How to implement 'takeUntil' of a list?

Question

I want to find all items before and equal the first 7:

val list = List(1,4,5,2,3,5,5,7,8,9,2,7,4)

My solution is:

Answer 1

You could use following function,

def takeUntil(list: List[Int]): List[Int] = list match {
  case x :: xs if (x != 7) => x :: takeUntil(xs)
  case x :: xs if (x == 7) => List(x)
  case Nil => Nil
}

val list = List(1,4,5,2,3,5,5,7,8,9,2,7,4)
takeUntil(list) //List(1,4,5,2,3,5,5,7)

Tail Recursive version

def takeUntilRec(list: List[Int]): List[Int] = {
    @annotation.tailrec
    def trf(head: Int, tail: List[Int], res: List[Int]): List[Int] = head match {
      case x if (x != 7 && tail != Nil) => trf(tail.head, tail.tail, x :: res)
      case x                            => x :: res
    }
    trf(list.head, list.tail, Nil).reverse
  }