public static void main(String[] args) {
        symbolTable = new SymbolTable();
        symbolTable.setFunction("add", new AddFunction());
        symbolTable.setFunction("square", new SquareFunction());
        
        Scanner scanner = new Scanner(System.in);
        String in = "";
        
        Parser p = new Parser();
        
        do {
           System.out.println();
           System.out.print("> ");
           in = scanner.nextLine();
           
           if(!in.equals("")) {
               System.out.print(p.evaluate(in).evaluate());
           }
        } while(!in.equals(""));
        
        scanner.close();
    }