Scalaで素数判定その4

PrimeNum.scala

import scala.math.sqrt
 
object PrimeNum {
  def main(args:Array[String]):Unit = {
    val num:Long = scala.io.StdIn.readLong
 
    if(isPrime(num)) println(num + " is Prime Number.")
    else println(num + " is NOT Prime Number.")
  }
 
  def isPrime(num:Long):Boolean = {
    if (num == 1 || num%2==0) false
    else (3L to sqrt(num).toLong by 2).forall(num%_ != 0)
  }
}