gonecoding

Important notice

I took down this Gist due to concerns about the security of the encryption/decryption part of this code (see comments below).

Rob Napier (@rnapier) has created a publicly available class that provides similar AES encryption/decryption functionality at https://github.com/rnapier/RNCryptor.

airspeedswift

// See @SwiftLDN's tweet for a short description of the Luhn algorithm:
//   https://twitter.com/SwiftLDN/status/529412592834338817
// or Wikipedia for a longer one.
//   http://en.wikipedia.org/wiki/Luhn_algorithm
//
// Only meant to show extending Swift's lazy() for infotainment purposes,
// not necessarily recommending best or even good practices!
//
// Alternative, saner, solutions here:

jonelf

func lunhCheck(number : String) -> Bool
{
    let reversed = reverse(number).map { String($0).toInt()! }
    return reduce(enumerate(reversed), 0, {(sum, val) in
        let odd = val.index % 2 == 1
        return sum + (odd ? (val.element == 9 ? 9 : (val.element * 2) % 9) : val.element)
        }) % 10 == 0
}

lunhCheck("49927398716")

Koze