object Zad1 extends App {

  def sum(l: List[Option[Int]]): Option[Int] = {
    @annotation.tailrec
    def sumTailRec(list: List[Option[Int]], accum: Option[Int]): Option[Int] = {
      list match {
        case Nil     => accum
        case head :: tail => sumTailRec(tail, (accum ++ head).reduceOption(_ + _))
      }
    }
    sumTailRec(l, None)
  }

  val lista: List[Option[Int]] = List(Some(1), Some(2), Some(3), None)
  println(sum(lista))

}
// #########################################

object Zad2 extends App {

  def compose[A, B, C](f: A => B, g: B => C): A => C = arg => g(f(arg))

  def prod[A,B,C,D](f: A => C, g: B => D): (A, B) => (C, D) = (x,y) => (f(x),g(y))

  def lift[A,T](op: (T,T) => T)(f: A => T, g: A => T): A => T = x => op(f(x), g(x))

  def fun1(a: Int): Int = a + 2
  def fun2(b: Int): Int = b - 6
  def funop(c : Int, d: Int): Int = c * d

  println(compose(fun1, fun2)(2))
  println(prod(fun1, fun2)(2, 1))
  println(lift(funop)(fun1, fun2)(2))

}