[antlr-interest] NullPointerException in TreeRewriter
Terence Parr
parrt at cs.usfca.edu
Thu Mar 26 13:40:56 PDT 2009
Doh! HMm...not sure it should create new state. here is super(input)
ctor:
public TreeParser(TreeNodeStream input) {
super(); // highlight that we go to super to set state object
setTreeNodeStream(input);
}
that super() calls
public BaseRecognizer() {
state = new RecognizerSharedState();
}
So I think state is set. We need the adaptor ....
Ok, TreeFilter/Rewriter need:
public TreeFilter(TreeNodeStream input) {
this(input, new RecognizerSharedState());
}
to call other ctor :) Try that.
Ter
On Mar 26, 2009, at 6:57 AM, Anders Hessellund wrote:
> Hi,
>
> I found the cause. When you call the 1-arg constructor in the
> TreeRewriter class, it does not set the TreeAdaptor:
>
> public TreeRewriter(TreeNodeStream input) {
> super(input);
> }
> public TreeRewriter(TreeNodeStream input, RecognizerSharedState
> state) {
> super(input, state);
> originalAdaptor = input.getTreeAdaptor();
> originalTokenStream = input.getTokenStream();
> }
>
> Shouldn't the 1-arg constructor rather be?
>
> public TreeRewriter(TreeNodeStream input) {
> super(input,new RecognizerSharedState());
> }
> public TreeRewriter(TreeNodeStream input, RecognizerSharedState
> state) {
> super(input, state);
> originalAdaptor = input.getTreeAdaptor();
> originalTokenStream = input.getTokenStream();
> }
>
> Cheers,
>
> Anders
>
> On Thu, Mar 26, 2009 at 9:39 AM, Anders Hessellund <anders.hessellund at gmail.com
> > wrote:
> Hi,
>
> You're right I did not set a tree adaptor. I was actually trying the
> example from the wiki but there is no mention of a tree adaptor there?
>
> http://www.antlr.org/wiki/display/~admin/2008/11/30/Example+tree
> +rewriting+with+patterns
>
> Any ideas?
>
> -- Anders
>
>
> On Wed, Mar 25, 2009 at 9:20 PM, Terence Parr <parrt at cs.usfca.edu>
> wrote:
> weird. oh, if you look at code it thinks the adaptor is null...maybe
> you set it incorrectly or don't have one on the nodestream or reducer?
> Ter
>
> On Mar 25, 2009, at 12:10 PM, Anders Hessellund wrote:
>
> Hi,
>
> I just updated to 3.1.3 to try TreeRewriter but I get a strange
> NullPointerException?
>
> This is my tree grammar:
>
> tree grammar Reducer;
> options {
> tokenVocab=Expression;
> ASTLabelType=CommonTree;
> output=AST;
> filter=true;
> }
> topdown
> : ^(MULT a=. b=INT {$b.int==0}?) -> $b // x*0 -> 0
> ;
> bottomup
> : ^(DIV a=. b=INT {$b.int==0}?) -> $b // x*0 -> 0
> ;
>
> I use the following code to invoke the Reducer. (tree is the
> CommonTree object from my parse)
>
> final CommonTreeNodeStream nodes = new CommonTreeNodeStream(tree);
> final McAntlrExpressionReducer reducer = new
> McAntlrExpressionReducer(nodes,env);
> tree = (CommonTree) reducer.downup(tree);
>
> When I run this on the following expression "3*0" I get the
> following error:
>
> 20:09:08.226 [main] DEBUG expression.Expression - parsing '3*0'
> results in this AST: (* 3 0)
> 20:09:08.226 [main] DEBUG expression.Expression - before reduction:
> (* 3 0)
> java.lang.NullPointerException
> at
> org
> .antlr
> .runtime.tree.CommonTreeNodeStream.<init>(CommonTreeNodeStream.java:
> 67)
> at
> org.antlr.runtime.tree.TreeRewriter.applyOnce(TreeRewriter.java:56)
> at org.antlr.runtime.tree.TreeRewriter$1.pre(TreeRewriter.java:86)
> at org.antlr.runtime.tree.TreeVisitor.visit(TreeVisitor.java:28)
> at org.antlr.runtime.tree.TreeRewriter.downup(TreeRewriter.java:89)
> at
> com
> .maconomy
> .expression.McAbstractExpression.reduce(McAbstractExpression.java:58)
> at
> com.maconomy.expression.test.MtReducerTest.add(MtReducerTest.java:27)
> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at
> sun
> .reflect
> .NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> at
> sun
> .reflect
> .DelegatingMethodAccessorImpl
> .invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at
> org
> .junit
> .internal
> .runners.TestMethodRunner.executeMethodBody(TestMethodRunner.java:99)
> at
> org
> .junit
> .internal
> .runners.TestMethodRunner.runUnprotected(TestMethodRunner.java:81)
> at
> org
> .junit
> .internal
> .runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:
> 34)
> at
> org
> .junit
> .internal.runners.TestMethodRunner.runMethod(TestMethodRunner.java:75)
> at
> org
> .junit.internal.runners.TestMethodRunner.run(TestMethodRunner.java:45)
> at
> org
> .junit
> .internal
> .runners
> .TestClassMethodsRunner.invokeTestMethod(TestClassMethodsRunner.java:
> 66)
> at
> org
> .junit
> .internal
> .runners.TestClassMethodsRunner.run(TestClassMethodsRunner.java:35)
> at org.junit.internal.runners.TestClassRunner
> $1.runUnprotected(TestClassRunner.java:42)
> at
> org
> .junit
> .internal
> .runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:
> 34)
> at
> org.junit.internal.runners.TestClassRunner.run(TestClassRunner.java:
> 52)
> at
> org
> .eclipse
> .jdt
> .internal
> .junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:45)
> at
> org
> .eclipse
> .jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
> at
> org
> .eclipse
> .jdt
> .internal
> .junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
> at
> org
> .eclipse
> .jdt
> .internal
> .junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
> at
> org
> .eclipse
> .jdt
> .internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
> at
> org
> .eclipse
> .jdt
> .internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:
> 196)
>
> Can anyone help me with this?
>
> -- Anders
>
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>
>
>
> --
> Anders Hessellund
> www.itu.dk/people/hessellund/
>
>
>
> --
> Anders Hessellund
> www.itu.dk/people/hessellund/
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