Synopsis

template <class E>
struct get_message;

This is a lazy template metafunction.

Description

Returns the error message of a parsing failure.

Header

#include <boost/metaparse/get_message.hpp>

Example

#include <boost/metaparse/get_message.hpp>
#include <boost/metaparse/start.hpp>
#include <boost/metaparse/reject.hpp>
#include <boost/metaparse/define_error.hpp>

#include <type_traits>

using namespace boost::metaparse;

BOOST_METAPARSE_DEFINE_ERROR(sample_error, "Sample error message");

struct returns_reject
{
  using type = reject<sample_error, start>;
};

static_assert(
  std::is_same<
    sample_error,
    get_message<reject<sample_error, start>>::type
  >::type::value,
  "It should return the message"
);

static_assert(
  std::is_same<sample_error, get_message<returns_reject>::type>::type::value,
  "It should support lazy evaluation"
);