TailCalls
object TailCalls
Methods exported by this object implement tail calls via trampolining.
Methods exported by this object implement tail calls via trampolining.
Tail calling methods have to return their result using done or call the
next method using tailcall. Both return a TailRec object. The result
of evaluating a tailcalling function can be retrieved from a Tailrec
value using method result.
Implemented as described in "Stackless Scala with Free Monads"
https://blog.higher-order.com/assets/trampolines.pdf
Here's a usage example:
import scala.util.control.TailCalls._
def isEven(xs: List[Int]): TailRec[Boolean] =
if (xs.isEmpty) done(true) else tailcall(isOdd(xs.tail))
def isOdd(xs: List[Int]): TailRec[Boolean] =
if (xs.isEmpty) done(false) else tailcall(isEven(xs.tail))
isEven((1 to 100000).toList).result
def fib(n: Int): TailRec[Int] =
if (n < 2) done(n) else for {
x <- tailcall(fib(n - 1))
y <- tailcall(fib(n - 2))
} yield x + y
fib(40).result