24 Ranges library [ranges]

24.7 Range adaptors [range.adaptors]

24.7.4 All view [range.all]

24.7.4.1 General [range.all.general]

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views​::​all returns a view that includes all elements of its range argument.
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The name views​::​all denotes a range adaptor object ([range.adaptor.object]).
Given a subexpression E, the expression views​::​all(E) is expression-equivalent to:
  • (2.1)
    decay-copy(E) if the decayed type of E models view.
  • (2.2)
    Otherwise, ref_­view{E} if that expression is well-formed.
  • (2.3)
    Otherwise, subrange{E}.

24.7.4.2 Class template ref_­view [range.ref.view]

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ref_­view is a view of the elements of some other range.
namespace std::ranges { template<range R> requires is_object_v<R> class ref_view : public view_interface<ref_view<R>> { private: R* r_ = nullptr; // exposition only public: constexpr ref_view() noexcept = default; template<not-same-as<ref_view> T> requires see below constexpr ref_view(T&& t); constexpr R& base() const { return *r_; } constexpr iterator_t<R> begin() const { return ranges::begin(*r_); } constexpr sentinel_t<R> end() const { return ranges::end(*r_); } constexpr bool empty() const requires requires { ranges::empty(*r_); } { return ranges::empty(*r_); } constexpr auto size() const requires sized_­range<R> { return ranges::size(*r_); } constexpr auto data() const requires contiguous_­range<R> { return ranges::data(*r_); } }; template<class R> ref_view(R&) -> ref_view<R>; }
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template<not-same-as<ref_view> T> requires see below constexpr ref_view(T&& t);
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Effects: Initializes r_­ with addressof(static_­cast<R&>(std​::​forward<T>(t))).
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Remarks: Let FUN denote the exposition-only functions void FUN(R&); void FUN(R&&) = delete;
The expression in the requires-clause is equivalent to: convertible_­to<T, R&> && requires { FUN(declval<T>()); }