This is a follow-up question for A Summation Function For Arbitrary Nested Vector Implementation In C++ and A Summation Function For Various Type Arbitrary Nested Iterable Implementation in C++. Besides the summation result, I am trying to get the element count in arbitrary nested iterable things. For example, there are three elements in std::vector<int> test_vector = { 1, 2, 3 };, so the element count of test_vector is 3. The experimental implementation of recursive_count is as below.

size_t recursive_count() { return 0; } template<class T> requires (!is_elements_iterable<T> && !is_iterable<T>) size_t recursive_count(const T& input) { return 1; } template<class T> requires (!is_elements_iterable<T> && is_iterable<T>) size_t recursive_count(const T& input) { return input.size(); } template<class T> requires (is_elements_iterable<T> && is_iterable<T>) size_t recursive_count(const T& input) { size_t output{}; for (auto &element : input) { output += recursive_count(element); } return output; } 

Some test cases of this recursive_count template function.

// std::vector<int> case std::vector<int> test_vector = { 1, 2, 3 }; auto recursive_count_result1 = recursive_count(test_vector); std::cout << recursive_count_result1 << std::endl; // std::vector<std::vector<int>> case std::vector<decltype(test_vector)> test_vector2 = { test_vector, test_vector, test_vector }; auto recursive_count_result2 = recursive_count(test_vector2); std::cout << recursive_count_result2 << std::endl; // std::deque<int> case std::deque<int> test_deque; test_deque.push_back(1); test_deque.push_back(1); test_deque.push_back(1); auto recursive_count_result3 = recursive_count(test_deque); std::cout << recursive_count_result3 << std::endl; // std::deque<std::deque<int>> case std::deque<decltype(test_deque)> test_deque2; test_deque2.push_back(test_deque); test_deque2.push_back(test_deque); test_deque2.push_back(test_deque); auto recursive_count_result4 = recursive_count(test_deque2); std::cout << recursive_count_result4 << std::endl; 

A Godbolt link is here.

All suggestions are welcome.

The summary information:

• Which question it is a follow-up to?

  A Summation Function For Arbitrary Nested Vector Implementation In C++ and

  A Summation Function For Various Type Arbitrary Nested Iterable Implementation in C++

• What changes has been made in the code since last question?

  The previous questions are focused on summation operation, and I am trying to implement a recursive_count template function here.

• Why a new review is being asked for?

  In my opinion, I am not sure the name of this function is good or not. I know there is a function std::count in STL which purpose is to count the elements that are equal to given specific value. If there is any better naming suggestion, please let me know.