operator==,<=> (std::counted_iterator)

Compares the underlying lengths (i.e. distances to the end).

The behavior is undefined if x and y do not point to elements of the same sequence. That is, there must exist some n such that std:: next ( x. base ( ) , x. count ( ) + n ) and std:: next ( y. base ( ) , y. count ( ) + n ) refer to the same element.

The < , <= , > , >= , and != operators are synthesized from operator <=> and operator == respectively.

This function template is not visible to ordinary unqualified or qualified lookup , and can only be found by argument-dependent lookup when std::counted_iterator<I> is an associated class of the arguments.

Parameters

Return value

Notes

Since the length counts down, not up, the order of the arguments of operator <=> in the underlying comparison expression is reversed, i.e. y is lhs , x is rhs .

Example

#include <initializer_list>
#include <iterator>
 
int main()
{
    static constexpr auto v = {1, 2, 3, 4, 5, 6};
    constexpr std::counted_iterator<std::initializer_list<int>::iterator>
        it1{v.begin(), 5},
        it2{v.begin(), 5},
        it3{v.begin() + 1, 4},
        it4{v.begin(), 0};
    static_assert(it1 == it2);
    static_assert(it2 != it3);
    static_assert(it2 <  it3);
    static_assert(it1 <= it2);
    static_assert(it3 != std::default_sentinel);
    static_assert(it4 == std::default_sentinel);
 
//  it2 == std::counted_iterator{v.begin(), 4}; // UB: operands do not refer to
                                                // elements of the same sequence
}

See also