[antlr-interest] Resetting an AST tree walker

[Steve Souza]

reset does work on BufferedTreeNodeStream does seem to work properly and my
code works 4 times faster with BufferedTreeNodeStream so that seems to fix
my problem.  I would think CommonTreeNodeStream should work however, so it
seems like a bug.

On Wed, Apr 22, 2009 at 9:56 PM, Michael Bedward
<michael.bedward at gmail.com>wrote:

> Hi Steve,
>
> I posted the message you're quoting.  Just to clarify - I call the
> reset method too.  My problem was that prior to 3.1.3 reset worked
> with CommonTreeNodeStream but with 3.1.3 the stream is empty after the
> tree walker has used it once so reset is useless.
>
> I think this should have been highlighted in the release notes for
> 3.1.3.  It seems like a fairly major change and it caused me a lot of
> grief for a while !
>
> Michael
>
> 2009/4/22 Steve Souza <steve at stevesouza.com>:
> > This question in the antlr archives is the same one I have:  "Is this now
> > the correct practice where a tree walker is to be invoked repeatedly ?"
> >
> > http://www.antlr.org/pipermail/antlr-interest/2009-March/033823.html
> >
> > The poster says that using BufferedTreeNodeStream instead of
> > CommonTreeNodeStream solved his problem.  This didn't work for me.
> However,
> > calling the following method after each tree walk worked.  Is this the
> > preferred way to handle multiple tree walks or is there a better way?
> >
> > Also is the only disadvantage of using BufferedNodeStream increased
> memory?
> > Does anyone know if this memory difference is significant.  fyi I am
> getting
> > about 4 times the performance on my test case with BufferedNodeStream.
> >
> >              private void resetStream() {
> >                 TreeNodeStream nodeStream=getTreeNodeStream();
> >                 if (nodeStream instanceof BufferedTreeNodeStream)
> >                   ((BufferedTreeNodeStream)nodeStream).reset();
> >                 else if (nodeStream instanceof CommonTreeNodeStream)
> >                   ((CommonTreeNodeStream)nodeStream).reset();
> >
> >              }
> >
> > On Mon, Apr 20, 2009 at 12:13 PM, Steve Souza <steve at stevesouza.com>
> wrote:
> >>
> >> I have an AST TreeWalker that inherits from TreeParser.  In the code
> below
> >> this class is called MyASTWalker.   The language I am creating takes a
> >> string like the following:  7*5+myvariable
> >>
> >> myvariable is determined at runtime.  The first call to calc() works
> (this
> >> calculates the answer), however subseqent calls cause an EOF error.  I
> could
> >> recreate MyASTWalker(nodes) for each call to calc(), however that seems
> >> inefficient.  Is there a way to accomplish the same thing by calling
> reset()
> >> on a particular object such as TreeParser or CommonTreeNodeStream?
> >>
> >> Also, what is the difference between CommonTreeNodeStream and
> >> BufferedTreeNodeStream?
> >>
> >> ...
> >>  CommonTree commonTree=(CommonTree)ast.getTree();
> >>  CommonTreeNodeStream nodes=new CommonTreeNodeStream(commonTree);
> >>  MyASTWalker walker=new MyASTWalker(nodes);
> >>
> >>
> >>                     for (int i=0;i<100;i++) {
> >>                         System.out.println(walker.calc());
> >>                     }
> >>
> >>
> >>
> >> antlr-interest at antlr.org
> >
> >
> >
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> >
> >
>
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