     HasAdd    = 0,     HasSub    = 0,     HasMul    = 0,     HasNegate = 0,     HasAbs    = 0,     HasAbs0   = 0,     HasMin    = 0,     HasMax    = 0,     HasConj   = 0,     HasSetLinear = 0   }; };  template<typename T> struct packet_traits