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

In math, factorial of n is just the gamma function of n+1
(see: http://en.wikipedia.org/wiki/Gamma_function)

Ruby has Math.gamma() so just use Math.gamma(n+1) and cast it back to an integer if desired.