[antlr-interest] Custom AST node type - guidance needed

[Bill Andersen]

Thanks John

Below is my class def..  Eclipse tells me the casts to Token below are required.  Running a grammar that executes these constructors tells me I can't cast to Token.

Here's a sample tree building expression where this class is used.

	^(AS_TYPE_LIST<ASNode>[s.getType($ID.text)] ID)

the getType method just looks up a ASType object by name from a table.

import org.antlr.runtime.tree.*;

import antlr.*;

public class ASNode extends CommonTree {
	
	public ASType type = null;
	
	public ASNode() { }
	
	public ASNode(int ttype, ASType type) {
		token = (Token) new CommonToken(ttype,"");
		this.type = type;
	}
	
	public ASNode(int ttype) {
		token = (Token) new CommonToken(ttype,"");
	}
	
	@Override
	public String toString() {
		return (token!=null?token.getText():"")+"<ASNode>;"+type;
	}

	@Override
	public Tree dupNode() {
		ASNode n = new ASNode();
		n.token = token;
		n.type = type;
		return n;
	}
	
}

On Jul 19, 2010, at 15:15 , John B. Brodie wrote:

> On Mon, 2010-07-19 at 14:29 -0400, Bill Andersen wrote:
>> Hi folks
> 
> Greetings!
> 
>> 
>> Having some trouble making ASTs using a custom node type.  Before I ask any stupid questions, what is the best place to look on how to do this ( I'm using 3.2 )?  I'm finding bits and pieces, some of them contradictory.  For example I find this example
>> 
>> static class V extends CommonTree {
>>  public int x,y,z;
>>  public V(int ttype, int x, int y, int z) {
>>    this.x=x; this.y=y; this.z=z; token=new CommonToken(ttype,"");
>>  }
>> at http://www.antlr.org/wiki/display/ANTLR3/Tree+construction
>> 
>> When I try to define a constructor like this I'm forced to put a cast between on CommonToken to Token, which causes a runtime can't cast error.
>> 
>> What I want is really quite simple.  Need to add one extra field to my AST nodes to carry DSL type information.
>> 
>> Any help appreciated.  Thanks.
> 
> Unable to reproduce.
> 
> Attached please find a complete example derived from the grammar on the
> above wiki page that uses the class V. maybe I'm using a different
> example than yours?
> 
> Need more info....
>   -jbb
> 
> <T.g>

Bill Andersen 
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