How do I support nested comments with ANTLR?
The standard example wont work with greedy/non-greedy, matching either
too much or not enough.
Here is a basic sample:
<!---
a comment
<!--- nested comment --->
still comment
--->
this is not commented
<!--- more commenting --->
I want to tokenise comments, rather than ignore them, since the text
inside might be significant later on.
How the comments are tokenised doesn't matter - so I don't mind if
that first comment is split into 1/2/3 tokens.
However, Given that comments can be nested to an arbitrary level, I'm
having trouble working out how to define the rule without recursing
into itself.
(For practical purposes, I could probably set a maximum of maybe
ten-twenty levels deep, but I'd prefer not to create potential edge
cases like that.)
Here's my current attempt...
COMMENT:
SUB_CommentStart
( SUB_NoComment | COMMENT )*
SUB_CommentEnd
;
fragment SUB_CommentStart : '<!---' ;
fragment SUB_CommentEnd : '--->' ;
fragment SUB_NoComment : ~(SUB_CommentStart|SUB_CommentEnd)+;
Which of course fails due to including itself - so what's the best way
to fix that?
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