std::ranges::views::take_while, std::ranges::take_while_view
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take_while_viewviews::take_while
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std::ranges::take_while_view
Defined in header
<ranges>
template< ranges::view V, class Pred >
(1)
(since C++20)
requires ranges::input_range <V> &&
std::is_object_v <Pred> &&
std::indirect_unary_predicate <const Pred, ranges::iterator_t <V>>
class take_while_view
namespace views {
(2)
(since C++20)
inline constexpr /*unspecified*/ take_while = /*unspecified*/;
Call signature
template< ranges::viewable_range R, class Pred >
(since C++20)
requires /* see below */
template< class Pred >
constexpr /*range adaptor closure*/ take_while( Pred&& pred );
(since C++20)
constexpr /*range adaptor closure*/ take_while( Pred&& pred );
1) A range adaptor that represents
view of the elements from an underlying sequence, starting at the beginning and ending at the first element for which the predicate returns false.2) RangeAdaptorObject. The expression views::take_while(e, f) is expression-equivalent to take_while_view(e, f) for any suitable subexpressions e and f.
take_while_view models the concepts contiguous_range, random_access_range, bidirectional_range, forward_range, and input_range when the underlying view V models respective concepts.
Contents
[edit] Data members
Member
Description
V base_ (private)
the underlying view(exposition-only member object*)
copyable-box <Pred>(until C++23)movable-box <Pred>(since C++23) pred_ (private)
the underlying function object(exposition-only member object*)
[edit] Member functions
Inherited from std::ranges::view_interface
returns whether the derived view is empty, provided only if it satisfies
(public member function of
sized_range or forward_range (public member function of
std::ranges::view_interface<D>) [edit]
(C++23)
(public member function of
std::ranges::view_interface<D>) [edit]
(C++23)
(public member function of
std::ranges::view_interface<D>) [edit]
returns whether the derived view is not empty, provided only if ranges::empty is applicable to it
(public member function of
(public member function of
std::ranges::view_interface<D>) [edit]
gets the address of derived view's data, provided only if its iterator type satisfies
(public member function of
contiguous_iterator (public member function of
std::ranges::view_interface<D>) [edit]
returns the first element in the derived view, provided if it satisfies
(public member function of
forward_range (public member function of
std::ranges::view_interface<D>) [edit]
returns the
(public member function of
nth element in the derived view, provided only if it satisfies random_access_range (public member function of
std::ranges::view_interface<D>) [edit]
[edit] Deduction guides
[edit] Nested classes
[edit] Notes
For forward_iterators, views::take_while(v, pred) is similar to ranges::subrange {ranges::begin (v), ranges::find_if_not (v, pred)}, but the latter invokes pred only during construction (while the former invokes pred each time a valid take_while iterator is compared to a sentinel).
[edit] Example
Run this code
#include <iostream> #include <ranges> int main() { for (int year : std::views::iota (2020) | std::views::take_while([](int y){ return y < 2026; })) std::cout << year << ' '; std::cout << '\n'; const char note[]{"Today is yesterday's tomorrow!..."}; auto not_dot = [](char c){ return c != '.'; }; for (char x : std::ranges::take_while_view(note, not_dot)) std::cout << x; std::cout << '\n'; }
Output:
2020 2021 2022 2023 2024 2025 Today is yesterday's tomorrow!
[edit] See also
(C++20)
view consisting of the first N elements of another view (class template) (range adaptor object)[edit]