a zipper-like merger function with tailrec

Merger.scala

object Merger {

  def merge[T](a: List[T], b: List[T]): List[T] = {

    @scala.annotation.tailrec
    def innerMerge(result: List[T], a: List[T], b: List[T]): List[T] = {
      (a, b) match {
        case (Nil, x) => result ++ x
        case (x, Nil) => result ++ x
        case (aHead :: aTail, bHead :: bTail) => innerMerge(List(aHead, bHead) , aTail, bTail)
      }
    }

    innerMerge(Nil, a, b)
  }

}