TheAlgorithms-Ruby/maths/factorial.rb

# A ruby program to find factorial of a given integer
# Factorial of a given integer is defined as the product of all the positive integers less than or equal to the given integer
# Mathematical representation: n! = n * (n - 1) * (n - 2) * ... * 1

def factorial(number)
  input = number
  factorial = 1
  if number < 0
    "Please check your input number! The given number is a negative number."
  else
    while number > 0
      factorial *= number
      number -= 1
    end
    "The factorial of #{input} is #{factorial}."
  end
  rescue
    "Error: Please provide integer only!"
end

# Valid inputs
puts factorial(0)
# The factorial of 0 is 1.

puts factorial(10)
# The factorial of 10 is 3628800.

puts factorial(1)
# The factorial of 1 is 1.

puts factorial(-5)
# Please check your input number! The given number is a negative number.

# Invalid inputs
puts factorial("a")
# Error: Please provide integer only!

puts factorial("2")
# Error: Please provide integer only!