bump version to 12.2.2-pve1

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

[#build_parser]
[section build_parser]

[h1 Synopsis]

  template <class P>
  struct build_parser;

This is a [link metafunction template metafunction].

[table Arguments
  [[Name] [Type]]
  [[`P`]  [[link parser parser]]]
]

[h1 Description]

It generates a simple interface for parser. It returns a metafunction class that
takes an input string, parses it with `P` and returns the result of parsing. It
generates a compilation error when parsing fails.

[h1 Return value]

It returns a [link metafunction_class template metafunction class]:

  struct
  {
    template <class S>
    struct apply;
  };

[table Arguments
  [[Name] [Type]]
  [[`S`] [[link string string]]]
]

[h1 Header]

  #include <boost/metaparse/build_parser.hpp>

[h1 Expression semantics]

For any `p` parser and `s` compile-time string

  build_parser<p>::type::apply<s>

is equivalent to

  get_result<p::apply<s>>

[h1 Example]

  #include <boost/metaparse/build_parser.hpp>
  #include <boost/metaparse/int_.hpp>
  #include <boost/metaparse/string.hpp>
  
  using namespace boost::metaparse;
  
  using string_to_int = build_parser<int_>::type;
  
  static_assert(
    string_to_int::apply<BOOST_METAPARSE_STRING("1113")>::type::value == 1113,
    "string_to_int should be a metafunction turning a string into an int"
  );

[endsect]