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

 

哋它亢++

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Language

Standard library

Standard library headers

Named requirements

Feature test macros (哋它亢++20)

Language support library

Concepts library (哋它亢++20)

Metaprogramming library (哋它亢++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (哋它亢++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (哋它亢++17)

Regular expressions library (哋它亢++11)

Concurrency support library (哋它亢++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
std::from_range_t std::from_range (哋它亢++23)(哋它亢++23)	to (哋它亢++23)
Range primitives
range_size_trange_difference_trange_value_trange_reference_t	iterator_tconst_iterator_tsentinel_tconst_sentinel_t (哋它亢++23)(哋它亢++23)	range_const_reference_trange_rvalue_reference_trange_common_reference_t (哋它亢++23)	elements_of (哋它亢++23)
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range constant_range (哋它亢++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 (哋它亢++23)(哋它亢++23)	basic_istream_viewviews::istream
Range adaptors
views::all_tviews::all ref_view owning_view as_rvalue_viewviews::as_rvalue (哋它亢++23)(哋它亢++23) filter_viewviews::filter transform_viewviews::transform take_viewviews::take take_while_viewviews::take_while concat_viewviews::concat (哋它亢++26)(哋它亢++26)	drop_viewviews::drop drop_while_viewviews::drop_while join_viewviews::join join_with_viewviews::join_with (哋它亢++23)(哋它亢++23) lazy_split_viewviews::lazy_split split_viewviews::split views::counted common_viewviews::common	reverse_viewviews::reverse as_const_viewviews::as_const (哋它亢++23)(哋它亢++23) elements_viewviews::elements keys_viewviews::keys values_viewviews::values enumerate_viewviews::enumerate (哋它亢++23)(哋它亢++23) zip_viewviews::zip (哋它亢++23)(哋它亢++23) zip_transform_viewviews::zip_transform (哋它亢++23)(哋它亢++23)	adjacent_viewviews::adjacent (哋它亢++23)(哋它亢++23) views::pairwise (哋它亢++23) adjacent_transform_viewviews::adjacent_transform (哋它亢++23)(哋它亢++23) views::pairwise_transform (哋它亢++23) chunk_viewviews::chunk (哋它亢++23)(哋它亢++23) slide_viewviews::slide (哋它亢++23)(哋它亢++23) chunk_by_viewviews::chunk_by (哋它亢++23)(哋它亢++23) stride_viewviews::stride (哋它亢++23)(哋它亢++23) cartesian_product_viewviews::cartesian_product (哋它亢++23)(哋它亢++23)
Range generators
std::generator (哋它亢++23)
Range adaptor objects
Range adaptor closure objects
range_adaptor_closure (哋它亢++23)
Helper items
copyable-box movable-box (until 哋它亢++23)(哋它亢++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 哋它亢++20)
namespace views {     inline constexpr /*unspecified*/ take_while = /*unspecified*/; }	(2)	(since 哋它亢++20)
Call signature
template< ranges::viewable_range R, class Pred >     requires /* see below */ constexpr ranges::view auto take_while( R&& r, Pred&& pred );		(since 哋它亢++20)
template< class Pred > constexpr /*range adaptor closure*/ take_while( Pred&& pred );		(since 哋它亢++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.

Member functions

(constructor) (哋它亢++20)	constructs a take_while_view (public member function)
base (哋它亢++20)	returns a copy of the underlying (adapted) view (public member function)
pred (哋它亢++20)	returns a reference to the stored predicate (public member function)
begin (哋它亢++20)	returns an iterator to the beginning (public member function)
end (哋它亢++20)	returns a sentinel representing the end (public member function)
Inherited from std::ranges::view_interface
empty (哋它亢++20)	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 (哋它亢++23)	returns a constant iterator to the beginning of the range. (public member function of std::ranges::view_interface<D>)
cend (哋它亢++23)	returns a sentinel for the constant iterator of the range. (public member function of std::ranges::view_interface<D>)
operator bool (哋它亢++20)	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 (哋它亢++20)	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 (哋它亢++20)	returns the first element in the derived view. Provided if it satisfies forward_range. (public member function of std::ranges::view_interface<D>)
operator[] (哋它亢++20)	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 <= 2023; }))
        std::cout << year << ' ';
    std::cout << '\n';
 
    const char idea[] {"Today is yesterday's tomorrow!..."};
    for (char x : std::ranges::take_while_view(idea, [](char c) { return c != '.'; }))
        std::cout << x;
    std::cout << '\n';
}

Output:

2020 2021 2022 2023
Today is yesterday's tomorrow!

See also

ranges::take_viewviews::take (哋它亢++20)	a view consisting of the first N elements of another view (class template) (range adaptor object)
ranges::drop_while_viewviews::drop_while (哋它亢++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)