[antlr-interest] RE: Treeparser question

[Jiho Han]

I figured out that it's referring to itself.  Makes sense now.

Another issue is - although non-critical - that I have duplicate
semantic actions for multiple rules and I don't know how to combine
them:

	compExpr	: #(OP_EQ IDENTIFIER literal) {
				AST op = compExpr_AST_in;
				AST id =
compExpr_AST_in.getFirstChild();
				AST value = id.getNextSibling();
				AddEntityQueryClause(op, id, value);
			}
			| #(OP_GT IDENTIFIER literal) {
				AST op = compExpr_AST_in;
				AST id =
compExpr_AST_in.getFirstChild();
				AST value = id.getNextSibling();
				AddEntityQueryClause(op, id, value);
			}
			| #(STARTSWITH IDENTIFIER literal) {
				AST op = compExpr_AST_in;
				AST id =
compExpr_AST_in.getFirstChild();
				AST value = id.getNextSibling();
				AddEntityQueryClause(op, id, value);
			} ;
With the rule like above, as you can see, all of the semantic actions
are identical.  Is there a way to combine them?
Also, if you take a look, I am having to use the generated code's
variable (hack) to get at the nodes.  I tried labeling them as:

#(op:OP_EQ id:IDENTIFIER value:literal) but then it complained for the
alternatives (for redeclaring them).  Then I added an init section that
declares them
{
    AST op, id, value;
}

And tried #(op=OP_EQ id=IDENTIFIER value=literal) but it croaked again.
What am I doing wrong?
Thanks

> _____________________________________________ 
> From: 	Jiho Han  
> Sent:	Tuesday, July 25, 2006 1:42 PM
> To:	antlr-interest at antlr.org
> Subject:	Treeparser question
> 
> In this example from a tutorial,
> 
> class ExpressionParser extends Parser;
> options { buildAST=true; }
> 
> expr     : sumExpr SEMI!;
> sumExpr  : prodExpr ((PLUS^|MINUS^) prodExpr)* ; 
> prodExpr : powExpr ((MUL^|DIV^|MOD^) powExpr)* ;
> powExpr  : atom (POW^ atom)? ;
> atom     : INT ;
> 
> class ExpressionLexer extends Lexer;
> 
> PLUS  : '+' ;
> MINUS : '-' ;
> MUL   : '*' ;
> DIV   : '/' ;
> MOD   : '%' ;
> POW   : '^' ;
> SEMI  : ';' ;
> protected DIGIT : '0'..'9' ;
> INT   : (DIGIT)+ ;
> 
> {import java.lang.Math;}
> class ExpressionTreeWalker extends TreeParser;
> 
> expr returns [double r]
>   { double a,b; r=0; }
> 
>   : #(PLUS  a=expr b=expr)  { r=a+b; }
>   | #(MINUS a=expr b=expr)  { r=a-b; }
>   | #(MUL   a=expr b=expr)  { r=a*b; }
>   | #(DIV   a=expr b=expr)  { r=a/b; }
>   | #(MOD   a=expr b=expr)  { r=a%b; }
>   | #(POW   a=expr b=expr)  { r=Math.pow(a,b); }
>   | i:INT { r=(double)Integer.parseInt(i.getText()); }
>   ;
>    
> Does expr reference in #(PLUS  a=expr b=expr) in the treeparser refer
> to itself or the one in ExpressionParser?
> Basically, I am having a hard time going from a parser to a tree
> parser in my own project.
> Thanks
> 
> Jiho Han
> Senior Software Engineer
> Infinity Info Systems
> The Sales Technology Experts
> Tel: 212.563.4400 x216
> Fax: 212.760.0540
> jhan at infinityinfo.com
> www.infinityinfo.com <http://www.infinityinfo.com/> 
> 
> 
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