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

I would do

(1..n).inject(1, :*)

Answer 2

Here is my version seems to be clear to me even though it's not as clean.

def factorial(num)
    step = 0
    (num - 1).times do (step += 1 ;num *= step) end
    return num
end

This was my irb testing line that showed each step.

num = 8;step = 0;(num - 1).times do (step += 1 ;num *= step; puts num) end;num

Answer 3

There is no factorial function in the standard library.

Answer 4

Like this is better

(1..n).inject(:*) || 1

Answer 5

You could also use Math.gamma function which boils down to factorial for integer parameters.

Answer 6

And yet another way (=

def factorial(number)
  number = number.to_i
  number_range = (number).downto(1).to_a
  factorial = number_range.inject(:*)
  puts "The factorial of #{number} is #{factorial}"
end
factorial(#number)