NAME¶

std::counted_iterator::base - std::counted_iterator::base

Synopsis¶

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.
2) An iterator move constructed from the underlying iterator.

Exceptions¶

May throw implementation-defined exceptions.

Example¶

// Run this code

#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> const&
>{});

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 returns a reference
the underlying iterator
LWG 3593 C++20 the const version of base returns a made noexcept
reference but might not be noexcept

See also¶

operator* accesses the pointed-to element
operator-> (public member function)
(C++20)
count returns the distance to the end
(C++20) (public member function)