fizzbuzz.rb

def fizzbuzz(startnumber,endnumber)
  #check input for Fixnum
  if !(startnumber.is_a?(Fixnum) && endnumber.is_a?(Fixnum))
    puts "invalid input"
    return nil
  end

  #check start number is smaller than end number
  if startnumber > endnumber
    puts "Start number #{startnumber} is greater than end number #{endnumber}, reverting the loop"
    tmp = endnumber
    endnumber = startnumber
    startnumber = tmp
  end 

  (startnumber..endnumber).each do |i|
    if i % 5 == 0 && i % 3 == 0
      puts "FizzBuzz"
    elsif i % 5 == 0
      puts "Buzz"
    elsif i % 3 == 0
      puts "Fizz"
    else
      puts i
    end
  end
end
fizzbuzz("1050",1000)
fizzbuzz(1050,"1000")
fizzbuzz(1050,1000)
fizzbuzz(1000,1050)