Adds an extension to the Int class to tell return whether an integer is prime or not

isPrime.swift

extension Int {
    func isPrime() -> Bool {
        if (self == 1) { return false }
        if (self == 2) { return true }

        var sqr = Int(sqrt(Float(self))) + 1
        for i in 2...sqr {
            if self % i == 0 {
                return false
            }
        }
        return true
    }
}