std::ranges::take_view<V>::begin
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.
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_), |
| no | std::counted_iterator(ranges::begin(base_), count_) |
||
Example
#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
|
(C++20)
|
returns an iterator or a sentinel to the end (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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