1[#BOOST_METAPARSE_STRING] 2[section BOOST_METAPARSE_STRING] 3 4[h1 Synopsis] 5 6 #define BOOST_METAPARSE_STRING(s) \ 7 // unspecified 8 9This is a macro. 10 11[table Arguments 12 [[Name] [Type]] 13 [[`s`] [string literal]] 14] 15 16[h1 Description] 17 18Macro for defining [link string `string`] values. `s` is expected to be a 19string literal. The macro requires C++11. 20 21The maximal length of the string is limited. This limit is defined by the 22`BOOST_METAPARSE_LIMIT_STRING_SIZE` macro. 23 24On platforms where `BOOST_METAPARSE_STRING` is not supported, the `string.hpp` 25header defines the `BOOST_METAPARSE_V1_CONFIG_NO_BOOST_METAPARSE_STRING` macro. 26Defining this macro before including the header disables the 27`BOOST_METAPARSE_STRING` macro. 28 29The upper limit for the maximum length, which can be used is 2048. The 30implementation of the `BOOST_METAPARSE_STRING` macro is generated using 31`tools/string_headers.py` and can be regenerated to extend this upper limit. 32Note that for Oracle Developer Studio the string length limit is 127. 33 34Metaparse supports changing the string length limit within a compilation unit. 35To change the length limit, redefine the `BOOST_METAPARSE_LIMIT_STRING_SIZE` 36macro. 37 38You can find benchmarks of this macro 39[link BOOST_METAPARSE_STRING_benchmark here]. 40 41[h1 Header] 42 43 #include <boost/metaparse/string.hpp> 44 45[h1 Expression semantics] 46 47The semantics of this macro is demonstrated by an example. The following 48 49 BOOST_METAPARSE_STRING("hello") 50 51is equivalent to 52 53 string<'h','e','l','l','o'> 54 55[h1 Example] 56 57 #define BOOST_METAPARSE_LIMIT_STRING_SIZE 8 58 #include <boost/metaparse/string.hpp> 59 60 #include <type_traits> 61 62 using namespace boost::metaparse; 63 64 using hello1 = string<'H','e','l','l','o'>; 65 using hello2 = BOOST_METAPARSE_STRING("Hello"); 66 67 static_assert( 68 std::is_same< 69 string<'H', 'e', 'l', 'l', 'o'>, 70 BOOST_METAPARSE_STRING("Hello") 71 >::type::value, 72 "The type generated by the macro should be identical to the hand-crafted one." 73 ); 74 75 #undef BOOST_METAPARSE_LIMIT_STRING_SIZE 76 #define BOOST_METAPARSE_LIMIT_STRING_SIZE 32 77 78 static_assert( 79 std::is_same< 80 string< 81 'A', ' ', 'l', 'o', 'n', 'g', 'e', 'r', 82 ' ', 's', 't', 'r', 'i', 'n', 'g' 83 >, 84 BOOST_METAPARSE_STRING("A longer string") 85 >::type::value, 86 "The type generated by the macro should be identical to the hand-crafted one." 87 ); 88 89[endsect] 90 91