问题
consider the following lexer rules in ANTLR4:
ID: [a-z]+;
INT: [0-9]+;
ARRAY: ID '[' INT ']';
Is it possible in a tree walking scenario where I have access to ctx.ARRAY() (where ctx is a subclass of ParserRuleContext that was generated out of a parser rule) to get the text representation of the lexer rules ID and INT?
I currently fetch the whole text representation with ctx.ARRAY().getText() and parse the contents of ID and INT using regexes and was just wondering if there is a 'cleaner' out of the box solution ANTLR provides.
Note: Because of external dependencies making ARRAY a parser rule is not an option.
Thanks in advance for meaningful answers.
回答1:
Lexer rules in ANTLR 4 cannot be broken down into parts. This was a design decision that we made as part of a massive speed and memory improvement for ANTLR 4 lexers over ANTLR 3 lexers. ANTLR 3 lexers were recursive descent recognizers with many of the same features as parsers. In ANTLR 4, the lexer is nothing more than a DFA recognizer with support for semantic predicates, so the boundaries between the individual components of a token are not tracked at all.
You'll have to either make ARRAY a parser rule, or separately parse the result of getText() when you need to break up the token's text.
来源：https://stackoverflow.com/questions/16354912/antlr-get-text-representation-of-a-sub-lexer-rule