tailrec.scala

import scala.annotation.tailrec

/**
 * To compile and look at the generated Java bytecode of this class, execute
 * these commands at the command-line prompt:
 *
 * > scalac tailrec.scala
 * > javap -p -c Test$.class
 * 
 * This is of value to observe the differences in the generated bytecode by 
 * the Scala compiler for tail recursive methods versus non-tail versus 
 * by-name param versus by-value param. This is discussed at length in the 
 * discussion forum for the Scala class "Functional Programming Principles 
 * in Scala" at this link: 
 * https://class.coursera.org/progfun-004/forum/thread?thread_id=162
 */

object Test {

  @tailrec final def tailRec(x: Int): Int = if (x == 0) x else tailRec(x - 1)

  final def nonTailRec(x: Int): Int = if (x == 0) x else nonTailRec(x) - 1

  final def nonTailRecAndByNameArgs(x: => Int): Int = if (x == 0) x else nonTailRecAndByNameArgs(x) - 1

  @tailrec final def tailRecAndByNameArg(x: => Int): Int = if (x == 0) x else tailRecAndByNameArg(x - 1)

}