// use one of these to force desired sort order in assoc. containers of DPX

  // use one of these to force desired sort order in assoc. containers of DPX

  bool

  bool

  {

  {

    return (r_ != p.r_) ? (r_ < p.r_) : ((g_ != p.g_) ? (g_ < p.g_) : (b_ < p.b_));

    return (r_ != p.r_) ? (r_ < p.r_) : ((g_ != p.g_) ? (g_ < p.g_) : (b_ < p.b_));

  }

  }