[antlr-interest] Difference between foo and #foo?

Michael Brade brade at informatik.uni-muenchen.de
Wed Mar 15 05:34:49 PST 2006

On Wednesday 15 March 2006 13:39, Martin Probst wrote:
> > what is the exact difference between the trees referenced by foo and #foo
> > if declared like this:
> >   #( ... foo:children )
> foo is just some Java text, and #foo is text that is supposed to be
> handled by ANTLR. Meaning: if your action contains #something, ANTLR
> will replace it with something, otherwise not.
Yup. So far, so good. But since ANTLR generates both variables, i.e.
                AST foo_AST = null;
                AST foo = null;
in every method for every label, I thought it has to have a reason.

> In your case in a TreeParser (I assume) there is actually no difference
> because the AST fragments are directly called "foo" and not "foo_AST" as in
> the parser (where just using foo will give you a compile error).
Thanks for your answer, in the meantime I sat down and tried to understand the 
generated code---successfully :-) So no, it's not the same: foo == #foo_in! 
So no wonder I didn't understand my results, in case you forget the '#', what 
you get is not the output tree but the input tree for that rule.... creepy ;)

Michael Brade;                 KDE Developer, Student of Computer Science
  |-mail: echo brade !#|tr -d "c oh"|s\e\d 's/e/\@/2;s/$/.org/;s/bra/k/2'
  °--web: http://www.kde.org/people/michaelb.html

KDE 4: Beyond Your Expectations
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