std::ranges::filter_view<V,Pred>::iterator

 

C++

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Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

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Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Ranges library

Range access
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
Range conversions
to (C++23)
Range primitives
range_size_trange_difference_trange_value_trange_reference_t	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (C++23)(C++23)	range_const_reference_trange_rvalue_reference_trange_common_reference_t (C++23)	elements_of (C++23)
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range constant_range (C++23)	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Range factories
empty_viewviews::empty single_viewviews::single	iota_viewviews::iota repeat_viewviews::repeat (C++23)(C++23)	basic_istream_viewviews::istream
Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (C++23)(C++23) filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (C++23)(C++23) lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	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 objects
Range adaptor closure objects
range_adaptor_closure (C++23)
Helper items
copyable-box movable-box (until C++23)(C++23)	simple-view non-propagating-cache

 

std::ranges::filter_view

Member functions

filter_view::filter_view (C++20)

filter_view::base (C++20)

filter_view::pred (C++20)

filter_view::begin (C++20)

filter_view::end (C++20)

Deduction guides (C++20)

Iterator

filter_view::iterator::iterator (C++20)

filter_view::iterator::base (C++20)

filter_view::iterator::operator*filter_view::iterator::operator-> (C++20)(C++20)

filter_view::iterator::operator++ filter_view::iterator::operator++(int) (C++20)(C++20)

filter_view::iterator::operator-- filter_view::iterator::operator--(int) (C++20)(C++20)

operator==(filter_view::iterator) (C++20)

iter_move(filter_view::iterator) (C++20)

iter_swap(filter_view::iterator) (C++20)

Sentinel

filter_view::sentinel::sentinel (C++20)

filter_view::sentinel::base (C++20)

operator==(filter_view::iterator, filter_view::sentinel) (C++20)

 

class /*iterator*/;		(since C++20) (exposition only*)

The return type of filter_view::begin.

This is a bidirectional_iterator if V models bidirectional_range, a forward_iterator if V models forward_range, and input_iterator otherwise.

Modification of the element denoted by this iterator is permitted, but results in undefined behavior if the resulting value does not satisfy the filter's predicate.

Member types

Member type	Definition
iterator_concept	std::bidirectional_iterator_tag, if V models bidirectional_range, std::forward_iterator_tag, if V models forward_iterator, std::input_iterator_tag otherwise.
iterator_category	Defined if and only if V models forward_range. Let C be the type std::iterator_traits<ranges::iterator_t<V>>::iterator_category. std::bidirectional_iterator_tag, if C models std::derived_from<std::bidirectional_iterator_tag>, std::forward_iterator_tag, if C models std::derived_from<std::forward_iterator_tag>, C otherwise.
value_type	ranges::range_value_t<V>
difference_type	ranges::range_difference_t<V>

Data members

Typical implementations of iterator hold two non-static data members:

• an iterator of type ranges::iterator_t<V> into the underlying view (shown here as current_ for exposition only), and
• a pointer of type ranges::filter_view<V, Pred>* to the parent filter_view object (shown here as parent_ for exposition only).

Member functions

(constructor) (C++20)	constructs an iterator (public member function)
base (C++20)	returns the underlying iterator (public member function)
operator*operator-> (C++20)	forwards to the underlying iterator (public member function)
operator++operator++(int) (C++20)	advances the iterator (public member function)
operator--operator--(int) (C++20)	decrements the iterator (public member function)

std::ranges::filter_view::iterator::iterator

/*iterator*/()   requires std::default_initializable<ranges::iterator_t<V>> = default;	(1)	(since C++20)
constexpr /*iterator*/( filter_view& parent,                         ranges::iterator_t<V> current );	(2)	(since C++20)

1) Initializes current_ and parent_ with their default member initializers, which are = ranges::iterator_t<V>() and = nullptr respectively.

2) Initializes current_ with std::move(current) and parent_ with std::addressof(parent).

std::ranges::filter_view::iterator::base

constexpr const ranges::iterator_t<V>& base() const & noexcept;	(1)	(since C++20)
constexpr ranges::iterator_t<V> base() &&;	(2)	(since C++20)

1) Equivalent to return current_;.

2) Equivalent to return std::move(current_);.

std::ranges::filter_view::iterator::operator*,->

constexpr ranges::range_reference_t<V> operator*() const;	(1)	(since C++20)
constexpr ranges::iterator_t<V> operator->() const   requires /*has-arrow*/<ranges::iterator_t<V>> &&            std::copyable<ranges::iterator_t<V>>;	(2)	(since C++20)

1) Equivalent to return *current_;.

2) Equivalent to return current_;.
For a type I, /*has-arrow*/<I> is modeled or satisfied, if and only if I models or satisfies input_iterator respectively, and either I is a pointer type or requires(I i){ i.operator->();} is true.

std::ranges::filter_view::iterator::operator++

constexpr /*iterator*/& operator++();	(1)	(since C++20)
constexpr void operator++( int );	(2)	(since C++20)
constexpr /*iterator*/ operator++( int )   requires ranges::forward_range<V>;	(3)	(since C++20)

1) Equivalent to
current_ = ranges::find_if(std::move(++current_), ranges::end(parent_->base_),

                           std::ref(*parent_->pred_));

return *this;.

2) Equivalent to ++*this;.

3) Equivalent to auto tmp = *this; ++*this; return tmp;.

std::ranges::filter_view::iterator::operator--

constexpr /*iterator*/& operator--()   requires ranges::bidirectional_range<V>;	(1)	(since C++20)
constexpr /*iterator*/ operator--( int )   requires ranges::bidirectional_range<V>;	(2)	(since C++20)

1) Equivalent to
do

    --current_;
while (!std::invoke(*parent_->pred_, *current_));

return *this;.

2) Equivalent to auto tmp = *this; --*this; return tmp;.

Non-member functions

operator== (C++20)	compares the underlying iterators (function)
iter_move (C++20)	casts the result of dereferencing the underlying iterator to its associated rvalue reference type (function)
iter_swap (C++20)	swaps the objects pointed to by two underlying iterators (function)

operator==(std::ranges::filter_view::iterator)

friend constexpr bool operator==( const /*iterator*/& x, const /*iterator*/& y )   requires std::equality_comparable<ranges::iterator_t<V>>;		(since C++20)

Equivalent to return x.current_ == y.current_;.

The != operator is synthesized from operator==.

This function is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::ranges::filter_view::iterator is an associated class of the arguments.

iter_move(std::ranges::filter_view::iterator)

friend constexpr ranges::range_rvalue_reference_t<V>   iter_move( const /*iterator*/& i )     noexcept(noexcept(ranges::iter_move(i.current_)));		(since C++20)

Equivalent to return ranges::iter_move(i.current_);.

This function is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::ranges::filter_view::iterator is an associated class of the arguments.

iter_swap(std::ranges::filter_view::iterator)

friend constexpr void iter_swap( const /*iterator*/& x, const /*iterator*/& y )   noexcept(noexcept(ranges::iter_swap(x.current_, y.current_)))     requires std::indirectly_swappable<ranges::iterator_t<V>>;		(since C++20)

Equivalent to ranges::iter_swap(x.current_, y.current_).

This function is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::ranges::filter_view::iterator is an associated class of the arguments.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
P2259R1	C++20	member type iterator_category was always defined	defined only if V is a forward_range
LWG 3533	C++20	the const& overload of base copied the underlying iterator	returns a reference to it
LWG 3593	C++20	the const& overload of base might not be noexcept	made noexcept