/**
* @param string must contain a well-formed formula string of boolean literals and operators..
* @return Formula corresponding to the string
*/
public static ParseTree parse(String string) {
// Create a stream of tokens using the lexer.
CharStream stream = new ANTLRInputStream(string);
FormulaLexer lexer = new FormulaLexer(stream);
lexer.reportErrorsAsExceptions();
TokenStream tokens = new CommonTokenStream(lexer);
// Feed the tokens into the parser.
FormulaParser parser = new FormulaParser(tokens);
parser.reportErrorsAsExceptions();
// Generate the parse tree using the starter rule.
ParseTree tree = parser.orExpr(); // "root" is the starter rule.
// debugging option #1: print the tree to the console
// System.err.println(tree.toStringTree(parser));
// debugging option #2: show the tree in a window
// ((RuleContext)tree).inspect(parser);
// debugging option #3: walk the tree with a listener
// new ParseTreeWalker().walk(new FormulaListener_PrintEverything(), tree);
// Finally, construct a Document value by walking over the parse tree.
// ParseTreeWalker walker = new ParseTreeWalker();
// FormulaListener_FormulaCreator listener = new FormulaListener_FormulaCreator();
// walker.walk(listener, tree);
// return the Document value that the listener created
return tree;
}
