ANTLR 正则表达式中的范围量词语法 [英] Range quantifier syntax in ANTLR Regex

问题描述

这应该相当简单.我正在使用 ANTLR 处理词法分析器语法，并希望将变量标识符的最大长度限制为 30 个字符.我试图用这一行来完成这个(遵循正常的正则表达式 - 除了 '' 东西 - 语法):

This should be fairly simple. I'm working on a lexer grammar using ANTLR, and want to limit the maximum length of variable identifiers to 30 characters. I attempted to accomplish this with this line(following normal regex - except for the '' thing - syntax):

ID  :   ('a'..'z'|'A'..'Z') ('a'..'z'|'A'..'Z'|'0'..'9'|'_'){0,29}  {System.out.println("IDENTIFIER FOUND.");}
    ;

代码生成中没有错误，但是由于生成的代码中的一行代码导致编译失败:

No errors in code generation, but compilation failed due to a line in the generated code that was simply:

0,29

显然 antlr 将括号之间的文本部分与打印行一起放置在接受状态区域中.我搜索了 ANTLR 站点，但没有找到任何示例或对等效表达式的引用.这个表达式的语法应该是什么?

Obviously antlr is taking the section of text between the brackets and placing it in the accept state area along with the print line. I searched the ANTLR site, and I found no example or reference to an equivalent expression. What should the syntax of this expression be?

推荐答案

ANTLR 不支持 {m,n} 量词语法.ANTLR 会看到您的量词的 {}，但无法将它们与围绕您的操作的 {} 区分开来.

ANTLR does not support the {m,n} quantifier syntax. ANTLR sees the {} of your quantifier and can't tell them apart from the {} that surround your actions.

解决方法:

1. 在语义上强制执行限制.让它收集一个无限大小的 ID，然后将其作为操作代码的一部分或稍后在编译器中抱怨/截断.
2. 手动创建量化规则.

这是将 ID 限制为 8 个的手动规则示例.

This is an example of a manual rule that limits IDs to 8.

SUBID : ('a'..'z'|'A'..'Z'|'0'..'9'|'_')
      ;
ID : ('a'..'z'|'A'..'Z')
     (SUBID (SUBID (SUBID (SUBID (SUBID (SUBID SUBID?)?)?)?)?)?)?
   ;

就我个人而言，我会选择语义解决方案 (#1).如今，几乎没有理由限制语言中的标识符，更没有理由在违反此类规则时导致语法错误(编译的早期中止).

Personally, I'd go with the semantic solution (#1). There is very little reason these days to limit the identifiers in a language, and even less reason to cause a syntax error (early abort of the compile) when such a rule is violated.

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