std::ranges::views::as_input, std::ranges::as_input_view

 

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Feature test macros (C++20)

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Concepts library (C++20)

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Ranges library (C++20)

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Technical specifications

Symbols index

External libraries

 

Ranges library

Range access begin cbegin   end cend rbegin crbegin   rend crend size ssize   data cdata reserve_hint (C++26)   empty

Range conversions std::from_range_t std::from_range (C++23)(C++23)     to (C++23)

Dangling iterator handling dangling borrowed_iterator_t borrowed_subrange_t

Range primitives
range_size_trange_difference_trange_value_t elements_of (C++23)	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_reference_trange_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)

Range concepts
range borrowed_range    common_range	sized_range viewable_range    view	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	approximately_sized_range (C++26) constant_range (C++23)

Views
view_interface	subrange

Range factories
empty_viewviews::empty	single_viewviews::single	basic_istream_viewviews::istream	iota_viewviews::iota	repeat_viewviews::repeat (C++23)(C++23)

Range adaptors
views::all_tviews::all as_rvalue_viewviews::as_rvalue (C++23)(C++23)   filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while common_viewviews::common views::counted as_input_viewviews::as_input (C++26)(C++26)	ref_view drop_viewviews::drop drop_while_viewviews::drop_while lazy_split_viewviews::lazy_split split_viewviews::split join_viewviews::join join_with_viewviews::join_with (C++23)(C++23)   concat_viewviews::concat (C++26)(C++26) cache_latest_viewviews::cache_latest (C++26)(C++26)	owning_view reverse_viewviews::reverse as_const_viewviews::as_const (C++23)(C++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (C++23)(C++23) zip_viewviews::zip (C++23)(C++23) zip_transform_viewviews::zip_transform (C++23)(C++23)	adjacent_viewviews::adjacent (C++23)(C++23) views::pairwise (C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23) views::pairwise_transform (C++23) chunk_viewviews::chunk (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23) stride_viewviews::stride (C++23)(C++23) cartesian_product_viewviews::cartesian_product (C++23)(C++23)

Range generators std::generator (C++23)

Range adaptor closure objects range_adaptor_closure (C++23)

Range adaptor objects

Helper items
copyable-box movable-box (until C++23)  (C++23)	simple-view non-propagating-cache

 

std::ranges::as_input_view

Member functions

as_input_view::as_input_view

as_input_view::base

as_input_view::begin

as_input_view::end

as_input_view::size

Deduction guides

Iterator

Member functions

as_input_view::iterator::iterator

as_input_view::iterator::base

as_input_view::iterator::operator*

as_input_view::iterator::operator++ as_input_view::iterator::operator++(int)

Non-member functions

operator==(as_input_view::iterator)

operator-(as_input_view::iterator)

iter_move(as_input_view::iterator)

iter_swap(as_input_view::iterator)

 

Defined in header <ranges>
template< ranges::input_range V > requires ranges::view<V> class as_input_view : public ranges::view_interface<as_input_view<V>>	(1)	(since C++26)
namespace views { inline constexpr /* unspecified */ as_input = /* unspecified */; }	(2)	(since C++26)
Call signature
template< ranges::viewable_range R > requires /* see below */ constexpr ranges::view auto as_input( R&& r );		(since C++26)

1) A range adaptor that represents a view of an underlying view as an input_range-only and not a common_range.

2) RangeAdaptorObject. Let e be a subexpression, and let T be decltype(e). Then the expression views::as_input(e) is expression-equivalent to:

• views::all(e), if it is a well-formed expression and all of the conditions below are true:
  • T models input_range,
  • T does not satisfy common_range, and
  • T does not satisfy forward_range.
• as_input_view{e} otherwise.

See More

Consequently, as_input_view never models range concepts that are stronger than input_range. In particular, it does not model all of these:

• forward_range
• bidirectional_range
• random_access_range
• contiguous_range

Additionally, as_input_view does not model common_range. However, it does model borrowed_range, constant_range, and sized_range when the underlying view V models respective concepts.

Data members

Member	Description
V base_ (private)	the underlying view (exposition-only member object*)

Member functions

(constructor)	constructs an as_input_view (public member function)
base	returns a copy of the underlying (adapted) view (public member function)
begin	returns an iterator to the beginning (public member function)
end	returns an iterator or a sentinel to the end (public member function)
size	returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range. (public member function)
Inherited from ranges::view_interface
empty	returns whether the derived view is empty, provided only if it satisfies sized_range or forward_range (public member function of std::ranges::view_interface<D>)
cbegin (C++23)	returns a constant iterator to the beginning of the range (public member function of std::ranges::view_interface<D>)
cend (C++23)	returns a sentinel for the constant iterator of the range (public member function of std::ranges::view_interface<D>)
operator bool	returns whether the derived view is not empty, provided only if ranges::empty is applicable to it (public member function of std::ranges::view_interface<D>)
data	gets the address of derived view's data, provided only if its iterator type satisfies contiguous_iterator (public member function of std::ranges::view_interface<D>)
front	returns the first element in the derived view, provided if it satisfies forward_range (public member function of std::ranges::view_interface<D>)
back	returns the last element in the derived view, provided only if it satisfies bidirectional_range and common_range (public member function of std::ranges::view_interface<D>)
operator[]	returns the nth element in the derived view, provided only if it satisfies random_access_range (public member function of std::ranges::view_interface<D>)

std::ranges::as_input_view::as_input_view

as_input_view() requires std::default_initializable<V> = default;	(1)	(since C++26)
constexpr explicit as_input_view( V base );	(2)	(since C++26)

1) Value-initializes base_ via its default member initializer (= V()).

2) Initializes base_ with std::move(base).

Parameters

base

-

a view

std::ranges::as_input_view::base

constexpr V base() const& requires std::copy_constructible<V>;	(1)	(since C++26)
constexpr V base() &&;	(2)	(since C++26)

1) Copy-constructs the result from the underlying view. Equivalent to return base_;.

2) Move-constructs the result from the underlying view. Equivalent to return std::move(base_);.

std::ranges::as_input_view::begin

constexpr auto begin() requires (!__simple_view<V>);	(1)	(since C++26)
constexpr auto begin() const requires ranges::range<const V>;	(2)	(since C++26)

1) Equivalent to return /*iterator*/<false>(ranges::begin(base_));

2) Equivalent to return /*iterator*/<true>(ranges::begin(base_));

std::ranges::as_input_view::end

constexpr auto end() requires (!__simple_view<V>);	(1)	(since C++26)
constexpr auto end() const requires ranges::range<const V>;	(2)	(since C++26)

1,2) Equivalent to return ranges::end(base_);

std::ranges::as_input_view::size

constexpr auto size() requires ranges::sized_range<V>;	(1)	(since C++26)
constexpr auto size() const requires ranges::sized_range<const V>;	(2)	(since C++26)

1,2) Equivalent to return ranges::size(base_);

Deduction guides

template< class R > as_input_view( R&& ) -> as_input_view<views::all_t<R>>;		(since C++26)

Nested classes

iterator

the iterator type (exposition-only member class template of Template:cpp/ranges/as input view/title*)

Helper templates

template< class T > constexpr bool enable_borrowed_range<std::ranges::as_input_view<T>> = ranges::enable_borrowed_range<T>;		(since C++26)

This specialization of std::ranges::enable_borrowed_range makes as_input_view satisfy borrowed_range when the underlying view satisfies it.

Notes

as_input_view can be useful to avoid the overhead necessary to provide support for the operations needed for greater iterator strength.

Feature-test macro	Value	Std	Feature
__cpp_lib_ranges_as_input	202502L	(C++26)	std::ranges::as_input_view

Example

See also

ranges::input_range (C++20)	specifies a range whose iterator type satisfies input_iterator (concept)
ranges::common_viewviews::common (C++20)	converts a view into a common_range (class template) (range adaptor object)