Synopsis

#define BOOST_METAPARSE_DEFINE_ERROR(name, msg) \
  // unspecified

This is a macro.

Description

Macro for defining a parsing error message class. name is the name of the class representing the error message and msg is a string literal containing the description of the error.

Header

#include <boost/metaparse/define_error.hpp>

Expression semantics

For any n name and m string literal, given the following is defined:

BOOST_METAPARSE_DEFINE_ERROR(n, m);

the following pairs of expressions are equivalent:

n::get_value()
std::string(m)

n::type
n

Example

#include <boost/metaparse/define_error.hpp>
#include <boost/metaparse/repeated1.hpp>
#include <boost/metaparse/letter.hpp>
#include <boost/metaparse/int_.hpp>
#include <boost/metaparse/token.hpp>
#include <boost/metaparse/sequence.hpp>
#include <boost/metaparse/change_error_message.hpp>
#include <boost/metaparse/start.hpp>
#include <boost/metaparse/get_message.hpp>
#include <boost/metaparse/string.hpp>

#include <type_traits>

using namespace boost::metaparse;

BOOST_METAPARSE_DEFINE_ERROR(age_expected, "Age expected");

using name_token = token<repeated1<letter>>;
using age_token = token<change_error_message<int_, age_expected>>;

using name_age = sequence<name_token, age_token>;

static_assert(
  std::is_same<
    age_expected,
    get_message<name_age::apply<BOOST_METAPARSE_STRING("Joe "), start>>::type
  >::type::value,
  "the error message should be age_expected when the age is missing"
);