bump version to 12.2.2-pve1

[ceph.git] / ceph / src / boost / libs / metaparse / doc / lit.qbk

[#lit]
[section lit]

[h1 Synopsis]

  template <class C>
  struct lit;

This is a [link parser parser].

[table Arguments
  [[Name] [Type]]
  [[`C`]  [[link boxed_value boxed] character value]]
]

[h1 Description]

Parser accepting only the `C` character. The result of parsing is the accepted
character.

[h1 Header]

  #include <boost/metaparse/lit.hpp>

[h1 Expression semantics]

For any `c` boxed character the following are equivalent:

  lit<c>
  
  accept_when<
    one_char,
    boost::mpl::lambda<boost::mpl::equal_to<boost::mpl::_1, c>>::type,
    error::literal_expected<c::type::value>
  >

[h1 Example]

  #include <boost/metaparse/lit.hpp>
  #include <boost/metaparse/start.hpp>
  #include <boost/metaparse/string.hpp>
  #include <boost/metaparse/is_error.hpp>
  #include <boost/metaparse/get_result.hpp>
  
  #include <type_traits>
  
  using namespace boost::metaparse;
  
  static_assert(
    is_error<
      lit<std::integral_constant<char, 'x'>>
        ::apply<BOOST_METAPARSE_STRING("a"), start>
    >::type::value,
    "a different character should be an error"
  );
  
  static_assert(
    is_error<
      lit<std::integral_constant<char, 'x'>>
        ::apply<BOOST_METAPARSE_STRING(""), start>
    >::type::value,
    "empty input should be an error"
  );
  
  static_assert(
    get_result<
      lit<std::integral_constant<char, 'x'>>
        ::apply<BOOST_METAPARSE_STRING("x"), start>
    >::type::value == 'x',
    "result of parsing should be the accepted character"
  );

[endsect]