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- [#repeated]
- [section repeated]
- [h1 Synopsis]
- template <class P>
- struct repeated;
- This is a [link parser_combinator parser combinator].
- [table Arguments
- [[Name] [Type]]
- [[`P`] [[link parser parser]]]
- ]
- [h1 Description]
- It applies `P` on the input string repeatedly as long as `P` accepts the input.
- The result of parsing is a sequence of the results of the individual
- applications of `P`.
- When `P` rejects the input for the first time, `repeated` still accepts the
- input and the result of parsing is an empty sequence.
- Here is a diagram showing how `repeated` works by example:
- using int_token = token<int_>;
- [$images/metaparse/repeated_diag1.png [width 70%]]
- Further details can be found in the [link repetition Repetition] section
- of the [link manual User Manual].
- [h1 Header]
- #include <boost/metaparse/repeated.hpp>
- [h1 Expression semantics]
- For any `p` parser the following are equivalent:
- repeated<p>
-
- foldl<
- p,
- /* unspecified empty sequence */,
- boost::mpl::push_back<_2, _1>
- >
- [h1 Example]
- #include <boost/metaparse/repeated.hpp>
- #include <boost/metaparse/digit_val.hpp>
- #include <boost/metaparse/start.hpp>
- #include <boost/metaparse/string.hpp>
- #include <boost/metaparse/get_result.hpp>
-
- #include <boost/mpl/equal.hpp>
- #include <boost/mpl/vector.hpp>
- #include <boost/mpl/int.hpp>
-
- using namespace boost::metaparse;
-
- using digits = repeated<digit_val>;
-
- static_assert(
- boost::mpl::equal<
- get_result<digits::apply<BOOST_METAPARSE_STRING("1234"), start>>::type,
- boost::mpl::vector<
- boost::mpl::int_<1>,
- boost::mpl::int_<2>,
- boost::mpl::int_<3>,
- boost::mpl::int_<4>
- >
- >::type::value,
- "the result of parsing should be the list of digit values"
- );
-
- static_assert(
- boost::mpl::equal<
- get_result<digits::apply<BOOST_METAPARSE_STRING("x"), start>>::type,
- boost::mpl::vector<>
- >::type::value,
- "repeated should accept the input when it can't parse anything with digit_val"
- );
- [endsect]
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