if (narg == 0) error->all("Illegal next command");

  // check that variables exist and are all the same style

  // exception: UNIVERSE and ULOOP variables can be mixed in same next command

  for (int iarg = 0; iarg < narg; iarg++) {

    ivar = find(arg[iarg]);

    if (ivar == -1) error->all("Invalid variable in next command");

    if (style[ivar] != style[find(arg[0])])

    if (style[ivar] == ULOOP && style[find(arg[0])] == UNIVERSE) continue;

    else if (style[ivar] == UNIVERSE && style[find(arg[0])] == ULOOP) continue;

    else if (style[ivar] != style[find(arg[0])])

      error->all("All variables in next command must be same style");

  }