anchor.diff:        case ANALYTICS:
           return analytics();
       }
  +    
  +    throw new Error();
     }
     
     Future executeCurl(List<String> processArgs) {
  
positive.code:   
    argParser.addOption('key', abbr: 'k',
        help: 'google api key', 
        defaultsTo: null);
    
    argParser.addOption('url', abbr: 'u',
        help: 'url',
        defaultsTo: "http://www.google.com");
    
    /* these are exclusive */
    argParser.addOption('type', abbr: 't',
        allowed: [UrlShortener.SHORTEN, UrlShortener.EXPAND, UrlShortener.ANALYTICS],
        help: "type of action to execute",
  
negative.code:   final String key;
    final String curlPath;
    
    UrlShortener({this.url: "http://www.google.com", this.command: "shorten", this.key: '', this.curlPath: "curl"});
    
    Future execute() {
      switch(command) {
        case SHORTEN:
          return shorten();
  