Regex that checks if a number is prime in Swift 2. From blog post "Demystifying The Regular Expression That Checks If A Number Is Prime" at https://iluxonchik.github.io/regular-expression-check-if-number-is-prime/ | Submitted by Russel: https://disqus.com/by/disqus_527bF1C8Ck/

IsPrimeRegex.swift

/*
Regex that checks if a number is prime in Swift 2. 
From blog post "Demystifying The Regular Expression That Checks If A Number Is Prime" 
at https://iluxonchik.github.io/regular-expression-check-if-number-is-prime/ 

Submitted by Russel: https://disqus.com/by/disqus_527bF1C8Ck/
*/
func isPrime(n: Int) -> Bool {
    do {
        return try NSRegularExpression(
            pattern: "^.?$|^(..+?)\\1+$",
            options: []).matchesInString(
            String(count: n, repeatedValue: Character("1")),
            options: [],
            range: NSMakeRange(0, n)
            ).count == 0
            } catch {
                return false
        }
}