[range.single]

# 25 Ranges library [[ranges]](./#ranges)

## 25.6 Range factories [[range.factories]](range.factories#range.single)

### 25.6.3 Single view [range.single]

#### [25.6.3.1](#overview) Overview [[range.single.overview]](range.single.overview)

[1](#overview-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2626)

single_view produces a view that contains
exactly one element of a specified value[.](#overview-1.sentence-1)

[2](#overview-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2630)

The name views​::​single denotes a
customization point object ([[customization.point.object]](customization.point.object "16.3.3.3.5 Customization Point Object types"))[.](#overview-2.sentence-1)

Given a subexpression E, the expressionviews​::​single(E) is expression-equivalent tosingle_view<decay_t<decltype((E))>>(E)[.](#overview-2.sentence-2)

[3](#overview-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2638)

[*Example [1](#overview-example-1)*: for (int i : views::single(4)) cout << i; // prints 4 — *end example*]

#### [25.6.3.2](#view) Class template single_view [[range.single.view]](range.single.view)

[🔗](#lib:single_view)

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>;}

[🔗](#lib:single_view,constructor)

`constexpr explicit single_view(const T& t) requires [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")<T>;
`

[1](#view-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2686)

*Effects*: Initializes *value_* with t[.](#view-1.sentence-1)

[🔗](#lib:single_view,constructor_)

`constexpr explicit single_view(T&& t);
`

[2](#view-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2697)

*Effects*: Initializes *value_* with std​::​move(t)[.](#view-2.sentence-1)

[🔗](#lib:single_view,constructor__)

`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);
`

[3](#view-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2710)

*Effects*: Initializes *value_* as if by*value_*{in_place, std​::​forward<Args>(args)...}[.](#view-3.sentence-1)

[🔗](#lib:begin,single_view)

`constexpr T* begin() noexcept;
constexpr const T* begin() const noexcept;
`

[4](#view-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2723)

*Effects*: Equivalent to: return data();

[🔗](#lib:end,single_view)

`constexpr T* end() noexcept;
constexpr const T* end() const noexcept;
`

[5](#view-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2735)

*Effects*: Equivalent to: return data() + 1;

[🔗](#lib:empty,single_view)

`static constexpr bool empty() noexcept;
`

[6](#view-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2746)

*Effects*: Equivalent to: return false;

[🔗](#lib:size,single_view)

`static constexpr size_t size() noexcept;
`

[7](#view-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2757)

*Effects*: Equivalent to: return 1;

[🔗](#lib:data,single_view)

`constexpr T* data() noexcept;
constexpr const T* data() const noexcept;
`

[8](#view-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/ranges.tex#L2769)

*Effects*: Equivalent to: return *value_*.operator->();