65 lines
1.5 KiB
Plaintext
65 lines
1.5 KiB
Plaintext
[#keyword]
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[section keyword]
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[h1 Synopsis]
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template <class S, class ResultType = /* unspecified */>
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struct keyword;
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This is a [link parser parser].
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[table Arguments
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[[Name] [Type]]
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[[`S`] [[link string string]]]
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[[`ResultType`] [[link metaprogramming_value template metaprogramming value]]]
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]
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[h1 Description]
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Parser accepting the keyword `S`. The result of parsing is `ResultType`, which
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is optional; when not given, the result of successful parsing is undefined.
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[h1 Header]
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#include <boost/metaparse/keyword.hpp>
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[h1 Expression semantics]
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For any `r` class and `s` compile-time string that is built from the characters
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`c1` ... `cn` the following are equivalent:
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keyword<s, r>
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last_of<lit<c1>, /* ... */, lit<cn>, return_<r>>
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[h1 Example]
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#include <boost/metaparse/keyword.hpp>
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#include <boost/metaparse/string.hpp>
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#include <boost/metaparse/start.hpp>
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#include <boost/metaparse/get_result.hpp>
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#include <boost/metaparse/is_error.hpp>
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#include <type_traits>
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using namespace boost::metaparse;
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static_assert(
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get_result<
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keyword<BOOST_METAPARSE_STRING("for"), std::integral_constant<int, 13>>
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::apply<BOOST_METAPARSE_STRING("for"), start>
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>::type::value == 13,
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"the result of parsing the keyword is keyword's second argument"
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);
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static_assert(
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is_error<
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keyword<BOOST_METAPARSE_STRING("for"), std::integral_constant<int, 13>>
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::apply<BOOST_METAPARSE_STRING("if"), start>
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>::type::value,
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"a word other than the keyword is an error"
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);
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[endsect]
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