New and improved (faster) Routing Number Generator

better_routing_number.rb

require 'rubygems'
require 'faker'

def generate_routing_number
  number = Faker::Number.number(8).to_s
  d = number.split('').map(&:to_i).select { |d| (0..9).include?(d) }
  checksum = (3 * (d[0] + d[3] + d[6])) + (7 * (d[1] + d[4] + d[7])) + (d[2] + d[5])
  if checksum%10 == 0
    d << 0
  else
    d << 10 - checksum%10
  end
  d.join('')
end