Synopsis

template <class S, class ResultType = /* unspecified */>
struct keyword;

This is a parser.

Description

Parser accepting the keyword S. The result of parsing is ResultType, which is optional; when not given, the result of successful parsing is undefined.

Header

#include <boost/metaparse/keyword.hpp>

Expression semantics

For any r class and s compile-time string that is built from the characters c1 ... cn the following are equivalent:

keyword<s, r>

last_of<lit<c1>, /* ... */, lit<cn>, return_<r>>

Example

#include <boost/metaparse/keyword.hpp>
#include <boost/metaparse/string.hpp>
#include <boost/metaparse/start.hpp>
#include <boost/metaparse/get_result.hpp>
#include <boost/metaparse/is_error.hpp>

#include <type_traits>

using namespace boost::metaparse;

static_assert(
  get_result<
    keyword<BOOST_METAPARSE_STRING("for"), std::integral_constant<int, 13>>
      ::apply<BOOST_METAPARSE_STRING("for"), start>
  >::type::value == 13,
  "the result of parsing the keyword is keyword's second argument"
);

static_assert(
  is_error<
    keyword<BOOST_METAPARSE_STRING("for"), std::integral_constant<int, 13>>
      ::apply<BOOST_METAPARSE_STRING("if"), start>
  >::type::value,
  "a word other than the keyword is an error"
);