class Numeric
  
  ##
  # Format a number as human readable currency.
  #
  # === Examples
  #
  #   10.format_currency => '10'
  #   10.99.format_currency => '10.99'
  #   10.9999.format_currency => '10.99'
  #   1000.99.format_currency => '1,000.99'
  #   1000000.99.format_currency => '1,000,000.99'
  #
  
  def format_currency
    parts = self.to_s.split '.'
    parts[0].gsub! /(\d)(?=(\d\d\d)+(?!\d))/, '\1,'
    parts.join('.').gsub /(\.\d{2})(\d+)/, '\1'     
  rescue 
    self.to_s
  end
end