Hi Søren, I see that error every so often and, so far al least, it has always been due to an error in my tree walker grammar - specifically an alternative that arises in the AST but that I forgot to consider in the grammar.
Michael On 28 March 2011 23:29, Søren Boisen <[email protected]> wrote: > Greetings, > I have a encountered a problem while trying to write a tree parser for my > grammar. Sometimes when trying to walk the AST and the tree parser fails to > match some input, I get the following exception: > > can't look backwards more than one token in this stream > org.antlr.runtime.misc.LookaheadStream.LB(LookaheadStream.java:159) > org.antlr.runtime.misc.LookaheadStream.LT(LookaheadStream.java:120) > > org.antlr.runtime.RecognitionException.extractInformationFromTreeNodeStream(RecognitionException.java:144) > org.antlr.runtime.RecognitionException.(RecognitionException.java:111) > > org.antlr.runtime.MismatchedTreeNodeException.(MismatchedTreeNodeException.java:42) > > org.antlr.runtime.tree.TreeParser.recoverFromMismatchedToken(TreeParser.java:135) > org.antlr.runtime.BaseRecognizer.match(BaseRecognizer.java:115) > > com.brunata.ws.rest.odata.query.NearestTelegramQueryWalker.queryOp(NearestTelegramQueryWalker.java:243) > > com.brunata.ws.rest.odata.query.NearestTelegramQueryWalker.stmt(NearestTelegramQueryWalker.java:128) > > I have looked through the FAQ, the issue tracker and Google, but I couldn't > find anything that looked related. > > From the stack trace it looks like an error in the > extractInformationFromTreeNodeStream, since I guess it shouldn't expect to > always be able to look back more than one token in a stream. > Is there a workaround for this? This is the code I use for creating parsers > and streams: > > String query = ...; // this is a parameter to the method > Map<String, String> propertyFilters = ...; // this is a field on the > class > > ANTLRStringStream input = new ANTLRStringStream(query); > QueryParserLexer lexer = new QueryParserLexer(input); > > CommonTokenStream tokens = new CommonTokenStream(lexer); > QueryParserParser parser = new QueryParserParser(tokens); > > QueryParserParser.stmt_return result = tryParse(parser, query); > ast = (CommonTree) result.getTree(); > > CommonTreeNodeStream nodes = new CommonTreeNodeStream(ast); > nodes.setTokenStream(tokens); > > NearestTelegramQueryWalker walker = new > NearestTelegramQueryWalker(nodes); > propertyFilters = tryWalk(walker, query); > > Am I using the wrong kind of token/node streams or something? > > Regards, > Søren Boisen > > List: http://www.antlr.org/mailman/listinfo/antlr-interest > Unsubscribe: > http://www.antlr.org/mailman/options/antlr-interest/your-email-address > List: http://www.antlr.org/mailman/listinfo/antlr-interest Unsubscribe: http://www.antlr.org/mailman/options/antlr-interest/your-email-address -- You received this message because you are subscribed to the Google Groups "il-antlr-interest" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/il-antlr-interest?hl=en.
