gistfile1.rb

def mod10_febraban(value)
  result_string = ""
  factor        = 2
  total         = 0
  value.each_char do |c| 
    result_string << (c.to_i * factor).to_s
    factor = (factor == 2 ? 1 : 2)
  end
  result_string.each_char { |c| total += c.to_i }
  result = 10 - total % 10
  result == 10 ? 0 : result
end