Utility functions
Returns the factorial of n
factorial(number) :: number
Returns the factorial of n.
iex(2)> factorial(0) 1 iex(3)> factorial(1) 1 iex(4)> factorial(2) 2 iex(5)> factorial(3) 6 iex(6)> factorial(4) 24 iex(7)> factorial(5) 120