def factorial(n: Int) :Int = {
    def _factorial(n: Int, result: Int) :Int = {
        if (n <= 0) result else _factorial(n-1, n * result)
    }
    _factorial(n, 1)
}
println(factorial(10000))
 
def simple_factorial(n: Int) :Int = {
    if (n <= 0) 1 else n * simple_factorial(n-1)
}
println(simple_factorial(10000)) // => java.lang.StackOverflowError