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- [#BOOST_METAPARSE_STRING]
- [section BOOST_METAPARSE_STRING]
- [h1 Synopsis]
- #define BOOST_METAPARSE_STRING(s) \
- // unspecified
- This is a macro.
- [table Arguments
- [[Name] [Type]]
- [[`s`] [string literal]]
- ]
- [h1 Description]
- Macro for defining [link string `string`] values. `s` is expected to be a
- string literal. The macro requires C++11.
- The maximal length of the string is limited. This limit is defined by the
- `BOOST_METAPARSE_LIMIT_STRING_SIZE` macro.
- On platforms where `BOOST_METAPARSE_STRING` is not supported, the `string.hpp`
- header defines the `BOOST_METAPARSE_V1_CONFIG_NO_BOOST_METAPARSE_STRING` macro.
- Defining this macro before including the header disables the
- `BOOST_METAPARSE_STRING` macro.
- The upper limit for the maximum length, which can be used is 2048. The
- implementation of the `BOOST_METAPARSE_STRING` macro is generated using
- `tools/string_headers.py` and can be regenerated to extend this upper limit.
- Note that for Oracle Developer Studio the string length limit is 127.
- Metaparse supports changing the string length limit within a compilation unit.
- To change the length limit, redefine the `BOOST_METAPARSE_LIMIT_STRING_SIZE`
- macro.
- You can find benchmarks of this macro
- [link BOOST_METAPARSE_STRING_benchmark here].
- [h1 Header]
- #include <boost/metaparse/string.hpp>
- [h1 Expression semantics]
- The semantics of this macro is demonstrated by an example. The following
- BOOST_METAPARSE_STRING("hello")
- is equivalent to
- string<'h','e','l','l','o'>
- [h1 Example]
- #define BOOST_METAPARSE_LIMIT_STRING_SIZE 8
- #include <boost/metaparse/string.hpp>
-
- #include <type_traits>
-
- using namespace boost::metaparse;
-
- using hello1 = string<'H','e','l','l','o'>;
- using hello2 = BOOST_METAPARSE_STRING("Hello");
-
- static_assert(
- std::is_same<
- string<'H', 'e', 'l', 'l', 'o'>,
- BOOST_METAPARSE_STRING("Hello")
- >::type::value,
- "The type generated by the macro should be identical to the hand-crafted one."
- );
- #undef BOOST_METAPARSE_LIMIT_STRING_SIZE
- #define BOOST_METAPARSE_LIMIT_STRING_SIZE 32
- static_assert(
- std::is_same<
- string<
- 'A', ' ', 'l', 'o', 'n', 'g', 'e', 'r',
- ' ', 's', 't', 'r', 'i', 'n', 'g'
- >,
- BOOST_METAPARSE_STRING("A longer string")
- >::type::value,
- "The type generated by the macro should be identical to the hand-crafted one."
- );
- [endsect]
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