#!/usr/bin/env ruby

#
# rFactorial.rb
#
# Victor Hanson-Smith
# QUESTIONS? -> victorhs@cs.uoregon.edu
#
# This Ruby script recursively computes the factorial of an integer.
#

def fact(n)
   if n < 0
	puts "factorial is undefined for negative numbers\n"
	exit
   end

   if n == 0
	1
   else
	return n * fact(n-1)
   end
end
     			
	
# Ensure that command-line arguments exist:		
if (ARGV.length < 1)
	puts "\n	Usage: rFactorial <number>\n"
else
	# compute the factorial:
	result = fact(ARGV[0].to_i)
	# display the results
	puts result
end