118 lines
2.7 KiB
Plaintext
118 lines
2.7 KiB
Plaintext
[#next_line]
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[section next_line]
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[h1 Synopsis]
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template <class SourcePosition, class Ch>
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struct next_line;
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This is a [link lazy_metafunction lazy template metafunction].
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[table Arguments
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[[Name] [Type]]
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[[`SourcePosition`] [[link source_position source position]]]
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[[`Ch`] [[link boxed_value boxed] character value. The character `SourcePosition` points to in the input.]]
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]
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[h1 Description]
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Returns a new source position, pointing to the beginning of the next line.
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[h1 Header]
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#include <boost/metaparse/next_line.hpp>
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[h1 Expression semantics]
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For any `s` source position and `c` wrapped character the following are
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equivalent
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get_col<next_line<s, c>>::type
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boost::mpl::int_<1>
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get_line<next_line<s, c>>
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boost::mpl::plus<get_line<s>::type, boost::mpl::int_<1>>
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get_prev_char<next_line<s, c>>::type
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c
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[h1 Example]
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#include <boost/metaparse/next_line.hpp>
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#include <boost/metaparse/source_position.hpp>
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#include <boost/metaparse/get_col.hpp>
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#include <boost/metaparse/get_line.hpp>
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#include <boost/metaparse/get_prev_char.hpp>
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#include <type_traits>
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using namespace boost::metaparse;
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struct returns_source_position
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{
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using type =
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source_position<
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std::integral_constant<int, 11>,
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std::integral_constant<int, 13>,
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std::integral_constant<char, 'a'>
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>;
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};
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struct returns_char
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{
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using type = std::integral_constant<char, '\n'>;
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};
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static_assert(
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get_col<
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next_line<
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source_position<
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std::integral_constant<int, 11>,
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std::integral_constant<int, 13>,
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std::integral_constant<char, 'a'>
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>,
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std::integral_constant<char, '\n'>
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>
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>::type::value == 1,
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"it should set the column to 1"
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);
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static_assert(
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get_line<
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next_line<
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source_position<
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std::integral_constant<int, 11>,
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std::integral_constant<int, 13>,
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std::integral_constant<char, 'a'>
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>,
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std::integral_constant<char, '\n'>
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>
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>::type::value == 12,
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"it should increase the line component of the source position"
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);
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static_assert(
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get_prev_char<
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next_line<
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source_position<
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std::integral_constant<int, 11>,
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std::integral_constant<int, 13>,
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std::integral_constant<char, 'a'>
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>,
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std::integral_constant<char, '\n'>
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>
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>::type::value == '\n',
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"it should update the prev char component of the source position"
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);
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static_assert(
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get_col<next_line<returns_source_position, returns_char>>::type::value == 1,
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"it should support lazy evaluation"
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);
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[endsect]
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