NAME¶

std::ranges::take_view::end - std::ranges::take_view::end

Synopsis¶

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

Returns a sentinel or an iterator representing the end of the take_view. The end of
the take_view is either one past the count-th element in the underlying range, or
the end of the underlying range if the latter has less than count elements.

1) Returns a take_view::/*sentinel*/<false>, a std::default_sentinel_t, or a
ranges::iterator_t<V>.
2) Returns a take_view::/*sentinel*/<true>, a std::default_sentinel_t, 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 possibly const-qualified underlying
view type Base_, that is V (for overload (1)) or const V (for overload (2)).

Let base_ be the underlying view.

The underlying random_access_range
view satisfies
... yes no
ranges::begin(base_) +
yes std::default_sentinel
sized_range ranges::range_difference_t<Base_>(this->size())
no 1) /*sentinel*/<false>{ranges::end(base_)}
2) /*sentinel*/<true>{ranges::end(base_)}

Example¶

// Run this code

#include <iostream>
#include <iterator>
#include <list>
#include <ranges>
#include <type_traits>

int main()
{
const auto list1 = {3, 1, 4, 1, 5};
const auto seq1 = list1 | std::views::take(4);
static_assert(std::ranges::sized_range<decltype(seq1)> &&
std::ranges::random_access_range<decltype(seq1)> &&
std::is_same_v<decltype(seq1.end()), decltype(list1.end())>);
for (auto it = seq1.begin(); it != seq1.end(); ++it)
std::cout << *it << ' ';
std::cout << '\n';

std::list list2 = {2, 7, 1, 8, 2};
const auto seq2 = list2 | std::views::take(4);
static_assert(std::ranges::sized_range<decltype(seq2)> &&
not std::ranges::random_access_range<decltype(seq2)> &&
std::is_same_v<decltype(seq2.end()), std::default_sentinel_t>);
for (auto it = seq2.begin(); it != std::default_sentinel; ++it)
std::cout << *it << ' ';
std::cout << '\n';
}

Output:¶

3 1 4 1
2 7 1 8

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 made explicit
integer-class types might fail

See also¶

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