anchor.diff:  
   let
   
  +  cfg = config.networking.wireless;
     configFile = "/etc/wpa_supplicant.conf";
   
     ifaces =
  -    config.networking.wireless.interfaces ++
  +    cfg.interfaces ++
       optional (config.networking.WLANInterface != "") config.networking.WLANInterface;
   
   in
  
positive.code:         ${config.system.build.upstart}/sbin/restart wpa_supplicant
        '';
  
    };
  
  }
  
negative.code: 
    options = {
    
      networking.WLANInterface = mkOption {
        default = "";
        description = "Obsolete. Use <option>networking.wireless.interfaces</option> instead.";
      };
  
      networking.wireless = {
        enable = mkOption {
          default = false;
          description = ''
            Whether to start <command>wpa_supplicant</command> to scan for
            and associate with wireless networks.  Note: NixOS currently
            does not generate <command>wpa_supplicant</command>'s
            configuration file, <filename>${configFile}</filename>.  You
            should edit this file yourself to define wireless networks,
            WPA keys and so on (see
            <citerefentry><refentrytitle>wpa_supplicant.conf</refentrytitle>
            <manvolnum>5</manvolnum></citerefentry>).
          '';
        };
  
        interfaces = mkOption {
          default = [];
          example = [ "wlan0" "wlan1" ];
          description = ''
            The interfaces <command>wpa_supplicant</command> will use.  If empty, it will
            automatically use all wireless interfaces.
          '';
        };
  
        driver = mkOption {
          default = "";
          example = "nl80211";
          description = "force a specific wpa_supplicant driver";
        };
  
        userControlled = {
          enable = mkOption {
            default = false;
            description = ''
              Allow normal users to control wpa_supplicant through wpa_gui or wpa_cli.
              This is useful for laptop users that switch networks a lot.
  
              When you want to use this, make sure ${configFile} doesn't exist.
              It will be created for you.
  
              Currently it is also necesarry to explicitly specify networking.wireless.interfaces
            '';
          };
  
          group = mkOption {
            default = "wheel";
            example = "network";
            type = types.string;
            description = "members of this group can control wpa_supplicant";
          };
        };
      };
    };
  
  
    ###### implementation
    
    config = mkIf cfg.enable {
  
      environment.systemPackages =  [ pkgs.wpa_supplicant ];
  
  