99 lines
2.2 KiB
Plaintext
99 lines
2.2 KiB
Plaintext
[#iterate]
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[section iterate]
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[h1 Synopsis]
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template <class P, class N>
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struct iterate;
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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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[[`P`] [[link parser parser]]]
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[[`N`] [[link boxed_value boxed] non-negative integer value]]
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]
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[h1 Description]
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It applies `P` on the input string `N` times. The result of parsing is a
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sequence of the results of the individual applications of `P`. `P` has to accept
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the input `N` times for `iterate` to accept it.
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[h1 Header]
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#include <boost/metaparse/iterate.hpp>
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[h1 Expression semantics]
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For any `p` parser, `n` wrapped integer the following are equivalent:
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iterate<p, n>
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iterate_c<p, n::type::value>
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[h1 Example]
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#include <boost/metaparse/iterate.hpp>
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#include <boost/metaparse/digit.hpp>
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#include <boost/metaparse/string.hpp>
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#include <boost/metaparse/start.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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#include <boost/mpl/vector.hpp>
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#include <boost/mpl/equal.hpp>
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#include <boost/mpl/char.hpp>
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#include <type_traits>
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using namespace boost::metaparse;
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static_assert(
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boost::mpl::equal<
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boost::mpl::vector<
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boost::mpl::char_<'1'>,
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boost::mpl::char_<'2'>,
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boost::mpl::char_<'3'>
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>,
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get_result<
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iterate<digit, std::integral_constant<int, 3>>::apply<
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BOOST_METAPARSE_STRING("123"),
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start
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>
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>::type
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>::type::value,
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"the result should be the sequence of the individual applications of digit"
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);
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static_assert(
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boost::mpl::equal<
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boost::mpl::vector<
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boost::mpl::char_<'1'>,
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boost::mpl::char_<'2'>,
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boost::mpl::char_<'3'>
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>,
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get_result<
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iterate<digit, std::integral_constant<int, 3>>::apply<
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BOOST_METAPARSE_STRING("1234"),
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start
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>
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>::type
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>::type::value,
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"only three iterations should be made"
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);
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static_assert(
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is_error<
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iterate<digit, std::integral_constant<int, 3>>::apply<
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BOOST_METAPARSE_STRING("12"),
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start
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>
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>::type::value,
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"it should fail when digit can not be applied three times"
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);
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[endsect]
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