A tail-recursion example

Here, we will write a Scala Application to demonstrate the tail-recursion technique.

Scala's @tailrec annotation ensures that tail recursive functions are optimized by the Scala compiler, to avoid StackOverflowErrors:

package com.packt.publishing.recursion 
 
object TailRecursionApp extends App { 
 
  val list = List(1,2,3,4,5,6,7,8,9) 
  val list2 = tailRecursion(list) 
 
  println("Original List = " + list) 
  println("After Tail Recursion of List = " + list2) 
 
  @tailrec 
  def tailRecursion[A](listOfElements: List[A]): List[A] = { 
    def reverse(updatedList: List[A], originalList: List[A]):
     List[A] = originalList match { 
      case Nil => updatedList 
      case head :: tail => reverse(head :: updatedList, tail) 
    } 
 
    reverse(Nil, listOfElements) 
  } 
 
} 

When we run the preceding application, we can observe the following output:

Original List = List(1, 2, 3, 4, 5, 6, 7, 8, 9)
After Tail Recursion of List = List(9, 8, 7, 6, 5, 4, 3, 2, 1)