// Scala primes
// This to my mind may not be the fastest algorithm,
//   I would think printing when finding would be better,
//   especially on memory, then storing the thing in a list 
//   and then running mkString on it, but it already
//   outperforms java for me, so here it is

object Primes {
	def main(args: Array[String]) {
		if (args.length < 1) {
			println("Usage: scala Primes [MAX]")
		} else print(primes(3, List(), args(0).toInt).mkString("\n") + "\n")
	}

	def is_prime(num: Int): Boolean = {
		def prime_loop(i: Int, max: Int): Boolean =
			if (i > max) true
			else if (num % i == 0) false
			else prime_loop(i+2, max)
		prime_loop(3, scala.math.sqrt(num).ceil.toInt)
	}

	def primes(i: Int, acc: List[Int], max: Int): List[Int] = 
		if (i >= max) acc
		else if (is_prime(i)) primes(i+2, acc ++ List(i), max)
		else primes(i+2, acc, max)

}