ANTLR4 grammar rule skip all comments except...

[Jörg Pichler]

Hi everybody,

I have the following lexer rule:

COMMENT : ('*'|'!'|'.') (.)*? '\n' -> skip;

My Input might contain *ABC or *CDE, now I want to have those (and only those) tokens to be available in my parse listener (in one way or another), meaning that the parser needs to get these tokens. Is there a special trick to do this?

Thanks.

[Sam Harwell]

No. The “skip” command completely suppresses even the generation of the token. If you want to generate the Token but hide it from the parser, use the following command instead:

 

COMMENT : ('*'|'!'|'.') (.)*? '\n' -> channel(HIDDEN);

 

Also, you should be aware that your current rule will not allow a COMMENT to appear at the end of a file which does not contain a final newline character. You might consider the following rule instead:

 

COMMENT : ('*'|'!'|'.') ~'\n'* -> channel(HIDDEN);

 

Thank you,

--

Sam Harwell

Owner, Lead Developer

http://tunnelvisionlabs.com

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