class Chunk attr_reader :value, :magnitude def initialize(value, magnitude = nil) @value = value @magnitude = magnitude.nil? ? '' : " #{magnitude}" end def to_s return '' if zero? s = say_hundreds s << say_double_digits s << magnitude end private def say_hundreds return +'' unless hundreds? "#{small_numbers[hundreds]} hundred" end def say_double_digits return '' if double_digits.zero? s = +' ' if double_digits < 20 s << small_numbers[double_digits] else s << decades[tens] unless ones.zero? s << '-' s << small_numbers[ones] end end s end def hundreds @hundreds ||= value / 100 end def double_digits @double_digits ||= value % 100 end def tens @tens ||= double_digits / 10 end def ones @ones ||= double_digits % 10 end def hundreds? !hundreds.zero? end def zero? value.zero? end def magnitude? !!magnitude end def small_numbers [nil] + %w(one two three four five six seven eight nine ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen) end def decades [nil, nil] + %w(twenty thirty forty fifty sixty seventy eighty ninety) end end class Say ONE_BILLION = 10**9 ONE_MILLION = 10**6 attr_reader :value def initialize(value) @value = value end def in_english guard_range return 'zero' if value.zero? chunks.join(' ').squeeze(' ').strip end private def chunks billions, i = chop(value, ONE_BILLION) millions, i = chop(i, ONE_MILLION) thousands, i = chop(i, 1000) [ Chunk.new(billions, 'billion'), Chunk.new(millions, 'million'), Chunk.new(thousands, 'thousand'), Chunk.new(i) ] end def chop(number, location) [number / location, number % location] end def guard_range unless in_range? message = 'Number must be between 0 and 999,999,999,999 inclusive.' fail ArgumentError.new(message) end end def in_range? value >= 0 && value < 10**12 end end