in
with ?? Your symbol's name). You can then access all its information like this:</p>
<pre>
expr      ::= expr:e1 PLUS expr:e2    
	      {: RESULT = BinExpr.createAdd(e1,e2);           :} 
	      | NUMBER:n                 
	      {: RESULT = Expr.createConst(nxleft,n,nxright); :}
</pre>
<p>In the example, we create an expression tree from our input language. Here,
we store the location information for the subexpressions in the AST. 
This can be seen in the action for the <code>NUMBER</code>, where we acc