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POHow to force ANTLR to generate NoViableAltException?
 

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  1. POHow to force ANTLR to generate NoViableAltException?
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    <p>I'm working with antlr 3.2. I have a simple grammar that consists of atoms (which are either the characters "0" or "1"), and a rule which accumulates a comma separated list of them into a list.</p> <p>When I pass in "00" as input, I don't get an error, which surprises me because this should not be valid input:</p> <pre><code>C:\Users\dan\workspace\antlrtest\test&gt;java -cp antlr-3.2.jar org.antlr.Tool Test.g C:\Users\dan\workspace\antlrtest\test&gt;javac -cp antlr-3.2.jar *.java C:\Users\dan\workspace\antlrtest\test&gt;java -cp .;antlr-3.2.jar TestParser [0] </code></pre> <p>How can I force a error to be generated in this case? It's particularly puzzling because when I use the interpreter in ANTLRWorks on this input, it <em>does</em> show a NoViableAltException.</p> <p>I find that if I change the grammar to require, say, a semicolon at the end, an error <em>is</em> generated, but that solution isn't available to me in the real grammar I am working on.</p> <p>Here is the grammar, which is self-contained and runnable:</p> <pre><code>grammar Test; @parser::members { public static void main(String[] args) throws Exception { String text = "00"; ANTLRStringStream in = new ANTLRStringStream(text); TestLexer lexer = new TestLexer(in); CommonTokenStream tokens = new CommonTokenStream(lexer); System.out.println(new TestParser(tokens).mainRule()); } } mainRule returns [List&lt;String&gt; words] @init{$words = new ArrayList&lt;String&gt;();} : w=atom {$words.add($w.text);} (',' w=atom {$words.add($w.text);} )* ; atom: '0' | '1'; WS : ( '\t' | ' ' | '\r' | '\n'| '\u000C' )+ { $channel = HIDDEN; } ; </code></pre>
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    1. USDan Becker
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