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- [#keyword]
- [section keyword]
- [h1 Synopsis]
- template <class S, class ResultType = /* unspecified */>
- struct keyword;
- This is a [link parser parser].
- [table Arguments
- [[Name] [Type]]
- [[`S`] [[link string string]]]
- [[`ResultType`] [[link metaprogramming_value template metaprogramming value]]]
- ]
- [h1 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.
- [h1 Header]
- #include <boost/metaparse/keyword.hpp>
- [h1 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>>
- [h1 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"
- );
- [endsect]
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