virtual multi1d<int> operator() (const multi1d<int>& coord, int sign) const
virtual multi1d<int> operator() (const multi1d<int>& coord, int sign, int dir) const
  virtual multi1d<int> operator() (const multi1d<int>& coord, int sign) const    {      multi1d<int> lc = coord;      const multi1d<int>& nrow = Layout::lattSize();      int m = 1;      lc[m] = (coord[m] + 1*sgnum(sign) + 4*nrow[m]) % nrow[m];      return lc;    }