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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