object Test extends App {
  import scala.collection.generic.{ CanBuildFrom, FromRepr, HasElem }

  def typed[T](t : => T) {}

  class FilterMapImpl[A, Repr](val r : Repr)(implicit hasElem : HasElem[Repr, A]) {
    def filterMap[B, That](f : A => Option[B])(implicit cbf : CanBuildFrom[Repr, B, That]) : That = r.flatMap(f(_).toSeq)
  }
  
  implicit def filterMap[Repr : FromRepr](r : Repr) = new FilterMapImpl(r)

  val l = List(1, 2, 3, 4, 5)
  val fml = l.filterMap(i => if(i % 2 == 0) Some(i) else None)
  typed[List[Int]](fml)
  println(fml)

  val a = Array(1, 2, 3, 4, 5)
  val fma = a.filterMap(i => if(i % 2 == 0) Some(i) else None)
  typed[Array[Int]](fma)
  println(fma.deep)
  
  val s = "Hello World"
  val fms1 = s.filterMap(c => if(c >= 'A' && c <= 'Z') Some(c) else None)
  typed[String](fms1)
  println(fms1)
  
  val fms2 = s.filterMap(c =>if(c % 2 == 0) Some(c.toInt) else None)
  typed[IndexedSeq[Int]](fms2)
  println(fms2)
}