[antlr-interest] NullPointerException in TreeRewriter

[Terence Parr]

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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