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- [#one_of_c]
- [section one_of_c]
- [h1 Synopsis]
- template <char... Cs>
- struct one_of_c;
- This is a [link parser parser].
- [table Arguments
- [[Name] [Type]]
- [[`Cs`] [character values]]
- ]
- [h1 Description]
- It accepts inputs beginning with any of the `Cs...` characters. The result of
- parsing is the first character of the input.
- On compilers, which are not C++11-compliant, the maximum number of characters
- that can be provided is defined by the `BOOST_METAPARSE_LIMIT_ONE_OF_SIZE`
- macro. Its default value is `20`.
- [h1 Header]
- #include <boost/metaparse/one_of_c.hpp>
- [h1 Expression semantics]
- For any `c1`, ..., `cn` characters
- one_of_c<c1, ..., cn>
- is equivalent to
- one_of<lit_c<c1>, /* ... */, lit_c<cn>>
- [h1 Example]
- #include <boost/metaparse/one_of_c.hpp>
- #include <boost/metaparse/start.hpp>
- #include <boost/metaparse/string.hpp>
- #include <boost/metaparse/get_result.hpp>
- #include <boost/metaparse/is_error.hpp>
-
- using namespace boost::metaparse;
-
- using whitespace = one_of_c<' ', '\n', '\r', '\t', '\v'>;
-
- static_assert(
- get_result<
- whitespace::apply<BOOST_METAPARSE_STRING(" "), start>
- >::type::value == ' ',
- "the result of parsing should be the first character of the input"
- );
-
- static_assert(
- is_error<whitespace::apply<BOOST_METAPARSE_STRING("x"), start>>::type::value,
- "it should return an error when the input does not begin with a whitespace"
- );
- [endsect]
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