Primes

Primes.scala

/**
 * @author Yaroslav Klymko
 */
object Primes {
  val naturals = {
    def loop(n: Long): Stream[Long] = n #:: loop(n + 1)
    loop(1)
  }

  val primes: Stream[Long] = {
    def loop(naturals: Stream[Long]): Stream[Long] =
      naturals.head #:: loop(naturals.tail.dropWhile(!isPrime(_)))
    loop(naturals.tail)
  }

  def isPrime(n: Long) = {
    val sqrt = math.sqrt(n)
    primes.collectFirst {
      case p if p > sqrt => true
      case p if n % p == 0 => false
    }.get
  }
}