anchor.diff:  #import('../../lib/petitparser.dart');
   #import('lisplib.dart');
   
  -void mainWithOptions(Options options) {
  +void main() {
   
     // default options
     bool standardLibrary = true;
  
positive.code:   if (interactiveMode || files.isEmpty()) {
      evalInteractive(parser, environment, stdin, stdout);
    }
  
  }
  
  void main() {
    mainWithOptions(new Options());
  }
  
negative.code:   List files = new List();
  
    // parse arguments
    var options = new Options();
    for (var option in options.arguments) {
      if (option.startsWith('-') && files.isEmpty()) {
        if (option == '-n') {
  