[antlr-interest] How to copy/reference hidden tokens in transformations

[dsfsdf fdsfdsf]

hi ter
Did that suggestion and it worked.
 
public void initialize(AST t)
{  hiddenBefore = ((CommonASTWithHiddenTokens)t).getHiddenBefore();
   hiddenAfter = ((CommonASTWithHiddenTokens)t).getHiddenAfter();
   super.initialize(t) 
}
 
Both hiddenBefore and hiddenAfter must be cast to type CommonASTWithHiddenTokens to allow access to the methods getHiddenAfter() and getHiddenBefore()
And replace CommonASTWithHiddenTokens objects with your new class in your parser class.
thanks for all the help.
ed. 
 

Terence Parr <parrt at cs.usfca.edu> wrote:


On Nov 16, 2004, at 8:53 AM, dsfsdf fdsfdsf wrote:

> When i am creating a new tree from my source tree that has some hidden 
> tokens, how do i copy these hidden across?
> At the moment it is not doing it automatically.
> thanks

Hi Ed. Can't remember so I did a test.

Here is a grammar:

class TP extends TreeParser;

options {
buildAST=true;
}

a : ID ;

It generates relevant code:

tmp1_AST = astFactory.create((AST)_t);
tmp1_AST_in = (AST)_t;
astFactory.addASTChild(currentAST, tmp1_AST);
match(_t,ID);

So I looked at:

/** Create a new empty AST node; if the user did not specify
* an AST node type, then create a default one: CommonAST.
*/
public AST create(AST tr) {
if (tr == null) return null; // create(null) == null
AST t = create(tr.getType());
if ( t!=null ) {
t.initialize(tr);
}
return t;
}

which invokes CommonASTWithHiddenTokens.initialize(AST) but that is 
inherited from CommonAST:

public void initialize(AST t) {
setText(t.getText());
setType(t.getType());
}

Hmm...seems like that should be override just like I do for Token arg:

public void initialize(Token tok) {
CommonHiddenStreamToken t = (CommonHiddenStreamToken)tok;
super.initialize(t);
hiddenBefore = t.getHiddenBefore();
hiddenAfter = t.getHiddenAfter();
}

Seems I forgot to do this. Ok, I suggest subclassing 
CommonASTWithHiddenTokens and overriding to be something like:

public void initialize(AST t) {
hiddenBefore = t.getHiddenBefore();
hiddenAfter = t.getHiddenAfter();
super.initialize(t);
}

Let me know if that works and I'll put it in ;)

Don't forget to use the new subclass when you set the AST type etc... 
in the parser/tree parser.

Ter
--
CS Professor & Grad Director, University of San Francisco
Creator, ANTLR Parser Generator, http://www.antlr.org
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