prime.scala

import scala.annotation.tailrec

object Prog {
  def primes(n: Int): List[Int] = {
    @tailrec
    def loop(cs: List[Int], ps: List[Int]): List[Int] = {
      cs.headOption match {
        case Some(n: Int) => loop(cs.tail.filterNot(_ % n == 0), n::ps)
        case None => ps
      }
    }
    loop((2 until n).toList, Nil).reverse
  }
}