ninety_nine_bottles_of_beer.rb

def english_number number
  if number < 0
    return 'Please enter number that isn\'t negative.'
  end
  if number == 0
    return 'zero'
  end
  
  num_string = '' # the string that will be returned
  
  ones_place = ['one', 'two', 'three',
                'four', 'five', 'six',
                'seven', 'eight', 'nine']

  tens_place = ['ten', 'twenty', 'thirty',
                'forty', 'fifty', 'sixty',
                'seventy', 'eighty', 'ninety']


  teenagers = ['eleven', 'twelve', 'thirteen',
               'fourteen', 'fifteen', 'sixteen',
               'seventeen', 'eighteen', 'nineteen']
               
  zillions = [['hundred', 2],
              ['thousand', 3],
              ['million', 6],
              ['billion', 9],
              ['trillion', 12],
              ['quadrillion', 15],
              ['quintillion', 18],
              ['sextillion', 21],
              ['septillion', 24],
              ['octillion', 27],
              ['nonillion', 30],
              ['decillion', 33],
              ['undecillion', 36],
              ['duodecillion', 39],
              ['tredecillion', 42],
              ['quattuordecillion', 45],
              ['quindecillion', 48],
              ['sexdecillion', 51],
              ['septendecillion', 54],
              ['octodecillion', 57],
              ['novemdecillion', 60],
              ['vigintillion', 63],
              ['googol', 100]]
              
  left = number
  
  while zillions.length > 0
    zil_pair = zillions.pop
    zil_name = zil_pair[0]
    zil_base = 10 ** zil_pair[1]
    write = left/zil_base # How many zillions left?
    left = left - write*zil_base # Subtract off those zillions.

    if write > 0
      # Now here's the recursion:
      prefix = english_number write
      num_string = num_string + prefix + ' ' + zil_name

      if left > 0
        # So we don't write 'two billionfifty-one'...
        num_string = num_string + ' '
      end
    end
  end

  write = left/10 # How many tens left?
  left = left - write*10 # Subtract off those tens.

  if write > 0
    if ((write == 1) and (left > 0))
      # Since we can't write "tenty-two" instead of
      # "twelve", we have to make a special exception
      # for these.
      num_string = num_string + teenagers[left-1]
      # The "-1" is because teenagers[3] is
      # 'fourteen', not 'thirteen'.

      # Since we took care of the digit in the
      # ones place already, we have nothing left to write.
      left = 0
    else
      num_string = num_string + tens_place[write-1]
      # The "-1" is because tens_place[3] is
      # 'forty', not 'thirty'.
    end

    if left > 0
      # So we don't write 'sixtyfour'...
      num_string = num_string + '-'
    end
  end

  write = left # How many ones left to write out?
  left = 0 # Subtract off those ones.

  if write > 0
    num_string = num_string + ones_place[write-1]
    # The "-1" is because ones_place[3] is
    # 'four', not 'three'.
  end

  # Now we just return "num_string"...
  num_string
end

num_start = 999
num_now = num_start
while num_now > 2
  puts english_number(num_now) + ' bottles of beer of the wall' + english_number(num_now) + ' bottles of beer!'
  num_now = num_now - 1
  puts 'Take one down, pass it around, ' + english_number(num_now) + ' bottles of beer on the wall!'
end