class Money
  def zero?
    self.cents.zero?
  end

  def to_f
    self.cents / 100.0
  end

  %w(abs ceil floor round).each do |method|
    define_method(method) do
      self.class.new(@cents.send(method), self.currency)
    end
  end

  def to_liquid
    format(:with_currency)
  end

  def self.penny
    @penny ||= Money.new(1)
  end

  def self.zero
    @zero ||= Money.empty
  end
end

class Integer
  def to_money(currency=Money.default_currency)
    Money.new(self, currency)
  end
end

class Float
  def to_money(currency=Money.default_currency)
    Money.new((self * 100.0).ceil, currency)
  end
end