A range adaptor that represents
view
of an underlying sequence with only the elements that satisfy the predicate.
filter_view models the concepts bidirectional_range, forward_range, input_range, and common_range when the underlying view V models respective concepts.
V base_ the underlying view
copyable-box<Pred>(until C++23)movable-box<Pred>(since C++23) pred_ wraps the predicate used to filter out elements of base_
begin_
V satisfies forward_range) an object that caches an iterator to the first element of base_ that satisfies the pred_
filter_view
V
filter_view
filter_view
filter_view
sized_range or forward_range
std::ranges::view_interface<D>) [edit] returns a constant iterator to the beginning of the range
std::ranges::view_interface<D>) [edit] returns a sentinel for the constant iterator of the range
std::ranges::view_interface<D>) [edit] returns whether the derived view is not empty, provided only if ranges::empty is applicable to it
std::ranges::view_interface<D>) [edit] returns the first element in the derived view, provided if it satisfies forward_range
std::ranges::view_interface<D>) [edit] returns the last element in the derived view, provided only if it satisfies bidirectional_range and common_range
std::ranges::view_interface<D>) [edit] std::ranges::filter_view::filter_view
1) Value-initializes base_ via its default member initializer (= V()) and default-initializes pred_ (which value-initializes the contained Pred).
2) Initializes base_ with std::move(base) and initializes pred_ with std::move(pred).
constexpr V base() &&;
(2) (since C++20)1) Equivalent to return base_;.
2) Equivalent to return std::move(base_);.
std::ranges::filter_view::predconstexpr const Pred& pred() const;
(since C++20)Returns a reference to the contained Pred object. The behavior is undefined if pred_ does not contain a value.
constexpr /*iterator*/ begin();
(exposition only*)In order to provide the amortized constant time complexity required by the range concept, this function caches the result within the filter_view object for use on subsequent calls. Equivalent to
The behavior is undefined if pred_ does not contain a value.
constexpr auto end();
(since C++20)Returns an iterator to the end. Equivalent to
[edit] Deduction guides template< class R, class Pred >filter_view
filter_view when the underlying view is not a common_range
#include <iostream>
#include <ranges>
int main()
{
auto even = [](int i) { return 0 == i % 2; };
auto square = [](int i) { return i * i; };
for (int i : std::views::iota(0, 6)
| std::views::filter(even)
| std::views::transform(square))
std::cout << i << ' ';
std::cout << '\n';
}
Output:
[edit] Defect reportsThe following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 3714Pred is not default_initializable, the default constructor
filter_view which does not contain a Pred the filter_view is also
default_initializable [edit] See also
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4