Building a ruby factorial calculator

Question

I'm working on writing a factorial program in ruby and I'm trying to write it where it does as follows:

1. Asks the user to enter a value to perform factorial on
2. takes in that value entered
3. performs factorial on it and 4. returns the factorial value using "puts"

My goal is to get this to work then expand on this by building it out to include other statistical functions.

So far this is the code I have:

puts "Welcome to the Calculator for Ruby"
puts "Please enter your value to value"

#N factorial value
def n
n = gets.chomp
end
def fact   
    n * fact(n-1)  

end  
puts fact(n) 

Fyi, I might add I've seen the generic factorial code available on the web but what I'm trying to do is set it so that the user defines n rather than setting n statically but when I try to do it, my code as above is erroring with the below error message: "fact" : wrong number of arguments (1 for 0) (ArgumentError)

My apologies for some of the wording and not including a specific question. My question would be 3 parts:

1. How would I properly write the factorial calculation to operate on the user provided value? (Which I see was answered).

2. Once the calculation is performed how can I store that value so it persists in case the user wants to recall it for other calculations.

3. Lastly, are there any good sources for guidance in writing statistical functions in ruby?

Thank you to all for the assistance

Answer 1

1. No need to declare n using def, simply assign it (e.g. as n = gets.chomp).

2. You must include a named argument to your fact function, like def fact(x).

3. The fact(x) function needs a base case since you are using recursion.

4. You must convert the user input string n to a number, like n.to_i.

puts "Welcome to the Calculator for Ruby"
puts "Please enter your value to value"
def fact(x)
  (x <= 1) ? 1 : x * fact(x-1)
end  
n = gets.chomp.to_i
puts "#{n}! => #{fact(n)}"

Answer 2

Simpler way. Just inject numbers from 1 till n.

puts 'Welcome to the Calculator for Ruby'
puts 'Please enter your value to value'
n = gets.chomp.to_i
puts (1..n).inject(:*)

Answer 3

Might no be the best of solutions but here you go

puts "Welcome to the Factorial Calculator for Ruby"
puts "Please enter your value to exaluate"

n = gets.chomp.to_i

def fact(num)
    return num <= 1 ? 1 : num * fact(num - 1)
end

puts "The factorial of #{n} is #{fact(n)}