Tail recursive map implementation

Mapper.scala

package org.example

import scala.annotation.tailrec

object Mapper {

  @tailrec
  def foldLeft[A, B](as: List[A], z: B)(f: (B, A) => B): B = as match {
    case Nil => z
    case a :: as => foldLeft(as, f(z, a))(f)
  }

  def reverse[A](as: List[A]): List[A] =
    foldLeft(as, List[A]())((z, a) => a :: z)

  def foldRight[A, B](as: List[A], z: B)(f: (A, B) => B): B =
    foldLeft(reverse(as), z)((z, a) => f(a, z))
  
  def map[A, B](as: List[A], f: A => B): List[B] =
    foldRight(as, Nil:List[B])((a, z) => f(a) :: z)
}