gistfile1.txt

module NumberPercentageExtension
  module InstanceMethods
    # the idea converting english to numbers taken from http://www.ruby-forum.com/topic/132735#591799
    ENGLISH_VALUE = {}
      %w| zero one two three four five six seven eight nine ten eleven
          twelve thirteen fourteen fifteen sixteen seventeen eighteen
          nineteen |.each_with_index{ |word,i| ENGLISH_VALUE[word] = i }

      %w| zero ten twenty thirty forty fifty sixty seventy eighty
          ninety|.each_with_index{ |word,i| ENGLISH_VALUE[word] = i*10 }
    ENGLISH_VALUE['hundred'] = 100

    def percent_method?(method)
      tokens = method.to_s.split('_')
      return false if tokens.size < 2
      is_percent = tokens[-1] == 'percent'
      tokens[0..-2].collect { |word| is_percent &&= ENGLISH_VALUE.has_key?(word) }
      return is_percent
    end

    def method_missing(method, *args)
      if percent_method?(method)
        method.to_s.split('_')[0..-2].map { |word| ENGLISH_VALUE[word] }.sum * self / 100.to_f
      else
        raise "NoMethodError: undefined method #{method} for class #{self.class.name}"
      end
    end

    def respond_to?(method)
      return true if percent_method?(method)
      super(method)
    end

  end

  Numeric.class_eval do
    include InstanceMethods
  end

end