factorial.scala

def factorial(n: Int): Int = {
  n match {
    case n if n <= 0 => 1
    case n => n * factorial(n - 1)
  }
}

println(factorial(100))

factorial_go.scala

def factorial(n: Int): Int = {
  def go(n: Int, acc: Int): Int =
    if (n <= 0) acc
    else go(n - 1, n*acc)

  go(n, 1)
}

println(factorial(100))