small script to compute happy numbers with scala (useful as a funny benchmark for very big max numbers ;-) NOTE: try to replace numbers.map(x => x * x).sum with: numbers.par.map(x => x * x).sum

gistfile1.scala

package happy

/**
 * @author seralf
 * 
 * small script to compute happy numbers with scala 
 * (useful as a funny benchmark for very big max numbers ;-)
 * 
 * NOTE: try to replace
 *   numbers.map(x => x * x).sum
 * with:
 * 	numbers.par.map(x => x * x).sum
 */
object Happy extends App {

  def happyNumbers(numbers: List[Int]): List[Int] =
    for (number <- numbers.filter(n => isHappy(n)).toList) yield number

  def isHappy(n: Int): Boolean = {

    def iterate(n: Int, sequence: List[Int]): Boolean = {

      val next = (x: Int) => {
        val numbers = for (x <- n.toString.toCharArray().toList) yield x.toString.toInt
        numbers.map(x => x * x).sum
      }

      n match {
        case 1 => true
        case x if (sequence.contains(n)) => false
        case x => iterate(next(x), x :: sequence)
      }

    }

    iterate(n, Nil)
  }

  // TEST -------------------------------------------------------

  val max = 1111;
  printf("List of firsts HAPPY numbers until %d:\n%s\n", max, happyNumbers((0 to max).toList))

}