特殊注释不能匹配词法分析器规则

问题描述

我想解析的一个示例文本就是这样-

One example text I like to parse is like this -

@comment {
    { something }
    { something else }
}

基本上，"@ comment"是搜索的关键，其后是一对匹配的花括号.我不需要分析括号之间的含义.由于这类似于C'的多行注释，因此我的语法是:

Basically "@comment" is the key to search, after that is a pair of matching braces. I do not need to parse what is between the braces. Since this is similar to C' multi-line comment, I have my grammar based on that:

grammar tryit;


tryit : top_cmd
        ;

WS : ('\t' | ' ')+  {$channel = HIDDEN;};

New_Line : ('\r' | '\n')+   {$channel = HIDDEN;};

top_cmd :cmds
        ;

cmds
    : cmd+
    ;

cmd
    : Comment
    ;

Comment
    : AtComment    Open_Brace  ( options {greedy = false; }: . )+  Close_Brace
    ;

AtComment
    : '@comment'
    ;

Open_Brace
    : '{'
    ;

Close_Brace
    : '}'
    ;

但是在ANTLRWORKS中进行测试时，我立即得到了EarlyExitException.

But in testing in ANTLRWORKS, I get a EarlyExitException immediately.

您看到什么地方了吗?

推荐答案

我看到了两个问题:

1. 您没有考虑"@ comment" 和第一个"{" 之间的空格.请注意，对于解析器规则，空格位于HIDDEN通道上；对于词法分析器规则，空格位于 不是 ！
2. 带有(options {greedy = false;}:.)+ ，您只是在匹配第一个}" ，而不是大括号.

1. you didn't account for the spaces between "@comment" and the first "{". Note that the spaces are put on the HIDDEN channel for parser rules, not for lexer rules!
2. with ( options {greedy = false; }: . )+ you're just matching the first "}", not balanced braces.

尝试这样的方法:

tryit
 : top_cmd
 ;

top_cmd
 : cmds
 ;

cmds
 : cmd+
 ;

cmd
 : Comment
 ;

Comment
 : '@comment' ('\t' | ' ')* BalancedBraces
 ;

WS
 : ('\t' | ' ')+  {$channel = HIDDEN;}
 ;

New_Line
 : ('\r' | '\n')+   {$channel = HIDDEN;}
 ;

fragment
BalancedBraces
 : '{' (~('{' | '}') | BalancedBraces)* '}'
 ;

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