std::ranges::views::take_while, std::ranges::take_while_view

 

C++

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Feature test macros (C++20)

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Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

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Numerics library

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Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

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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 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    sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range    random_access_range contiguous_range	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 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 concat_viewviews::concat (C++26)(C++26)	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 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::take_while_view

Member functions

take_while_view::take_while_view

take_while_view::base

take_while_view::pred

take_while_view::begin

take_while_view::end

Deduction guides

Sentinel

take_while_view::sentinel::sentinel

take_while_view::sentinel::base

operator==(take_while_view::sentinel)

 

Defined in header <ranges>
template< ranges::view V, class Pred >     requires ranges::input_range<V> &&              std::is_object_v<Pred> &&              std::indirect_unary_predicate<const Pred, ranges::iterator_t<V>> class take_while_view     : public ranges::view_interface<take_while_view<V, Pred>>	(1)	(since C++20)
namespace views {     inline constexpr /*unspecified*/ take_while = /*unspecified*/; }	(2)	(since C++20)
Call signature
template< ranges::viewable_range R, class Pred >     requires /* see below */ constexpr ranges::view auto take_while( R&& r, Pred&& pred );		(since C++20)
template< class Pred > constexpr /*range adaptor closure*/ take_while( Pred&& pred );		(since C++20)

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.

Data members

Member name	Definition
base_ (private)	the underlying view of type V (exposition-only member object*)
pred_ (private)	the underlying function object of type copyable-box<Pred>(until C++23)movable-box<Pred>(since C++23) (exposition-only member object*)

Member functions

(constructor)	constructs a take_while_view (public member function)
base	returns a copy of the underlying (adapted) view (public member function)
pred	returns a reference to the stored predicate (public member function)
begin	returns an iterator to the beginning (public member function)
end	returns a sentinel representing the end (public member function)
Inherited from std::ranges::view_interface
empty	returns whether the derived view is empty. Provided 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 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 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>)
operator[]	returns the nth element in the derived view. Provided if it satisfies random_access_range. (public member function of std::ranges::view_interface<D>)

Nested classes

sentinel

the sentinel type (exposition-only member class template*)

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!

See also

ranges::take_viewviews::take (C++20)	a view consisting of the first N elements of another view (class template) (range adaptor object)
ranges::drop_while_viewviews::drop_while (C++20)	a view consisting of the elements of another view, skipping the initial subsequence of elements until the first element where the predicate returns false (class template) (range adaptor object)