code: private static final void add(long10 xy, long10 x, long10 y) {
  		xy._0 = x._0 + y._0;	xy._1 = x._1 + y._1;
  		xy._2 = x._2 + y._2;	xy._3 = x._3 + y._3;
  		xy._4 = x._4 + y._4;	xy._5 = x._5 + y._5;
  		xy._6 = x._6 + y._6;	xy._7 = x._7 + y._7;
  		xy._8 = x._8 + y._8;	xy._9 = x._9 + y._9;
  	}
docs: /* Add/subtract two numbers.  The inputs must be in reduced form, and the
  output isn't, so to do another addition or subtraction on the output,
  first multiply it by one to reduce it.