# \[QUIZ\] Checking Credit Cards (#122) **URL:** https://rubytalk.org/t/quiz-checking-credit-cards-122/37348 **Category:** ruby-talk **Created:** [2 May 2007 18:37 UTC](https://rubytalk.org/t/quiz-checking-credit-cards-122/37348 "2007-05-02T18:37:31Z") **Posts on this page:** 1 **Page:** 1
### Author: ![Chase\_Southard](https://avatars.discourse-cdn.com/v4/letter/c/439d5e/32.png) [@Chase\_Southard](https://rubytalk.org/u/Chase_Southard) #### Post date: [2 May 2007 18:37 UTC](https://rubytalk.org/t/quiz-checking-credit-cards-122/37348/1 "2007-05-02T18:37:31Z")
This is my first time submitting a solution to the quiz. I'll attach my .rb file and copy / paste my solution below. It's ugly, but it works. Thanks, Chase Southard #!/usr/bin/env ruby [Quiz122\_CardValidator.rb](https://rubytalk.org/uploads/short-url/nRdU089VzkyFlX5Ps7x23u9Ihdo.rb) (4.27 KB) > **ยทยทยท** > > # > # Created by Chase Southard on 2007-05-01. > > class CardValidator > >   def get\_card\_number >     if $\*[0] == nil >       puts "I need a card number. Please enter one now:" >       cardnumber = $stdin.gets.strip! >     else >       cardnumber = ARGV.shift >     end >     puts "You entered: #{cardnumber}" >     @card\_array = cardnumber.split(//).collect >     #remove spaces >     @card\_array.compact! >   end > >   def validate\_card\_prefix >     #case statement to grab the first few digits >     case @card\_array.first.to\_i >     when 3 >       prefix = @card\_array.slice(0, 2).join.to\_i >       #debug >       #puts prefix >       #puts prefix.class >       if prefix == 34 || 37 >         if @card\_array.length == 15 >           card\_type = "AMEX" >           puts "The card type entered was: #{card\_type}" >         else >           "You might have bogus card." >         end >       else >         "You might have a bogus card." >       end >     when 6 >       prefix = @card\_array.slice(0,4).join.to\_i >       #debug >       #puts prefix >       #puts prefix.class >       #puts "card length: #{@card\_array.length}" >       if prefix == 6011 && @card\_array.length == 16 >           card\_type = "Discover" >           puts "The card type entered was: #{card\_type}" >       else >         "You might have a bogus card." >       end >     when 4 >       if @card\_array.length == 13 || 16 >         card\_type = "Visa" >         puts "The card type entered was: #{card\_type}" >       else >         "You might have a bogus card." >       end >     when 5 >       prefix = @card\_array.slice(0, 2).join.to\_i >       #puts prefix >       #puts prefix.class >       if prefix == 51 || 52 || 53 || 54 >         if @card\_array.length == 16 >           card\_type = "MasterCard" >           puts "The card type entered was: #{card\_type}" >         else >           "You might have a bogus card." >         end >       end >     end >   end > >   def validate\_luhn >     array\_size = @card\_array.length > >     #starting at the LAST digit and working backwards gathering digits to > get the untouched elements of the card number > >     untouched\_elements\_index = Array.new >     while array\_size \> 1 >       untouched\_elements\_index.push(array\_size - 1) >       array\_size -= 2 >     end > >     untouched\_elements = Array.new >     untouched\_elements\_index.each { |e| > untouched\_elements.push(@card\_array[e].to\_i) } > >     #reset array size for the next part >     array\_size = @card\_array.length > >     #Starting at the NEXT TO LAST digit and working backwards gathering > digits to get the touched elements of the card number >     every\_other\_element = Array.new >     while array\_size \> 1 >       every\_other\_element.push(array\_size - 2) >       array\_size -= 2 >     end > >     #debug >     #puts "Every other element: #{every\_other\_element}" > >     #multiply each element by 2 >     touched\_array = Array.new >     every\_other\_element.each { |element| > touched\_array.push(@card\_array[element].to\_i\*2) } > >     #debug >     #puts "Touched array: #{touched\_array}" > >     #split each into digits >     split\_touched\_array = Array.new >     touched\_array.each { |e| split\_touched\_array.push(e.to\_s.split(//)) } >     split\_touched\_array.flatten! > >     #debug >     #puts "Split touched array:" >     #puts split\_touched\_array > >     #return digits to integer form >     split\_touched\_array\_integers = Array.new >     split\_touched\_array.each { |e| split\_touched\_array\_integers.push(e.to\_i) > } > >     #debug >     #split\_touched\_array\_total = 0 >     #split\_touched\_array\_integers.each { |e| split\_touched\_array\_total += e > } >     #puts "split total = #{split\_touched\_array\_total}" > >     #concatentate the two arrays >     all\_digit\_array = untouched\_elements + split\_touched\_array\_integers > >     #find the total value of the touched and untouched digits from the card > number >     array\_total\_value = 0 >     all\_digit\_array.each { |x| array\_total\_value += x } > >     #debug >     #puts "array total value = #{array\_total\_value}" > >     #final determination of validity by Luhn algorithm >     @numerical\_validation = false > >     if array\_total\_value % 10 == 0 >       @numerical\_validation = true >       puts "This card number, #{@card\_array}, is valid [by Luhn algorithm]" >     else >       puts "This card number, #{@card\_array}, is in-valid [by Luhn > algorithm]" >     end > >   end > > end > > my\_card = CardValidator.new > my\_card.get\_card\_number > my\_card.validate\_card\_prefix > my\_card.validate\_luhn