std::ranges::take_view<V>::begin

 

C++

Compiler support

Freestanding and hosted

Language

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++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
to (C++23)
Range primitives
range_size_trange_difference_t range_value_t	range_reference_trange_const_reference_trange_rvalue_reference_t   (C++23)	iterator_tconst_iterator_tsentinel_t (C++23)
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range    sized_range constant_range (C++23)	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Factories
empty_viewviews::empty iota_viewviews::iota	single_viewviews::single basic_istream_viewviews::istream	repeat_viewviews::repeat (C++23)(C++23)
Adaptors
ref_view views::all_tviews::all common_viewviews::common owning_view views::counted reverse_viewviews::reverse zip_viewviews::zip (C++23)(C++23) as_const_viewviews::as_const (C++23)(C++23) as_rvalue_viewviews::as_rvalue (C++23)(C++23)	take_viewviews::take take_while_viewviews::take_while drop_viewviews::drop drop_while_viewviews::drop_while zip_transform_viewviews::zip_transform (C++23)(C++23) adjacent_transform_viewviews::adjacent_transform (C++23)(C++23)   cartesian_product_viewviews::cartesian_product (C++23)(C++23)	elements_viewviews::elements keys_viewviews::keys values_viewviews::values transform_viewviews::transform adjacent_viewviews::adjacent (C++23)(C++23) slide_viewviews::slide (C++23)(C++23) stride_viewviews::stride (C++23)(C++23)	filter_viewviews::filter join_viewviews::join split_viewviews::split lazy_split_viewviews::lazy_split join_with_viewviews::join_with (C++23)(C++23) chunk_viewviews::chunk (C++23)(C++23) chunk_by_viewviews::chunk_by (C++23)(C++23)
Range adaptor objects
Range adaptor closure objects
Helper items
copyable-box	simple-view

 

std::ranges::take_view

Member functions

take_view::take_view (C++20)

take_view::base (C++20)

take_view::begin (C++20)

take_view::end (C++20)

take_view::size (C++20)

Deduction guides

Sentinel

take_view::sentinel::sentinel (C++20)

take_view::sentinel::base (C++20)

operator==(std::counted_iterator,take_view::sentinel) (C++20)

 

constexpr auto begin() requires (!__SimpleView<V>);	(1)	(since C++20)
constexpr auto begin() const requires ranges::range<const V>;	(2)	(since C++20)

Returns an iterator to the first element of the take_view.

1) Returns a std::counted_iterator or a ranges::iterator_t<V>.

2) Returns a std::counted_iterator or a ranges::iterator_t<const V>.

Overload (1) does not participate in overload resolution if V is a simple view (that is, if V and const V are views with the same iterator and sentinel types).

Parameters

(none)

Return value

The result depends on the concepts satisfied by possible const-qualified underlying view type Base_, which is V (for overload (1)) or const V (for overload (2)).

Let base_ be the underlying view, count_ be the number passed to the constructor (​0​ if default initialized).

The underlying view satisfies ...		random_access_range
		yes	no
sized_range	yes	ranges::begin(base_)	std::counted_iterator(ranges::begin(base_), ranges::range_difference_t<Base_>(this->size()))
	no	std::counted_iterator(ranges::begin(base_), count_)

Example

Run this code

#include <ranges>
#include <iostream>
#include <string_view>
using namespace std::literals;
 
int main()
{
    static constexpr auto sv = {"∀x"sv, "∃y"sv, "ε"sv, "δ"sv};
 
    std::cout << *std::ranges::take_view(sv, 8).begin() << '\n';
}

Output:

∀x

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
P2393R1	C++20	implicit conversions between signed and unsigned integer-class types might fail	made explicit

See also

end (C++20)	returns an iterator or a sentinel to the end (public member function)
counted_iterator (C++20)	iterator adaptor that tracks the distance to the end of the range (class template)
operator== (C++20)	compares a sentinel with an iterator returned from take_view::begin (function)