Humanize numbers with a 1-999 cache

mini_humanize_numbers.rb

class Numeric
  def humanize
    if ONE_TO_NINE_NINETY_NINE_CACHE.length == 1
      1.upto(999) do |n|
        ONE_TO_NINE_NINETY_NINE_CACHE << if n < 10
          HUMANIZE_ONES_TEXT[n]
        elsif n < 20
          HUMANIZE_ELEVEN2NINETEEN_TEXT[n - 10]
        elsif n < 100
          d = n % 10
          HUMANIZE_TENS_TEXT[n / 10] + (d == 0 ? '' : " " + HUMANIZE_ONES_TEXT[d])
        else
          q, r = n / 100, n % 100
          (q != 0 ? HUMANIZE_ONES_TEXT[q] + ' hundred' : '') + (r != 0 ? (q != 0 && r != 0 ? ' and ' : '') + ONE_TO_NINE_NINETY_NINE_CACHE[r] : '')  
        end
      end
    end

    num, output = self.to_i, ''

    if self < 0
      output << 'negative '
      num = -num
    end

    output << if self == 0
      'zero'
    else
      out, quotient, i, last_had = [], 1, 0, false
      while quotient != 0
        quotient, remainder = num / 1000, num % 1000

        out << (HUMANIZE_GROUP_TEXT[i] + (!out.empty? ? (last_had ? " and" : ",") : "")) unless remainder == 0 || i == 0
        last_had = true if i == 0 && remainder < 100
        i += 1
        
        out << ONE_TO_NINE_NINETY_NINE_CACHE[remainder] if remainder != 0

        num = quotient
      end
      out.reverse.join(' ').strip
    end

    output << " point " << self.to_s.split('.', 2).last.scan(/./).map { |n| HUMANIZE_ONES_TEXT[n.to_i] }.join(' ') if self % 1 != 0
    output
  end

  private
  HUMANIZE_GROUP_TEXT = [''] + %w(thousand million billion trillion quadrillion quintrillion sextillion septillion octillion nonillion decillion undecillion
  duodecillion tredecillion quattuordecillion quindecillion sexdecillion septendecillion octodecillion novemdecillion vigintillion unvigintillion
  duovigintillion trevigintillion quattuortillion quinvigintillion sexvigintillion septenvigintillion octovigintillion novemvigintillion trigintillion
  untrigintillion duotrigintillion trestrigintillion quattuortrigintillion quintrigintillion sextrigintillion septentrigintillion octotrigintillion
  novemtrigintillion quadragintillion unquadragintillion duoquadragintillion trequadragintillion quattuorquadragintillion quinquadragintillion
  sesquadragintillion septenquadragintillion octoquadragintillion novenquadragintillion quinquagintillion).freeze
  HUMANIZE_TENS_TEXT = %w(X X twenty thirty forty fifty sixty seventy eighty ninety).freeze
  HUMANIZE_ELEVEN2NINETEEN_TEXT = %w(ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen).freeze
  HUMANIZE_ONES_TEXT = %w(zero one two three four five six seven eight nine).freeze
  ONE_TO_NINE_NINETY_NINE_CACHE = ['X']
end