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