mirror of https://gitee.com/bigwinds/arangodb
64 lines
1.4 KiB
Plaintext
64 lines
1.4 KiB
Plaintext
[#one_of_c]
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[section one_of_c]
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[h1 Synopsis]
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template <long P1, long P2, /* ... */ long Pn>
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struct one_of_c;
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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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[[`P1` .. `Pn`] [character values]]
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]
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[h1 Description]
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It accepts inputs beginning with any of the `P1`, ..., `Pn` characters. The
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result of parsing is the first character of the input.
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The maximum number of characters that can be provided is defined by the
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`BOOST_METAPARSE_LIMIT_ONE_OF_SIZE` macro. Its default value is `20`.
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[h1 Header]
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#include <boost/metaparse/one_of_c.hpp>
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[h1 Expression semantics]
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For any `c1`, ..., `cn` characters
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one_of_c<c1, ..., cn>
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is equivalent to
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one_of<lit_c<c1>, /* ... */, lit_c<cn>>
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[h1 Example]
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#include <boost/metaparse/one_of_c.hpp>
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#include <boost/metaparse/start.hpp>
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#include <boost/metaparse/string.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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using namespace boost::metaparse;
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using whitespace = one_of_c<' ', '\n', '\r', '\t', '\v'>;
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static_assert(
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get_result<
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whitespace::apply<BOOST_METAPARSE_STRING(" "), start>
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>::type::value == ' ',
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"the result of parsing should be the first character of the input"
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);
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static_assert(
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is_error<whitespace::apply<BOOST_METAPARSE_STRING("x"), start>>::type::value,
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"it should return an error when the input does not begin with a whitespace"
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);
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[endsect]
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