Cantor Pairing in Swift 3

Int+CantorPairing.swift

/// Generates a unique integer from the combination of two integers
/// using the Cantor Pairing function.
/// 
/// # Examples 
///
/// f(47, 32) = 3192
///
/// f(32, 47) = 3207
///
/// - seealso: https://en.wikipedia.org/wiki/Pairing_function#Cantor_pairing_function
public func pair(_ a: Int, _ b: Int) -> Int {
    return ((a + b) * (a + b + 1) / 2) + b
}

/// Resolves a cantor paired integer to its original values
///
/// # Examples
///
/// f(3192) = (47, 32)
///
/// f(3207) = (32, 47)
///
/// - seealso: pair(_:_:)
public func unpair(_ z: Int) -> (x: Int, y: Int) {
    let d = Double(z)
    let t = Int(floor((sqrt(8 * d + 1) - 1) / 2))
    let x = t * (t + 3) / 2 - z
    let y = z - t * (t + 1) / 2
    
    return (x, y)
}