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