Scala example source code file (tailrec.scala)

This example Scala source code file (tailrec.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

failures, failures, int, int, list, list, nil, nil, tom, winners

The Scala tailrec.scala source code

import scala.annotation.tailrec

// putting @tailrec through the paces
object Winners {
  @tailrec
  def facsucc(n: Int, acc: Int): Int =
    if (n == 0) acc
    else facsucc(n - 1, n * acc)

  @tailrec def loopsucc1(x: Int): Int = loopsucc1(x - 1)
  @tailrec def loopsucc2[T](x: Int): Int = loopsucc2[T](x - 1)
  
  def ding() {
    object dong {
      @tailrec def loopsucc3(x: Int): Int = loopsucc3(x)
    }
    ()
  }
  
  def inner(q: Int) = {
    @tailrec
    def loopsucc4(x: Int): Int = loopsucc4(x + 1)
    
    loopsucc4(q)
  }
  
  object innerBob {
    @tailrec def loopsucc5(x: Int): Int = loopsucc5(x)
  }
}

class Winners {
  @tailrec private def succ1(x: Int): Int = succ1(x)
  @tailrec final def succ2(x: Int): Int = succ2(x)
  @tailrec final def succ3[T](in: List[T], acc: List[T]): List[T] = in match {
    case Nil      => Nil
    case x :: xs  => succ3(xs, x :: acc)
  }
}

object Failures {
  @tailrec
  def facfail(n: Int): Int =
    if (n == 0) 1
    else n * facfail(n - 1)
}

class Failures {  
  // not private, not final
  @tailrec def fail1(x: Int): Int = fail1(x)
  
  // a typical between-chair-and-keyboard error
  @tailrec final def fail2[T](xs: List[T]): List[T] = xs match {
    case Nil      => Nil
    case x :: xs  => x :: fail2[T](xs)
  }
  
  // unsafe
  @tailrec final def fail3[T](x: Int): Int = fail3(x - 1)
  
  // unsafe
  class Tom[T](x: Int) {
    @tailrec final def fail4[U](other: Tom[U], x: Int): Int = other.fail4[U](other, x - 1)
  }
}