gistfile1.scala

import scala.collection.generic.CanBuildFrom

object Batik extends App {
  val fun: Int => Option[Int] = { 
    case 3 => Some(1337)
    case 5 => None
    case n => Some(n * 3)
  }
  
  val mustare = List(1,2,3,4,5).filterMap(fun)
  val setMust = Set(1,2,3,4,5).filterMap(fun)
  val mustSeq: IndexedSeq[Int] = List(1,2,3,4,5).filterMap(fun)(scala.collection.breakOut)
  
  println(mustare)
  println(setMust)
  println(mustSeq)
  
  implicit class SeqW[CC[X] <: TraversableOnce[X], T](val seq: CC[T]) extends AnyVal {
    def filterMap[U, TO](fun: T => Option[U])(implicit cbf: CanBuildFrom[CC[T], U, TO]): TO = {
      val b = cbf()
      seq.foreach{ fun(_).foreach{ b+= } }
      b.result()
    } 
  }
}