Ruby factorial function

Question

I\'m going crazy: Where is the Ruby function for factorial? No, I don\'t need tutorial implementations, I just want the function from the library. It\'s not in Math!

Answer 1

Why would the standard library require a factorial method, when there is a built-in iterator for this exact purpose? It is called upto.

No you do not need to use recursion, like all these other answers show.

def fact(n)
  n == 0 ? 1 : n * fact(n - 1)
end  

Rather, the built-in iterator upto can be used to calculate factorials:

factorial = 1
1.upto(10) {|x| factorial *= x }
factorial
 => 3628800