[antlr-interest] Re: JavaTreeParser? What does it do?

[jw9315]

Hi,
Thanks, that's cleared things up for me, but I've still got some 
questions if that's ok... 

I have used the example in the Java grammars directory to get the AST 
window up on my screen. All I want to be able to do from here is 
parse this tree and get the statements and constants etc, so I can 
build an interpreter... So do I just declare a treeparser and then 
invoke the "getFirstChildMethods (or whatever method I need to)" on 
the instance? For example:

JavaTreeParser tparse = new JavaTreeParser();
tparse.compilationUnit(t); //(Where t is an AST tree)
and then t.getFirstChild();

The thing is, I don't wish to manipulate the tree at all, I just want 
to read it? Does this mean that I shouldn't have to change the java 
grammars in the directory, its just a case of accessing the AST 
object in memory and extracting information from it.
Thanks,

Jon

--- In antlr-interest at yahoogroups.com, "lgcraymer" <lgc at m...> wrote:
> Tree parsers do the "getFirstChild()" and "getNextSibling()" for 
> you as well as matching a tree pattern--the whole idea is to extend 
> the ANTLR parsing concept to trees.  About the only case where you 
> might want to walk a tree without a tree parser is when 
the "Visitor" 
> pattern is appropriate.
> 
> --Loring
> 
> 
> 
> --- In antlr-interest at yahoogroups.com, "jw9315" <jw9315 at b...> wrote:
> > 
> > Hi,
> > yeah, sorry I did see that linkm but I'm new to this and didn't 
> quite 
> > understand. What I'm trying to do is build an interpreter for a 
> > *small* subset of the Java language. I ran the example in the 
Java 
> > grammars folder to give me a nice AST tree for any program I type 
in 
> > at the command line, and was planning on parsing and interpreting 
> the 
> > program using the method calls such as .getChild(). 
> > 
> > What I was confused about is the fact that I call such as "AST 
myAST 
> > = r.getFirstChild();", but what is the difference between this 
and 
> > the line "JavaTreeParser tparse = new JavaTreeParser();". I can't 
> > understand what you can do differently with the two different 
> > commands! Sorry if this is a really stupid question but if 
there's a 
> > short answer that anyone's willing to give I would be glad to 
hear 
> it.
> > Thanks,
> > Jon
> > 
> > --- In antlr-interest at yahoogroups.com, Terence Parr <parrt at j...> 
> > wrote:
> > > Hi.  Have you checked the faq entry that answers your question?
> > > 
> > > http://www.jguru.com/faq/view.jsp?EID=818959
> > > 
> > > It's called: What is a tree parser and why would I want to use 
> one?
> > > 
> > > <snicker>
> > > 
> > > Terence
> > > 
> > > On Monday, April 28, 2003, at 10:17  AM, jw9315 wrote:
> > > 
> > > > Hi,
> > > > I'm a brand new ANTLR user. I'm using the AST tree it 
produces 
> to
> > > > create an interpreter for a small subset of the Java 
programming
> > > > language. I was looking at the Main.java file in the grammar 
> > examples
> > > > directory, and one of the last lines says:
> > > > '
> > > > 		JavaTreeParser tparse = new JavaTreeParser();
> > > > 		try
> > > > 			{
> > > > 			tparse.compilationUnit(t);
> > > > 			System.err.println("successful walk 
of result
> > > > AST for "+f);
> > > > 		}
> > > > 		catch (RecognitionException e) {
> > > > 			System.err.println(e.getMessage());
> > > > 			e.printStackTrace();
> > > > 		}
> > > > ' Could anyone tell me what this block does in the program, 
what 
> > is
> > > > a JavaTreeParser?
> > > > Thanks,
> > > > Jon
> > > >
> > > >
> > > >
> > > >
> > > > Your use of Yahoo! Groups is subject to 
> > > > http://docs.yahoo.com/info/terms/
> > > >
> > > >
> > > >
> > > --
> > > Co-founder, http://www.jguru.com
> > > Creator, ANTLR Parser Generator: http://www.antlr.org
> > > Co-founder, http://www.peerscope.com link sharing, pure-n-simple
> > > Lecturer in Comp. Sci., University of San Francisco


 

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