std::ranges::take_view<V>::end
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.
take_view::/*sentinel*/<false>, a
std::default_sentinel_t, or a
ranges::range_iterator_t<V>.
take_view::/*sentinel*/<true>, a
std::default_sentinel_t, or a
ranges::range_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_, that is V (for overload (1)) or const V (for overload (2)).
Let base_ be the underlying view.
| The underlying view satisfies ... | random_access_range |
||
|---|---|---|---|
| yes | no | ||
sized_range |
yes | ranges::begin(base_) + |
std::default_sentinel |
| no | 1) /*sentinel*/<false>{ranges::end(base_)} 2) /*sentinel*/<true>{ranges::end(base_)} |
||
Example
#include <list>
#include <ranges>
#include <iterator>
#include <iostream>
#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)> and
std::ranges::random_access_range<decltype(seq1)> and
std::is_same_v<decltype(seq1.end()), decltype(list1.end())>);
for (auto it = seq1.begin(); it != seq1.end(); 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)> and
not std::ranges::random_access_range<decltype(seq2)> and
std::is_same_v<decltype(seq2.end()), std::default_sentinel_t>);
for (auto it = seq2.begin(); it != std::default_sentinel; 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 integer-class types might fail | made explicit |
See also
|
(C++20)
|
returns an iterator to the beginning (public member function) |
|
(C++20)
|
iterator adaptor that tracks the distance to the end of the range (class template) |
|
(C++20)
|
compares a sentinel with an iterator returned from take_view::begin (function) |
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