std:: iterator_traits <std::counted_iterator>

Inherits the properties from customized (generated from either a standard partial specialization or a program-defined specialization) std:: iterator_traits < I > , with the member type pointer adjusted, where I models input_iterator .

Notably, the iterator_concept (if present) and iterator_category are inherited from std:: iterator_traits < I > .

The condition in the requires-clause is true if and only if std:: iterator_traits < I > is not generated from the primary template.

Note

Before P2259R1 , this specialization is used even if std:: iterator_traits < I > is generated from the primary template. As a result, when testing std:: counted_iterator < I > against an iterator concept (e.g. forward_iterator ), the determination of /*ITER_CONCEPT*/ does not take I::iterator_concept into account, and thus std:: counted_iterator < I > sometimes erroneously behaves as if it cannot model that concept. This incorrect behavior is implemented in libstdc++ prior to 10.4, and in MSVC STL prior to VS 2022 17.0 Preview 3.

The standard library provides partial specializations of std::iterator_traits for pointer types, std::counted_iterator , and std::common_iterator .

Example

#include <iterator>
#include <list>
#include <type_traits>
#include <vector>
 
int main()
{
    std::vector v{1, 2, 3, 4};
    std::list l{1, 2, 3, 4};
    std::counted_iterator iv{v.begin(), 3};
    std::counted_iterator il{l.begin(), 3};
    static_assert(std::is_same<int*, std::iterator_traits<decltype(iv)>::pointer>());
    static_assert(std::is_same<void, std::iterator_traits<decltype(il)>::pointer>());
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

See also