Movatterモバイル変換

[0]ホーム
URL:

cppreference.com
Namespaces
Variants
    Actions

      std::ranges::owning_view

      From cppreference.com
      <cpp‎ |ranges
       
       
      Ranges library
      Range adaptors
       
      Defined in header<ranges>
      template<ranges::range R>

          requiresstd::movable<R>&&(!/*is-initializer-list*/<R>)
      class owning_view

         :publicranges::view_interface<owning_view<R>>
      		(since C++20)

      owning_view is aview that has unique ownership of arange. It is move-only and stores thatrange within it.

      The constant/*is-initializer-list*/<R> in therequires clause istrue if and only ifstd::remove_cvref_t<R> is a specialization ofstd::initializer_list.

      Contents

      [edit]Data members

      Member Description
      Rr_ the underlying range
      (exposition-only member object*)

      [edit]Member functions

      constructs anowning_view by value-initializing or move-constructing the stored range
      (public member function)
      move-assigns the stored range
      (public member function)
      returns a reference to the stored range
      (public member function)
      returns the beginning iterator of the stored range
      (public member function)
      returns the sentinel of the stored range
      (public member function)
      checks whether the stored range is empty
      (public member function)
      returns the size of the storedsized_range
      (public member function)
      returns the approximate size of the storedapproximately_sized_range
      (public member function)
      returns the pointer to the beginning of the storedcontiguous_range
      (public member function)
      Inherited fromstd::ranges::view_interface
      (C++23)
      		 returns a constant iterator to the beginning of the range
      (public member function ofstd::ranges::view_interface<D>)[edit]
      (C++23)
      		 returns a sentinel for the constant iterator of the range
      (public member function ofstd::ranges::view_interface<D>)[edit]
      returns whether the derived view is not empty, provided only ifranges::empty is applicable to it
      (public member function ofstd::ranges::view_interface<D>)[edit]
      returns the first element in the derived view, provided if it satisfiesforward_range
      (public member function ofstd::ranges::view_interface<D>)[edit]
      returns the last element in the derived view, provided only if it satisfiesbidirectional_range andcommon_range
      (public member function ofstd::ranges::view_interface<D>)[edit]
      returns thenth element in the derived view, provided only if it satisfiesrandom_access_range
      (public member function ofstd::ranges::view_interface<D>)[edit]

      std::ranges::owning_view::owning_view

      owning_view() requiresstd::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)
      1) Default constructor. Value-initializesr_ by its default member initializer (= R()).
      2) Move constructor. Move constructsr_ from that ofother.
      3) Move constructsr_ fromt.

      Parameters

      other - anotherowning_view to move from
      t - range to move from

      Notes

      owning_view does not explicitly define a copy constructor.owning_view is move-only.

      std::ranges::owning_view::operator=

      owning_view& operator=( owning_view&& other)=default;
      		(since C++20)

      Move assignment operator. Move assignsr_ from that ofother.

      Parameters

      other - anotherowning_view to move from

      Return value

      *this

      Notes

      owning_view does not explicitly define a copy assignment operator.owning_view is move-only.

      std::ranges::owning_view::base

      constexpr R& base()&noexcept;
      		 (1)(since C++20)
      constexprconst R& base()const&noexcept;
      		 (2)(since C++20)
      constexpr R&& base()&&noexcept;
      		 (3)(since C++20)
      constexprconst R&& base()const&&noexcept;
      		 (4)(since C++20)

      Returns a reference to the stored range, keeping value category and const-qualification.

      Return value

      1,2)r_
      3,4)std::move(r_ )

      std::ranges::owning_view::begin

      constexprranges::iterator_t<R> begin();
      		 (1)(since C++20)
      constexprauto begin()const requiresranges::range<const R>;
      		 (2)(since C++20)

      Returnsranges::begin(r_ ).

      std::ranges::owning_view::end

      constexprranges::sentinel_t<R> end();
      		 (1)(since C++20)
      constexprauto end()const requiresranges::range<const R>;
      		 (2)(since C++20)

      Returnsranges::end(r_ ).

      std::ranges::owning_view::empty

      constexprbool empty() requires requires{ranges::empty(r_);};
      		 (1)(since C++20)
      constexprbool empty()const requires requires{ranges::empty(r_);};
      		 (2)(since C++20)

      Returnsranges::empty(r_ ).

      std::ranges::owning_view::size

      constexprauto size() requiresranges::sized_range<R>;
      		 (1)(since C++20)
      constexprauto size()const requiresranges::sized_range<const R>;
      		 (2)(since C++20)

      Returnsranges::size(r_ ).

      std::ranges::owning_view::reserve_hint

      constexprauto reserve_hint()
          requires ranges::approximately_sized_range<R>;
      		 (1)(since C++26)
      constexprauto reserve_hint()const
          requires ranges::approximately_sized_range<const R>;
      		 (2)(since C++26)

      Returnsranges::reserve_hint(r_ ).

      std::ranges::owning_view::data

      constexprauto data() requiresranges::contiguous_range<R>;
      		 (1)(since C++20)
      constexprauto data()const requiresranges::contiguous_range<const R>;
      		 (2)(since C++20)

      Returnsranges::data(r_ ).

      [edit]Helper templates

      template<class T>

      constexprbool enable_borrowed_range<std::ranges::owning_view<T>>=

         ranges::enable_borrowed_range<T>;
      		(since C++20)

      This specialization ofranges::enable_borrowed_range makesowning_view satisfyborrowed_range when the underlying range satisfies it.

      [edit]Notes

      Feature-test macroValueStdFeature
      __cpp_lib_ranges_reserve_hint202502L(C++26)ranges::approximately_sized_range andreserve_hint

      [edit]Example

      Run this code
      #include <cassert>#include <iostream>#include <ranges>#include <string> int main(){usingnamespace std::literals;    std::ranges::owning_view ov{"cosmos"s};// the deduced type of R is std::string;// “ov” is the only owner of this stringassert(        ov.empty()==false&&        ov.size()==6&&        ov.size()== ov.base().size()&&        ov.front()=='c'&&        ov.front()==*ov.begin()&&        ov.back()=='s'&&        ov.back()==*(ov.end()-1)&&        ov.data()== ov.base()); std::cout<<"sizeof(ov): "<< sizeof ov<<'\n'// typically equal to sizeof(R)<<"range-for: ";for(constchar ch: ov)std::cout<< ch;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);// OKassert(ov2.size()==6);}

      Possible output:

      sizeof(ov): 32range-for: cosmos

      [edit]See also

      aview of the elements of some otherrange
      (class template)[edit]
      aview that includes all elements of arange
      (alias template)(range adaptor object)[edit]
      Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/ranges/owning_view&oldid=182371"
      [8]ページ先頭
      ©2009-2025 Movatter.jp