It's generally not a great idea to force cast items. If you pass in an array of Array, this crashes.

Thanks for your reminder~

Why concatenate when you have it converting to a String?

Camel case is your friend! This isnt web dev here, it's Swift! :)

THIS!!!!! I had to spend time looking up OLD and DEPRECATED code just to pass a Kata that didnt recoginze a map function on a String even though in Swift 4 in Playgrounds it would pass easily.

Because in an application use, an extention can be used globally without any issues or headaches. Simply call the exention function on any Int and you're done.