[antlr-interest] Problem runnign ANTLR

[Ed Keith]

I am at a machine running Windows XP.

I downloaded antlrworks-1.2.2.jar and ran it.

Then I tried to work through the tutorial at http://www.antlr.org/works/help/tutorial/calculator.html.

I pasted the Expr grammar into the editor window, selected the interpreter tab, entered "2+3*4", selected "prog", clicked on the indicated button. . .

A message in red appeared at the bottom of the window. It Read "Errors reported in console", So I clicked on the console tab and found the following message:

[16:56:01] java.lang.NullPointerException
	at org.antlr.xjlib.foundation.XJUtils.concatPath(Unknown Source)
	at org.antlr.xjlib.foundation.XJUtils.concatPath(Unknown Source)
	at org.antlr.works.components.editor.ComponentEditorGrammar.getOutputPath(Unknown Source)
	at org.antlr.works.components.editor.ComponentEditorGrammar.getANTLRTool(Unknown Source)
	at org.antlr.works.grammar.engine.GrammarEngineImpl.getANTLRTool(Unknown Source)
	at org.antlr.works.grammar.antlr.ANTLRGrammarEngineImpl.createNewGrammar(Unknown Source)
	at org.antlr.works.grammar.antlr.ANTLRGrammarEngineImpl.createParserGrammar(Unknown Source)
	at org.antlr.works.grammar.antlr.ANTLRGrammarEngineImpl.createCombinedGrammar(Unknown Source)
	at org.antlr.works.grammar.antlr.ANTLRGrammarEngineImpl.createGrammars(Unknown Source)
	at org.antlr.works.grammar.antlr.ANTLRGrammarEngineImpl.analyze(Unknown Source)
	at org.antlr.works.grammar.engine.GrammarEngineImpl.analyze(Unknown Source)
	at org.antlr.works.interpreter.EditorInterpreter.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)


A friend who is trying to convince to to give up C++ and move to Java tells me the main reason I should change is that you do not need to worry about NULL pointers in Java, looks like he is wrong.

Can anyone point me to a solution for this problem?

Thanks in advance,

   -EdK



Ed Keith
e_d_k at yahoo.com

Blog: edkeith.blogspot.com