NAME¶

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

Synopsis¶

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
* std::bidirectional_iterator_tag, if V models
iterator_concept bidirectional_range,
* std::forward_iterator_tag, if V models forward_iterator,
* std::input_iterator_tag otherwise.
Defined if and only if V models forward_range. Let C be the type
std::iterator_traits<ranges::iterator_t<V>>::iterator_category.

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

Member name Definition
An iterator of type ranges::iterator_t<V> into the underlying
current_ (private) view.
(exposition-only member object*)
A pointer of type ranges::filter_view<V, Pred>* to the parent
parent_ (private) filter_view object.
(exposition-only member object*)

Member functions¶

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

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

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

std::copyable<ranges::iterator_t<V>>;

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 ) (3) (since C++20)
requires ranges::forward_range<V>;

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

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

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

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

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 ) (since C++20)

noexcept(noexcept(ranges::iter_move(i.current_)));

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 )
(since C++20)
noexcept(noexcept(ranges::iter_swap(x.current_, y.current_)))

requires std::indirectly_swappable<ranges::iterator_t<V>>;

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 defined only if V is a
always defined forward_range
LWG 3533 C++20 the const& overload of base copied returns a reference to it
the underlying iterator
LWG 3593 C++20 the const& overload of base might not made noexcept
be noexcept