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- [#sequence]
- [section sequence]
- [h1 Synopsis]
- template <class... Ps>
- struct sequence;
- This is a [link parser_combinator parser combinator].
- [table Arguments
- [[Name] [Type]]
- [[`Ps`] [[link parser parser]s]]
- ]
- [h1 Description]
- `sequence` applies the `Ps...` parsers in sequence on the input. It accepts an
- input when all of these parsers accept it. The result of parsing is a sequence
- of the results of the parsers.
- On compilers, which are not C++11-compliant, the maximum number of parsers
- `sequence` accepts can be specified with the
- `BOOST_METAPARSE_LIMIT_SEQUENCE_SIZE` macro. Its default value is `5`.
- [h1 Header]
- #include <boost/metaparse/sequence.hpp>
- [h1 Expression semantics]
- For any `n > 0`, `p0`, ..., `pn` parsers the result of `sequence<p0, ..., p1>`
- is a compile-time sequence of the results of the parsers, applied after each
- other in order on the input string when none of them returns an error.
- The remaining string is the remaining string the last parser returns.
- When one of the parsers returns an error, the combinator returns that error.
- [h1 Example]
- #include <boost/metaparse/sequence.hpp>
- #include <boost/metaparse/token.hpp>
- #include <boost/metaparse/int_.hpp>
- #include <boost/metaparse/lit_c.hpp>
- #include <boost/metaparse/start.hpp>
- #include <boost/metaparse/string.hpp>
- #include <boost/metaparse/is_error.hpp>
- #include <boost/metaparse/get_result.hpp>
-
- #include <boost/mpl/at.hpp>
-
- using namespace boost::metaparse;
-
- using int_token = token<int_>;
- using plus_token = token<lit_c<'+'>>;
-
- using a_plus_b = sequence<int_token, plus_token, int_token>;
-
- static_assert(
- boost::mpl::at_c<
- get_result<a_plus_b::apply<BOOST_METAPARSE_STRING("1 + 2"), start>>::type,
- 0
- >::type::value == 1,
- "the first element of the sequence should be the first number"
- );
-
- static_assert(
- boost::mpl::at_c<
- get_result<a_plus_b::apply<BOOST_METAPARSE_STRING("1 + 2"), start>>::type,
- 1
- >::type::value == '+',
- "the second element of the sequence should be the plus"
- );
-
- static_assert(
- boost::mpl::at_c<
- get_result<a_plus_b::apply<BOOST_METAPARSE_STRING("1 + 2"), start>>::type,
- 2
- >::type::value == 2,
- "the third element of the sequence should be the second number"
- );
-
- static_assert(
- is_error<a_plus_b::apply<BOOST_METAPARSE_STRING("1 +"), start>>::type::value,
- "when not all of the parsers accept the input, sequence should fail"
- );
- [endsect]
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