[antlr-interest] Another (hopefully easy) newby question
ssmith at mainstreamdata.com
Thu Aug 4 18:15:23 PDT 2011
I have created a parser/lexer. When I run it as a standard parser (no ASTs), it runs fine. I've verified with the debugger, that it generates a reasonable tree.
But, I want to run it to generate ASTs. So, I modified the code to do that (using ^ to promote operators and ! to eliminate some things). I believe that is working just fine as well.
So, here's the problem. My test harness looks like:
String filename = ".\\somefile.txt";
CharStream stream = new ANTLRFileStream(filename);
MyFilterLexer lexer = new MyFilterLexer(stream);
TokenStream tokenStream = new CommonTokenStream(lexer);
MyFilterParser parser = new MyFilterParser(tokenStream);
filter_return f = parser.filter();
I want the print out to display the AST version of the parsed data. I know it exists (at least mostly) because I can modify the top level parser item in my combined grammer as follows:
FQ '='^ filter_expr EOF!
if ($filter_expr.tree != null)
System.out.println("must be null");
This compiles and does display (almost all) the ASTs as I would expect. Note that it is referencing the "filter_expr" and not the "filter". It does not display the "(= FQ" but the rest of my ASTs appear to be properly parsed and ordered. If I change to use $filter instead, then I get the "must be null" message.
Isn't there a way to display the string of ASTs from the filter_return object? Scott Stanchfield's video would say you could do "System.out.println(f.tree.getStringTree());", but that doesn't compile with Antlr 3.4.
If I run the harness as I have it above, it simply prints "=".
What am I missing?
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