131 lines
5.2 KiB
Markdown
131 lines
5.2 KiB
Markdown
[range.single]
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# 25 Ranges library [[ranges]](./#ranges)
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## 25.6 Range factories [[range.factories]](range.factories#range.single)
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### 25.6.3 Single view [range.single]
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#### [25.6.3.1](#overview) Overview [[range.single.overview]](range.single.overview)
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[1](#overview-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2626)
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single_view produces a view that contains
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exactly one element of a specified value[.](#overview-1.sentence-1)
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[2](#overview-2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2630)
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The name views::single denotes a
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customization point object ([[customization.point.object]](customization.point.object "16.3.3.3.5 Customization Point Object types"))[.](#overview-2.sentence-1)
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Given a subexpression E, the expressionviews::single(E) is expression-equivalent tosingle_view<decay_t<decltype((E))>>(E)[.](#overview-2.sentence-2)
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[3](#overview-3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2638)
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[*Example [1](#overview-example-1)*: for (int i : views::single(4)) cout << i; // prints 4 â *end example*]
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#### [25.6.3.2](#view) Class template single_view [[range.single.view]](range.single.view)
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[ð](#lib:single_view)
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namespace std::ranges {template<[move_constructible](concept.moveconstructible#concept:move_constructible "18.4.13 Concept move_constructible [concept.moveconstructible]") T>requires is_object_v<T>class single_view : public view_interface<single_view<T>> {private:*movable-box*<T> *value_*; // *exposition only* (see [[range.move.wrap]](range.move.wrap "25.7.3 Movable wrapper"))public: single_view() requires [default_initializable](concept.default.init#concept:default_initializable "18.4.12 Concept default_initializable [concept.default.init]")<T> = default; constexpr explicit single_view(const T& t) requires [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_constructible [concept.copyconstructible]")<T>; constexpr explicit single_view(T&& t); template<class... Args>requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_from [concept.constructible]")<T, Args...>constexpr explicit single_view(in_place_t, Args&&... args); constexpr T* begin() noexcept; constexpr const T* begin() const noexcept; constexpr T* end() noexcept; constexpr const T* end() const noexcept; static constexpr bool empty() noexcept; static constexpr size_t size() noexcept; constexpr T* data() noexcept; constexpr const T* data() const noexcept; }; template<class T> single_view(T) -> single_view<T>;}
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[ð](#lib:single_view,constructor)
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`constexpr explicit single_view(const T& t) requires [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_constructible [concept.copyconstructible]")<T>;
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`
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[1](#view-1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2686)
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*Effects*: Initializes *value_* with t[.](#view-1.sentence-1)
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[ð](#lib:single_view,constructor_)
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`constexpr explicit single_view(T&& t);
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`
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[2](#view-2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2697)
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*Effects*: Initializes *value_* with std::move(t)[.](#view-2.sentence-1)
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[ð](#lib:single_view,constructor__)
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`template<class... Args>
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requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_from [concept.constructible]")<T, Args...>
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constexpr explicit single_view(in_place_t, Args&&... args);
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`
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[3](#view-3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2710)
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*Effects*: Initializes *value_* as if by*value_*{in_place, std::forward<Args>(args)...}[.](#view-3.sentence-1)
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[ð](#lib:begin,single_view)
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`constexpr T* begin() noexcept;
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constexpr const T* begin() const noexcept;
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`
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[4](#view-4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2723)
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*Effects*: Equivalent to: return data();
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[ð](#lib:end,single_view)
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`constexpr T* end() noexcept;
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constexpr const T* end() const noexcept;
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`
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[5](#view-5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2735)
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*Effects*: Equivalent to: return data() + 1;
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[ð](#lib:empty,single_view)
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`static constexpr bool empty() noexcept;
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`
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[6](#view-6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2746)
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*Effects*: Equivalent to: return false;
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[ð](#lib:size,single_view)
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`static constexpr size_t size() noexcept;
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`
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[7](#view-7)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2757)
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*Effects*: Equivalent to: return 1;
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[ð](#lib:data,single_view)
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`constexpr T* data() noexcept;
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constexpr const T* data() const noexcept;
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`
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[8](#view-8)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2769)
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*Effects*: Equivalent to: return *value_*.operator->();
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