std:: tuple_element <std::ranges::subrange>

The partial specializations of std::tuple_element for std::ranges::subrange provide compile-time access to the iterator or sentinel type of a subrange , using tuple-like syntax. They are provided for structured binding support.

Member types

Notes

As get functions for subrange return iterators and sentinels by value, const qualifier is not added to the result types when the subrange is const-qualified (but not volatile-qualified).

If the subrange is volatile-qualified, the result types are also volatile-qualified because the partial specialization for volatile or const volatile types are used. Such usage is deprecated.

Example

#include <iterator>
#include <list>
#include <ranges>
#include <type_traits>
 
int main()
{
    std::list<int> list{3, 1, 4, 1, 5, 9, 2, 6};
 
    std::ranges::subrange subrange
    {
        std::counted_iterator{std::begin(list), 4},
        std::default_sentinel
    };
 
    static_assert(
        std::is_same_v<
            std::tuple_element_t<0, decltype(subrange)>,
            // implementation-defined type:
            std::counted_iterator<std::_List_iterator<int>>
            >);
 
    static_assert(
        std::is_same_v<
            std::tuple_element_t<1, decltype(subrange)>,
            std::default_sentinel_t
            >);
}

See also