Better null pointer example

  void  output(int*  p)  {
          if  (p)
                   std::cout  <<  *p  <<  std::endl;
  }
  int  main()  {
          int  i  =  42;
          int  *p  =  &i;
          int  *q  =  NULL;
          output(p);
          output(q);
  }