// A function to test if a number is prime, takes an integer and returns a
// boolean.
func isPrime(_ n: Int) -> Bool {
if n < 2 {
return false
}
// Try dividing by all numbers from 2 to sqrt(n).
var i = 2
while i*i <= n {
if n % i == 0 {
return false
}
i += 1
}
// If we get here, we didn't find a factor, so n is prime.
return true
}
// Main program starts here.
print("What is your name? ", terminator: "")
let name = readLine()!
print("Hello, \(name)!")
print("What is your favorite number? ", terminator: "")
let number = Int(readLine()!)!
print("Your favorite number is \(number)", terminator: "")
if isPrime(number) {
print(", and that's a prime number!")
} else {
print(". It's not a prime number, but that's okay!")
}
