[antlr-interest] Another Newbie Question

Tiller, Michael (M.M.) mtiller at ford.com
Mon Oct 8 10:25:56 PDT 2001

While I'm still hoping for additional responses to my previous e-mail titled "Newbie Question", I have another related question that I was hoping somebody might be able to answer.
I have a rule in my grammar that looks like this:
  : (within:within_clause)? (defs:stored_definition)* EOF!
This is my top-level production rule.  The strange thing for me is that when I write code like this:
     t = (CommonAST)parser.getAST();
The variable "t" is returned with the tree for the within clause and not for the entire "modelica_file" rule.  Is this normal?  I notice that the generated code looks like this:
   modelica_file_AST = (AST)currentAST.root;
What I was hoping for was more like:
   modelica_file_AST = (AST)currentAST;
In order to make it so that the "stored_definition" trees didn't get cut off, I changed my top level rule to:
  : (within:within_clause)? (defs:stored_definition)* EOF!
    { ## = #(#[FILE, "<file>"], ##); }

I introduced this "FILE" token type in my lexer (as protected) and I thought this was an appropriate way to deal with this situation (I'm also trying to use it in other contexts to identify important structural entities).  Anyway, this works (although it took me a while to figure out exactly how to do it).  Now, the AST returned after the "modelica_file" method is called on the parser does include both the within_clause production and all stored_definitions as well.
I guess my first question is, have I done something stupid here?
OK, next question.  I tried to write a TreeParser for this with a toplevel rule that looked like this:
  : #(FILE (within_clause)? (stored_definition)*)
Isn't this the correct way to represent this "artificial" node type?
I ask because when I run the tree parser, it fails with an error saying:
expecting FILE, found '<file>'
First, I don't quite understand why it is even paying attention to the token text as opposed to the token type?!?  I obviously don't understand something about tree parsers.  But that isn't even the problem.  If I change the token text to be "FILE", then I get this message:
expecting FILE, found 'FILE'
So, my second question is what am I doing wrong here?!?!?  I'm totally confused by this.
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