在 JavaTokenParsers 中将空格设置为分隔符 [英] Setting Whitespace as Delimiter in JavaTokenParsers

问题描述

扩展 JavaTokenParsers，我有以下内容:

Extending JavaTokenParsers, I have the following:

class Foo extends JavaTokenParsers { 
  lazy val check = id ~ action ~ obj

  lazy val id     = "FOO" | "BAR"
  lazy val action = "GET" | "SET"
  lazy val obj = "BAZ" | "BIZ"
}

我曾假设空格将充当分隔符.换句话说，当 check 成功解析以下表达式时，我变得很困惑:FOO GETBAZ.

I had assumed that whitespace would act as a delimiter. In other words, I became confused when check parsed the following expression successfully: FOO GETBAZ.

val result = parseAll(check, "FOO GETBAZ")
println(result.get)

结果

((FOO~GET)~BAZ)

((FOO~GET)~BAZ)

我如何使用空格作为 delimiter，即上述内容无法成功解析，因为 GETBAZ 与 action 中的任何一个都不匹配's GET 还是 SET?

How can I use whitespace as a delimiter, i.e. the above wouldn't parse successfully since GETBAZ does not match either of action's GET or SET?

推荐答案

JavaTokenParser 向 RegexParsers 添加了一些方法，但它不会改变 的行为文字，它会匹配它的参数而不用担心它周围的东西.

JavaTokenParser adds some methods to RegexParsers, but it doesn't change the behavior of literal, which will match its argument without worrying about what's around it.

skipWhitespace 设置也不会帮助您，因为它只指定是否忽略空格 - 而不是是否需要.

The skipWhitespace setting isn't going to help you, either, since it only specifies whether whitespace will be ignored—not whether it's required.

您有几个选择.一种是使用带有单词边界的正则表达式:

You have a couple of options. One would be to use regular expressions with word boundaries:

class Foo extends JavaTokenParsers {
  def word(s: String): Parser[String] = regex(s"\\b$s\\b".r)

  lazy val check = id ~ action ~ obj    

  val id     = word("FOO") | word("BAR")
  val action = word("GET") | word("SET")
  val obj    = word("BAZ") | word("BIZ")
}

或ident:

class Foo extends JavaTokenParsers {
  def word(s: String): Parser[String] = ident.filter(_ == s)

  lazy val check = id ~ action ~ obj    

  val id     = word("FOO") | word("BAR")
  val action = word("GET") | word("SET")
  val obj    = word("BAZ") | word("BIZ")
}

或者您可以在每个项目之间手动添加空格解析器.

Or you could manually add whitespace parsers between each of your items.

我可能会采用 \b 解决方案，但这在很大程度上取决于品味和偏好.

I'd probably go with the \b solution, but it's largely a matter of taste and preferences.

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