std::counted_iterator<I>::base
constexpr const I& base() const & noexcept; |
(1) | (since C++20) |
constexpr I base() &&; |
(2) | (since C++20) |
Returns the underlying base iterator.
1) Returns a reference to the underlying iterator.
2) Move constructs the return value from the underlying iterator.
Parameters
(none).
Return value
1) A reference to the underlying iterator.
1) An iterator move constructed from the underlying iterator.
Exceptions
May throw implementation-defined exceptions.
Example
#include <algorithm>
#include <iostream>
#include <iterator>
#include <type_traits>
#include <vector>
int main()
{
std::vector<int> v = { 0, 1, 2, 3, 4 };
std::reverse_iterator<std::vector<int>::iterator> reverse{v.rbegin()};
std::counted_iterator counted{reverse, 3};
static_assert(std::is_same<decltype(counted.base()),
std::reverse_iterator<std::vector<int>::iterator>>{});
std::cout << "Print with reverse_iterator: ";
for (auto r = counted.base(); r != v.rend(); ++r)
std::cout << *r << ' ';
std::cout << '\n';
std::cout << "Print with counted_iterator: ";
for (; counted != std::default_sentinel; ++counted)
std::cout << counted[0] << ' ';
std::cout << '\n';
}
Output:
Print with reverse_iterator: 4 3 2 1 0 Print with counted_iterator: 4 3 2
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| LWG 3391 | C++20 | the const version of base returns a copy of the underlying iterator |
returns a reference |
| LWG 3593 | C++20 | the const version of base returns a reference but might not be noexcept |
made noexcept |
See also
|
(C++20)
|
accesses the pointed-to element (public member function) |
|
(C++20)
|
returns the distance to the end (public member function) |
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