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// 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)
}