std::ranges::views::empty, std::ranges::empty_view
From cppreference.com
Defined in header <ranges>
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template<class T> requires std::is_object_v<T> |
(1) | (since C++20) |
namespace views { template<class T> inline constexpr empty_view<T> empty{}; |
(2) | (since C++20) |
1) A range adaptor that produces a
view
of no elements of a particular type.2) Variable template for
empty_view
.Contents |
[edit] Helper templates
template<class T> inline constexpr bool enable_borrowed_range<ranges::empty_view<T>> = true; |
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This specialization of std::ranges::enable_borrowed_range makes empty_view
satisfy borrowed_range
.
[edit] Member functions
begin [static] |
returns nullptr (public static member function) |
end [static] |
returns nullptr (public static member function) |
data [static] |
returns nullptr (public static member function) |
size [static] |
returns 0 (zero) (public static member function) |
empty [static] |
returns true (public static member function) |
std::ranges::empty_view::begin
static constexpr T* begin() noexcept { return nullptr; } |
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empty_view
does not reference any element.
std::ranges::empty_view::end
static constexpr T* end() noexcept { return nullptr; } |
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empty_view
does not reference any element.
std::ranges::empty_view::data
static constexpr T* data() noexcept { return nullptr; } |
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empty_view
does not reference any element.
std::ranges::empty_view::size
static constexpr std::size_t size() noexcept { return 0; } |
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empty_view
is always empty.
std::ranges::empty_view::empty
static constexpr bool empty() noexcept { return true; } |
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empty_view
is always empty.
[edit] Example
Run this code
#include <ranges> int main() { std::ranges::empty_view<long> e; static_assert(std::ranges::empty(e)); static_assert(0 == e.size()); static_assert(nullptr == e.data()); static_assert(nullptr == e.begin()); static_assert(nullptr == e.end()); }
[edit] See also
a view that contains a single element of a specified value (class template) (customization point object) | |
(C++20) |
a view that includes all elements of a range (alias template) (range adaptor object) |
(C++20) |
a view of the elements of some other range (class template) |