[email protected] wrote:
On 09-08-18 12:43 PM, David-Sarah Hopwood wrote:
[email protected] wrote:
The last line, b., doesn't match the MC_INCORRECT token because there's
no newline after it. Is there an easy way to match this in ANTLR?
Yes. I had the same problem when matching the end of a //-style comment,
and solved it like this:
fragment ENDOFLINE
: NEWLINE
| { input.LA(1) == EOF }?
;
(If this were a non-fragment rule, it would be a problem that it can
sometimes match no characters, but since it's a fragment, that's OK.)
I want to use your solution, however it throws errors about "The
following alternatives can never be matched: 1" for MC_QUESTION and
MC_INCORRECT. Shouldn't the below work?
MC_QUESTION : INT ('.'|')') .* ENDOFLINE;
MC_INCORRECT : LETTER '.' .* ENDOFLINE;
MC_CORRECT : '*' MC_INCORRECT;
fragment ENDOFLINE : NEWLINE | { input.LA(1) == EOF }?;
fragment NEWLINE : '\r'? '\n';
fragment LETTER : ('a'..'z'|'A'..'Z');
fragment INT : '0'..'9'+;
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You probably want to move a lot of this structure into the parser and
not the lexer. It is a lot easier to just add the missing \n yourself
before parsing, especially as your lexer gets bigger/more complicated.
Jim
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