public static void main(String[] args) {
        CalculatorGrammar cg = new CalculatorGrammar();
        if (args.length == 1) {
            CharStream cs = new CharArray(args[0].toCharArray());
            System.out.println(cg.parse("prog", cs) ? (cs.next() == -1 ? "" : "ERROR2!") : "ERROR1!");
            cg.semantics.trans("tree", cg.treeBuildingHandler.getAST(), null);
            cg.semantics.trans("default", cg.treeBuildingHandler.getAST(), new Stack<BigInteger>());
//            System.out.println(cg.treeBuildingHandler.getAST());
        }
    }