#### say.rb

 ```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75``` ```# Say a number in English (well, American actually) class Say UNDER_TWENTY = %w( zero one two three four five six seven eight nine ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen ).freeze TENS = %w( zero ten twenty thirty forty fifty sixty seventy eighty ninety ).freeze POWERS = { 1_000_000_000 => 'billion', 1_000_000 => 'million', 1_000 => 'thousand', 100 => 'hundred' }.freeze def initialize(number) raise ArgumentError, 'Negative number not allowed' unless number >= 0 raise ArgumentError, 'Number is too large ' unless number < 1e12 @number = number end def in_english Say.say(@number) end class << self # Say a number def say(number) if number < 20 under_20(number) elsif number < 100 under_100(number) else over_100(number) end end # Say a number under 20 def under_20(number) UNDER_TWENTY[number] end # Say a number between 20 and 99 def under_100(number) tens = TENS[number / 10] if number % 10 == 0 # e.g. forty tens else # e.g. forty-two "#{tens}-#{say(number % 10)}" end end # Say a number 100 or over def over_100(number) power = POWERS.keys.select { |p| p <= number }.max name = POWERS[power] say_power = "#{say(number / power)} #{name}" remainder = number % power if remainder == 0 # e.g. two hundred say_power else # e.g. two hundred twenty-three "#{say_power} #{say(remainder)}" end end end end ```