25 Ranges library [ranges]

25.6 Range factories [range.factories]

25.6.3 Single view [range.single]

25.6.3.1 Overview [range.single.overview]

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single_view produces a view that contains exactly one element of a specified value.
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The name views​::​single denotes a customization point object ([customization.point.object]).
Given a subexpression E, the expression views​::​single(E) is expression-equivalent to single_view<decay_t<decltype((E))>>(E).
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[Example 1: for (int i : views::single(4)) cout << i; // prints 4 — end example]

25.6.3.2 Class template single_view [range.single.view]

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namespace std::ranges { template<move_constructible 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]) public: single_view() requires default_initializable<T> = default; constexpr explicit single_view(const T& t) requires copy_constructible<T>; constexpr explicit single_view(T&& t); template<class... Args> requires constructible_from<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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constexpr explicit single_view(const T& t) requires copy_constructible<T>;
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Effects: Initializes value_ with t.
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constexpr explicit single_view(T&& t);
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Effects: Initializes value_ with std​::​move(t).
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template<class... Args> requires constructible_from<T, Args...> constexpr explicit single_view(in_place_t, Args&&... args);
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Effects: Initializes value_ as if by value_{in_place, std​::​forward<Args>(args)...}.
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constexpr T* begin() noexcept; constexpr const T* begin() const noexcept;
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Effects: Equivalent to: return data();
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constexpr T* end() noexcept; constexpr const T* end() const noexcept;
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Effects: Equivalent to: return data() + 1;
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static constexpr bool empty() noexcept;
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Effects: Equivalent to: return false;
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static constexpr size_t size() noexcept;
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Effects: Equivalent to: return 1;
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constexpr T* data() noexcept; constexpr const T* data() const noexcept;
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Effects: Equivalent to: return value_.operator->();