for bits = 8 downto 0
  for i = 8 downto 0    
    if i>4 or (bits-i)>4 then shortcut to next bits *
      for j = 1 to length[row[i]]
        for k = 1 to length[row[bits-i]]
          output concatenation of row[i][j] and row[bits-i][k]
        next k
      next j
  next i
next bits