std::ranges::owning_view
Defined in header <ranges> |
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|---|---|---|
template<ranges::range R>
requires std::movable<R> && (!/*is-initializer-list*/<R>)
class owning_view : public ranges::view_interface<owning_view<R>> |
(since C++20) |
owning_view is a view that has unique ownership of a range. It is move only and stores that range within it.
The constant /*is-initializer-list*/<R> in the requires-clause is true if and only if std::remove_cvref_t<R> is a specialization of std::initializer_list.
Data members
Typical implementations of owning_view have only one non-static data member: the underlying range of type R. The member is shown as r_ here (the name is exposition-only).
Member functions
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(constructor)
(C++20)
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constructs a owning_view by value-initializing or move-constructing the stored range (public member function) |
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operator=
(C++20)
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move-assigns the stored range (public member function) |
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base
(C++20)
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returns a reference to the stored range (public member function) |
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begin
(C++20)
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returns the beginning iterator of the stored range (public member function) |
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end
(C++20)
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returns the sentinel of the stored range (public member function) |
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empty
(C++20)
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checks whether the stored range is empty (public member function) |
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size
(C++20)
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returns the size of the stored sized_range (public member function) |
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data
(C++20)
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returns the pointer to the beginning of the stored contiguous_range (public member function) |
Inherited from |
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(C++20)
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Returns whether the derived view is not empty. Provided if ranges::empty is applicable to it. (public member function of std::ranges::view_interface<D>) |
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(C++20)
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Returns the first element in the derived view. Provided if it satisfies forward_range. (public member function of std::ranges::view_interface<D>) |
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(C++20)
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Returns the last element in the derived view. Provided if it satisfies bidirectional_range and common_range. (public member function of std::ranges::view_interface<D>) |
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(C++20)
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Returns the nth element in the derived view. Provided if it satisfies random_access_range. (public member function of std::ranges::view_interface<D>) |
std::ranges::owning_view::owning_view
owning_view() requires std::default_initializable<R> = default; |
(1) | (since C++20) |
owning_view( owning_view&& other ) = default; |
(2) | (since C++20) |
constexpr owning_view( R&& t ); |
(3) | (since C++20) |
owning_view( const owning_view& ) = delete; |
(4) | (since C++20) |
1) Default constructor. Value-initializes the stored range by its default member initializer (
= R()).
2) Move constructor. Move constructs the stored range from that of
other.
3) Move constructs the stored range from
t.
4) Copy constructor is deleted.
owning_view is move-only.
Parameters
| other | - | another owning_view to move from |
| t | - | range to move from |
std::ranges::owning_view::operator=
owning_view& operator=( owning_view&& other ) = default; |
(1) | (since C++20) |
owning_view& operator=( const owning_view& ) = delete; |
(2) | (since C++20) |
1) Move assignment operator. Move assigns the stored range from that of
other.
2) Copy assignment operator is deleted.
owning_view is move-only.
Parameters
| other | - | another owning_view to move from |
Return value
*this.
std::ranges::owning_view::base
constexpr R& base() & noexcept; |
(1) | (since C++20) |
constexpr const R& base() const & noexcept; |
(2) | (since C++20) |
constexpr R&& base() && noexcept; |
(3) | (since C++20) |
constexpr const R&& base() const && noexcept; |
(4) | (since C++20) |
Returns a reference to the stored range, keeping value category and const-qualification.
1-2) Equivalent to
return r_;.
3-4) Equivalent to
return std::move(r_);.
std::ranges::owning_view::begin
constexpr ranges::iterator_t<R> begin(); |
(1) | (since C++20) |
constexpr auto begin() const requires ranges::range<const R>; |
(2) | (since C++20) |
Equivalent to return ranges::begin(r_);.
std::ranges::owning_view::end
constexpr ranges::sentinel_t<R> end(); |
(1) | (since C++20) |
constexpr auto end() const requires ranges::range<const R>; |
(2) | (since C++20) |
Equivalent to return ranges::end(r_);.
std::ranges::owning_view::empty
constexpr bool empty() requires requires { ranges::empty(r_); }; |
(1) | (since C++20) |
constexpr bool empty() const requires requires { ranges::empty(r_); }; |
(2) | (since C++20) |
Equivalent to return ranges::empty(r_);.
std::ranges::owning_view::size
constexpr auto size() requires ranges::sized_range<R>; |
(1) | (since C++20) |
constexpr auto size() const requires ranges::sized_range<const R>; |
(2) | (since C++20) |
Equivalent to return ranges::size(r_);.
std::ranges::owning_view::data
constexpr auto data() requires ranges::contiguous_range<R>; |
(1) | (since C++20) |
constexpr auto data() const requires ranges::contiguous_range<const R>; |
(2) | (since C++20) |
Equivalent to return ranges::data(r_);.
Helper templates
template<class T>
inline constexpr bool enable_borrowed_range<std::ranges::owning_view<T>> =
std::ranges::enable_borrowed_range<T>; |
(since C++20) |
This specialization of std::ranges::enable_borrowed_range makes owning_view satisfy borrowed_range when the underlying range satisfies it.
Example
#include <ranges>
#include <string>
#include <cassert>
#include <iostream>
int main()
{
using namespace std::literals;
std::ranges::owning_view ov{ "cosmos"s }; // the deduced type of R is std::string;
// `ov` is the only owner of this string
std::cout
<< std::boolalpha
<< "call empty() : " << ov.empty() << '\n'
<< "call size() : " << ov.size() << '\n'
<< "call front() : " << ov.front() << '\n' // same as *(ov.begin())
<< "call back() : " << ov.back() << '\n' // equals to *(ov.end()-1)
<< "call data() : " << ov.data() << '\n'
<< "call base() : " << ov.base().size() << '\n' // ~> ov.size()
<< "sizeof(ov) : " << sizeof(ov) << '\n' // typically equals to sizeof(R)
<< "range-for : \"";
for (const char c: ov)
std::cout << c;
std::cout << "\"\n";
std::ranges::owning_view<std::string> ov2;
assert(ov2.empty());
// ov2 = ov; // compile-time error: copy assignment operator is deleted
ov2 = std::move(ov); // OK
assert(ov.empty());
assert(ov2.size() == 6);
}
Possible output:
call empty() : false call size() : 6 call front() : c call back() : s call data() : cosmos call base() : 6 sizeof(ov) : 32 range-for : "cosmos"
See also
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(C++20)
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a view of the elements of some other range (class template) |
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(C++20)
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a view that includes all elements of a range (alias template) (range adaptor object) |
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