[antlr-interest] Re: Tree weirdness C++ mode

[Brad Schick]

>In a parser with C++ as a target, building a tree the
>following way does not work:
>
>  ##->addChild(#[EMPTY,"empty"]);
>
>Instead I have do to this:
> 
>astFactory->addASTChild(currentAST, #[EMPTY,"empty"]);

I can think of two possible work arounds that are more language 
agnostic.

1) Add a bogus empty rule that injects the fake node:

rule: A B empty;
empty : { ##=#[DECLARE,"empty"]; };

2) Label everything and build the entire tree manually:

rule : a:A b:B {##=#(#antlr::nullAST,#a,#b,#[EMPTY,"empty"]);};

The second solution messes with your grammar less, but it still 
language dependent. It seems cleaner than the calling astFactory 
directly though.

-Brad



 
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