User input to create factorial

Question

Need some help on making the def fact(n) command to work off user input. My script works great when I input something like "Ruby factorial.rb 5". However, I need this to run with prompts. The script should run something like:

puts 'Please input a non-negative integer:'
n = gets.chomp.to_i
puts "The factorial of #{n} is #{factorial}

Here's what my code looks like now. Like I said however, it does work. It's when I add n = gets.chomp.to_i before the def fact(n) command that I automatically receive a value of 1. It doesn't matter what number the user puts in, it always returns 1.

#!/user/bin/ruby
def fact(n)
  if n==0
    1
  else
    n * fact(n-1)
  end
end
puts fact(ARGV[0].to_i)

How do I make this work with the user input? I think I'm just having a syntax issue, but don't know how to make it work.

Try `puts 'Please input a non-negative integer'`, then `n = gets.to_i`, then `puts "The factorial of #{n} is #{fact(n)}"` — Eli Sadoff, Nov 04 '16 at 17:04
Check out the full answer I just gave below. It shows you how to do both of the things you're asking about. — Eli Sadoff, Nov 04 '16 at 17:12

score 0 · Accepted Answer · answered Nov 04 '16 at 17:09

You actually seem to be asking for two different things. The first thing you want is an application that does something like this

$ ruby factorial.rb
> Please input a non-negative integer
(GET USER INPUT)
> The factorial of (USER INPUT) is (FACTORAIL OF USER INPUT)

And a command line tool that does something like this

$ fact 10
> 3628800

The first one could look something like this

def fact(n)
  (1..n).inject(:*)
end
puts 'Please input a non-negative integer'
a = gets.to_i
puts "The factorial of #{a} is #{fact(a)}"

The second one could look something like this

#!/usr/bin/ruby
puts (1..ARGV[0].to_i).inject(:*)

User input to create factorial

1 Answers1