r
}

当我执行时，

val caql = new CAQueryLanguage
caql.parseAll(caql.expression, "START one two END")

它会打印 words: List(one,two, END)，表明 words 解析器已消耗了 END 关键字我的输入，使表达式解析器无法匹配。我希望 END 不与 words 匹配，这将允许 expression 成功解析。

原文

I'm trying to figure out how to terminate a repetition of words using a keyword. An example:

class CAQueryLanguage extends JavaTokenParsers {
    def expression = ("START" ~ words ~ "END") ^^ { x =>
        println("expression: " + x);
        x
    }
    def words = rep(word) ^^ { x =>
        println("words: " + x)
        x
    }
    def word = """\w+""".r
}

When I execute

val caql = new CAQueryLanguage
caql.parseAll(caql.expression, "START one two END")

It prints words: List(one, two, END), indicating the words parser has consumed the END keyword in my input, leaving the expression parser unable to match. I would like END to not be matched by words, which will allow expression to successfully parse.

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你另情深 2024-08-14 12:53:57

这是您要找的吗？

import scala.util.parsing.combinator.syntactical._

object CAQuery extends StandardTokenParsers {
    lexical.reserved += ("START", "END")
    lexical.delimiters += (" ")

    def query:Parser[Any]= "START" ~> rep1(ident) <~ "END"

    def parse(s:String) = {
       val tokens = new lexical.Scanner(s)
       phrase(query)(tokens)
   }   
}

println(CAQuery.parse("""START a END"""))       //List(a)
println(CAQuery.parse("""START a b c END"""))   //List(a, b, c)

如果您想了解更多详细信息，可以查看这篇博文

Is this what you are looking for?

import scala.util.parsing.combinator.syntactical._

object CAQuery extends StandardTokenParsers {
    lexical.reserved += ("START", "END")
    lexical.delimiters += (" ")

    def query:Parser[Any]= "START" ~> rep1(ident) <~ "END"

    def parse(s:String) = {
       val tokens = new lexical.Scanner(s)
       phrase(query)(tokens)
   }   
}

println(CAQuery.parse("""START a END"""))       //List(a)
println(CAQuery.parse("""START a b c END"""))   //List(a, b, c)

If you would like more details, you can check out this blog post

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