ANTL – First Steps

I’ve done very good on my C# test (I scored 929 out of 1000), so I have now a MCTS 70-536 certificate.

Today I’ve started a little ANTLR tutorial. I need to get used to using ANTLR for one of my homeworks, for the compilers class. I use the following link:

http://javadude.com/articles/antlrtut/

I am still at the lexer part and I’ve encountered a problem. First, the tutorial uses ” for quotes and the ANTLR version I’m using (1.2.1) uses simple quotes. The problmes was related to the CHARLIT rule:

CHARLIT
  : '\''! . '\''!
  ;

Because I was writting a parser grammar, I couldn’t use ! to ignore simple quotes, so I constantly got the following error message:

(133): XL.g: illegal option output
Consult the console for more information.

The console was empty, so no hints there… So in order to ignore simple quotes I’ve added a protected rule (for protected rules the lexer doesn’t create tokens):

protected QUOTE
    :    '\''
    ;

and I’ve added a filtering option:

options {
    filter=QUOTE;
}

So now my chars literal rule looks like this:

CHARLIT
    : QUOTE ~(QUOTE) QUOTE
    ;

Next step: string literals:)

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