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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)
}
}
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