Что такое функция батута?

Позвольте мне добавить несколько language-agnostic примеров факториальной функции, реализованной c с помощью батутов, на разных language-independent языках:

Scala:

sealed trait Bounce[A]
case class Done[A](result: A) extends Bounce[A]
case class Call[A](thunk: () => Bounce[A]) extends Bounce[A]

def trampoline[A](bounce: Bounce[A]): A = bounce match {
  case Call(thunk) => trampoline(thunk())
  case Done(x) => x
}

def factorial(n: Int, product: BigInt): Bounce[BigInt] = {
    if (n <= 2) Done(product)
    else Call(() => factorial(n - 1, n * product))
}

object Factorial extends Application {
    println(trampoline(factorial(100000, 1)))
}

Java:

import java.math.BigInteger;

class Trampoline 
{
    public T get() { return null; }
    public Trampoline  run() { return null; }

    T execute() {
        Trampoline  trampoline = this;

        while (trampoline.get() == null) {
            trampoline = trampoline.run();
        }

        return trampoline.get();
    }
}

public class Factorial
{
    public static Trampoline factorial(final int n, final BigInteger product)
    {
        if(n <= 1) {
            return new Trampoline() { public BigInteger get() { return product; } };
        }   
        else {
            return new Trampoline() { 
                public Trampoline run() { 
                    return factorial(n - 1, product.multiply(BigInteger.valueOf(n)));
                } 
            };
        }
    }

    public static void main( String [ ] args )
    {
        System.out.println(factorial(100000, BigInteger.ONE).execute());
    }
}

C (не повезло c без реализации больших чисел):

#include 

typedef struct _trampoline_data {
  void(*callback)(struct _trampoline_data*);
  void* parameters;
} trampoline_data;

void trampoline(trampoline_data* data) {
  while(data->callback != NULL)
    data->callback(data);
}

//-----------------------------------------

typedef struct _factorialParameters {
  int n;
  int product;
} factorialParameters;

void factorial(trampoline_data* data) {
  factorialParameters* parameters = (factorialParameters*) data->parameters;

  if (parameters->n <= 1) {
    data->callback = NULL;
  }
  else {
    parameters->product *= parameters->n;
    parameters->n--;
  }
}

int main() {
  factorialParameters params = {5, 1};
  trampoline_data t = {&factorial, ¶ms};

  trampoline(&t);
  printf("\n%d\n", params.product);

  return 0;
}