// In header: <boost/program_options/errors.hpp>


class validation_error : public boost::program_options::error {
public:

  enum kind_t { multiple_values_not_allowed =  30, 
                at_least_one_value_required, invalid_bool_value, 
                invalid_option_value, invalid_option };
  // construct/copy/destruct
  validation_error(kind_t, const std::string & = "", const std::string & = "");
  ~validation_error();

  // public member functions
  void set_option_name(const std::string &);
  const std::string & get_option_name() const;
  const char * what() const;

  // protected static functions
  static std::string error_message(kind_t);
};