```Begin forwarded message:

> From: "Colin A. Bartlett" <colin / kineticweb.com>
> Date: May 2, 2007 3:47:53 AM CDT
> To: <submission / rubyquiz.com>
> Subject: Please Forward: Ruby Quiz Submission
>
> # (C) Copyright 2007, Kinetic Web Solutions, LLC.
>
> # Transliterate out anything that's not a digit
> card_number = ARGV[0].tr("^[0-9]","")
>
> def valid?(card_number)
>   # Setup a couple of variables to use
>   @sum, @digits = 0, ""
>   # Split the number into individual digits,
>   # then reverse them and pass each and it's index
>   # to the block
>   card_number.split("").reverse.each_with_index do |n,i|
>     if i % 2 == 0
>       # If its sequence in the array is even,
>       # append the digit to the string
>       @digits << n
>     else
>       # Otherwise, double it first and then
>       # append it to the string
>       @digits << (n.to_i * 2).to_s
>     end
>   end
>   # Sum up all the individual digits
>   @digits.split("").each {|n| @sum = @sum + n.to_i}
>   # Determine if it's divisible evenly by 10
>   if @sum % 10 == 0
>     return true
>   else
>     return false
>   end
> end
>
> def which_card?(card_number)
>   # Not too  much going on here, just a bunch
>   # of regexp to see which card format it matches.
>   # Source for these patterns was Wikipedia
>   case card_number
>     when /^(35[0-9]{14}|(1800|2131)[0-9]{11})\$/
>       "JCB"
>     when /^(5020|5038|6759)[0-9]{12}\$/
>       "Maestro"
>     when /^(6334|6767)([0-9]{12}|[0-9]{14}|[0-9]{15})\$/
>       "Solo"
>     when
> /^((4903|4905|4911|4936|6333|6759)([0-9]{12}|[0-9]{14}|[0-9]{15})|
> (564182|63
> 3110)([0-9]{10}|[0-9]{12}|[0-9]{13}))\$/
>       "Switch"
>     when /^((4917|4913)[0-9]{12}|417500[0-9]{10})\$/
>       "Visa Electron"
>     when /^(34|37)[0-9]{13}\$/
>       "AMEX"
>     when /^6011[0-9]{12}\$/
>       "Discover"
>     when /^5[1-5][0-9]{14}\$/
>       "MasterCard"
>     when /^4([0-9]{12}|[0-9]{15})\$/
>       "Visa"
>     when /^36[0-9]{12}\$/
>       "Diners Club (International)"
>     when /^55[0-9]{12}\$/
>       "Diners Club (North America)"
>     when /^30[0-5]{11}\$/
>       "Diners Club (Carte Blanche)"
>     else
>       "Unknown"
>   end
> end
>
> # Spit out the results
> puts "Card Number: #{card_number}"
> puts "Valid? #{valid?(card_number)}"
> puts "Card Type: #{which_card?(card_number)}"
>

```