Swift Lazy Prime Factorization

LazyPrimeFactorization.swift

import Darwin

extension Int {
	// Lazily computes prime factors
	public var primeFactors: AnySequence<Int> {
		func factor(input: Int) -> (prime: Int, remainder: Int) {
			let end = Int(sqrt(Float(input)))
			if end > 2 {
				for prime in 2...end {
					if input % prime == 0 {
						return (prime, input / prime)
					}
				}
			}
			return (input, 1)
		}
		var current = self
		return AnySequence(anyGenerator {
			guard current != 1 else { return nil }
			
			let result = factor(current)
			current = result.remainder
			return result.prime
		})
	}
}

print(Array(18.primeFactors))