TailCalls

TailCalls.Example

package org.darion.yaphet.scala.examples.other

import scala.util.control.TailCalls._
import scala.annotation._

object Sum extends App {
  def evenLength(xs: Seq[Int]): TailRec[Boolean] =
    if (xs.isEmpty) done(true) else tailcall(oddLength(xs.tail))

  def oddLength(xs: Seq[Int]): TailRec[Boolean] =
    if (xs.isEmpty) done(false) else tailcall(evenLength(xs.tail))

  println(evenLength(1 to 1000000).result)

  def sum1(xs: Seq[Int], partial: BigInt): TailRec[BigInt] =
    if (xs.isEmpty) done(partial) else tailcall(sum1(xs.tail, xs.head + partial))

  println(sum1(1 to 1000000, 0).result)

  @tailrec def sum2(xs: Seq[Int], partial: BigInt): BigInt =
  if (xs.isEmpty) partial else sum2(xs.tail, xs.head + partial)

  println(sum2(1 to 1000000, 0))

  def sum3(xs: Seq[Int]): BigInt =
    if (xs.isEmpty) 0 else xs.head + sum3(xs.tail)

  try {
    println(sum3(1 to 1000000))
  } catch {
    case _ => println("wrong")
  }
}