testing for proximity to the end of an iterator.

main.cpp

#include <string>
#include <iostream>
#include <vector>

int main() {
    std::vector<uint64_t> elems{1, 2, 3, 4, 5, 6};
    
    // print
    std::cout << "[ ";
    for (auto itr = elems.begin(); itr != elems.end(); ++itr) {
        std::cout << *itr;
        if (itr + 1 != elems.end()) std::cout << ", ";
    }
    std::cout << " ]";
    
    return 0;
}

Results in (written to console):

[ 1, 2, 3, 4, 5, 6 ]