Chapter 23 // Exercise 7 - Principles & Practice Using C++

In this exercise I am using Visual Studio 2019 and a modified version of the std_lib_facilities header found here.

Chapter 23 // Exercise 7

Write a program (similar to the one in the previous exercise) that finds credit card numbers in a file. Do a bit of research to find out what credit card formats are really used.

Github: https://github.com/l-paz91/principles-practice/tree/master/Chapter%2023/Exercise%207

So I thought credit card numbers were straight forward; literally just 16 digits separated by a space (at least that's what it is on my credit card). I never realised they were all different, I've only ever had a mastercard.

I found this site:

https://moneytips.com/anatomy-of-a-credit-card/#:~:text=The%20first%20digit%20is%20different,a%207%20has%2015%20digits

and decided to write patterns for the 3 most common; visa, mastercard and amex. This site was also incredibly useful:

https://baymard.com/checkout-usability/credit-card-patterns

I got a load of test credit card numbers from this site and added some more to it:

https://support.bluesnap.com/docs/test-credit-card-numbers

Whilst doing this I saw more posts about how regex should not be used for data validation. I even found sites like paypal providing test credit card numbers and they had all spaces stripped out.

I did check for any whitespace separating characters after the max length of the number though because, well they should be separated in a text file anyway.