class RubyXL::Reference

def self.ind2ref(row = 0, col = 0)

<0> A...Z, AA...AZ, BA... ...ZZ, AAA... ...AZZ, BAA... ...XFD <16383>
Converts +row+ and +col+ zero-based indices to Excel-style cell reference 
def self.ind2ref(row = 0, col = 0)
  str = ''
  loop do
    x = col % 26
    str = ('A'.ord + x).chr + str
    col = (col / 26).floor - 1
    break if col < 0
  end
  str += (row + 1).to_s
end