return fun.toString();
return fun.toString() + super.toString();
  public String toString()  {    StringBuffer result = new StringBuffer();    if (args.length == 0) {      return fun.toString();    }    result.append(fun.toString());    result.append('(');    for (int i=0; i<args.length; i++) {      if (i != 0) {	result.append(',');      }      result.append(args[i].toString());    }    result.append(')');    return result.toString();  }