cppdraft_translate/cppdraft/range/drop/view.md

[range.drop.view]

25 Ranges library [ranges]

25.7 Range adaptors [range.adaptors]

25.7.12 Drop view [range.drop]

25.7.12.2 Class template drop_view [range.drop.view]

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namespace std::ranges {template<view V>class drop_view : public view_interface<drop_view> {public: drop_view() requires default_initializable = default; constexpr explicit drop_view(V base, range_difference_t count); constexpr V base() const & requires copy_constructible { return base_; }constexpr V base() && { return std::move(base_); }constexpr auto begin()requires (!(simple-view &&random_access_range && sized_range)); constexpr auto begin() constrequires random_access_range && sized_range; constexpr auto end() requires (){ return ranges::end(base_); }constexpr auto end() const requires range{ return ranges::end(base_); }constexpr auto size() requires sized_range {const auto s = ranges::size(base_); const auto c = static_cast<decltype(s)>(count_); return s < c ? 0 : s - c; }constexpr auto size() const requires sized_range {const auto s = ranges::size(base_); const auto c = static_cast<decltype(s)>(count_); return s < c ? 0 : s - c; }constexpr auto reserve_hint() requires approximately_sized_range {const auto s = static_cast<range_difference_t>(ranges::reserve_hint(base_)); return to-unsigned-like(s < count_ ? 0 : s - count_); }constexpr auto reserve_hint() const requires approximately_sized_range {const auto s = static_cast<range_difference_t>(ranges::reserve_hint(base_)); return to-unsigned-like(s < count_ ? 0 : s - count_); }private: V base_ = V(); // exposition only range_difference_t count_ = 0; // exposition only}; template drop_view(R&&, range_difference_t) -> drop_view<views::all_t>;}

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constexpr explicit drop_view(V base, range_difference_t<V> count);

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Preconditions: count >= 0 is true.

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Effects: Initializes base_ with std​::​move(base) andcount_ with count.

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constexpr auto begin() requires (!([simple-view](range.utility.helpers#concept:simple-view "25.5.2 Helper concepts [range.utility.helpers]")<V> && [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<const V> && [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<const V>)); constexpr auto begin() const requires [random_access_range](range.refinements#concept:random_access_range "25.4.6 Other range refinements [range.refinements]")<const V> && [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<const V>;

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Returns: ranges​::​next(ranges​::​begin(base_), count_, ranges​::​end(base_)).

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Remarks: In order to provide the amortized constant-time complexity required by the range concept when drop_view models forward_range, the first overload caches the result within the drop_view for use on subsequent calls.

[Note 1:

Without this, applying a reverse_view over a drop_view would have quadratic iteration complexity.

— end note]