How to count the number of files in a directory using standard?

Question

The new standard expected for 2017 adds std::filesystem. Using it, how can I count the number of files (including sub-directories) in a directory?

I kno

Answer 1

std::size_t number_of_files_in_directory(std::filesystem::path path)
{
    return (std::size_t)std::distance(std::filesystem::directory_iterator{path}, std::filesystem::directory_iterator{});
}

There is no function to find out how many files are in a directory, only functions to iterate over it. The OS only has functions like readdir(), ftw(), FindFirstFileW() so the standard cannot offer a better way.

(On the plus side that allows you to decide whether to, or how deep into, recurse into subdirectories)