[antlr-interest] your Or ast question

[John B. Brodie]

On Thursday 02 October 2008 09:34:11 pm Randall R Schulz wrote:
> On Thursday 02 October 2008 17:54, you wrote:
> > Mr. Schulz :-
>
> I'm sorry. My father isn't here right now...

I happen to believe that everyone deserves respect...

> > Sorry for this disconnected reply to your last message to me.
>
> It's OK. I hope you don't mind my sending the reply back to the list.

It is okay with me.

> I'm surprised this seems so difficult (not yet conceding
> impossibility!), so I think it would be generally interesting to have
> the whole list membership observe the attempts.
>

I do not think that your question is really all that difficult.

> > ...
> >
> > recapping from memory, you want
> >
> > p | q | r | s
> >
> > to be represented, essentially, as an ast of
> >
> > (| p q r s)
>
> Precisely.
>
> > ...
> >
> > maybe try this
> >
> > o : (a->a) ( ('|' a)+ -> ^('|' a+) )? ;
>
> The result is the same:
>
> 	(Or p (Or q (Or r (Or s))))

Not for me. I use the toStringTree method of the java CommonTree to obtain my 
result - is that what you are using?


this grammar file, Test.g :

-----begin cut here ----- cut here ----- cut here
grammar Test;

options {
	output = AST;
	ASTLabelType = CommonTree;
}

@members {
    private static final String [] x = new String[]{
        "s", "p | q | r | s"
    };

    public static void main(String [] args) {
        for( int i = 0; i < x.length; ++i ) {
            try {
                System.out.println("about to parse:`"+x[i]+"`");
                TestLexer lexer = new TestLexer(new ANTLRStringStream(x[i]));
                CommonTokenStream tokens = new CommonTokenStream(lexer);

                TestParser parser = new TestParser(tokens);
                TestParser.start_return p_result = parser.start();

                CommonTree ast = p_result.tree;
                if( ast == null ) {
                   System.out.println("resultant tree: is NULL");
                } else {
                   System.out.println("resultant tree: "+ast.toStringTree());
                }
                System.out.println();
            } catch(Exception e) {
                e.printStackTrace();
            }
        }
    }
}

start : o EOF! ;

o : (a->a) ( ('|' a)+ -> ^('|' a+) )? ;

a : 'p' | 'q' | 'r' | 's' ;

WS : ' '+ { $channel=HIDDEN; } ;
-----end cut here ----- cut here ----- cut here -----


using this command line in Ubuntu 8.04 Linux :

-----begin cut here ----- cut here ----- cut here
java org.antlr.Tool Test.g ; javac *.java ; java TestParser
-----end cut here ----- cut here ----- cut here -----


gets this result printed on the unix standard output device:

-----begin cut here ----- cut here ----- cut here
ANTLR Parser Generator  Version 3.1 (August 12, 2008)  1989-2008
about to parse:`s`
resultant tree: s

about to parse:`p | q | r | s`
resultant tree: (| q r s)
-----end cut here ----- cut here ----- cut here -----


do you get anything similiar to the above?

still not what you want, but perhaps closer.

so, i think, we just need to work out an appropriate use of the ANTLR tree 
building operator += on the Left Hand Side of the -> operator in order to 
compose a complete list of sub-terms.

Does this seem reasonable? 

Is that really so hard?

>....remainder of quoted message snipped....