# std::reverse_iterator<Iter>::reverse_iterator

From cppreference.com
< cpp‎ | iterator‎ | reverse iterator

reverse_iterator(); | (1) | (constexpr since C++17)
explicit reverse_iterator( iterator_type x ); | (2) | (constexpr since C++17)
template< class U > reverse_iterator( const reverse_iterator<U>& other ); | (3) | (constexpr since C++17)

Constructs a new `reverse_iterator`.

Overload | `current`
--- | ---
(1) | value-initialized
(2) | initialized with x
(3) | initialized with other.`current`

3) The converting constructor.

This overload participates in overload resolution only if std::is_same_v <U, Iter> is false and std::convertible_to <const U&, Iter> is modeled. | (since C++20)

### Parameters

x | - | iterator to adapt
other | - | iterator adaptor to copy

### Example

Run this code

    #include <cassert>
    #include <concepts>
    #include <iterator>
    #include <vector>

    int main()
    {
        std::vector v{0, 1, 2, 3, 4};

        using ReverseIt = std::reverse_iterator<std::vector<int>::const_iterator>;

        ReverseIt i1; // overload (1)
        i1 = v.crbegin();
        assert(*i1 == 4);

        ReverseIt i2(i1); // overload (2)
        assert(i2[0] == 4);

        int x[]{1, 2, 3};
        auto i3 = std::reverse_iterator<int*>(x + std::size(x)); // overload (1)
        i3[0] = -3;
        assert(x[2] == -3);
        std::reverse_iterator<int const*> i4(i3); // overload (3): int => const int
        static_assert(std::convertible_to<decltype(i3)::value_type,
                                          decltype(i4)::value_type>);
        // i4[0] = 5; // Error: assignment of read-only location
    }

### 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 235 | C++98 | the effect of overload (1) was not specified | specified
LWG 1012 | C++98 | overload (1) default-initialized `current` | it is value-initialized
LWG 3435 | C++20 | overload (3) was not constrained | constrained

### See also

operator= | assigns another iterator adaptor (public member function)
make_reverse_iterator (C++14) | creates a std::reverse_iterator of type inferred from the argument (function template)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/iterator/reverse_iterator/reverse_iterator&oldid=177471"