reverse using foldLeft in scala

def foldLeft[A, B] (as: List[A], z: B) (f: (B, A) => B) : B = as match {
  case Nil => z
  case Cons(x, xs) => foldLeft(xs, f(z, x))(f)
}

def reverse[A] (as: List[A]): List[A] =
  foldLeft(as, List[A]())((h, acc) => Cons(acc, h))

I am not sure how List[A] in foldLeft is of type B. Can anyone clear the process happening in this functions?

reverse using foldLeft in scala

2 Answers