[SOLVED] How to return every nth even number in a list with foldLeft in Scala?

How to return every nth even number in a list with foldLeft in Scala?

For a university project I have to implement a function called takeNthEven which finds the nth even number in a list with the aid of foldLeft. For example:

takeNthEven(SinglyLinkedIntList(0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15,18,5,3), 3)

should return: SinglyLinkedIntList(4, 10,18)

My attempt so far:

def takeNthEven(input: IntList, n: Int): IntList = {
   var temp = SinglyLinkedIntList()

    input.foldLeft(0 -> 0) {
      case(acc,n) => if (acc == 2 || !(2 to (acc-1)).exists(x => i % x == 0)) temp.append(acc)
    }._n

  }

But unfortunately this does not even compile. I am not sure how to continue with this algorithm, could someone help me figure this out? I am new to functional programming and dont know how to go about this

Solution

Here's my take on it. You'll probably have to make adjustments depending on how your IntList is composed.

type IntList = List[Int]

def takeNthEven(input: IntList, n: Int): IntList = input.foldLeft(List.empty[Int]->1){
  case ((acc,cnt),elem) if elem%2 < 1 => if (cnt%n < 1) (elem::acc, cnt+1)
                                         else           (acc, cnt+1)
  case (skip,_) => skip
}._1.reverse