Validate Estonian national identification code with Ruby.

isikukood.rb

#
# Validate Estonian national identification code.
#
# Copyright (c) 2011 Dmitri Smirnov, Mika Tuupola
#
# Adapted from:
# http://www.dmitri.me/misc/isikukood/isikukood.rb
#
# Licensed under the MIT license:
# http://www.opensource.org/licenses/mit-license.php
#

def isikukood_is_valid?(code)
  code = code.to_s
  control = code[10].chr.to_i
  2.times do |i|
    sum = 0
    j = 2 * i + 1
    10.times do |c|
      sum += j * code[c].chr.to_i
      j = 9 == j ? 1 : j + 1;
    end
    return sum == control if ((sum %= 11) < 10)
  end
end