Project Euler 10: Summation of Primes

projecteuler10.scala

package ysl.p10

object PrimeSum extends App {
  def naturals(from: Int): Stream[Int] =
    Stream.cons(from, naturals(from + 1))
  def sieve(s: Stream[Int]): Stream[Int] =
    Stream.cons(s.head, sieve(s.tail filter { _ % s.head != 0 }))
  def primes = sieve(naturals(2).takeWhile( _ < 2000000))
  // TODO: ...
}